RUI library

The RUI (Remoute User Interface) library is designed to create web applications in the go language.

The peculiarity of the library is that all data processing is carried out on the server, and the browser is used as a thin client. WebSocket is used for client-server communication.

Hello world

type helloWorldSession struct {
}

func (content *helloWorldSession) CreateRootView(session rui.Session) rui.View {
	return rui.NewTextView(session, rui.Params {
		rui.Text : "Hello world!!!",
	})
}

func createHelloWorldSession(session rui.Session) rui.SessionContent {
	return new(helloWorldSession)
}

func main() {
	app := rui.NewApplication("Hello world", "icon.svg", createHelloWorldSession)
	app.Start("localhost:8000")
}

In the main function, a rui application is created and the main loop is started. When creating an application, 3 parameters are set: the name of the application, the name of the icon, and the createHelloWorldSession function. The createHelloWorldSession function creates a structure that implements the SessionContent interface:

type SessionContent interface {
	CreateRootView(session rui.Session) rui.View
}

A new instance of the helloWorldSession structure is created for each new session,

The CreateRootView function of the SessionContent interface creates a root element. When the user accesses the application by typing the address "localhost: 8000" in the browser, a new session is created. A new instance of the helloWorldSession structure is created for it, and at the end the CreateRootView function is called. The createRootView function returns a representation of a text that is created using the NewTextView function.

If you want the application to be visible outside your computer, then change the address in the Start function:

app.Start(rui.GetLocalIP() + ":80")

Used data types

SizeUnit

The SizeUnit structure is used to set various sizes of interface elements such as width, height, padding, font size, etc. SizeUnit is declared as

type SizeUnit struct {
	Type  SizeUnitType
	Value float64
}

where Type is the type of size; Value is the size.

The Type can take the following values:

Value	Constant	Description
0	Auto	default value. The Value field is ignored
1	SizeInPixel	the Value field specifies the size in pixels.
2	SizeInEM	the Value field specifies the size in em units. 1em is equal to the base font size, which is set in the browser settings
3	SizeInEX	the Value field specifies the size in ex units.
4	SizeInPercent	the Value field specifies the size as a percentage of the parent element size.
5	SizeInPt	the Value field specifies the size in pt units (1pt = 1/72").
6	SizeInPc	the Value field specifies the size in pc units (1pc = 12pt).
7	SizeInInch	the Value field specifies the size in inches.
8	SizeInMM	the Value field specifies the size in millimeters.
9	SizeInCM	the Value field defines the size in centimeters.
10	SizeInFraction	the Value field specifies the size in parts. Used only for sizing cells of the GridLayout.

For a more visual and simple setting of variables of the SizeUnit type, the functions below can be used.

Function	Equivalent definition
rui.AutoSize()	rui.SizeUnit{ Type: rui.Auto, Value: 0 }
rui.Px(n)	rui.SizeUnit{ Type: rui.SizeInPixel, Value: n }
rui.Em(n)	rui.SizeUnit{ Type: rui.SizeInEM, Value: n }
rui.Ex(n)	rui.SizeUnit{ Type: rui.SizeInEX, Value: n }
rui.Percent(n)	rui.SizeUnit{ Type: rui.SizeInPercent, Value: n }
rui.Pt(n)	rui.SizeUnit{ Type: rui.SizeInPt, Value: n }
rui.Pc(n)	rui.SizeUnit{ Type: rui.SizeInPc, Value: n }
rui.Inch(n)	rui.SizeUnit{ Type: rui.SizeInInch, Value: n }
rui.Mm(n)	rui.SizeUnit{ Type: rui.SizeInMM, Value: n }
rui.Cm(n)	rui.SizeUnit{ Type: rui.SizeInCM, Value: n }
rui.Fr(n)	rui.SizeUnit{ Type: rui.SizeInFraction, Value: n }

Variables of the SizeUnit type have a textual representation (why you need it will be described below). The textual representation consists of a number (equal to the value of the Value field) followed by a suffix defining the type. An exception is a value of type Auto, which has the representation “auto”. The suffixes are listed in the following table:

Suffix	Type
px	SizeInPixel
em	SizeInEM
ex	SizeInEX
%	SizeInPercent
pt	SizeInPt
pc	SizeInPc
in	SizeInInch
mm	SizeInMM
cm	SizeInCM
fr	SizeInFraction

Examples: auto, 50%, 32px, 1.5in, 0.8em

To convert the textual representation to the SizeUnit structure, is used the function:

func StringToSizeUnit(value string) (SizeUnit, bool)

You can get a textual representation of the structure using the String() function of SizeUnit structure

Color

The Color type describes a 32-bit ARGB color:

type Color uint32

The Color type has three types of text representations:

1. #AARRGGBB, #RRGGBB, #ARGB, #RGB

where A, R, G, B is a hexadecimal digit describing the corresponding component. If the alpha channel is not specified, then it is considered equal to FF. If the color component is specified by one digit, then it is doubled. For example, “# 48AD” is equivalent to “# 4488AADD”

2. argb(A, R, G, B), rgb(R, G, B)

where A, R, G, B is the representation of the color component. The component can be west as a float number in the range [0 … 1], or as an integer in the range [0 … 255], or as a percentage from 0% to 100%.

Examples:

“argb(255, 128, 96, 0)”
“rgb(1.0, .5, .8)”
“rgb(0%, 50%, 25%)”
“argb(50%, 128, .5, 100%)”

The String function is used to convert a Color to a string. To convert a string to Color, is used the function:

func StringToColor(value string) (Color, bool)

3. The name of the color. The RUI library defines the following colors

Name	Color
black	#ff000000
silver	#ffc0c0c0
gray	#ff808080
white	#ffffffff
maroon	#ff800000
red	#ffff0000
purple	#ff800080
fuchsia	#ffff00ff
green	#ff008000
lime	#ff00ff00
olive	#ff808000
yellow	#ffffff00
navy	#ff000080
blue	#ff0000ff
teal	#ff008080
aqua	#ff00ffff
orange	#ffffa500
aliceblue	#fff0f8ff
antiquewhite	#fffaebd7
aquamarine	#ff7fffd4
azure	#fff0ffff
beige	#fff5f5dc
bisque	#ffffe4c4
blanchedalmond	#ffffebcd
blueviolet	#ff8a2be2
brown	#ffa52a2a
burlywood	#ffdeb887
cadetblue	#ff5f9ea0
chartreuse	#ff7fff00
chocolate	#ffd2691e
coral	#ffff7f50
cornflowerblue	#ff6495ed
cornsilk	#fffff8dc
crimson	#ffdc143c
cyan	#ff00ffff
darkblue	#ff00008b
darkcyan	#ff008b8b
darkgoldenrod	#ffb8860b
darkgray	#ffa9a9a9
darkgreen	#ff006400
darkgrey	#ffa9a9a9
darkkhaki	#ffbdb76b
darkmagenta	#ff8b008b
darkolivegreen	#ff556b2f
darkorange	#ffff8c00
darkorchid	#ff9932cc
darkred	#ff8b0000
darksalmon	#ffe9967a
darkseagreen	#ff8fbc8f
darkslateblue	#ff483d8b
darkslategray	#ff2f4f4f
darkslategrey	#ff2f4f4f
darkturquoise	#ff00ced1
darkviolet	#ff9400d3
deeppink	#ffff1493
deepskyblue	#ff00bfff
dimgray	#ff696969
dimgrey	#ff696969
dodgerblue	#ff1e90ff
firebrick	#ffb22222
floralwhite	#fffffaf0
forestgreen	#ff228b22
gainsboro	#ffdcdcdc
ghostwhite	#fff8f8ff
gold	#ffffd700
goldenrod	#ffdaa520
greenyellow	#ffadff2f
grey	#ff808080
honeydew	#fff0fff0
hotpink	#ffff69b4
indianred	#ffcd5c5c
indigo	#ff4b0082
ivory	#fffffff0
khaki	#fff0e68c
lavender	#ffe6e6fa
lavenderblush	#fffff0f5
lawngreen	#ff7cfc00
lemonchiffon	#fffffacd
lightblue	#ffadd8e6
lightcoral	#fff08080
lightcyan	#ffe0ffff
lightgoldenrodyellow	#fffafad2
lightgray	#ffd3d3d3
lightgreen	#ff90ee90
lightgrey	#ffd3d3d3
lightpink	#ffffb6c1
lightsalmon	#ffffa07a
lightseagreen	#ff20b2aa
lightskyblue	#ff87cefa
lightslategray	#ff778899
lightslategrey	#ff778899
lightsteelblue	#ffb0c4de
lightyellow	#ffffffe0
limegreen	#ff32cd32
linen	#fffaf0e6
magenta	#ffff00ff
mediumaquamarine	#ff66cdaa
mediumblue	#ff0000cd
mediumorchid	#ffba55d3
mediumpurple	#ff9370db
mediumseagreen	#ff3cb371
mediumslateblue	#ff7b68ee
mediumspringgreen	#ff00fa9a
mediumturquoise	#ff48d1cc
mediumvioletred	#ffc71585
midnightblue	#ff191970
mintcream	#fff5fffa
mistyrose	#ffffe4e1
moccasin	#ffffe4b5
navajowhite	#ffffdead
oldlace	#fffdf5e6
olivedrab	#ff6b8e23
orangered	#ffff4500
orchid	#ffda70d6
palegoldenrod	#ffeee8aa
palegreen	#ff98fb98
paleturquoise	#ffafeeee
palevioletred	#ffdb7093
papayawhip	#ffffefd5
peachpuff	#ffffdab9
peru	#ffcd853f
pink	#ffffc0cb
plum	#ffdda0dd
powderblue	#ffb0e0e6
rosybrown	#ffbc8f8f
royalblue	#ff4169e1
saddlebrown	#ff8b4513
salmon	#fffa8072
sandybrown	#fff4a460
seagreen	#ff2e8b57
seashell	#fffff5ee
sienna	#ffa0522d
skyblue	#ff87ceeb
slateblue	#ff6a5acd
slategray	#ff708090
slategrey	#ff708090
snow	#fffffafa
springgreen	#ff00ff7f
steelblue	#ff4682b4
tan	#ffd2b48c
thistle	#ffd8bfd8
tomato	#ffff6347
turquoise	#ff40e0d0
violet	#ffee82ee
wheat	#fff5deb3
whitesmoke	#fff5f5f5
yellowgreen	#ff9acd32

AngleUnit

The AngleUnit type is used to set angular values. AngleUnit is declared as

type AngleUnit struct {
	Type  AngleUnitType
	Value float64
}

where Type is the type of angular value; Value is the angular value

The Type can take the following values:

• Radian (0) - the Value field defines the angular value in radians.
• PiRadian (1) - the Value field defines the angular value in radians multiplied by π.
• Degree (2) - the Value field defines the angular value in degrees.
• Gradian (3) - the Value field defines the angular value in grades (gradians).
• Turn (4) - the Value field defines the angular value in turns (1 turn == 360°).

For a more visual and simple setting of variables of the AngleUnit type, the functions below can be used.

Function	Equivalent definition
rui.Rad(n)	rui.AngleUnit{ Type: rui.Radian, Value: n }
rui.PiRad(n)	rui.AngleUnit{ Type: rui.PiRadian, Value: n }
rui.Deg(n)	rui.AngleUnit{ Type: rui.Degree, Value: n }
rui.Grad(n)	rui.AngleUnit{ Type: rui.Gradian, Value: n }

Variables of type AngleUnit have a textual representation consisting of a number (equal to the value of the Value field) followed by a suffix defining the type. The suffixes are listed in the following table:

Suffix	Type
deg	Degree
°	Degree
rad	Radian
π	PiRadian
pi	PiRadian
grad	Gradian
turn	Turn

Examples: “45deg”, “90°”, “3.14rad”, “2π”, “0.5pi”

The String function is used to convert AngleUnit to a string. To convert a string to AngleUnit is used the function:

func StringToAngleUnit(value string) (AngleUnit, bool)

View

View is an interface for accessing an element of "View" type. View is a rectangular area of the screen. All interface elements extend the View interface, i.e. View is the base element for all other elements in the library.

View has a number of properties like height, width, color, text parameters, etc. Each property has a text name. The Properties interface is used to read and write the property value (View implements this interface):

type Properties interface {
	Get(tag string) interface{}
	Set(tag string, value interface{}) bool
	Remove(tag string)
	Clear()
	AllTags() []string
}

The Get function returns the value of the property, or nil if the property is not set.

The Set function sets the value of a property. If the property value is set successfully, then the function returns true, if not, then false and a description of the error that occurred is written to the log.

The Remove function removes property value, equivalent to Set(nil)

To simplify setting / reading properties, there are also two global functions Get and Set:

func Get(rootView View, viewID, tag string) interface{}
func Set(rootView View, viewID, tag string, value interface{}) bool

These functions get/set the value of the child View

Events

When interacting with the application, various events arise: clicks, resizing, changing input data, etc.

Event listeners are designed to respond to events. A listener is a function that is called every time an event occurs. Each event can have multiple listeners. Let's analyze the listeners using the example of the "edit-text-changed" text change event in the "EditView" editor.

The event listener is a function of the form

func(<View>[, <parameters>])

where the first argument is the View in which the event occurred. Further there are additional parameters of the event.

For "edit-text-changed", the main listener will look like this:

func(EditView, string)

where the second argument is the new text value

If you do not plan to use the first argument, you can omit it. This will be an additional listener

func(string)

In order to assign a listener, you must assign it to a property with the event name

view.Set(rui.EditTextChanged, func(edit EditView, newText string) {
	// do something
})

or

view.Set(rui.EditTextChanged, func(newText string) {
	// do something
})

Each event can have multiple listeners. In this regard, five data types can be used as listeners:

• func(< View >[, < parameters >])
• func([< parameters>])
• []func(< View >[, < parameters >])
• []func([< parameters >])
• []interface{} which only contains func(< View >[, < parameters >]) and func([< parameters >])

After being assigned to a property, all these types are converted to an array of []func(< View >, [< parameters >]). Accordingly, the Get function always returns an array of []func(< View >, [< parameters >]). If there are no listeners, this array will be empty.

For the "edit-text-changed" event, this

• func(editor EditView, newText string)
• func(newText string)
• []func(editor EditView, newText string)
• []func(newText string)
• []interface{} содержащий только func(editor EditView, newText string) и func(newText string)

And the "edit-text-changed" property always stores and returns []func(EditView, string).

In what follows, when describing specific events, only the format of the main listener will be presented.

"id" property

The "id" property is an optional textual identifier for the View. With it, you can find the child View. To do this, use the ViewByID function

func ViewByID(rootView View, id string) View

This function looks for a child View with id. The search starts from rootView. If View is not found, the function returns nil and an error message is written to the log.

Usually id is set when the View is created and is not changed later. But this is an optional condition. You can change the id at any time.

The Set function is used to set a new value for id. For example

view.Set(rui.ID, "myView")
view.Set("id", "myView")

There are two ways to get the id. The first is using the Get function:

if value := view.Get(rui.ID); value != nil {
	id = value.(string)
}

And the second one is using the ID() function:

id = view.ID()

"width", "height", "min-width", "min-height", "max-width", "max-height" properties

These properties are set:

Property	Constant	Description
"width"	rui.Width	The width of View
"height"	rui.Height	The height of View
"min-width"	rui.MinWidth	The minimum width of View
"min-height"	rui.MinHeight	The minimum height of View
"max-width"	rui.MaxWidth	The maximum width of View
"max-height"	rui.MaxHeight	The maximum height of View

These properties are of type SizeUnit. If the "width" / "height" value is not set or is set to Auto, then the height/width of the View is determined by its content and limited to the minimum and maximum height/width. As the value of these properties, you can set the SizeUnit structure, the textual representation of the SizeUnit, or the name of the constant (about the constants below):

view.Set("width", rui.Px(8))
view.Set(rui.MaxHeight, "80%")
view.Set(rui.Height, "@viewHeight")

After getting the value with the Get function, you must typecast:

if value := view.Get(rui.Width); value != nil {
	switch value.(type) {
		case string:
			text := value.(string)
			// TODO

		case SizeUnit:	
			size := value.(SizeUnit)
			// TODO
	}
}

This is quite cumbersome, therefore for each property there is a global function of the same name with the Get prefix, which performs the given cast, gets the value of the constant, if necessary, and returns it. All functions of this type have two arguments: View and subviewID string. The first argument is the root View, the second is the ID of the child View. If the ID of the child View is passed as "", then the value of the root View is returned. For the properties "width", "height", "min-width", "min-height", "max-width", "max-height" these are functions:

func GetWidth(view View, subviewID string) SizeUnit
func GetHeight(view View, subviewID string) SizeUnit
func GetMinWidth(view View, subviewID string) SizeUnit
func GetMinHeight(view View, subviewID string) SizeUnit
func GetMaxWidth(view View, subviewID string) SizeUnit
func GetMaxHeight(view View, subviewID string) SizeUnit

"margin" и "padding" properties

The "margin" property determines the outer margins from this View to its neighbors. The "padding" property sets the padding from the border of the View to the content. The values of the "margin" and "padding" properties are stored as the BoundsProperty interface, which implements the Properties interface (see above). BoundsProperty has 4 SizeUnit properties:

Property	Constant	Description
"top"	rui.Top	Top padding
"right"	rui.Right	Right padding
"bottom"	rui.Bottom	Bottom padding
"left"	rui.Left	Дуае padding

The NewBoundsProperty function is used to create the BoundsProperty interface. Example

view.Set(rui.Margin, NewBoundsProperty(rui.Params {
	rui.Top:  rui.Px(8),
	rui.Left: "@topMargin",
	"right":   "1.5em",
	"bottom":  rui.Inch(0.3),
})))

Accordingly, if you request the "margin" or "padding" property using the Get method, the BoundsProperty interface will return:

if value := view.Get(rui.Margin); value != nil {
	margin := value.(BoundsProperty)
}

BoundsProperty using the "Bounds (session Session) Bounds" function of the BoundsProperty interface can be converted to a more convenient Bounds structure:

type Bounds struct {
	Top, Right, Bottom, Left SizeUnit
}

Global functions can also be used for this:

func GetMargin(view View, subviewID string) Bounds
func GetPadding(view View, subviewID string) Bounds

The textual representation of the BoundsProperty is as follows:

"_{ top = <top padding>, right = <right padding>, bottom = <bottom padding>, left = <left padding> }"

The value of the "margin" and "padding" properties can be passed to the Set method:

• BoundsProperty interface or its textual representation;

• Bounds structure;

• SizeUnit or the name of a constant of type SizeUnit, in which case this value is set to all indents. Those.

  view.Set(rui.Margin, rui.Px(8))

equivalent to

view.Set(rui.Margin, rui.Bounds{Top: rui.Px(8), Right: rui.Px(8), Bottom: rui.Px(8), Left: rui.Px(8)})

Since the value of the "margin" and "padding" property is always stored as the BoundsProperty interface, if you read the "margin" or "padding" property set by the Bounds or SizeUnit with the Get function, then you get the BoundsProperty, not the Bounds or SizeUnit.

