rui/shadow.go

package rui

import (
	"fmt"
	"strings"
)

const (
	// ColorProperty is the name of the color property of the shadow.
	ColorProperty = "color"
	// Inset is the name of bool property of the shadow. If it is set to "false" (default) then the shadow
	// is assumed to be a drop shadow (as if the box were raised above the content).
	// If it is set to  "true" then the shadow to one inside the frame (as if the content was depressed inside the box).
	// Inset shadows are drawn inside the border (even transparent ones), above the background, but below content.
	Inset = "inset"
	// XOffset is the name of the SizeUnit property of the shadow that determines the shadow horizontal offset.
	// Negative values place the shadow to the left of the element.
	XOffset = "x-offset"
	// YOffset is the name of the SizeUnit property of the shadow that determines the shadow vertical offset.
	// Negative values place the shadow above the element.
	YOffset = "y-offset"
	// BlurRadius is the name of the SizeUnit property of the shadow that determines the radius of the blur effect.
	// The larger this value, the bigger the blur, so the shadow becomes bigger and lighter. Negative values are not allowed.
	BlurRadius = "blur"
	// SpreadRadius is the name of the SizeUnit property of the shadow. Positive values will cause the shadow to expand
	// and grow bigger, negative values will cause the shadow to shrink.
	SpreadRadius = "spread-radius"
)

// ViewShadow contains attributes of the view shadow
type ViewShadow interface {
	Properties
	fmt.Stringer
	ruiStringer
	cssStyle(buffer *strings.Builder, session Session, lead string) bool
	cssTextStyle(buffer *strings.Builder, session Session, lead string) bool
	visible(session Session) bool
}

type viewShadowData struct {
	propertyList
}

// NewViewShadow create the new shadow for a view. Arguments:
// offsetX, offsetY - x and y offset of the shadow
// blurRadius - the blur radius of the shadow
// spreadRadius - the spread radius of the shadow
// color - the color of the shadow
func NewViewShadow(offsetX, offsetY, blurRadius, spreadRadius SizeUnit, color Color) ViewShadow {
	return NewShadowWithParams(Params{
		XOffset:       offsetX,
		YOffset:       offsetY,
		BlurRadius:    blurRadius,
		SpreadRadius:  spreadRadius,
		ColorProperty: color,
	})
}

// NewInsetViewShadow create the new inset shadow for a view. Arguments:
// offsetX, offsetY - x and y offset of the shadow
// blurRadius - the blur radius of the shadow
// spreadRadius - the spread radius of the shadow
// color - the color of the shadow
func NewInsetViewShadow(offsetX, offsetY, blurRadius, spreadRadius SizeUnit, color Color) ViewShadow {
	return NewShadowWithParams(Params{
		XOffset:       offsetX,
		YOffset:       offsetY,
		BlurRadius:    blurRadius,
		SpreadRadius:  spreadRadius,
		ColorProperty: color,
		Inset:         true,
	})
}

// NewTextShadow create the new text shadow. Arguments:
// offsetX, offsetY - x and y offset of the shadow
// blurRadius - the blur radius of the shadow
// color - the color of the shadow
func NewTextShadow(offsetX, offsetY, blurRadius SizeUnit, color Color) ViewShadow {
	return NewShadowWithParams(Params{
		XOffset:       offsetX,
		YOffset:       offsetY,
		BlurRadius:    blurRadius,
		ColorProperty: color,
	})
}

// NewShadowWithParams create the new shadow for a view.
func NewShadowWithParams(params Params) ViewShadow {
	shadow := new(viewShadowData)
	shadow.propertyList.init()
	if params != nil {
		for _, tag := range []string{ColorProperty, Inset, XOffset, YOffset, BlurRadius, SpreadRadius} {
			if value, ok := params[tag]; ok && value != nil {
				shadow.Set(tag, value)
			}
		}
	}
	return shadow
}

// parseViewShadow parse DataObject and create ViewShadow object
func parseViewShadow(object DataObject) ViewShadow {
	shadow := new(viewShadowData)
	shadow.propertyList.init()
	parseProperties(shadow, object)
	return shadow
}

func (shadow *viewShadowData) Remove(tag string) {
	delete(shadow.properties, strings.ToLower(tag))
}

func (shadow *viewShadowData) Set(tag string, value interface{}) bool {
	if value == nil {
		shadow.Remove(tag)
		return true
	}

	tag = strings.ToLower(tag)
	switch tag {
	case ColorProperty, Inset, XOffset, YOffset, BlurRadius, SpreadRadius:
		return shadow.propertyList.Set(tag, value)
	}