The "margin" and "padding" properties are used to set four margins at once. The following properties are used to set individual paddings:

Property	Constant	Description
"margin-top"	rui.MarginTop	The top margin
"margin-right"	rui.MarginRight	The right margin
"margin-bottom"	rui.MarginBottom	The bottom margin
"margin-left"	rui.MarginLeft	The left margin
"padding-top"	rui.PaddingTop	The top padding
"padding-right"	rui.PaddingRight	The right padding
"padding-bottom"	rui.PaddingBottom	The bottom padding
"padding-left"	rui.PaddingLeft	The left padding

Example

view.Set(rui.Margin, rui.Px(8))
view.Set(rui.TopMargin, rui.Px(12))

equivalent to

view.Set(rui.Margin, rui.Bounds{Top: rui.Px(12), Right: rui.Px(8), Bottom: rui.Px(8), Left: rui.Px(8)})

Свойство "border"

The "border" property defines a border around the View. The frame line is described by three attributes: line style, thickness and color.

The value of the "border" property is stored as the BorderProperty interface, which implements the Properties interface (see above). BorderProperty can contain the following properties:

Property	Constant	Type	Description
"left-style"	LeftStyle	int	Left border line style
"right-style"	RightStyle	int	Right border line style
"top-style"	TopStyle	int	Top border line style
"bottom-style"	BottomStyle	int	Bottom border line style
"left-width"	LeftWidth	SizeUnit	Left border line width
"right-width"	RightWidth	SizeUnit	Right border line width
"top-width"	TopWidth	SizeUnit	Top border line width
"bottom-width"	BottomWidth	SizeUnit	Bottom border line width
"left-color"	LeftColor	Color	Left border line color
"right-color"	RightColor	Color	Right border line color
"top-color"	TopColor	Color	Top border line color
"bottom-color"	BottomColor	Color	Bottom border line color

Line style can take the following values:

Value	Constant	Name	Description
0	NoneLine	"none"	No frame
1	SolidLine	"solid"	Solid line
2	DashedLine	"dashed"	Dashed line
3	DottedLine	"dotted"	Dotted line
4	DoubleLine	"double"	Double solid line

All other style values are ignored.

The NewBorder function is used to create the BorderProperty interface.

If all the lines of the frame are the same, then the following properties can be used to set the style, thickness and color:

Property	Constant	Type	Description
"style"	Style	int	Border line style
"width"	Width	SizeUnit	Border line width
"color"	Color	Color	Border line color

Example

view.Set(rui.Border, NewBorder(rui.Params{
	rui.LeftStyle:   rui.SolidBorder,
	rui.RightStyle:  rui.SolidBorder,
	rui.TopStyle:    rui.SolidBorder,
	rui.BottomStyle: rui.SolidBorder,
	rui.LeftWidth:   rui.Px(1),
	rui.RightWidth:  rui.Px(1),
	rui.TopWidth:    rui.Px(1),
	rui.BottomWidth: rui.Px(1),
	rui.LeftColor:   rui.Black,
	rui.RightColor:  rui.Black,
	rui.TopColor:    rui.Black,
	rui.BottomColor: rui.Black,
}))

equivalent to

view.Set(rui.Border, NewBorder(rui.Params{
	rui.Style: rui.SolidBorder,
	rui.Width: rui.Px(1),
	rui.ColorProperty: rui.Black,
}))

The BorderProperty interface can be converted to a ViewBorders structure using the Border function. When converted, all text constants are replaced with real values. ViewBorders is described as

 type ViewBorders struct {
	Top, Right, Bottom, Left ViewBorder
}

where the ViewBorder structure is described as

type ViewBorder struct {
	Style int
	Color Color
	Width SizeUnit
}

The ViewBorders structure can be passed as a parameter to the Set function when setting the value of the "border" property. This converts the ViewBorders to BorderProperty. Therefore, when the property is read, the Get function will return the BorderProperty interface, not the ViewBorders structure. You can get the ViewBorders structure without additional transformations using the global function

func GetBorder(view View, subviewID string) ViewBorders

Besides the auxiliary properties "style", "width" and "color" there are 4 more: "left", "right", "top" and "bottom". As a value, these properties can only take the ViewBorder structure and allow you to set all the attributes of the line of the side of the same name.

You can also set individual frame attributes using the Set function of the View interface. For this, the following properties are used

Property	Constant	Type	Description
"border-left-style"	BorderLeftStyle	int	Left border line style
"border-right-style"	BorderRightStyle	int	Right border line style
"border-top-style"	BorderTopStyle	int	Top border line style
"border-bottom-style"	BorderBottomStyle	int	Bottom border line style
"border-left-width"	BorderLeftWidth	SizeUnit	Left border line width
"border-right-width"	BorderRightWidth	SizeUnit	Right border line width
"border-top-width"	BorderTopWidth	SizeUnit	Top border line width
"border-bottom-width"	BorderBottomWidth	SizeUnit	Bottom border line width
"border-left-color"	BorderLeftColor	Color	Left border line color
"border-right-color"	BorderRightColor	Color	Right border line color
"border-top-color"	BorderTopColor	Color	Top border line color
"border-bottom-color"	BorderBottomColor	Color	Bottom border line color
"border-style"	BorderStyle	int	Border line style
"border-width"	BorderWidth	SizeUnit	Border line width
"border-color"	BorderColor	Color	Border line color
"border-left"	BorderLeft	ViewBorder	Left border line
"border-right"	BorderRight	ViewBorder	Right border line
"border-top"	BorderTop	ViewBorder	Top border line
"border-bottom"	BorderBottom	ViewBorder	Bottom border line

Example

view.Set(rui.BorderStyle, rui.SolidBorder)
view.Set(rui.BorderWidth, rui.Px(1))
view.Set(rui.BorderColor, rui.Black)

equivalent to

view.Set(rui.Border, NewBorder(rui.Params{
	rui.Style: rui.SolidBorder,
	rui.Width: rui.Px(1),
	rui.ColorProperty: rui.Black,
}))

"radius" property

The "radius" property sets the elliptical corner radius of the View. Radii are specified by the RadiusProperty interface that implements the Properties interface (see above). For this, the following properties of the SizeUnit type are used:

Property	Constant	Description
"top-left-x"	TopLeftX	x-radius of the top left corner
"top-left-y"	TopLeftY	y-radius of the top left corner
"top-right-x"	TopRightX	x-radius of the top right corner
"top-right-y"	TopRightY	y-radius of the top right corner
"bottom-left-x"	BottomLeftX	x-radius of the bottom left corner
"bottom-left-y"	BottomLeftY	y-radius of the bottom left corner
"bottom-right-x"	BottomRightX	x-radius of the bottom right corner
"bottom-right-y"	BottomRightY	y-radius of the bottom right corner

If the x- and y-radii are the same, then you can use the auxiliary properties

Property	Constant	Description
"top-left"	TopLeft	top left corner radius
"top-right"	TopRight	top right corner radius
"bottom-left"	BottomLeft	bottom left corner radius
"bottom-right"	BottomRight	bottom right corner radius

To set all radii to the same values, use the "x" and "y" properties

The RadiusProperty interface is created using the NewRadiusProperty function. Example

view.Set(rui.Radius, NewRadiusProperty(rui.Params{
	rui.X: rui.Px(16),
	rui.Y: rui.Px(8),
	rui.TopLeft: rui.Px(0),
	rui.BottomRight: rui.Px(0),
}))

equivalent to

view.Set(rui.Radius, NewRadiusProperty(rui.Params{
	rui.TopRightX: rui.Px(16),
	rui.TopRightY: rui.Px(8),
	rui.BottomLeftX: rui.Px(16),
	rui.BottomLeftY: rui.Px(8),
	rui.TopLeftX: rui.Px(0),
	rui.TopLeftX: rui.Px(0),
	rui.BottomRightX: rui.Px(0),
	rui.BottomRightY: rui.Px(0),
}))

If all radii are the same, then the given SizeUnit value can be directly assigned to the "radius" property

view.Set(rui.Radius, rui.Px(4))

RadiusProperty has a textual representation of the following form:

_{ <radius id> = <SizeUnit text> [/ <SizeUnit text>] [, <radius id> = <SizeUnit text> [/ <SizeUnit text>]] … }

where can take the following values: "x", "y", "top-left", "top-left-x", "top-left-y", "top-right", "top-right-x", "top-right-y", "bottom-left", "bottom-left-x", "bottom-left-y", "bottom-right", "bottom-right-x", "bottom-right-y".

Values like " / " can only be assigned to the "top-left", "top-right", "bottom-left" and "bottom-right" properties.

Examples:

_{ x = 4px, y = 4px, top-left = 8px, bottom-right = 8px }

equivalent to

_{ top-left = 8px, top-right = 4px, bottom-left = 4px, bottom-right = 8px }

or

_{ top-left = 8px / 8px, top-right = 4px / 4px, bottom-left = 4px / 4px, bottom-right = 8px / 8px }

or

_{ top-left-x = 8px, top-left-y = 8px, top-right-x = 4px, top-right-y = 4px,
	bottom-left-x = 4px, bottom-left-y = 4px, bottom-right-x = 8px, bottom-right-y = 8px }

The RadiusProperty interface can be converted to a BoxRadius structure using the BoxRadius function. When converted, all text constants are replaced with real values. BoxRadius is described as

type BoxRadius struct {
	TopLeftX, TopLeftY, TopRightX, TopRightY, BottomLeftX, BottomLeftY, BottomRightX, BottomRightY SizeUnit
}

The BoxRadius structure can be passed as a parameter to the Set function by setting the value of the "radius" property. This converts BoxRadius to RadiusProperty. Therefore, when the property is read, the Get function will return the RadiusProperty interface, not the BoxRadius structure. You can get the BoxRadius structure without additional transformations using the global function

func GetRadius(view View, subviewID string) BoxRadius

You can also set individual radii using the Set function of the View interface. For this, the following properties are used

Property	Constant	Description
"radius-x"	RadiusX	All x-radii
"radius-y"	RadiusY	All y-radii
"radius-top-left-x"	RadiusTopLeftX	x-radius of the top left corner
"radius-top-left-y"	RadiusTopLeftY	y-radius of the top left corner
"radius-top-right-x"	RadiusTopRightX	x-radius of the top right corner
"radius-top-right-y"	RadiusTopRightY	y-radius of the top right corner
"radius-bottom-left-x"	RadiusBottomLeftX	x-radius of the bottom left corner
"radius-bottom-left-y"	RadiusBottomLeftY	y-radius of the bottom left corner
"radius-bottom-right-x"	RadiusBottomRightX	x-radius of the bottom right corner
"radius-bottom-right-y"	RadiusBottomRightY	y-radius of the bottom right corner
"radius-top-left"	RadiusTopLeft	top left corner radius
"radius-top-right"	RadiusTopRight	top right corner radius
"radius-bottom-left"	RadiusBottomLeft	bottom left corner radius
"radius-bottom-right"	RadiusBottomRight	bottom right corner radius

Example

view.Set(rui.RadiusX, rui.Px(4))
view.Set(rui.RadiusY, rui.Px(32))

equivalent to

view.Set(rui.Border, NewRadiusProperty(rui.Params{
	rui.X: rui.Px(4),
	rui.Y: rui.Px(32),
}))

"shadow" property

The "shadow" property allows you to set shadows for the View. There may be several shadows. The shadow is described using the ViewShadow interface extending the Properties interface (see above). The shadow has the following properties:

Property	Constant	Type	Description
"color"	ColorProperty	Color	Shadow color
"inset"	Inset	bool	true - the shadow inside the View, false - outside
"x-offset"	XOffset	SizeUnit	Offset the shadow along the X axis
"y-offset"	YOffset	SizeUnit	Offset the shadow along the Y axis
"blur"	BlurRadius	float	Shadow blur radius. The value must be >= 0
"spread-radius"	SpreadRadius	float	Increase the shadow. Value > 0 increases shadow, < 0 decreases shadow

Three functions are used to create a ViewShadow:

func NewViewShadow(offsetX, offsetY, blurRadius, spread-radius SizeUnit, color Color) ViewShadow
func NewInsetViewShadow(offsetX, offsetY, blurRadius, spread-radius SizeUnit, color Color) ViewShadow
func NewShadowWithParams(params Params) ViewShadow

The NewViewShadow function creates an outer shadow (Inset == false), NewInsetViewShadow - an inner one (Inset == true). The NewShadowWithParams function is used when constants must be used as parameters. For example:

shadow := NewShadowWithParams(rui.Params{
	rui.ColorProperty : "@shadowColor",
	rui.BlurRadius : 8.0,
	rui.Dilation : 16.0,
})

ViewShadow, ViewShadow array, and ViewShadow textual representation can be assigned as a value to the "shadow" property.

The ViewShadow text representation has the following format:

_{ color = <color> [, x-offset = <offset>] [, y-offset = <offset>] [, blur = <radius>]
	[, spread-radius = <increase>] [, inset = <type>] }

You can get the value of "shadow" property using the function

func GetViewShadows(view View, subviewID string) []ViewShadow

If no shadow is specified, then this function will return an empty array

"background-color" property

Constant: rui.BackgroundColor. Get function: GetBackgroundColor() Color

The "background-color" property sets the background color. Valid values are Color, an integer, the textual representation of Color, and a constant name starting with '@'. An integer must encode the color in the AARRGGBB format

In addition to color, images and gradients can also be used as backgrounds (see below). In this case, "background-color" is used for transparent areas of images.

"background-clip" property

The "background-clip" property determines how the background color and / or background image will be displayed below the box borders.

If no background image or color is specified, this property will have a visual effect only if the border has transparent areas or partially opaque areas; otherwise, the border hides the difference.

The property can take the following values:

Value	Constant	Name	Description
0	BorderBoxClip	"border-box"	The background extends to the outer edge of the border (but below the border in z-order).
1	PaddingBoxClip	"padding-box"	The background extends to the outer edge of the padding. No background is drawn below the border.
2	ContentBoxClip	"content-box"	The background is painted inside (clipped) of the content box.

"background" property

In addition to color, pictures and / or gradient fills can also be specified as the background of the View. The property "background" is used for this. The background can contain multiple images and gradients. Each background element is described by the BackgroundElement interface. BackgroundElement can be of three types: linear gradient, radial gradient, and image.

Linear gradient

A linear gradient is created using the function

func NewBackgroundLinearGradient(params Params) BackgroundElement

The linear gradient has the following options:

• Direction ("direction") - defines the direction of the gradient line (the line along which the color changes). Optional parameter. The default direction is from bottom to top. It can be either AngleUnit (the angle of inclination of the line relative to the vertical) or one of the following int values:

Value	Constant	Name	Description
0	ToTopGradient	"to-top"	Line goes from bottom to top (default)
1	ToRightTopGradient	"to-right-top"	From bottom left to top right
2	ToRightGradient	"to-right"	From left to right
3	ToRightBottomGradient	"to-right-bottom"	From top left to bottom right
4	ToBottomGradient	"to-bottom"	From top to bottom
5	ToLeftBottomGradient	"to-left-bottom"	From the upper right corner to the lower left
6	ToLeftGradient	"to-left"	From right to left
7	ToLeftTopGradient	"to-left-top"	From the bottom right corner to the top left

• Gradient ("gradient") - array of gradient key points (required parameter). Each point is described by a BackgroundGradientPoint structure, which has two fields: Pos of type SizeUnit and Color. Pos defines the position of the point relative to the start of the gradient line. The array must have at least 2 points. You can also pass a Color array as the gradient value. In this case, the points are evenly distributed along the gradient line. You can also use an array of []interface{} as an array of cue points. The elements of this array can be BackgroundGradientPoint, Color, BackgroundGradientPoint or Color text representation, and the name of the constant

• Repeat ("repeat") - a boolean value that determines whether the gradient will repeat after the last key point. Optional parameter. The default is false (do not repeat)

The linear gradient text representation is as follows:

linear-gradient { gradient = <value> [, direction = <value>] [, repeat = <value>] }

Radial gradient

A radial gradient is created using the function

func NewBackgroundRadialGradient(params Params) BackgroundElement

The radial gradient has the following parameters:

• Gradient ("gradient") - array of gradient key points (required parameter). Identical to the linear gradient parameter of the same name.

• Repeat ("repeat") - a boolean value that determines whether the gradient will repeat after the last key point. Optional parameter. The default is false (do not repeat)

• RadialGradientShape ("radial-gradient-shape") or Shape ("shape") - defines the shape of the gradient. It can take one of two int values:

Value	Constant	Name	Description
0	EllipseGradient	"ellipse"	The shape is an axis-aligned ellipse
1	CircleGradient	"circle"	The shape is a circle with a constant radius

Optional parameter. The default is EllipseGradient

• RadialGradientRadius ("radial-gradient-radius") or Radius ("radius") - sets the radius of the gradient. Can be either SizeUnit or one of the following int values:

Value	Constant	Name	Description
0	ClosestSideGradient	"closest-side"	The final shape of the gradient corresponds to the side of the rectangle closest to its center (for circles), or both vertical and horizontal sides closest to the center (for ellipses)
1	ClosestCornerGradient	"closest-corner"	The final shape of the gradient is defined so that it exactly matches the closest corner of the window from its center
2	FarthestSideGradient	"farthest-side"	Similar to ClosestSideGradient, except that the size of the shape is determined by the farthest side from its center (or vertical and horizontal sides)
3	FarthestCornerGradient	"farthest-corner"	The final shape of the gradient is defined so that it exactly matches the farthest corner of the rectangle from its center

Optional parameter. The default is ClosestSideGradient

• CenterX ("center-x"), CenterY ("center-y") - sets the center of the gradient relative to the upper left corner of the View. Takes in a SizeUnit value. Optional parameter. The default value is "50%", i.e. the center of the gradient is the center of the View.

The linear gradient text representation is as follows:

radial-gradient { gradient = <Value> [, repeat = <Value>] [, shape = <Value>]
	[, radius = <Value>][, center-x = <Value>][, center-y = <Value>]}

Image

The image has the following parameters:

• Source ("src") - Specifies the URL of the image

• Fit ("fit") - an optional parameter that determines the scaling of the image. Can be one of the following Int values:

Constant	Value	Name	Description
NoneFit	0	"none"	No scaling (default). The dimensions of the image are determined by the Width and Height parameters.
ContainFit	1	"contain"	The image is scaled proportionally so that its width or height is equal to the width or height of the background area. Image can be cropped to width or height
CoverFit	2	"cover"	The image is scaled with the same proportions so that the whole picture fits inside the background area

• Width ("width"), Height (height) - optional SizeUnit parameters that specify the height and width of the image. Used only if Fit is NoneFit. The default is Auto (original size). The percentage value sets the size relative to the height and width of the background area, respectively

• Attachment -

• Repeat (repeat) - an optional parameter specifying the repetition of the image. Can be one of the following int values:

Constant	Value	Name	Description
NoRepeat	0	"no-repeat"	Image does not repeat (default)
RepeatXY	1	"repeat"	The image repeats horizontally and vertically
RepeatX	2	"repeat-x"	The image repeats only horizontally
RepeatY	3	"repeat-y"	Image repeats vertically only
RepeatRound	4	"round"	The image is repeated so that an integer number of images fit into the background area; if this fails, then the background images are scaled
RepeatSpace	5	"space"	The image is repeated as many times as necessary to fill the background area; if this fails, an empty space is added between the pictures

• ImageHorizontalAlign,

• ImageVerticalAlign,

"clip" property

The "clip" property (Clip constant) of the ClipShape type specifies the crop area. There are 4 types of crop areas

inset

Rectangular cropping area. Created with the function:

func InsetClip(top, right, bottom, left SizeUnit, radius RadiusProperty) ClipShape

where top, right, bottom, left are the distance from respectively the top, right, bottom and left borders of the View to the cropping border of the same name; radius - sets the radii of the corners of the cropping area (see the description of the RadiusProperty type above). If there should be no rounding of corners, then nil must be passed as radius

The textual description of the rectangular cropping area is in the following format

inset{ top = <top value>, right = <right value>, bottom = <bottom value>, left = <left value>,
	[radius = <RadiusProperty text>] }
}

circle

Round cropping area. Created with the function:

func CircleClip(x, y, radius SizeUnit) ClipShape

where x, y - coordinates of the center of the circle; radius - radius

The textual description of the circular cropping area is in the following format

circle{ x = <x value>, y = <y value>, radius = <radius value> }

ellipse

Elliptical cropping area. Created with the function:

func EllipseClip(x, y, rx, ry SizeUnit) ClipShape

where x, y - coordinates of the center of the ellipse; rх - radius of the ellipse along the X axis; ry is the radius of the ellipse along the Y axis.

The textual description of the elliptical clipping region is in the following format

ellipse{ x = <x value>, y = <y value>, radius-x = <x radius value>, radius-y = <y radius value> }

polygon

Polygonal cropping area. Created using functions:

func PolygonClip(points []interface{}) ClipShape
func PolygonPointsClip(points []SizeUnit) ClipShape

an array of corner points of the polygon is passed as an argument in the following order: x1, y1, x2, y2, … The elements of the argument to the PolygonClip function can be either text constants, or the text representation of SizeUnit, or elements of type SizeUnit.

The textual description of the polygonal cropping area is in the following format

polygon{ points = "<x1 value>, <y1 value>, <x2 value>, <y2 value>,…" }

"оpacity" property

The "opacity" property (constant Opacity) of the float64 type sets the transparency of the View. Valid values are from 0 to 1. Where 1 - View is fully opaque, 0 - fully transparent.

You can get the value of this property using the function

func GetOpacity(view View, subviewID string) float64

"z-index" property

The "z-index" property (constant ZIndex) of type int defines the position of the element and its children along the z-axis. In the case of overlapping elements, this value determines the stacking order. In general, the elements higher z-indexes overlap elements with lower.

You can get the value of this property using the function

func GetZIndex(view View, subviewID string) int

"visibility" property

The "visibility" property (constant Visibility) of type int specifies the visibility of the View. Valid values

Value	Constant	Name	Visibility
0	Visible	"visible"	View is visible. Default value.
1	Invisible	"invisible"	View is invisible but takes up space.
2	Gone	"gone"	View is invisible and does not take up space.

You can get the value of this property using the function

func GetVisibility(view View, subviewID string) int

"filter" property

The "filter" property (Filter constant) applies graphical effects such as blur and color shift to the View. Only the ViewFilter interface is used as the value of the "filter" property. ViewFilter is created using the function

func NewViewFilter(params Params) ViewFilter

The argument lists the effects to apply. The following effects are possible:

Effect	Constant	Type	Description
"blur"	Blur	float64 0…10000px	Gaussian blur
"brightness"	Brightness	float64 0…10000%	Brightness change
"contrast"	Contrast	float64 0…10000%	Contrast change
"drop-shadow"	DropShadow	[]ViewShadow	Adding shadow
"grayscale"	Grayscale	float64 0…100%	Converting to grayscale
"hue-rotate"	HueRotate	AngleUnit	Hue rotation
"invert"	Invert	float64 0…100%	Invert colors
"opacity"	Opacity	float64 0…100%	Changing transparency
"saturate"	Saturate	float64 0…10000%	Saturation change
"sepia"	Sepia	float64 0…100%	Conversion to serpia

Example

rui.Set(view, "subview", rui.Filter, rui.NewFilter(rui.Params{
    rui.Brightness: 200,
    rui.Contrast: 150,
}))

You can get the value of the current filter using the function

func GetFilter(view View, subviewID string) ViewFilter

"semantics" property

The "semantics" string property (Semantics constant) defines the semantic meaning of the View. This property may have no visible effect, but it allows search engines to understand the structure of your application. It also helps to voice the interface to systems for people with disabilities:

Value	Name	Semantics
0	"default"	Unspecified. Default value.
1	"article"	A stand-alone part of the application intended for independent distribution or reuse.
2	"section"	A stand-alone section that cannot be represented by a more precise semantically element
3	"aside"	A part of a document whose content is only indirectly related to the main content (footnote, label)
4	"header"	Application Title
5	"main"	Main content (content) of the application
6	"footer"	Footer
7	"navigation"	Navigation bar
8	"figure"	Image
9	"figure-caption"	Image Title. Should be inside "figure"
10	"button"	Button
11	"p"	Paragraph
12	"h1"	Level 1 text heading. Changes the style of the text
13	"h2"	Level 2 text heading. Changes the style of the text
14	"h3"	Level 3 text heading. Changes the style of the text
15	"h4"	Level 4 text heading. Changes the style of the text
16	"h5"	Level 5 text heading. Changes the style of the text
17	"h6"	Level 6 text heading. Changes the style of the text
18	"blockquote"	Quote. Changes the style of the text
19	"code"	Program code. Changes the style of the text

Text properties

All properties listed in this section are inherited, i.e. the property will apply not only to the View for which it is set, but also to all Views nested in it.

The following properties are available to customize the text display options:

"font-name" property

Property "font-name" (constant FontName) - the text property specifies the name of the font to use. Multiple fonts can be specified. In this case, they are separated by a space. Fonts are applied in the order in which they are listed. Those, the first is applied first, if it is not available, then the second, third, etc.

You can get the value of this property using the function

func GetFontName(view View, subviewID string) string

"text-color" property

Property "text-color" (constant TextColor) - the Color property determines the color of the text.

You can get the value of this property using the function

func GetTextColor(view View, subviewID string) Color

"text-size" property

Property "text-size" (constant TextSize) - the SizeUnit property determines the size of the font.

You can get the value of this property using the function

func GetTextSize(view View, subviewID string) SizeUnit

"italic" property

The "italic" property (constant Italic) is the bool property. If the value is true, then italics are applied to the text

You can get the value of this property using the function

func IsItalic(view View, subviewID string) bool

"small-caps" property

The "small-caps" property (SmallCaps constant) is the bool property. If the value is true, then small-caps is applied to the text.

You can get the value of this property using the function

func IsSmallCaps(view View, subviewID string) bool

"white-space" property

The "white-space" (WhiteSpace constant) int property controls how whitespace is handled within the View. The "white-space" property can take the following values:

0 (constant WhiteSpaceNormal, name "normal") - sequences of spaces are concatenated into one space. Newlines in the source are treated as a single space. Applying this value optionally splits lines to fill inline boxes.

1 (constant WhiteSpaceNowrap, name "nowrap") - Concatenates sequences of spaces into one space, like a normal value, but does not wrap lines (text wrapping) within the text.

2 (constant WhiteSpacePre, name "pre") - sequences of spaces are saved as they are specified in the source. Lines are wrapped only where newlines are specified in the source and where "br" elements are specified in the source.

3 (constant WhiteSpacePreWrap, name "pre-wrap") - sequences of spaces are saved as they are indicated in the source. Lines are wrapped only where newlines are specified in the source and there, where "br" elements are specified in the source, and optionally to fill inline boxes.

4 (constant WhiteSpacePreLine, name "pre-line") - sequences of spaces are concatenated into one space. Lines are split on newlines, on "br" elements, and optionally to fill inline boxes.

5 (constant WhiteSpaceBreakSpaces, name "break-spaces") - the behavior is identical to pre-wrap with the following differences:

• Sequences of spaces are preserved as specified in the source, including spaces at the end of lines.
• Lines are wrapped on any spaces, including in the middle of a sequence of spaces.
• Spaces take up space and do not hang at the ends of lines, which means they affect the internal dimensions (min-content and max-content).

The table below shows the behavior of various values ​​of the "white-space" property.

	New lines	Spaces and Tabs	Text wrapping	End of line spaces	End-of-line other space separators
WhiteSpaceNormal	Collapse	Collapse	Wrap	Remove	Hang
WhiteSpaceNowrap	Collapse	Collapse	No wrap	Remove	Hang
WhiteSpacePre	Preserve	Preserve	No wrap	Preserve	No wrap
WhiteSpacePreWrap	Preserve	Preserve	Wrap	Hang	Hang
WhiteSpacePreLine	Preserve	Collapse	Wrap	Remove	Hang
WhiteSpaceBreakSpaces	Preserve	Preserve	Wrap	Wrap	Wrap

"word-break" property

The "word-break" int property (WordBreak constant) determines where the newline will be set if the text exceeds the block boundaries. The "white-space" property can take the following values:

0 (constant WordBreak, name "normal) - default behavior for linefeed placement.

1 (constant WordBreakAll, name "break-all) - if the block boundaries are exceeded, a line break will be inserted between any two characters (except for Chinese/Japanese/Korean text).

2 (constant WordBreakKeepAll, name "keep-all) - Line break will not be used in Chinese/Japanese/ Korean text. For text in other languages, the default behavior (normal) will be applied.

3 (constant WordBreakWord, name "break-word) - when the block boundaries are exceeded, the remaining whole words can be broken in an arbitrary place, if a more suitable place for line break is not found.

"strikethrough", "overline", "underline" properties

These bool properties set decorative lines on the text:

Property	Constant	Decorative line type
"strikethrough"	Strikethrough	Strikethrough line text
"overline"	Overline	Line above the text
"underline"	Underline	Line under the text

You can get the value of these properties using the functions

func IsStrikethrough(view View, subviewID string) bool
func IsOverline(view View, subviewID string) bool
func IsUnderline(view View, subviewID string) bool

"text-line-thickness" property

The "text-line-thickness" SizeUnit property (TextLineThickness constant) sets the thickness of decorative lines on the text set using the "strikethrough", "overline" and "underline" properties.

You can get the value of this property using the function

GetTextLineThickness(view View, subviewID string) SizeUnit

"text-line-style" property

The "text-line-style" int property (constant TextLineStyle) sets the style of decorative lines on the text set using the "strikethrough", "overline" and "underline" properties.

Possible values are:

Value	Constant	Name	Description
1	SolidLine	"solid"	Solid line (default value)
2	DashedLine	"dashed"	Dashed line
3	DottedLine	"dotted"	Dotted line
4	DoubleLine	"double"	Double solid line
5	WavyLine	"wavy"	Wavy line

You can get the value of this property using the function

func GetTextLineStyle(view View, subviewID string) int

"text-line-color" property

The "text-line-color" Color property (constant TextLineColor) sets the color of decorative lines on the text set using the "strikethrough", "overline" and "underline" properties. If the property is not defined, then the text color specified by the "text-color" property is used for lines.

You can get the value of this property using the function

func GetTextLineColor(view View, subviewID string) Color

"text-weight" property

Свойство "text-weight" (константа TextWeight) - свойство типа int устанавливает начертание шрифта. Допустимые значения:

Value	Constant	Common name of the face
1	ThinFont	Thin (Hairline)
2	ExtraLightFont	Extra Light (Ultra Light)
3	LightFont	Light
4	NormalFont	Normal. Default value
5	MediumFont	Medium
6	SemiBoldFont	Semi Bold (Demi Bold)
7	BoldFont	Bold
8	ExtraBoldFont	Extra Bold (Ultra Bold)
9	BlackFont	Black (Heavy)

Some fonts are only available in normal or bold style. In this case, the value of this property is ignored.

You can get the value of this property using the function

func GetTextWeight(view View, subviewID string) int

"text-shadow" property

The "text-shadow" property allows you to set shadows for the text. There may be several shadows. The shadow is described using the ViewShadow interface (see above, section "The 'shadow' property"). For text shadow, only the "color", "x-offset", "y-offset" and "blur" properties are used. The "inset" and "spread-radius" properties are ignored (i.e. setting them is not an error, they just have no effect on the text shadow).

To create a ViewShadow for the text shadow, the following functions are used:

func NewTextShadow(offsetX, offsetY, blurRadius SizeUnit, color Color) ViewShadow
func NewShadowWithParams(params Params) ViewShadow

The NewShadowWithParams function is used when constants must be used as parameters. For example:

shadow := NewShadowWithParams(rui.Params{
	rui.ColorProperty : "@shadowColor",
	rui.BlurRadius    : 8.0,
})

ViewShadow, ViewShadow array, ViewShadow textual representation can be assigned as a value to the "text-shadow" property (see above, section "The 'shadow' property").

You can get the value of this property using the function

func GetTextShadows(view View, subviewID string) []ViewShadow

If no shadow is specified, then this function will return an empty array

"text-align" property

The "text-align" int property (constant TextAlign) sets the alignment of the text. Valid values:

Value	Constant	Name	Value
0	LeftAlign	"left"	Left alignment
1	RightAlign	"right"	Right alignment
2	CenterAlign	"center"	Center alignment
3	JustifyAlign	"justify"	Justify alignment

You can get the value of this property using the function

func GetTextAlign(view View, subviewID string) int

"text-indent" property

The "text-indent" (TextIndent constant) SizeUnit property determines the size of the indent (empty space) before the first line of text.

You can get the value of this property using the function

func GetTextIndent(view View, subviewID string) SizeUnit

"letter-spacing" property

The "Letter-spacing" (LetterSpacing constant) SizeUnit property determines the letter spacing in the text. The value can be negative, but there can be implementation-specific restrictions. The user agent can choose not to increase or decrease the letter spacing to align the text.

You can get the value of this property using the function

func GetLetterSpacing(view View, subviewID string) SizeUnit

"word-spacing" property

The "word-spacing" (WordSpacing constant) SizeUnit property determines the length of the space between words. If the value is specified as a percentage, then it defines the extra spacing as a percentage of the preliminary character width. Otherwise, it specifies additional spacing in addition to the inner word spacing as defined by the font.

You can get the value of this property using the function

func GetWordSpacing(view View, subviewID string) SizeUnit

"line-height" property

The "line-height" (LineHeight constant) SizeUnit property sets the amount of space between lines.

You can get the value of this property using the function

func GetLineHeight(view View, subviewID string) SizeUnit

"text-transform" property

The "text-transform" (TextTransform constant) int property defines the case of characters. Valid values:

Value	Constant	Case conversion
0	NoneTextTransform	Original case of characters
1	CapitalizeTextTransform	Every word starts with a capital letter
2	LowerCaseTextTransform	All characters are lowercase
3	UpperCaseTextTransform	All characters are uppercase

You can get the value of this property using the function

func GetTextTransform(view View, subviewID string) int

"text-direction" property

The "text-direction" (TextDirection constant) int property determines the direction of text output. Valid values:

Value	Constant	Text output direction
0	SystemTextDirection	Systemic direction. Determined by the language of the operating system.
1	LeftToRightDirection	From left to right. Used for English and most other languages.
2	RightToLeftDirection	From right to left. Used for Hebrew, Arabic and some others.

You can get the value of this property using the function

func GetTextDirection(view View, subviewID string) int

"writing-mode" property

The "writing-mode" (WritingMode constant) int property defines how the lines of text are arranged vertically or horizontally, as well as the direction in which the lines are displayed. Possible values ​​are:

Value	Constant	Description
0	HorizontalTopToBottom	Horizontal lines are displayed from top to bottom. Default value
1	HorizontalBottomToTop	Horizontal lines are displayed from bottom to top.
2	VerticalRightToLeft	Vertical lines are output from right to left.
3	VerticalLeftToRight	Vertical lines are output from left to right.

You can get the value of this property using the function

func GetWritingMode(view View, subviewID string) int

"vertical-text-orientation" property

The "vertical-text-orientation" (VerticalTextOrientation constant) int property is used only if "writing-mode" is set to VerticalRightToLeft (2) or VerticalLeftToRight (3) and determines the position of the vertical line characters. Possible values are:

Value	Constant	Value
0	MixedTextOrientation	Symbols rotated 90 clockwise. Default value.
1	UprightTextOrientation	Symbols are arranged normally (vertically).

You can get the value of this property using the function

func GetVerticalTextOrientation(view View, subviewID string) int

Transformation properties

These properties are used to transform (skew, scale, etc.) the content of the View.

"perspective" property

The "perspective" SizeUnit property (Perspective constant) defines the distance between the z = 0 plane and the user in order to give the 3D positioned element a perspective effect. Each transformed element with z > 0 will become larger, with z < 0, respectively, less.

Elements of the part that are behind the user, i.e. the z-coordinate of these elements is greater than the value of the perspective property, and are not rendered.

The vanishing point is by default located in the center of the element, but it can be moved using the "perspective-origin-x" and "perspective-origin-y" properties.