	ErrorLogF(`"%s" property is not supported by Shadow`, tag)
	return false
}

func (shadow *viewShadowData) Get(tag string) interface{} {
	return shadow.propertyList.Get(strings.ToLower(tag))
}

func (shadow *viewShadowData) cssStyle(buffer *strings.Builder, session Session, lead string) bool {
	color, _ := colorProperty(shadow, ColorProperty, session)
	offsetX, _ := sizeProperty(shadow, XOffset, session)
	offsetY, _ := sizeProperty(shadow, YOffset, session)
	blurRadius, _ := sizeProperty(shadow, BlurRadius, session)
	spreadRadius, _ := sizeProperty(shadow, SpreadRadius, session)

	if color.Alpha() == 0 ||
		((offsetX.Type == Auto || offsetX.Value == 0) &&
			(offsetY.Type == Auto || offsetY.Value == 0) &&
			(blurRadius.Type == Auto || blurRadius.Value == 0) &&
			(spreadRadius.Type == Auto || spreadRadius.Value == 0)) {
		return false
	}

	buffer.WriteString(lead)
	if inset, _ := boolProperty(shadow, Inset, session); inset {
		buffer.WriteString("inset ")
	}

	buffer.WriteString(offsetX.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(offsetY.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(blurRadius.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(spreadRadius.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(color.cssString())
	return true
}

func (shadow *viewShadowData) cssTextStyle(buffer *strings.Builder, session Session, lead string) bool {
	color, _ := colorProperty(shadow, ColorProperty, session)
	offsetX, _ := sizeProperty(shadow, XOffset, session)
	offsetY, _ := sizeProperty(shadow, YOffset, session)
	blurRadius, _ := sizeProperty(shadow, BlurRadius, session)

	if color.Alpha() == 0 ||
		((offsetX.Type == Auto || offsetX.Value == 0) &&
			(offsetY.Type == Auto || offsetY.Value == 0) &&
			(blurRadius.Type == Auto || blurRadius.Value == 0)) {
		return false
	}

	buffer.WriteString(lead)
	buffer.WriteString(offsetX.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(offsetY.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(blurRadius.cssString("0"))
	buffer.WriteByte(' ')
	buffer.WriteString(color.cssString())
	return true
}

func (shadow *viewShadowData) visible(session Session) bool {
	color, _ := colorProperty(shadow, ColorProperty, session)
	offsetX, _ := sizeProperty(shadow, XOffset, session)
	offsetY, _ := sizeProperty(shadow, YOffset, session)
	blurRadius, _ := sizeProperty(shadow, BlurRadius, session)
	spreadRadius, _ := sizeProperty(shadow, SpreadRadius, session)

	if color.Alpha() == 0 ||
		((offsetX.Type == Auto || offsetX.Value == 0) &&
			(offsetY.Type == Auto || offsetY.Value == 0) &&
			(blurRadius.Type == Auto || blurRadius.Value == 0) &&
			(spreadRadius.Type == Auto || spreadRadius.Value == 0)) {
		return false
	}
	return true
}

func (shadow *viewShadowData) String() string {
	writer := newRUIWriter()
	shadow.ruiString(writer)
	return writer.finish()
}

func (shadow *viewShadowData) ruiString(writer ruiWriter) {
	writer.startObject("_")
	for _, tag := range shadow.AllTags() {
		if value := shadow.Get(tag); value != nil {
			writer.writeProperty(tag, value)
		}
	}
	writer.endObject()
}

func (properties *propertyList) setShadow(tag string, value interface{}) bool {

	if value == nil {
		delete(properties.properties, tag)
		return true
	}

	switch value := value.(type) {
	case ViewShadow:
		properties.properties[tag] = []ViewShadow{value}

	case []ViewShadow:
		if len(value) == 0 {
			delete(properties.properties, tag)
		} else {
			properties.properties[tag] = value
		}

	case DataValue:
		if !value.IsObject() {
			return false
		}
		properties.properties[tag] = []ViewShadow{parseViewShadow(value.Object())}

	case []DataValue:
		shadows := []ViewShadow{}
		for _, data := range value {
			if data.IsObject() {
				shadows = append(shadows, parseViewShadow(data.Object()))
			}
		}
		if len(shadows) == 0 {
			return false
		}
		properties.properties[tag] = shadows

	case string:
		obj := NewDataObject(value)
		if obj == nil {
			notCompatibleType(tag, value)
			return false
		}
		properties.properties[tag] = []ViewShadow{parseViewShadow(obj)}

	default:
		notCompatibleType(tag, value)
		return false
	}

	return true
}

func getShadows(properties Properties, tag string) []ViewShadow {
	if value := properties.Get(tag); value != nil {
		switch value := value.(type) {
		case []ViewShadow:
			return value

		case ViewShadow:
			return []ViewShadow{value}
		}
	}
	return []ViewShadow{}
}

func shadowCSS(properties Properties, tag string, session Session) string {
	shadows := getShadows(properties, tag)
	if len(shadows) == 0 {
		return ""
	}

	buffer := allocStringBuilder()
	defer freeStringBuilder(buffer)

	lead := ""
	if tag == Shadow {
		for _, shadow := range shadows {
			if shadow.cssStyle(buffer, session, lead) {
				lead = ", "
			}
		}
	} else {
		for _, shadow := range shadows {
			if shadow.cssTextStyle(buffer, session, lead) {
				lead = ", "
			}
		}
	}
	return buffer.String()
}