You can get the value of this property using the function

func GetPerspective(view View, subviewID string) SizeUnit

"perspective-origin-x" and "perspective-origin-y" properties

The "Perspective-origin-x" and "perspective-origin-y" SizeUnit properties (PerspectiveOriginX and PerspectiveOriginY constants) determine the position from which the viewer is looking. It is used by the perspective property as a vanishing point.

By default, the "perspective-origin-x" and "perspective-origin-y" properties are set to 50%. point to the center of the View.

You can get the value of these properties using the function

func GetPerspectiveOrigin(view View, subviewID string) (SizeUnit, SizeUnit)

"backface-visibility" property

The "backface-visibility" bool property (BackfaceVisible constant) determines whether the back face of an element is visible when it is facing the user.

The back surface of an element is a mirror image of its front surface. However, invisible in 2D, the back face can be visible when the transformation causes the element to rotate in 3D space. (This property has no effect on 2D transforms that have no perspective.)

You can get the value of this property using the function

func GetBackfaceVisible(view View, subviewID string) bool

"origin-x", "origin-y", and "origin-z" properties

The "origin-x", "origin-y", and "origin-z" SizeUnit properties (OriginX, OriginY, and OriginZ constants) set the origin for element transformations.

The origin of the transformation is the point around which the transformation takes place. For example, rotation.

The "origin-z" property is ignored if the perspective property is not set.

You can get the value of these properties using the function

func GetOrigin(view View, subviewID string) (SizeUnit, SizeUnit, SizeUnit)

"translate-x", "translate-y", and "translate-z" properties

The "translate-x", "translate-y" and "translate-z" SizeUnit properties (TranslateX, TranslateY, and TranslateZ constants) set the offset of the content of the View.

The translate-z property is ignored if the perspective property is not set.

You can get the value of these properties using the function

func GetTranslate(view View, subviewID string) (SizeUnit, SizeUnit, SizeUnit)

"scale-x", "scale-y" and "scale-z" properties

The "scale-x", "scale-y" and "scale-z" float64 properties (ScaleX, ScaleY and ScaleZ constants) set the scaling factor along the x, y and z axes, respectively. The original scale is 1. A value between 0 and 1 is used to zoom out. More than 1 - to increase. Values less than or equal to 0 are invalid (the Set function will return false)

The "scale-z" property is ignored if the "perspective" property is not set.

You can get the value of these properties using the function

func GetScale(view View, subviewID string) (float64, float64, float64)

"rotate" property

The "rotate" AngleUnit property (Rotate constant) sets the angle of rotation of the content around the vector specified by the "rotate-x", "rotate-y" and "rotate-z" properties.

"rotate-x", "rotate-y", and "rotate-z" properties

The "rotate-x", "rotate-y" and "rotate-z" float64 properties (constant RotateX, RotateY and RotateZ) set the vector around which the rotation is performed by the angle specified by the "rotate" property. This vector passes through the point specified by the "origin-x", "origin-y" and "origin-z" properties.

The "rotate-z" property is ignored if the "perspective" property is not set.

You can get the value of these properties, as well as the "rotate" property, using the function

func GetRotate(view View, subviewID string) (float64, float64, float64, AngleUnit)

"skew-x" and "skew-y" properties

The "skew-x" and "skew-y" AngleUnit properties (SkewX and SkewY constants) set the skew (skew) of the content, thus turning it from a rectangle into a parallelogram. The bevel is carried out around the point specified by the transform-origin-x and transform-origin-y properties.

You can get the value of these properties using the function

func GetSkew(view View, subviewID string) (AngleUnit, AngleUnit)

Keyboard events

Two kinds of keyboard events can be generated for a View that has received input focus.

Event	Constant	Description
"key-down-event"	KeyDownEvent	The key has been pressed.
"key-up-event"	KeyUpEvent	The key has been released.

The main event data listener has the following format:

func(View, KeyEvent)

where the second argument describes the parameters of the keys pressed. The KeyEvent structure has the following fields:

Field	Type	Description
TimeStamp	uint64	The time the event was created (in milliseconds). The starting point depends on the browser implementation (EPOCH, browser launch, etc.).
Key	string	The value of the key on which the event occurred. The value is returned taking into account the current language and case.
Code	string	The key code of the represented event. The value is independent of the current language and case.
Repeat	bool	Repeated pressing: the key was pressed until its input began to be automatically repeated.
CtrlKey	bool	The Ctrl key was active when the event occurred.
ShiftKey	bool	The Shift key was active when the event occurred.
AltKey	bool	The Alt (Option or ⌥ in OS X) key was active when the event occurred.
MetaKey	bool	The Meta key (for Mac, this is the ⌘ Command key; for Windows, the Windows key ⊞) was active when the event occurred.

You can also use listeners in the following formats:

• func(KeyEvent)
• func(View)
• func()

You can get lists of listeners for keyboard events using the functions:

func GetKeyDownListeners(view View, subviewID string) []func(View, KeyEvent)
func GetKeyUpListeners(view View, subviewID string) []func(View, KeyEvent)

Focus events

Focus events are fired when a View gains or loses input focus. Accordingly, two events are possible:

Event	Constant	Description
"focus-event"	FocusEvent	View receives input focus (becomes active)
"lost-focus-event"	LostFocusEvent	View loses input focus (becomes inactive)

The main event data listener has the following format:

func(View).

You can also use a listener in the following format:

func()

You can get lists of listeners for focus events using the functions:

func GetFocusListeners(view View, subviewID string) []func(View)
func GetLostFocusListeners(view View, subviewID string) []func(View)

Mouse events

Several kinds of mouse events can be generated for the View

Event	Constant	Description
"mouse-down"	MouseDown	The mouse button was pressed.
"mouse-up"	MouseUp	The mouse button has been released.
"mouse-move"	MouseMove	Mouse cursor moved
"mouse-out"	MouseOut	The mouse cursor has moved outside the View, or entered the child View
"mouse-over"	MouseOver	The mouse cursor has moved within the arrea of View
"click-event"	ClickEvent	There was a mouse click
"double-click-event"	DoubleClickEvent	There was a double mouse click
"context-menu-event"	ContextMenuEvent	The key for calling the context menu (right mouse button) is pressed

The main event data listener has the following format:

func(View, MouseEvent)

where the second argument describes the parameters of the mouse event. The MouseEvent structure has the following fields:

Field	Type	Description
TimeStamp	uint64	The time the event was created (in milliseconds). The starting point depends on the browser implementation (EPOCH, browser launch, etc.).
Button	int	The number of the mouse button clicked on which triggered the event
Buttons	int	Bitmask showing which mouse buttons were pressed when the event occurred
X	float64	The horizontal position of the mouse relative to the origin View
Y	float64	The vertical position of the mouse relative to the origin View
ClientX	float64	Horizontal position of the mouse relative to the upper left corner of the application
ClientY	float64	The vertical position of the mouse relative to the upper left corner of the application
ScreenX	float64	Horizontal position of the mouse relative to the upper left corner of the screen
ScreenY	float64	Vertical position of the mouse relative to the upper left corner of the screen
CtrlKey	bool	The Ctrl key was active when the event occurred.
ShiftKey	bool	The Shift key was active when the event occurred.
AltKey	bool	The Alt (Option or ⌥ in OS X) key was active when the event occurred.
MetaKey	bool	The Meta key (for Mac this is the ⌘ Command key, for Windows is the Windows key ⊞) was active when the event occurred.

Button field can take the following values

Value	Constant	Description
<0		No buttons pressed
0	PrimaryMouseButton	Main button. Usually the left mouse button (can be changed in the OS settings)
1	AuxiliaryMouseButton	Auxiliary button (wheel or middle mouse button)
2	SecondaryMouseButton	Secondary button. Usually the right mouse button (can be changed in the OS settings)
3	MouseButton4	Fourth mouse button. Usually the browser's Back button
4	MouseButton5	Fifth mouse button. Usually the browser button Forward

The Button field is a bit mask combining (using OR) the following values

Value	Constant	Description
1	PrimaryMouseMask	Main button
2	SecondaryMouseMask	Secondary button
4	AuxiliaryMouseMask	Auxiliary button
8	MouseMask4	Fourth button
16	MouseMask5	Fifth button

You can also use listeners in the following formats:

• func(MouseEvent)
• func(View)
• func()

You can get lists of listeners for mouse events using the functions:

func GetMouseDownListeners(view View, subviewID string) []func(View, MouseEvent)
func GetMouseUpListeners(view View, subviewID string) []func(View, MouseEvent)
func GetMouseMoveListeners(view View, subviewID string) []func(View, MouseEvent)
func GetMouseOverListeners(view View, subviewID string) []func(View, MouseEvent)
func GetMouseOutListeners(view View, subviewID string) []func(View, MouseEvent)
func GetClickListeners(view View, subviewID string) []func(View, MouseEvent)
func GetDoubleClickListeners(view View, subviewID string) []func(View, MouseEvent)
func GetContextMenuListeners(view View, subviewID string) []func(View, MouseEvent)

Pointer Events

A pointer is a device-independent representation of input devices (such as a mouse, pen, or point of contact on a touch surface). A pointer can point to a specific coordinate (or set of coordinates) on a contact surface such as a screen.

All pointers can generate several kinds of events

Event	Constant	Description
"pointer-down"	PointerDown	The pointer was pressed.
"pointer-up"	PointerUp	The pointer was released.
"pointer-move"	PointerMove	The pointer has been moved
"pointer-cancel"	PointerCancel	Pointer events aborted.
"pointer-out"	PointerOut	The pointer went out of bounds of the View, or went into the child View
"pointer-over"	PointerOver	The pointer is within the limits of View

The main event data listener has the following format:

func(View, PointerEvent)

where the second argument describes the parameters of the pointer. PointerEvent structure extends MouseEvent structure and has the following additional fields:

Field	Type	Description
PointerID	int	The unique identifier of the pointer that raised the event.
Width	float64	The width (X-axis value) in pixels of the pointer's contact geometry.
Height	float64	The height (Y-axis value) in pixels of the pointer's contact geometry.
Pressure	float64	Normalized gauge inlet pressure ranging from 0 to 1, where 0 and 1 represent the minimum and maximum pressure that the hardware is capable of detecting, respectively.
TangentialPressure	float64	Normalized gauge inlet tangential pressure (also known as cylinder pressure or cylinder voltage) ranges from -1 to 1, where 0 is the neutral position of the control.
TiltX	float64	The planar angle (in degrees, ranging from -90 to 90) between the Y – Z plane and the plane that contains both the pointer (such as a stylus) axis and the Y axis.
TiltY	float64	The planar angle (in degrees, ranging from -90 to 90) between the X – Z plane and the plane containing both the pointer (such as a stylus) axis and the X axis.
Twist	float64	Rotation of a pointer (for example, a stylus) clockwise around its main axis in degrees with a value in the range from 0 to 359.
PointerType	string	the type of device that triggered the event: "mouse", "pen", "touch", etc.
IsPrimary	bool	a pointer is the primary pointer of this type.

You can also use listeners in the following formats:

• func(PointerEvent)
• func(View)
• func()

You can get lists of pointer event listeners using the functions:

func GetPointerDownListeners(view View, subviewID string) []func(View, PointerEvent)
func GetPointerUpListeners(view View, subviewID string) []func(View, PointerEvent)
func GetPointerMoveListeners(view View, subviewID string) []func(View, PointerEvent)
func GetPointerCancelListeners(view View, subviewID string) []func(View, PointerEvent)
func GetPointerOverListeners(view View, subviewID string) []func(View, PointerEvent)
func GetPointerOutListeners(view View, subviewID string) []func(View, PointerEvent)

Touch events

These events are used to track multipoint touches. Single touches emulate mouse events. If you do not need to track multi-point touches, then it is easier to use mouse events

Event	Constant	Description
"touch-start"	TouchStart	The surface touched.
"touch-end"	TouchEnd	Surface touch completed.
"touch-move"	TouchMove	One or more touches changed position
"touch-cancel"	TouchCancel	The touch is interrupted.

The main event data listener has the following format:

func(View, TouchEvent)

where the second argument describes the touch parameters. The TouchEvent structure has the following fields:

Field	Type	Description
TimeStamp	uint64	The time the event was created (in milliseconds). The starting point depends on the browser implementation (EPOCH, browser launch, etc.).
Touches	[]Touch	Array of Touch structures, each describing one touch
CtrlKey	bool	The Ctrl key was active when the event occurred.
ShiftKey	bool	The Shift key was active when the event occurred.
AltKey	bool	The Alt (Option or ⌥ in OS X) key was active when the event occurred.
MetaKey	bool	The Meta key (for Mac, this is the ⌘ Command key; for Windows, the Windows key ⊞) was active when the event occurred.

The Touch structure describes a single touch and has the following fields

Field	Type	Description
Identifier	int	A unique identifier assigned to each touch and does not change until it is completed.
X	float64	The horizontal position of the mouse relative to the origin View
Y	float64	The vertical position of the mouse relative to the origin View
ClientX	float64	Horizontal position of the mouse relative to the upper left corner of the application
ClientY	float64	The vertical position of the mouse relative to the upper left corner of the application
ScreenX	float64	Horizontal position of the mouse relative to the upper left corner of the screen
ScreenY	float64	Vertical position of the mouse relative to the upper left corner of the screen
RadiusX	float64	The x-radius of the ellipse, in pixels, that most closely delimits the area of ​​contact with the screen.
RadiusY	float64	The y-radius of the ellipse, in pixels, that most closely delimits the area of ​​contact with the screen.
RotationAngle	float64	The angle (in degrees) to rotate the ellipse clockwise, described by the radiusX and radiusY parameters, to best cover the contact area between the user and the surface.
Force	float64	The amount of pressure from 0.0 (no pressure) to 1.0 (maximum pressure) that the user applies to the surface.

You can also use listeners in the following formats:

• func(TouchEvent)
• func(View)
• func()

You can get lists of listeners for touch events using the functions:

func GetTouchStartListeners(view View, subviewID string) []func(View, TouchEvent)
func GetTouchEndListeners(view View, subviewID string) []func(View, TouchEvent)
func GetTouchMoveListeners(view View, subviewID string) []func(View, TouchEvent)
func GetTouchCancelListeners(view View, subviewID string) []func(View, TouchEvent)

Resize-event

The "resize-event" (ResizeEvent constant) is called when the View changes its position and/or size. The main event data listener has the following format:

func(View, Frame)

where the structure is declared as

type Frame struct {
	Left, Top, Width, Height float64
}

Frame elements contain the following data

• Left - the new horizontal offset in pixels relative to the parent View (left position);
• Top - the new vertical offset in pixels relative to the parent View (top position)
• Width - the new width of the visible part of the View in pixels;
• Height - the new height of the visible part of the View in pixels.

You can also use listeners in the following formats:

• func(Frame)
• func(View)
• func()

You can get a list of listeners for this event using the function:

func GetResizeListeners(view View, subviewID string) []func(View, Frame)

The current position and dimensions of the visible part of the View can be obtained using the View interface function:

Frame() Frame

or global function

func GetViewFrame(view View, subviewID string) Frame

Scroll event

The "scroll-event" (ScrollEvent constant) is raised when the contents of the View are scrolled. The main event data listener has the following format:

func(View, Frame)

where the Frame elements contain the following data

• Left - the new horizontal shift of the visible area (in pixels);
• Top - the new vertical offset of the visible area (in pixels);
• Width - the total width of the View in pixels;
• Height - the total height of the View in pixels.

You can also use listeners in the following formats:

• func(Frame)
• func(View)
• func()

You can get a list of listeners for this event using the function:

func GetScrollListeners(view View) []func(View, Frame)

The current position of the viewable area and the overall dimensions of the View can be obtained using the View interface function:

Scroll() Frame

or global function

func GetViewScroll(view View, subviewID string) Frame

The following global functions can be used for manual scrolling

func ScrollViewTo(view View, subviewID string, x, y float64)
func ScrollViewToStart(view View, subviewID string)
func ScrollViewToEnd(view View, subviewID string)

which scroll the view, respectively, to the given position, start and end

ViewsContainer

The ViewsContainer interface, which implements View, describes a container that contains several child interface elements (View). ViewsContainer is the base for other containers (ListLayout, GridLayout, StackLayout, etc.) and is not used on its own.

In addition to all View properties, this element has only one additional property "content"

"content" property

The "content" property (constant Сontent) defines an array of child Views. Interface Get function always returns []View for the given property.

The following 5 data types can be passed as the value of the "content" property:

• View - converted to []View containing one element;

• []View - nil-elements are prohibited, if the array contains nil, then the property will not be set, and the Set function will return false and an error message will be written to the log;

• string - if the string is a text representation of the View, then the corresponding View is created, otherwise a TextView is created, to which the given string is passed as text. Next, a []View is created containing the resulting View;

• []string - each element of the array is converted to View as described in the previous paragraph;

• []interface{} - this array must contain only View and string. Each string element is converted to a View as described above. If the array contains invalid values, the "content" property will not be set, and the Set function will return false and an error message will be written to the log.

You can learn the value of the "content" property using the ViewsContainer interface function

Views() []View

The following functions of the ViewsContainer interface can be used to edit the "content" property:

Append(view View)

This function adds an argument to the end of the View list.

Insert(view View, index uint)

This function inserts an argument at the specified position in the View list. If index is greater than the length of the list, then the View is added to the end of the list. If index is less than 0, then to the beginning of the list.

RemoveView(index uint) View

This function removes the View from the given position and returns it. If index points outside the bounds of the list, then nothing is removed, and the function returns nil.

ListLayout

ListLayout is a container that implements the ViewsContainer interface. To create it, use the function

func NewListLayout(session Session, params Params) ListLayout

Items in this container are arranged as a list. The position of the children can be controlled. For this, ListLayout has a number of properties

"orientation" property

The "orientation" int property (Orientation constant) specifies how the children will be positioned relative to each other. The property can take the following values:

Value	Constant	Location
0	TopDownOrientation	Child elements are arranged in a column from top to bottom.
1	StartToEndOrientation	Child elements are laid out in a row from beginning to end.
2	BottomUpOrientation	Child elements are arranged in a column from bottom to top.
3	EndToStartOrientation	Child elements are laid out in a line from end to beginning.

The start and end positions for StartToEndOrientation and EndToStartOrientation depend on the value of the "text-direction" property. For languages ​​written from right to left (Arabic, Hebrew), the beginning is on the right, for other languages ​​- on the left.

"wrap" property

The "wrap" int property (Wrap constant) defines the position of elements in case of reaching the border of the container. There are three options:

• WrapOff (0) - the column / row of elements continues and goes beyond the bounds of the visible area.

• WrapOn (1) - starts a new column / row of items. The new column is positioned towards the end (for the position of the beginning and end, see above), the new line is at the bottom.

• WrapReverse (2) - starts a new column / row of elements. The new column is positioned towards the beginning (for the position of the beginning and end, see above), the new line is at the top.

"vertical-align" property

The "vertical-align" property (VerticalAlign constant) of type int sets the vertical alignment of items in the container. Valid values:

Value	Constant	Name	Alignment
0	TopAlign	"top"	Top alignment
1	BottomAlign	"bottom"	Bottom alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Height alignment

"horizontal-align" property

The "horizontal-align" int property (HorizontalAlign constant) sets the horizontal alignment of items in the list. Valid values:

Value	Constant	Name	Alignment
0	LeftAlign	"left"	Left alignment
1	RightAlign	"right"	Right alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Width alignment

GridLayout

GridLayout is a container that implements the ViewsContainer interface. To create it, use the function

func NewGridLayout(session Session, params Params) GridLayout

The container space of this container is split into cells in the form of a table. All children are located in the cells of the table. A cell is addressed by row and column number. Row and column numbers start at 0.

"column" and "row" properties

The location of the View inside the GridLayout is determined using the "column" and "row" properties. These properties must be set for each of the child Views. Child View can span multiple cells within the GridLayout and they can overlap.

The values "column" and "row" can be set by:

• an integer greater than or equal to 0;

• textual representation of an integer greater than or equal to 0 or a constant;

• a Range structure specifying a range of rows / columns:

  type Range struct { First, Last int }

where First is the number of the first column / row, Last is the number of the last column / row;

• a line of the form "< number of the first column / row >: < number of the last column / row >", which is a textual representation of the Range structure

Example

grid := rui.NewGridLayout(session, rui.Params {
	rui.Content : []View{
		NewView(session, rui.Params {
			rui.ID     : "view1",
			rui.Row    : 0,
			rui.Column : rui.Range{ First: 1, Last: 2 },
		}),
		NewView(session, rui.Params {
			rui.ID     : "view2",
			rui.Row    : "0:2",
			rui.Column : "0",
		}),
	},
})

In this example, view1 occupies columns 1 and 2 in row 0, and view1 occupies rows 0, 1, and 2 in column 0.

"cell-width" and "cell-height" properties

By default, the sizes of the cells are calculated based on the sizes of the child Views placed in them. The "cell-width" and "cell-height" properties (CellWidth and CellHeight constants) allow you to set a fixed width and height of cells regardless of the size of the child elements. These properties are of type []SizeUnit. Each element in the array determines the size of the corresponding column or row.

These properties can be assigned the following data types:

• SizeUnit or textual representation of SizeUnit (or SizeUnit constant). In this case, the corresponding dimensions of all cells are set to the same;

• [] SizeUnit;

• string containing textual representations of SizeUnit (or SizeUnit constants) separated by commas;

• [] string. Each element must be a textual representation of a SizeUnit (or a SizeUnit constant)

• [] interface {}. Each element must either be of type SizeUnit or be a textual representation of SizeUnit (or a SizeUnit constant)

If the number of elements in the "cell-width" and "cell-height" properties is less than the number of columns and rows used, then the missing elements are set to Auto.

The values of the "cell-width" and "cell-height" properties can use the SizeUnit type SizeInFraction. This type means 1 part. The part is calculated as follows: the size of all cells that are not of type SizeInFraction is subtracted from the size of the container, and then the remaining size is divided by the number of parts. The SizeUnit value of type SizeInFraction can be either integer or fractional.

"grid-row-gap" and "grid-column-gap" properties

The "grid-row-gap" and "grid-column-gap" SizeUnit properties (GridRowGap and GridColumnGap constants) allow you to set the distance between the rows and columns of the container, respectively. The default is 0px.

"cell-vertical-align" property

The "cell-vertical-align" property (constant CellVerticalAlign) of type int sets the vertical alignment of children within the cell they are occupying. Valid values:

Value	Constant	Name	Alignment
0	TopAlign	"top"	Top alignment
1	BottomAlign	"bottom"	Bottom alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Full height stretch

The default value is StretchAlign (3)

"cell-horizontal-align" property

The "cell-horizontal-align" property (constant CellHorizontalAlign) of type int sets the horizontal alignment of children within the occupied cell. Valid values:

Value	Constant	Name	Alignment
0	LeftAlign	"left"	Left alignment
1	RightAlign	"right"	Right alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Full width stretch

The default value is StretchAlign (3)

ColumnLayout

ColumnLayout is a container that implements the ViewsContainer interface. All child Views are arranged in a vertical list aligned to the left or right and split into several columns. The alignment depends on the "text-direction" property.

To create the ColumnLayout, use the function

func NewColumnLayout(session Session, params Params) ColumnLayout

"column-count" property

The "column-count" int property (ColumnCount constant) sets the number of columns.

If this property is 0 and the "column-width" property is not set, then no column splitting is performed and the container is scrolled down.

If the value of this property is greater than 0, then the list is split into columns. The column height is equal to the ColumnLayout height, and the width is calculated as the ColumnLayout width divided by "column-count". Each next column is located depending on the "text-direction" property to the right or left of the previous one, and the container is scrolled horizontally.

You can get the value of this property using the function

func GetColumnCount(view View, subviewID string) int

"column-width" property

The "column-width" SizeUnit property (ColumnWidth constant) sets the column width. This property is used only if "column-count" is 0, otherwise it is ignored.

IMPORTANT! Percentages cannot be used as the "column-width" value (i.e. if you specify a value in percent, the system will ignore it)

You can get the value of this property using the function

func GetColumnWidth(view View, subviewID string) SizeUnit

"column-gap" property

The "column-gap" SizeUnit property (ColumnGap constant) sets the width of the gap between columns.

You can get the value of this property using the function

func GetColumnGap(view View, subviewID string) SizeUnit

"column-separator" property

The "column-separator" property (ColumnSeparator constant) allows you to set a line that will be drawn at column breaks. The separator line is described by three attributes: line style, thickness, and color.

The value of the "column-separator" property is stored as the ColumnSeparatorProperty interface, which implements the Properties interface (see above). ColumnSeparatorProperty can contain the following properties:

Property	Constant	Type	Description
"style"	Style	int	Line style
"width"	Width	SizeUnit	Line thickness
"color"	ColorProperty	Color	Line color

Line style can take the following values:

Value	Constant	Name	Description
0	NoneLine	"none"	No frame
1	SolidLine	"solid"	Solid line
2	DashedLine	"dashed"	Dashed line
3	DottedLine	"dotted"	Dotted line
4	DoubleLine	"double"	Double solid line

All other style values are ignored.

To create the ColumnSeparatorProperty interface, use the function

func NewColumnSeparator(params Params) ColumnSeparatorProperty

The ColumnSeparatorProperty interface can be converted to a ViewBorder structure using the ViewBorder function. When converted, all text constants are replaced with real values. ViewBorder is described as

type ViewBorder struct {
	Style int
	Color Color
	Width SizeUnit
}

The ViewBorder structure can be passed as a parameter to the Set function when setting the value of the "column-separator" property. This converts the ViewBorder to ColumnSeparatorProperty. Therefore, when reading the property, the Get function will return the ColumnSeparatorProperty interface, not the ViewBorder structure.

You can get the ViewBorders structure without additional transformations using the global function

func GetColumnSeparator(view View, subviewID string) ViewBorder

You can also set individual line attributes using the Set function of the View interface. For this, the following properties are used

Property	Constant	Type	Description
"column-separator-style"	ColumnSeparatorStyle	int	Line style
"column-separator-width"	ColumnSeparatorWidth	SizeUnit	Line thickness
"column-separator-color"	ColumnSeparatorColor	Color	Line color

For example

view.Set(rui.ColumnSeparatorStyle, rui.SolidBorder)
view.Set(rui.ColumnSeparatorWidth, rui.Px(1))
view.Set(rui.ColumnSeparatorColor, rui.Black)

equivalent to

view.Set(rui.ColumnSeparator, ColumnSeparatorProperty(rui.Params{
	rui.Style: rui.SolidBorder,
	rui.Width: rui.Px(1),
	rui.ColorProperty: rui.Black,
}))

"avoid-break" property

When forming columns, ColumnLayout can break some types of View, so that the beginning will be at the end of one column and the end in the next. For example, the TextView, the title of the picture and the picture itself are broken, etc.

The "avoid-break" bool property (AvoidBreak constant) avoids this effect. You must set this property to "true" for a non-breakable View. Accordingly, the value "false" of this property allows the View to be broken. The default is "false".

You can get the value of this property using the function

func GetAvoidBreak(view View, subviewID string) bool

StackLayout

StackLayout is a container that implements the ViewsContainer interface. All child Views are stacked on top of each other and each takes up the entire container space. Only one child View (current) is available at a time.

To create a StackLayout, use the function

func NewStackLayout(session Session, params Params) StackLayout

In addition to the Append, Insert, RemoveView properties and the "content" property of the ViewsContainer, the StackLayout container has two other interface functions for manipulating child Views: Push and Pop.

Push(view View, animation int, onPushFinished func())

This function adds a new View to the container and makes it current. It is similar to Append, but the addition is done using an animation effect. The animation type is specified by the second argument and can take the following values:

Value	Constant	Animation
0	DefaultAnimation	Default animation. For the Push function it is EndToStartAnimation, for Pop - StartToEndAnimation
1	StartToEndAnimation	Animation from beginning to end. The beginning and the end are determined by the direction of the text output
2	EndToStartAnimation	End-to-Beginning animation.
3	TopDownAnimation	Top-down animation.
4	BottomUpAnimation	Bottom up animation.

The third argument onPushFinished is the function to be called when the animation ends. It may be nil.

Pop(animation int, onPopFinished func(View)) bool

This function removes the current View from the container using animation. The second argument onPopFinished is the function to be called when the animation ends. It may be nil. The function will return false if the StackLayout is empty and true if the current item has been removed.

You can get the current (visible) View using the interface function

Peek() View

In order to make any child View current (visible), the interface functions are used:

MoveToFront(view View) bool
MoveToFrontByID(viewID string) bool

This function will return true if successful and false if the child View or View with id does not exist and an error message will be written to the log.

AbsoluteLayout

AbsoluteLayout is a container that implements the ViewsContainer interface. Child Views can be positioned at arbitrary positions in the container space.

To create an AbsoluteLayout, use the function

func NewAbsoluteLayout(session Session, params Params) AbsoluteLayout

The child View is positioned using the properties of the SizeUnit type: "left", "right", "top" and "bottom" (respectively, the constants Left, Right, Top and Bottom). You can set any of these properties on the child View. If neither "left" or "right" is specified, then the child View will be pinned to the left edge of the container. If neither top nor bottom is specified, then the child View will be pinned to the top edge of the container.

DetailsView

DetailsView is a container that implements the ViewsContainer interface. To create a DetailsView, the function is used

func NewDetailsView(session Session, params Params) DetailsView

In addition to child Views, this container has a "summary" property (Summary constant). The value of the "summary" property can be either View or a string of text.

The DetailsView can be in one of two states:

• only the content of the "summary" property is displayed. Child Views are hidden and do not take up screen space

• the content of the "summary" property is displayed first, and below the child Views. The layout of the child Views is the same as ColumnLayout with "column-count" equal to 0.

DetailsView switches between states by clicking on "summary" view.

For forced switching of the DetailsView states, the bool property "expanded" (Expanded constant) is used. Accordingly, the value "true" shows child Views, "false" - hides.

You can get the value of the "expanded" property using the function

func IsDetailsExpanded(view View, subviewID string) bool

and the value of the "summary" property can be obtained using the function

func GetDetailsSummary(view View, subviewID string) View

Resizable

Resizable is a container in which only one View can be placed. Resizable allows you to interactively resize the content View. To create a Resizable view, the function is used

func NewResizable(session Session, params Params) Resizable

A frame is created around the content View, and you can drag it to resize.

Resizable does not implement the ViewsContainer interface. Only the Content property is used to control the content View. This property can be assigned a value of type View or a string of text. In the second case, a TextView is created.

The frame around the content View can be either from all sides, or only from separate ones. To set the sides of the frame, use the "side" int property (Side constant). It can take the following values:

Value	Constant	Name	Frame side
1	TopSide	"top"	Top
2	RightSide	"right"	Right
4	BottomSide	"bottom"	Bottom
8	LeftSide	"left"	Left
15	AllSides	"all"	All sides. Default value

In addition to these values, an or-combination of TopSide, RightSide, BottomSide and LeftSide can also be used. AllSides is defined as

AllSides = TopSide | RightSide | BottomSide | LeftSide

To set the border width, use the SizeUnit property "resize-border-width" (ResizeBorderWidth constant). The default value of "resize-border-width" is 4px.

TextView

The TextView element, which extends the View interface, is intended for displaying text.

To create a TextView, the function is used:

func NewTextView(session Session, params Params) TextView

The displayed text is set by the string property "text" (Text constant). In addition to the Get method, the value of the "text" property can be obtained using the function

func GetText (view View, subviewID string) string

TextView inherits from View all properties of text parameters ("font-name", "text-size", "text-color", etc.). In addition to them, the "text-overflow" int property (TextOverflow constant) is added. It determines how the text is cut if it goes out of bounds. This property of type int can take the following values

Value	Constant	Name	Cropping Text
0	TextOverflowClip	"clip"	Text is clipped at the border (default)
1	TextOverflowEllipsis	"ellipsis"	At the end of the visible part of the text '…' is displayed

EditView

The EditView element is a test editor and extends the View interface.

To create an EditView, the function is used:

func NewEditView(session Session, params Params) EditView

Several options for editable text are possible. The type of the edited text is set using the int property "edit-view-type" (EditViewType constant). This property can take the following values:

Value	Constant	Name	Editor type
0	SingleLineText	"text"	One-line text editor. Default value
1	PasswordText	"password"	Password editor. The text is hidden by asterisks
2	EmailText	"email"	Single e-mail editor
3	EmailsText	"emails"	Multiple e-mail editor
4	URLText	"url"	Internet address input editor
5	PhoneText	"phone"	Phone number editor
6	MultiLineText	"multiline"	Multi-Line Text Editor

To simplify the text of the program, you can use the "type" properties (Type constant) instead of the "edit-view-type". These property names are synonymous. But when describing the style, "type" cannot be used.

To set/get edited text, use the string property "text" (Text constant)

The maximum length of editable text is set using the "max-length" int property (MaxLength constant).

You can limit the input text using a regular expression. To do this, use the string property "edit-view-pattern" (EditViewPattern constant). Instead of "edit-view-pattern", you can use the synonym "pattern" (Pattern constant), except for the style description.

To prohibit text editing, use the bool property "readonly" (ReadOnly constant).

To enable / disable the built-in spell checker, use the bool "spellcheck" property (Spellcheck constant). Spell checking can only be enabled if the editor type is set to SingleLineText or MultiLineText.

For the editor, you can set a hint that will be shown while the editor is empty. To do this, use the string property "hint" (Hint constant).

For a multi-line editor, auto-wrap mode can be enabled. The bool property "wrap" (constant Wrap) is used for this. If "wrap" is off (default), then horizontal scrolling is used. If enabled, the text wraps to a new line when the EditView border is reached.

The following functions can be used to get the values ​​of the properties of an EditView:

func GetText(view View, subviewID string) string
func GetHint(view View, subviewID string) string
func GetMaxLength(view View, subviewID string) int
func GetEditViewType(view View, subviewID string) int
func GetEditViewPattern(view View, subviewID string) string
func IsReadOnly(view View, subviewID string) bool
func IsEditViewWrap(view View, subviewID string) bool
func IsSpellcheck(view View, subviewID string) bool

The "edit-text-changed" event (EditTextChangedEvent constant) is used to track changes to the text. The main event listener has the following format:

func(EditView, string)

where the second argument is the new text value

You can get the current list of text change listeners using the function

func GetTextChangedListeners(view View, subviewID string) []func(EditView, string)

NumberPicker

The NumberPicker element extends the View interface to enter numbers.

To create a NumberPicker, the function is used:

func NewNumberPicker(session Session, params Params) NumberPicker

NumberPicker can work in two modes: text editor and slider. The mode sets the int property "date-picker-type" (NumberPickerType constant). The "date-picker-type" property can take the following values:

Value	Constant	Name	Editor type
0	NumberEditor	"editor"	Text editor. Default value
1	NumberSlider	"slider"	Slider

You can set/get the current value using the "date-picker-value" property (NumberPickerValue constant). The following can be passed as a value to the "date-picker-value" property:

• float64
• float32
• int
• int8 … int64
• uint
• uint8 … uint64
• textual representation of any of the above types

All of these types are cast to float64. Accordingly, the Get function always returns a float64 value. The value of the "date-picker-value" property can also be read using the function:

func GetNumberPickerValue(view View, subviewID string) float64

The entered values ​​may be subject to restrictions. For this, the following properties are used:

Property	Constant	Restriction
"date-picker-min"	NumberPickerMin	Minimum value
"date-picker-max"	NumberPickerMax	Maximum value
"date-picker-step"	NumberPickerStep	Value change step

Assignments to these properties can be the same value types as "date-picker-value".

By default, if "date-picker-type" is equal to NumberSlider, the minimum value is 0, maximum is 1. If "date-picker-type" is equal to NumberEditor, then the entered numbers, by default, are limited only by the range of float64 values.

You can read the values ​​of these properties using the functions:

func GetNumberPickerMinMax(view View, subviewID string) (float64, float64)
func GetNumberPickerStep(view View, subviewID string) float64

The "date-changed" event (NumberChangedEvent constant) is used to track the change in the entered value. The main event listener has the following format:

func(picker NumberPicker, newValue float64)

where the second argument is the new value

You can get the current list of value change listeners using the function

func GetNumberChangedListeners(view View, subviewID string) []func(NumberPicker, float64)

DatePicker

The DatePicker element extends the View interface to enter dates.

To create DatePicker function is used:

func NewDatePicker(session Session, params Params) DatePicker

You can set/get the current value using the "date-picker-value" property (the DatePickerValue constant). The following can be passed as a value to the "date-picker-value" property:

• time.Time

• constant

• text that can be converted to time.Time by function

  func time.Parse(layout string, value string) (time.Time, error)

The text is converted to time.Time. Accordingly, the Get function always returns a time.Time value. The value of the "date-picker-value" property can also be read using the function:

func GetDatePickerValue(view View, subviewID string) time.Time

The dates you enter may be subject to restrictions. For this, the following properties are used:

Property	Constant	Data type	Restriction
"date-picker-min"	DatePickerMin	time.Time	Minimum date value
"date-picker-max"	DatePickerMax	time.Time	Maximum date value
"date-picker-step"	DatePickerStep	int	Date change step in days

You can read the values of these properties using the functions:

func GetDatePickerMin(view View, subviewID string) (time.Time, bool)
func GetDatePickerMax(view View, subviewID string) (time.Time, bool)
func GetDatePickerStep(view View, subviewID string) int

The "date-changed" event (DateChangedEvent constant) is used to track the change in the entered value. The main event listener has the following format:

func(picker DatePicker, newDate time.Time)

where the second argument is the new date value

You can get the current list of date change listeners using the function

func GetDateChangedListeners(view View, subviewID string) []func(DatePicker, time.Time)

TimePicker

The TimePicker element extends the View interface and is intended for entering time.

To create a TimePicker, the function is used:

func NewTimePicker(session Session, params Params) TimePicker

You can set/get the current value using the "time-picker-value" property (TimePickerValue constant). The following can be passed as a value to the "time-picker-value" property:

• time.Time

• constant

• text that can be converted to time.Time by function

  func time.Parse(layout string, value string) (time.Time, error)

The text is converted to time.Time. Accordingly, the Get function always returns a time.Time value. The value of the "time-picker-value" property can also be read using the function:

func GetTimePickerValue(view View, subviewID string) time.Time

The time entered may be subject to restrictions. For this, the following properties are used:

Property	Constant	Data type	Restriction
"time-picker-min"	TimePickerMin	time.Time	Minimum time value
"time-picker-max"	TimePickerMax	time.Time	The maximum value of time
"time-picker-step"	TimePickerStep	int	Time step in seconds

You can read the values of these properties using the functions:

func GetTimePickerMin(view View, subviewID string) (time.Time, bool)
func GetTimePickerMax(view View, subviewID string) (time.Time, bool)
func GetTimePickerStep(view View, subviewID string) int

The "time-changed" event (TimeChangedEvent constant) is used to track the change in the entered value. The main event listener has the following format:

func(picker TimePicker, newTime time.Time)

where the second argument is the new time value

You can get the current list of date change listeners using the function

func GetTimeChangedListeners(view View, subviewID string) []func(TimePicker, time.Time)

ColorPicker

The ColorPicker element extends the View interface and is designed to select a color in RGB format without an alpha channel.

To create a ColorPicker, the function is used:

func NewColorPicker(session Session, params Params) ColorPicker

You can set/get the current color value using the "color-picker-value" property (ColorPickerValue constant). The following can be passed as a value to the "color-picker-value" property:

• Color
• text representation of Color
• constant

The value of the property "color-picker-value" can also be read using the function:

func GetColorPickerValue(view View, subviewID string) Color

The "color-changed" event (ColorChangedEvent constant) is used to track the change in the selected color. The main event listener has the following format:

func(picker ColorPicker, newColor Color)

where the second argument is the new color value

You can get the current list of date change listeners using the function

func GetColorChangedListeners(view View, subviewID string) []func(ColorPicker, Color)

DropDownList

The DropDownList element extends the View interface and is designed to select a value from a drop-down list.

To create a DropDownList, use the function:

func NewDropDownList(session Session, params Params) DropDownList

The list of possible values is set using the "items" property (Items constant). The following data types can be passed as a value to the "items" property

• []string
• []fmt.Stringer
• []interface{} containing as elements only: string, fmt.Stringer, bool, rune, float32, float64, int, int8 … int64, uint, uint8 … uint64.

All of these data types are converted to []string and assigned to the "items" property. You can read the value of the "items" property using the function

func GetDropDownItems(view View, subviewID string) []string

The selected value is determined by the int property "current" (Current constant). The default is 0. You can read the value of this property using the function

func GetDropDownCurrent(view View, subviewID string) int

To track the change of the "current" property, the "drop-down-event" event (DropDownEvent constant) is used. The main event listener has the following format:

func(list DropDownList, newCurrent int)

where the second argument is the index of the selected item

You can get the current list of date change listeners using the function

func GetDropDownListeners(view View, subviewID string) []func(DropDownList, int)

ProgressBar

The DropDownList element extends the View interface and is designed to display progress as a fillable bar.

To create a ProgressBar, the function is used:

func NewProgressBar(session Session, params Params) ProgressBar

ProgressBar has two float64 properties:

• "progress-max" (ProgressBarMax constant) - maximum value (default 1);
• "progress-value" (ProgressBarValue constant) - current value (default 0).

The minimum is always 0. In addition to float64, float32, int, int8 … int64, uint, uint8 … uint64

You can read the value of these properties using the functions

func GetProgressBarMax(view View, subviewID string) float64
func GetProgressBarValue(view View, subviewID string) float64

Button

The Button element implements a clickable button. This is a CustomView (about it below) based on ListLayout and, accordingly, has all the properties of ListLayout. But unlike ListLayout, it can receive input focus.

Content is centered by default.

To create a Button, use the function:

func NewButton(session Session, params Params) Button

ListView

The ListView element implements a list. The ListView is created using the function:

func NewListView(session Session, params Params) ListView

The "items" property

List items are set using the "items" property (Items constant). The main value of the "items" property is the ListAdapter interface:

type ListAdapter interface {
	ListSize() int
	ListItem(index int, session Session) View
	IsListItemEnabled(index int) bool
}

Accordingly, the functions of this interface must return the number of elements, the View of the i-th element and the status of the i-th element (allowed/denied).

You can implement this interface yourself or use helper functions:

func NewTextListAdapter(items []string, params Params) ListAdapter
func NewViewListAdapter(items []View) ListAdapter

NewTextListAdapter creates an adapter from an array of strings, the second argument is the parameters of the TextView used to display the text. NewViewListAdapter creates an adapter from the View array.

The "items" property can be assigned the following data types:

• ListAdapter;
• [] View, when assigned, is converted to a ListAdapter using the NewViewListAdapter function;
• [] string, when assigned, is converted to a ListAdapter using the NewTextListAdapter function;
• [] interface {} which can contain elements of type View, string, fmt.Stringer, bool, rune, float32, float64, int, int8 ... int64, uint, uint8 ... uint64. When assigning, all types except View and string are converted to string, then all string in TextView and from the resulting View array using the NewViewListAdapter function, a ListAdapter is obtained.

If the list items change during operation, then after the change, either the ReloadListViewData() function of the ListView interface or the global ReloadListViewData(view View, subviewID string) function must be called. These functions update the displayed list items.

"Orientation" property

List items can be arranged both vertically (in columns) and horizontally (in rows). The "orientation" property (Orientation constant) of int type specifies how the list items will be positioned relative to each other. The property can take the following values:

Value	Constant	Location
0	TopDownOrientation	Items are arranged in a column from top to bottom.
1	StartToEndOrientation	Elements are laid out on a line from beginning to end.
2	BottomUpOrientation	Items are arranged in a column from bottom to top.
3	EndToStartOrientation	Elements are arranged in a row from end to beginning.

The start and end positions for StartToEndOrientation and EndToStartOrientation depend on the value of the "text-direction" property. For languages ​​written from right to left (Arabic, Hebrew), the beginning is on the right, for other languages ​​- on the left.

You can get the value of this property using the function

func GetListOrientation(view View, subviewID string) int

"wrap" property

The "wrap" int property (Wrap constant) defines the position of elements in case of reaching the border of the container. There are three options:

• WrapOff (0) - the column/row of elements continues and goes beyond the bounds of the visible area.

• WrapOn (1) - starts a new column/row of items. The new column is positioned towards the end (for the position of the beginning and end, see above), the new line is at the bottom.

• WrapReverse (2) - starts a new column/row of elements. The new column is positioned towards the beginning (for the position of the beginning and end, see above), the new line is at the top.

You can get the value of this property using the function

func GetListWrap(view View, subviewID string) int

"item-width" and "item-height" properties

By default, the height and width of list items are calculated based on their content. This leads to the fact that the elements of the vertical list can have different heights, and the elements of the horizontal - different widths.

You can set a fixed height and width of the list item. To do this, use the SizeUnit properties "item-width" and "item-height"

You can get the values of these properties using the functions

func GetListItemWidth(view View, subviewID string) SizeUnit
func GetListItemHeight(view View, subviewID string) SizeUnit

"item-vertical-align" property

The "item-vertical-align" int property (ItemVerticalAlign constant) sets the vertical alignment of the contents of the list items. Valid values:

Value	Constant	Name	Alignment
0	TopAlign	"top"	Top alignment
1	BottomAlign	"bottom"	Bottom alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Height alignment

You can get the value of this property using the function

func GetListItemVerticalAlign(view View, subviewID string) int

"item-horizontal-align" property

The "item-horizontal-align" int property (ItemHorizontalAlign constant) sets the horizontal alignment of the contents of the list items. Valid values:

Value	Constant	Name	Alignment
0	LeftAlign	"left"	Left alignment
1	RightAlign	"right"	Right alignment
2	CenterAlign	"center"	Center alignment
3	StretchAlign	"stretch"	Height alignment

You can get the value of this property using the function

GetListItemHorizontalAlign(view View, subviewID string) int

"current" property

ListView allows you to select list items with the "allowed" status (see ListAdapter). The item can be selected both interactively and programmatically. To do this, use the int property "current" (constant Current). The value "current" is less than 0 means that no item is selected

You can get the value of this property using the function

func GetListViewCurrent(view View, subviewID string) int

"list-item-style", "current-style", and "current-inactive-style" properties

These three properties are responsible for the background style and text properties of each list item.

Property	Constant	Style
"list-item-style"	ListItemStyle	Unselected element style
"current-style"	CurrentStyle	The style of the selected item. ListView in focus
"current-inactive-style"	CurrentInactiveStyle	The style of the selected item. ListView is out of focus

"checkbox", "checked", "checkbox-horizontal-align", and "checkbox-vertical-align" properties

The "current" property allows you to select one item in the list. The "checkbox" properties allow you to add a checkbox to each item in the list with which you can select several items in the list. The "checkbox" int property (ItemCheckbox constant) can take the following values

Value	Constant	Name	Checkbox view
0	NoneCheckbox	"none"	There is no checkbox. Default value
1	SingleCheckbox	"single"	◉ A checkbox that allows you to mark only one item
2	MultipleCheckbox	"multiple"	☑ A checkbox that allows you to mark several items

You can get the value of this property using the function

func GetListViewCheckbox(view View, subviewID string) int

You can get/set the list of checked items using the "checked" property (Checked constant). This property is of type []int and stores the indexes of the marked elements. You can get the value of this property using the function

func GetListViewCheckedItems(view View, subviewID string) []int

You can check if a specific element is marked using the function

func IsListViewCheckedItem(view View, subviewID string, index int) bool

By default, the checkbox is located in the upper left corner of the element. You can change its position using int properties "checkbox-horizontal-align" and "checkbox-vertical-align" (CheckboxHorizontalAlign and CheckboxVerticalAlign constants)

The "checkbox-horizontal-align" int property can take the following values:

Value	Constant	Name	Checkbox location
0	LeftAlign	"left"	At the left edge. Content on the right
1	RightAlign	"right"	At the right edge. Content on the left
2	CenterAlign	"center"	Center horizontally. Content below or above

The "checkbox-vertical-align" int property can take the following values:

Value	Constant	Name	Checkbox location
0	TopAlign	"top"	Top alignment
1	BottomAlign	"bottom"	Bottom alignment
2	CenterAlign	"center"	Center alignment

Special case where both "checkbox-horizontal-align" and "checkbox-vertical-align" are CenterAlign (2). In this case, the checkbox is centered horizontally, the content is below

You can get property values for "checkbox-horizontal-align" and "checkbox-vertical-align" using the functions

func GetListViewCheckboxHorizontalAlign(view View, subviewID string) int
func GetListViewCheckboxVerticalAlign(view View, subviewID string) int

ListView events

There are three specific events for ListView

• "list-item-clicked" (ListItemClickedEvent constant) event occurs when the user clicks on a list item. The main listener for this event has the following format: func(ListView, int). Where the second argument is the index of the element.

• "list-item-selected" (ListItemSelectedEvent constant) event occurs when the user selects a list item. The main listener for this event has the following format: func(ListView, int). Where the second argument is the index of the element.

• "list-item-checked" (ListItemCheckedEvent constant) event occurs when the user checks/unchecks the checkbox of a list item. The main listener for this event has the following format: func(ListView, []int). Where the second argument is an array of indexes of the tagged items.

You can get lists of listeners for these events using the functions:

func GetListItemClickedListeners(view View, subviewID string) []func(ListView, int)
func GetListItemSelectedListeners(view View, subviewID string) []func(ListView, int)
func GetListItemCheckedListeners(view View, subviewID string) []func(ListView, []int)

TableView

The TableView element implements a table. To create a TableView, the function is used:

func NewTableView(session Session, params Params) TableView

"content" property

The "content" property defines the content of the table. To describe the content, you need to implement the TableAdapter interface declared as

type TableAdapter interface {
	RowCount() int
	ColumnCount() int
	Cell(row, column int) interface{}
}

where RowCount() and ColumnCount() functions must return the number of rows and columns in the table; Cell(row, column int) returns the contents of a table cell. The Cell() function can return elements of the following types:

• string
• rune
• float32, float64
• integer values: int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64
• bool
• rui.Color
• rui.View
• fmt.Stringer

The "content" property can also be assigned the following data types

• TableAdapter
• [][]interface{}
• [][]string

[][]interface{} and [][]string are converted to a TableAdapter when assigned.

"cell-style" property

The "cell-style" property (CellStyle constant) is used to customize the appearance of a table cell. Only an implementation of the TableCellStyle interface can be assigned to this property.

type TableCellStyle interface {
	CellStyle(row, column int) Params
}

This interface contains only one CellStyle function that returns the styling parameters for a given table cell. Any properties of the View interface can be used. For example

func (style *myTableCellStyle) CellStyle(row, column int) rui.Params {
	if row == 0 {
		return rui.Params {
			rui.BackgroundColor: rui.Gray,
			rui.Italic:          true,
		}
	}
	return nil
}

If you don't need to change the appearance of a cell, you can return nil for it.

"row-span" and "column-span" properties

In addition to the properties of the View interface, the CellStyle function can return two more properties of type int: "row-span" (RowSpan constant) and "column-span" (ColumnSpan constant). These properties are used to combine table cells.

The "row-span" property specifies how many cells to merge vertically, and the "column-span" property - horizontally. For example

func (style *myTableCellStyle) CellStyle(row, column int) rui.Params {
	if row == 0 && column == 0 {
		return rui.Params { rui.RowSpan: 2 }
	}
	if row == 0 && column == 1 {
		return rui.Params { rui.ColumnSpan: 2 }
	}
	return nil
}

In this case, the table will look like this

|------|----------------| | | | | |-------|--------|

If [][]interface{} is used as the value of the "content" property, then empty structures are used to merge cells

type VerticalTableJoin struct {
}

type HorizontalTableJoin struct {
}

These structures attach the cell to the top/left, respectively. The description of the above table will be as follows

content := [][]interface{} {
	{"", "", rui.HorizontalTableJoin{}},
	{rui.VerticalTableJoin{}, "", ""},
}

"row-style" property

The "row-style" property (RowStyle constant) is used to customize the appearance of a table row. This property can be assigned either an implementation of the TableRowStyle interface or []Params. TableRowStyle is declared as

type TableRowStyle interface {
	RowStyle(row int) Params
}

The RowStyle function returns parameters that apply to the entire row of the table. The "row-style" property has a lower priority than the "cell-style" property, i.e. properties set in "cell-style" will be used instead of those set in "row-style"

"column-style" property

The "column-style" property (ColumnStyle constant) is used to customize the appearance of a table column. This property can be assigned either an implementation of the TableColumnStyle interface or []Params. TableColumnStyle is declared as

type TableColumnStyle interface {
	ColumnStyle(column int) Params
}

The ColumnStyle function returns the parameters applied to the entire column of the table. The "column-style" property has a lower precedence over the "cell-style" and "row-style" properties.

"head-height" and "head-style" properties

The table can have a header. The "head-height" int property (constant HeadHeight) indicates how many first rows of the table form the header. The "head-style" property (constant HeadStyle) sets the style of the heading. The "head-style" property can be assigned, value of type:

• string - style name;
• []Params - enumeration of header properties.

"foot-height" and "foot-style" properties

The table can have finalizing lines at the end (footer). For example, the "total" line. The "foot-height" int property (the FootHeight constant) indicates the number of these footer lines. The "foot-style" property (constant FootStyle) sets footer style. The values for the "foot-style" property are the same as for the "head-style" property.

"cell-padding" property

The "cell-padding" BoundsProperty property (CellPadding constant) sets the padding from the cell borders to the content. This property is equivalent to

func (style *myTableCellStyle) CellStyle(row, column int) rui.Params {
	return rui.Params { rui.Padding: <my padding> }
}

And it was introduced for convenience, so that you do not have to write an adapter to set indents. The cell-padding property has a lower priority than the "cell-style" property.

"cell-padding" can also be used when setting parameters in the "row-style", "column-style", "foot-style", and "head-style" properties

"cell-border" property

The "cell-border" property (CellBorder constant) sets the memory for all table cells. This property is equivalent to

func (style *myTableCellStyle) CellStyle(row, column int) rui.Params {
	return rui.Params { rui.Border: <my padding> }
}

And it was introduced for convenience, so that it is not necessary to write an adapter for the frame. The "cell-border" property has a lower precedence over the "cell-style" property.

"cell-border" can also be used when setting parameters in properties "row-style", "column-style", "foot-style" and "head-style"

"table-vertical-align" property

The "table-vertical-align" int property (TableVerticalAlign constant) specifies the vertical alignment of data within a table cell. Valid values:

Value	Constant	Name	Alignment
0	TopAlign	"top"	Top alignment
1	BottomAlign	"bottom"	Bottom alignment
2	CenterAlign	"center"	Center alignment
3, 4	BaselineAlign	"baseline"	Baseline alignment

For horizontal alignment, use the "text-align" property

Custom View

A custom View must implement the CustomView interface, which extends the ViewsContainer and View interfaces. A custom View is created based on another, which is named Super View.

To simplify the task, there is already a basic CustomView implementation in the form of a CustomViewData structure.

Let's consider creating a custom View using the built-in Buttom element as an example:

1. declare the Button interface as extending CustomView, and the buttonData structure as extending CustomViewData

   type Button interface { rui.CustomView }

   type buttonData struct { rui.CustomViewData }

2. implement the CreateSuperView function

   func (button *buttonData) CreateSuperView(session Session) View { return rui.NewListLayout(session, rui.Params{ rui.Semantics: rui.ButtonSemantics, rui.Style: "ruiButton", rui.StyleDisabled: "ruiDisabledButton", rui.HorizontalAlign: rui.CenterAlign, rui.VerticalAlign: rui.CenterAlign, rui.Orientation: rui.StartToEndOrientation, }) }

3. if necessary, override the methods of the CustomView interface, for Button this is the Focusable() function (since the button can receive focus, but ListLayout does not)

   func (button *buttonData) Focusable() bool { return true }

4. write a function to create a Button:

   func NewButton(session rui.Session, params rui.Params) Button { button := new(buttonData) rui.InitCustomView(button, "Button", session, params) return button }

When creating a CustomView, it is mandatory to call the InitCustomView function. This function initializes the CustomViewData structure. The first argument is a pointer to the structure to be initialized, the second is the name assigned to your View, the third is the session and the fourth is the parameters

5. registering the item. It is recommended to register in the init method of the package

   rui.RegisterViewCreator("Button", func(session rui.Session) rui.View { return NewButton(session, nil) })

All! The new element is ready

CanvasView

CanvasView is an area in which you can draw. To create a CanvasView, the function is used:

func NewCanvasView(session Session, params Params) CanvasView

CanvasView has only one additional property: "draw-function" (DrawFunction constant). Using this property, a drawing function is set with the following description

func(Canvas)

where Canvas is the drawing context with which to draw

The Canvas interface contains a number of functions for customizing styles, text and drawing itself.

All coordinates and sizes are set only in pixels, so SizeUnit is not used when drawing. float64 used everywhere

Setting the line style

The following functions of the Canvas interface are used to customize the line color:

• SetSolidColorStrokeStyle(color Color) - the line will be drawn with a solid color

• SetLinearGradientStrokeStyle(x0, y0 float64, color0 Color, x1, y1 float64, color1 Color, stopPoints []GradientPoint) - the line will be drawn using a linear gradient. The gradient starts at x0, y0, and color0, and the gradient ends at x1, y1, and color1. The []GradientPoint array specifies the intermediate points of the gradient. If there are no intermediate points, then nil can be passed as the last parameter

• SetRadialGradientStrokeStyle(x0, y0, r0 float64, color0 Color, x1, y1, r1 float64, color1 Color, stopPoints []GradientPoint) - the line will be drawn using a radial gradient. x0, y0, r0, color0 - center coordinates, radius and color of the starting circle. x1, y1, r1, color1 - center coordinates, radius and color of the end circle. The []GradientPoint array specifies intermediate points of the gradient

The GradientPoint structure is described as

type GradientPoint struct {
	Offset float64
	Color Color
}

where Offset is a value in the range from 0 to 1 specifies the relative position of the intermediate point, Color is the color of this point.

Line width in pixels is set by the function

SetLineWidth(width float64)

The type of line ends is set using the function

SetLineCap(cap int)

where cap can take the following values

Value	Constant	View
0	ButtCap	The ends of lines are squared off at the endpoints. Default value.
1	RoundCap	The ends of lines are rounded. The center of the circle is at the end point.
2	SquareCap	the ends of lines are squared off by adding a box with an equal width and half the height of the line's thickness.

The shape used to connect two line segments at their intersection is specified by the function

SetLineJoin(join int)

where join can take the following values

Value	Constant	View
0	MiterJoin	Connected segments are joined by extending their outside edges to connect at a single point, with the effect of filling an additional lozenge-shaped area. This setting is affected by the miterLimit property
1	RoundJoin	rounds off the corners of a shape by filling an additional sector of disc centered at the common endpoint of connected segments. The radius for these rounded corners is equal to the line width.
2	BevelJoin	Fills an additional triangular area between the common endpoint of connected segments, and the separate outside rectangular corners of each segment.

By default, a solid line is drawn. If you want to draw a broken line, you must first set the pattern using the function

SetLineDash(dash []float64, offset float64)

where dash []float64 specifies the line pattern in the form of alternating line lengths and gaps. The second argument is the offset of the template relative to the beginning of the line.

Example

canvas.SetLineDash([]float64{16, 8, 4, 8}, 0)

The line is drawn as follows: a 16-pixel segment, then an 8-pixel gap, then a 4-pixel segment, then an 8-pixel gap, then a 16-pixel segment again, and so on.

Setting the fill style

The following functions of the Canvas interface are used to customize the fill style:

• SetSolidColorFillStyle(color Color) - the shape will be filled with a solid color

• SetLinearGradientFillStyle(x0, y0 float64, color0 Color, x1, y1 float64, color1 Color, stopPoints []GradientPoint) - the shape will be filled with a linear gradient. The gradient starts at x0, y0, and color0, and the gradient ends at x1, y1, and color1. The []GradientPoint array specifies the intermediate points of the gradient. If there are no intermediate points, then nil can be passed as the last parameter

• SetRadialGradientFillStyle(x0, y0, r0 float64, color0 Color, x1, y1, r1 float64, color1 Color, stopPoints []GradientPoint) - the shape will be filled with a radial gradient. x0, y0, r0, color0 - center coordinates, radius and color of the starting circle. x1, y1, r1, color1 - center coordinates, radius and color of the end circle. Array []GradientPoint specifies intermediate points of the gradient

Drawing geometric shapes

Rectangle

Three functions can be used to draw rectangles:

FillRect(x, y, width, height float64)
StrokeRect(x, y, width, height float64)
FillAndStrokeRect(x, y, width, height float64)

FillRect draws a filled rectangle.

StrokeRect draws the outline of a rectangle.

FillAndStrokeRect draws a path and fills in the interior.

Rounded Rectangle

Similar to the rectangle, there are three drawing functions

FillRoundedRect(x, y, width, height, r float64)
StrokeRoundedRect(x, y, width, height, r float64)
FillAndStrokeRoundedRect(x, y, width, height, r float64)

where r is the radius of the rounding

Ellipse

Three functions can also be used to draw ellipses:

FillEllipse(x, y, radiusX, radiusY, rotation float64)
StrokeEllipse(x, y, radiusX, radiusY, rotation float64)
FillAndStrokeEllipse(x, y, radiusX, radiusY, rotation float64)

where x, y is the center of the ellipse, radiusX, radiusY are the radii of the ellipse along the X and Y axes, rotation - the angle of rotation of the ellipse relative to the center in radians.

Path

The Path interface allows you to describe a complex shape. Path is created using the NewPath () function.

Once created, you must describe the shape. For this, the following interface functions can be used:

• MoveTo(x, y float64) - move the current point to the specified coordinates;

• LineTo(x, y float64) - add a line from the current point to the specified one;

• ArcTo(x0, y0, x1, y1, radius float64) - add a circular arc using the specified control points and radius. If necessary, the arc is automatically connected to the last point of the path with a straight line. x0, y0 - coordinates of the first control point; x1, y1 - coordinates of the second control point; radius - radius of the arc. Must be non-negative.

• Arc(x, y, radius, startAngle, endAngle float64, clockwise bool) - add a circular arc. x, y - coordinates of the arc center; radius - radius of the arc. Must be non-negative; startAngle - The angle, in radians, at which the arc begins, measured clockwise from the positive X-axis. endAngle - The angle, in radians, at which the arc ends, measured clockwise from the positive X-axis. clockwise - if true, the arc will be drawn clockwise between the start and end corners, otherwise counterclockwise

• BezierCurveTo(cp0x, cp0y, cp1x, cp1y, x, y float64) - add a cubic Bezier curve from the current point. cp0x, cp0y - coordinates of the first control point; cp1x, cp1y - coordinates of the second control point; x, y - coordinates of the end point.

• QuadraticCurveTo(cpx, cpy, x, y float64) - add a quadratic Bezier curve from the current point. cpx, cpy - coordinates of the control point; x, y - coordinates of the end point.

• Ellipse(x, y, radiusX, radiusY, rotation, startAngle, endAngle float64, clockwise bool) - add an elliptical arc. x, y - coordinates of the center of the ellipse; radiusX is the radius of the major axis of the ellipse. Must be non-negative; radiusY - radius of the minor axis of the ellipse. Must be non-negative; rotation - the rotation of the ellipse, expressed in radians; startAngle The angle of the start of the ellipse in radians, measured clockwise from the positive x-axis. endAngle The angle, in radians, at which the ellipse ends, measured clockwise from the positive x-axis. clockwise - if true, draws the ellipse clockwise, otherwise counterclockwise.

The Close () function is called at the end and connects the start and end points of the shape. Used only for closed shapes.

After the Path is formed, it can be drawn using the following 3 functions

FillPath(path Path)
StrokePath(path Path)
FillAndStrokePath(path Path)

Line

To draw a line, use the function

DrawLine(x0, y0, x1, y1 float64)

Text

To display text in specified coordinates, two functions are used

FillText(x, y float64, text string)
StrokeText(x, y float64, text string)

The StrokeText function draws the outline of the text, FillText draws the text itself.

The horizontal alignment of the text relative to the specified coordinates is set using the function

SetTextAlign(align int)

where align can be one of the following values:

Value	Constant	Alignment
0	LeftAlign	The specified point is the leftmost point of the text
1	RightAlign	The specified point is the rightmost point of the text
2	CenterAlign	The text is centered on the specified point
3	StartAlign	If the text is displayed from left to right, then the text output is equivalent to LeftAlign, otherwise RightAlign
4	EndAlign	If the text is displayed from left to right, then the text output is equivalent to RightAlign, otherwise LeftAlign

The vertical alignment of the text relative to the specified coordinates is set using the function

SetTextBaseline(baseline int)

where baseline can be one of the following values:

Value	Constant	Alignment
0	AlphabeticBaseline	Relatively normal baseline of text
1	TopBaseline	Relative to the top border of the text
2	MiddleBaseline	About the middle of the text
3	BottomBaseline	To the bottom of the text
4	HangingBaseline	Relative to the dangling baseline of the text (used in Tibetan and other Indian scripts)
5	IdeographicBaseline	Relative to the ideographic baseline of the text

An ideographic baseline is the bottom of a character display if the main character is outside the alphabet baseline (Used in Chinese, Japanese, and Korean fonts).

To set the font parameters of the displayed text, use the functions

SetFont(name string, size SizeUnit)
SetFontWithParams(name string, size SizeUnit, params FontParams)

where FontParams is defined as

type FontParams struct {
	// Italic - if true then a font is italic
	Italic bool
	// SmallCaps - if true then a font uses small-caps glyphs
	SmallCaps bool
	// Weight - a font weight. Valid values: 0…9, there
	//   0 - a weight does not specify;
	//   1 - a minimal weight;
	//   4 - a normal weight;
	//   7 - a bold weight;
	//   9 - a maximal weight.
	Weight int
	// LineHeight - the height (relative to the font size of the element itself) of a line box.
	LineHeight SizeUnit
}

The TextWidth function allows you to find out the width of the displayed text in pixels

TextWidth(text string, fontName string, fontSize SizeUnit) float64

Image

Before drawing an image, it must first be loaded. The global function is used for this:

func LoadImage(url string, onLoaded func(Image), session Session) Image {

The image is loaded asynchronously. After the download is finished, the function passed in the second argument will be called. If the image was loaded successfully, then the LoadingStatus() function of the Image interface will return the value ImageReady (1), if an error occurred while loading, then this function will return ImageLoadingError (2). The textual description of the error is returned by the LoadingError() function

Unlike an ImageView, loading an Image does not take into account the pixel density. It is up to you to decide which image to upload. You can do it like this:

var url string
if session.PixelRatio() == 2 {
	url = "image@2x.png"
} else {
	url = "image.png"
}

The following functions are used to draw the image:

DrawImage(x, y float64, image Image)
DrawImageInRect(x, y, width, height float64, image Image)
DrawImageFragment(srcX, srcY, srcWidth, srcHeight, dstX, dstY, dstWidth, dstHeight float64, image Image)

The DrawImage function displays the image as it is (without scaling): x, y - coordinates of the upper left corner of the image

The DrawImageInRect function displays the image with scaling: x, y are coordinates of the upper left corner of the image, width, height are width and height of the result

The DrawImageFragment function displays a fragment of the image with scaling: srcX, srcY, srcWidth, srcHeight describe the original area of the image, dstX, dstY, dstWidth, dstHeight describe the resulting area.

Image can also be used in fill style

SetImageFillStyle(image Image, repeat int)

where repeat can take on the following values:

Value	Constant	Description
0	NoRepeat	Image is not repeated
1	RepeatXY	Image is repeated vertically and horizontally
2	RepeatX	The image is repeated horizontally only
3	RepeatY	The image is repeated vertically only

AudioPlayer, VideoPlayer, MediaPlayer

AudioPlayer and VideoPlayer are elements for audio and video playback. Both elements implement the MediaPlayer interface. Most of the properties and all events of AudioPlayer and VideoPlayer are implemented through the MediaPlayer.

Свойство "src"

The "src" property (Source constant) specifies one or more media sources. The "src" property can take on the following types:

• string,
• MediaSource,
• []MediaSource.

The MediaSource structure is declared as

type MediaSource struct {
	Url      string
	MimeType string
}

where Url is a required parameter, MimeType is an optional mime file type

Since different browsers support different file formats and codecs, it is recommended to specify multiple sources in different formats. The player chooses the most suitable one from the list of sources. Setting mime types makes this process easier for the browser

"controls" property

The "controls" bool property (Controls constant) specifies whether UI elements should be displayed to control playback of the media resource. The default is false.

If the "controls" property is false for the AudioPlayer, then it will be invisible and will not take up screen space.

"loop" property

The "loop" bool property (Loop constant). If it set to true, then the media file will start over when it reaches the end. The default is false.

"muted" property

The "muted" bool property (constant Muted) enables (true) / disables (false) silent mode. The default is false.

"preload" property

The "preload" int property (constant Preload) defines what data should be preloaded. Valid values:

Value	Constant	Name	Description
0	PreloadNone	"none"	Media file must not be pre-loaded
1	PreloadMetadata	"metadata"	Only metadata is preloaded
2	PreloadAuto	"auto"	The entire media file can be downloaded even if the user doesn't have to use it.

The default value is PreloadAuto (2)

"poster" property

The "poster" string property (Poster constant) is used only for VideoPlayer. It sets the url of the image that will be shown until the video is loaded. If this property is not set, then a black screen will be shown first, and then the first frame (as soon as it is loaded).

"video-width" and "video-height" properties

The "video-width" (VideoWidth constant) and "video-height" (VideoHeight constant) float64 properties are used only for VideoPlayer. It defines the width and height of the rendered video in pixels.

If "video-width" and "video-height" are not specified, then the actual dimensions of the video are used, while the dimensions of the container in which the video is placed are ignored and the video may overlap other interface elements. Therefore, it is recommended to set these values, for example, like this

rui.Set(view, "videoPlayerContainer", rui.ResizeEvent, func(frame rui.Frame) {
	rui.Set(view, "videoPlayer", rui.VideoWidth, frame.Width)
	rui.Set(view, "videoPlayer", rui.VideoHeight, frame.Height)
})

If only one of the "video-width" or "video-height" properties is set, then the second is calculated based on the aspect ratio of the video

Developments

MediaPlayer has two groups of events:

1. has a handler like

   func(MediaPlayer)

You can also use func(). This group includes the following events:

• "abort-event" (constant AbortEvent) - Fires when the resource is not fully loaded, but not as a result of an error.

• "can-play-event" (CanPlayEvent constant) is fired when the user agent is able to play media but judges that there is not enough data loaded to play the media to the end without having to stop to further buffer the content.

• "can-play-through-event" (constant CanPlayThroughEvent) is fired when the user agent is able to play the media and evaluates that enough data has been loaded to play the media to its end, without having to stop to further buffer the content.

• "complete-event" (CompleteEvent constant) -

• "emptied-event" (EmptiedEvent constant) is fired when the media becomes empty; for example when the media is already loaded (or partially loaded)

• "ended-event" (EndedEvent constant) - Fires when playback stops, when the end of media is reached, or if no further data is available.

• "loaded-data-event" (LoadedDataEvent constant) is fired when the first frame of the media has finished loading.

• "loaded-metadata-event" (LoadedMetadataEvent constant) is fired when the metadata has been loaded.

• "loadstart-event" (LoadstartEvent constant) is fired when the browser starts loading the resource.

• "pause-event" (PauseEvent constant) is fired when a pause request is processed and the action pauses, most often when the Pause () method is called.

• "play-event" (PlayEvent constant) is fired when the media file starts playing, for example, as a result of using the Play () method

• "playing-event" (PlayingEvent constant) is fired when playback is about to start after being paused or delayed due to lack of data.

• "progress-event" (ProgressEvent constant) is fired periodically when the browser loads the resource.

• "seeked-event" (SeekedEvent constant) is fired when the playback speed has changed.

• "seeking-event" (SeekingEvent constant) is fired when a seeking operation begins.

• "stalled-event" (StalledEvent constant) is fired when the user agent tries to retrieve media data, but no data arrives unexpectedly.

• "suspend-event" (SuspendEvent constant) is fired when media loading has been suspended.

• "waiting-event" (WaitingEvent constant) is fired when playback is stopped due to a temporary lack of data

2. has a handler like

   func(MediaPlayer, float64)

You can also use func(float64), func(MediaPlayer) and func(). This group includes events related to changing the parameters of the player. The new value of the changed parameter is passed as the second argument.

• "duration-changed-event" (DurationChangedEvent constant) is fired when the duration attribute has been updated.

• "time-updated-event" (TimeUpdatedEvent constant) is fired when the current time has been updated.

• "volume-changed-event" (VolumeChangedEvent constant) is fired when the volume changes.

• "rate-changed-event" (RateChangedEvent constant) is fired when the playback speed has changed.

A separate event that does not belong to these two groups, "player-error-event" (PlayerErrorEvent constant) is fired when the resource cannot be loaded due to an error (eg network error).

The handler for this event looks like

func(player MediaPlayer, code int, message string) 

You can also use func(int, string), func(MediaPlayer) and func(). Where the argument "message" is the error message, "code" is the error code:

Error code	Constant	Value
0	PlayerErrorUnknown	Unknown error
1	PlayerErrorAborted	Fetching the associated resource was interrupted by a user request.
2	PlayerErrorNetwork	Some kind of network error has occurred that prevented the media from successfully ejecting, even though it was previously available.
3	PlayerErrorDecode	Although the resource was previously identified as being used, an error occurred while trying to decode the media resource.
4	PlayerErrorSourceNotSupported	The associated resource object or media provider was found to be invalid.

Methods

MediaPlayer has a number of methods for controlling player parameters:

• Play() starts playback of a media file;

• Pause() pauses playback;

• SetCurrentTime(seconds float64) sets the current playback time in seconds;

• CurrentTime() float64 returns the current playing time in seconds;

• Duration() float64 returns the duration of the media file in seconds;

• SetPlaybackRate(rate float64) sets the playback speed. Normal speed is 1.0;

• PlaybackRate() float64 returns the current playback speed;

• SetVolume(volume float64) sets the volume speed in the range from 0 (silence) to 1 (maximum volume);

• Volume() float64 returns the current volume;

• IsEnded() bool returns true if the end of the media file is reached;

• IsPaused() bool returns true if playback is paused.

For quick access to these methods, there are global functions:

func MediaPlayerPlay(view View, playerID string)
func MediaPlayerPause(view View, playerID string)
func SetMediaPlayerCurrentTime(view View, playerID string, seconds float64)
func MediaPlayerCurrentTime(view View, playerID string) float64
func MediaPlayerDuration(view View, playerID string) float64
func SetMediaPlayerVolume(view View, playerID string, volume float64)
func MediaPlayerVolume(view View, playerID string) float64
func SetMediaPlayerPlaybackRate(view View, playerID string, rate float64)
func MediaPlayerPlaybackRate(view View, playerID string) float64
func IsMediaPlayerEnded(view View, playerID string) bool
func IsMediaPlayerPaused(view View, playerID string) bool

where view is the root View, playerID is the id of AudioPlayer or VideoPlayer

Session

When a client creates a connection to a server, a Session interface is created for that connection. This interface is used to interact with the client. You can get the current Session interface by calling the Session() method of the View interface.

When a session is created, it gets a custom implementation of the SessionContent interface.

type SessionContent interface {
	CreateRootView(session rui.Session) rui.View
}

This interface is created by the function passed as a parameter when creating an application by the NewApplication function.

In addition to the mandatory CreateRootView() function, SessionContent can have several optional functions:

OnStart(session rui.Session)
OnFinish(session rui.Session)
OnResume(session rui.Session)
OnPause(session rui.Session)
OnDisconnect(session rui.Session)
OnReconnect(session rui.Session)

Immediately after creating a session, the CreateRootView function is called. After creating the root View, the OnStart function is called (if implemented)

The OnFinish function (if implemented) is called when the user closes the application page in the browser

The OnPause function is called when the application page in the client's browser becomes inactive. This happens if the user switches to a different browser tab / window, minimizes the browser, or switches to another application.

The OnResume function is called when the application page in the client's browser becomes active. Also, this function is called immediately after OnStart

The OnDisconnect function is called if the server loses connection with the client. This happens either when the connection is broken.

The OnReconnect function is called after the server reconnects with the client.

The Session interface provides the following methods:

• DarkTheme() bool returns true if a dark theme is used. Determined by client-side settings

• TouchScreen() bool returns true if client supports touch screen

• PixelRatio() float64 returns the size of a logical pixel, i.e. how many physical pixels form a logical. For example, for iPhone, this value will be 2 or 3

• TextDirection() int returns the direction of the letter: LeftToRightDirection (1) or RightToLeftDirection (2)

• Constant(tag string) (string, bool) returns the value of a constant

• Color(tag string) (Color, bool) returns the value of the color constant

• SetCustomTheme(name string) bool sets the theme with the given name as the current one. Returns false if no topic with this name was found. Themes named "" are the default theme.

• Language() string returns the current interface language, for example: "en", "ru", "ptBr"

• SetLanguage(lang string) sets the current interface language (see "Support for multiple languages")

• GetString(tag string) (string, bool) returns a textual text value for the current language (see "Support for multiple languages")

• Content() SessionContent returns the current SessionContent instance

• RootView() View returns the root View of the session

• Get(viewID, tag string) interface{} returns the value of the View property named tag. Equivalent to

  rui.Get(session.RootView(), viewID, tag)

• Set(viewID, tag string, value interface {}) bool sets the value of the View property named tag.

  rui.Set(session.RootView(), viewID, tag, value)

Resource description format

Application resources (themes, views, translations) can be described as text (utf-8). This text is placed in a file with the ".rui" extension.

The root element of the resource file must be an object. It has the following format:

< object name > {
	< object data >
}

if the object name contains the following characters: '=', '{', '}', '[', ']', ',', '', '\t', '\n', '' ',' "','` ',' / 'and any spaces, then the object name must be enclosed in quotation marks. If these characters are not used, then quotation marks are optional.

You can use three types of quotation marks:

• "…" is equivalent to the same string in the go language, i.e. inside you can use escape sequences: \n, \r, \, ", ', \0, \t, \x00, \u0000

• '…' is similar to the line "…"

• … is equivalent to the same string in the go language, i.e. the text within this line remains as is. Inside you cannot use the ` character.

Object data is a set of < key > = < value > pairs separated by commas.

The key is a string of text. The design rules are the same as for the object name.

Values can be of 3 types:

• Simple value - a line of text formatted according to the same rules as the name of the object

• An object

• Array of values

An array of values is enclosed in square brackets. Array elements are separated by commas. Elements can be simple values or objects.

There may be comments in the text. The design rules are the same as in the go language: // and / * ... * /

Example:

GridLayout {
	id = gridLayout, width = 100%, height = 100%,
	cell-width = "150px, 1fr, 30%", cell-height = "25%, 200px, 1fr",
	content = [
		// Subviews
		TextView { row = 0, column = 0:1,
			text = "View 1", text-align = center, vertical-align = center,
			background-color = #DDFF0000, radius = 8px, padding = 32px,
			border = _{ style = solid, width = 1px, color = #FFA0A0A0 }
		},
		TextView { row = 0:1, column = 2,
			text = "View 2", text-align = center, vertical-align = center,
			background-color = #DD00FF00, radius = 8px, padding = 32px,
			border = _{ style = solid, width = 1px, color = #FFA0A0A0 }
		},
		TextView { row = 1:2, column = 0,
			text = "View 3", text-align = center, vertical-align = center,
			background-color = #DD0000FF, radius = 8px, padding = 32px,
			border = _{ style = solid, width = 1px, color = #FFA0A0A0 }
		},
		TextView { row = 1, column = 1,
			text = "View 4", text-align = center, vertical-align = center,
			background-color = #DDFF00FF, radius = 8px, padding = 32px,
			border = _{ style = solid, width = 1px, color = #FFA0A0A0 }
		},
		TextView { row = 2, column = 1:2,
			text = "View 5", text-align = center, vertical-align = center,
			background-color = #DD00FFFF, radius = 8px, padding = 32px,
			border = _{ style = solid, width = 1px, color = #FFA0A0A0 }
		},
	]
}

To work with text resources, the DataNode interface is used

type DataNode interface {
	Tag() string
	Type() int
	Text() string
	Object() DataObject
	ArraySize() int
	ArrayElement(index int) DataValue
	ArrayElements() []DataValue
}

This element describes the underlying data element.

The Tag method returns the value of the key.

The data type is returned by the Type method. It returns one of 3 values

Value	Constant	Data type
0	TextNode	Simple value
1	ObjectNode	Object
2	ArrayNode	Array

The Text() method is used to get a simple value. To get an object, use the Object() method. To get the elements of an array, use the ArraySize, ArrayElement and ArrayElements methods

Resources

Resources (pictures, themes, translations, etc.) with which the application works should be placed in subdirectories within one resource directory. Resources should be located in the following subdirectories:

• images - all images are placed in this subdirectory. Here you can make nested subdirectories. In this case, they must be included in the file name. For example, "subdir/image1.png"

• themes - application themes are placed in this subdirectory (see below)

• views - View descriptions are placed in this subdirectory

• strings - translations of text resources are placed in this subdirectory (see Support for multiple languages)

• raw - all other resources are placed in this subdirectory: sounds, video, binary data, etc.

The resource directory can either be included in the executable file or located separately.

If the resources need to be included in the executable file, then the name of the directory must be "resources" and it must be connected as follows:

import (
	"embed"

	"github.com/anoshenko/rui"
)

//go:embed resources
var resources embed.FS

func main() {
	rui.AddEmbedResources(&resources)
	
	app := rui.NewApplication("Hello world", createHelloWorldSession)
	app.Start("localhost:8000")
}

If the resources are supplied as a separate directory, then it must be registered using the SetResourcePath function before creating the Application:

func main() {
	rui.SetResourcePath(path)
	
	app := rui.NewApplication("Hello world", createHelloWorldSession)
	app.Start("localhost:8000")
}

Images for screens with different pixel densities

If you need to add separate images to the resources for screens with different pixel densities, then this is done in the style of iOS, i.e. '@< density >x' is appended to the filename. For example

image@2x.png
image@3x.jpg
image@1.5x.gif

For example, you have images for three densities: image.png, image@2x.png, and image@3x.png. In this case, you only assign the value "image.png" to the "src" field of the ImageView. The library itself will find the rest in the "images" directory and transfer the image to the client with the required density

Themes

The topic includes three types of data:

• constants
• color constants
• View styles

Themes are designed as a rui file and placed in the themes folder.

The root of the theme is an object named 'theme'. This object can contain the following properties:

• name - an optional text property that specifies the name of the theme. If this property is not set or is equal to an empty string, then this is the default theme.

• constants - property object defining constants. The name of the object can be anything. It is recommended to use "_". An object can have any number of text properties specifying the "constant name" = "value" pair. This section contains constants of type SizeUnit, AngleUnit, text and numeric. In order to assign a constant to any View property, you need to assign the name of the constant to the property by adding the '@' symbol at the beginning. For example

  theme { constants = _{ defaultPadding = 4px, buttonPadding = @defaultPadding, angle = 30deg, } }

  rui.Set(view, "subView", rui.Padding, "@defaultPadding")

• constants:touch is property object defining constants used only for touch screen. For example, how to make indents larger on a touch screen:

  theme { constants = _{ defaultPadding = 4px, }, constants:touch = _{ defaultPadding = 12px, }, }

• colors is an object property that defines color constants for a light skin (default theme). An object can have any number of text properties specifying the "color name" = "color" pair. Similar to constants, when assigning, you must add '@' at the beginning of the color name. For example

  theme { colors = _{ textColor = #FF101010, borderColor = @textColor, backgroundColor = white, } }

  rui.Set(view, "subView", rui.TextColor, "@textColor")

Color names such as "black", "white", "red", etc. are used without the '@' character. However, you can specify color constants with the same names. For example

theme {
	colors = _{
		red = blue,
	}
}

rui.Set(view, "subView", rui.TextColor, "@red") // blue text
rui.Set(view, "subView", rui.TextColor, "red")  // red text

• colors:dark is an object property that defines color constants for a dark theme

• styles is an array of common styles. Each element of the array must be an object. The object name is and is the name of the style. For example,

  theme { styles = [ demoPage { width = 100%, height = 100%, cell-width = "1fr, auto", }, demoPanel { width = 100%, height = 100%, orientation = start-to-end, }, ] }

To use styles, the View has two text properties "style" (Style constant) and "style-disabled" (StyleDisabled constant). The "style" property is assigned the property name that is applied to the View when the "disabled" property is set to false. The "style-disabled" property is assigned the property name that is applied to the View when the "disabled" property is set to true. If "style-disabled" is not specified, then the "style" property is used in both modes.

Attention! The '@' symbol should NOT be added to the style name. If you add the '@' symbol to the name, then the style name will be extracted from the constant of the same name. For example

theme {
	constants = _{
		@demoPanel = demoPage
	},
	styles = [
		demoPage {
			width = 100%,
			height = 100%,
			cell-width = "1fr, auto",
		},
		demoPanel {
			width = 100%,
			height = 100%,
			orientation = start-to-end,
		},
	]
}

rui.Set(view, "subView", rui.Style, "demoPanel")   // style == demoPanel
rui.Set(view, "subView", rui.Style, "@demoPanel")  // style == demoPage

In addition to general styles, you can add styles for specific work modes. To do this, the following modifiers are added to the name "styles":

• ":portrait" or ":landscape" are respectively styles for portrait or landscape mode of the program. Attention means the aspect ratio of the program window, not the screen.

• ":width< size >" are styles for a screen whose width does not exceed the specified size in logical pixels.

• ":height< size >" are styles for a screen whose height does not exceed the specified size in logical pixels.

For example

theme {
	styles = [
		demoPage {
			width = 100%,
			height = 100%,
			cell-width = "1fr, auto",
		},
		demoPage2 {
			row = 0,
			column = 1,
		}
	],
	styles:landscape = [
		demoPage {
			width = 100%,
			height = 100%,
			cell-height = "1fr, auto",
		},
		demoPage2 {
			row = 1,
			column = 0,
		}
	],
	styles:portrait:width320 = [
		sapmplePage {
			width = 100%,
			height = 50%,
		},
	]
}

Standard constants and styles

The library defines a number of constants and styles. You can override them in your themes.

System styles that you can override:

Style name	Описание
ruiApp	This style is used to set the default text style (font, size, etc.)
ruiView	Default View Style
ruiArticle	The style to use if the "semantics" property is set to "article"
ruiSection	The style used if the "semantics" property is set to "section"
ruiAside	The style used if the "semantics" property is set to "aside"
ruiHeader	The style used if the "semantics" property is set to "header"
ruiMain	The style used if the "semantics" property is set to "main"
ruiFooter	Style used if the "semantics" property is set to "footer"
ruiNavigation	Style used if property "semantics" is set to "navigation"
ruiFigure	Style used if property "semantics" is set to "figure"
ruiFigureCaption	Style used if property "semantics" is set to "figure-caption"
ruiButton	Style used if property "semantics" is set to "button"
ruiParagraph	The style used if the "semantics" property is set to "paragraph"
ruiH1	Style used if property "semantics" is set to "h1"
ruiH2	Style used if property "semantics" is set to "h2"
ruiH3	Style used if property "semantics" is set to "h3"
ruiH4	Style used if property "semantics" is set to "h4"
ruiH5	Style used if property "semantics" is set to "h5"
ruiH6	Style used if property "semantics" is set to "h6"
ruiBlockquote	Style used if the "semantics" property is set to "blockquote"
ruiCode	Style used if property "semantics" is set to "code"
ruiTable	Default TableView style
ruiTableHead	Default TableView header style
ruiTableFoot	Default TableView footer style
ruiTableRow	Default TableView row style
ruiTableColumn	Default TableView column style
ruiTableCell	Default TableView cell style
ruiDisabledButton	Button style if property "disabled" is set to true
ruiCheckbox	Checkbox style
ruiListItem	ListView item style
ruiListItemSelected	Style the selected ListView item when the ListView does not have focus
ruiListItemFocused	Style the selected ListView item when the ListView has focus
ruiPopup	Popup style
ruiPopupTitle	Popup title style
ruiMessageText	Popup text style (Message, Question)
ruiPopupMenuItem	Popup menu item style

System color constants that you can override:

Color constant name	Description
ruiBackgroundColor	Background color
ruiTextColor	Text color
ruiDisabledTextColor	Banned text color
ruiHighlightColor	Backlight color
ruiHighlightTextColor	Highlighted text color
ruiButtonColor	Button color
ruiButtonActiveColor	Focus button color
ruiButtonTextColor	Button text color
ruiButtonDisabledColor	Denied button color
ruiButtonDisabledTextColor	Disabled button text color
ruiSelectedColor	Background color of inactive selected ListView item
ruiSelectedTextColor	Text color of inactive selected ListView item
ruiPopupBackgroundColor	Popup background color
ruiPopupTextColor	Popup text color
ruiPopupTitleColor	Popup title background color
ruiPopupTitleTextColor	Popup Title Text Color

Constants that you can override:

Constant name	Description
ruiButtonHorizontalPadding	Horizontal padding inside the button
ruiButtonVerticalPadding	Vertical padding inside the button
ruiButtonMargin	External button access
ruiButtonRadius	Button corner radius
ruiButtonHighlightDilation	Width of the outer border of the active button
ruiButtonHighlightBlur	Blur the active button frame
ruiCheckboxGap	Break between checkbox and content
ruiListItemHorizontalPadding	Horizontal padding inside a ListView item
ruiListItemVerticalPadding	Vertical padding inside a ListView item
ruiPopupTitleHeight	Popup title height
ruiPopupTitlePadding	Popup title padding
ruiPopupButtonGap	Break between popup buttons

Multi-language support

If you want to add support for several languages to the program, you need to place the translation files in the "strings" folder of the resources. Translation files must have the "rui" extension and the following format

strings {
	<language 1> = _{
		<text 1> = <translation 1>,
		<text 2> = <translation 2>,
		…
	},
	<язык 2> = _{
		<text 1> = <translation 1>,
		<text 2> = <translation 2>,
		…
	},
	…
}

If the translation for each language is placed in a separate file, then the following format can be used

strings:<language> {
	<text 1> = <translation 1>,
	<text 2> = <translation 2>,
	…
}

For example, if all translations are in one file strings.rui

strings {
	ru = _{
		"Yes" = "Да",
		"No" = "Нет",
	},
	de = _{
		"Yes" = "Ja",
		"No" = "Nein",
	},
}

If in different. ru.rui file:

strings:ru {
	"Yes" = "Да",
	"No" = "Нет",
}

de.rui file:

strings:de {
	"Yes" = "Ja",
	"No" = "Nein",
}

The translation can also be split into multiple files.

Translations are automatically inserted in all Views.

However, if you are drawing text in a CanvasView, then you must request the translation yourself. To do this, there is a method in the Session interface:

GetString(tag string) (string, bool)

If there is no translation of the given string, then the method will return the original string and false as the second parameter.

You can get the current language using the Language() method of the Session interface. The current language is determined by the user's browser settings. You can change the session language using the SetLanguage(lang string) method of the Session interface.