From 12df67cfb4d53606b816a32fad5f46327a7b421e Mon Sep 17 00:00:00 2001
From: anoshenko <anoshenko@gmail.com>
Date: Wed, 2 Nov 2022 23:16:45 +0300
Subject: [PATCH] Update wasmBridge.go

---
 wasmBridge.go | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/wasmBridge.go b/wasmBridge.go
index e7e087b..e98ca03 100644
--- a/wasmBridge.go
+++ b/wasmBridge.go
@@ -93,6 +93,9 @@ func (bridge *wasmBridge) writeMessage(script string) bool {
 
 func (bridge *wasmBridge) cavnasStart(htmlID string) {
 	bridge.canvas = js.Global().Call("getCanvasContext", htmlID)
+	if !bridge.canvas.IsNull() {
+		bridge.canvas.Call("save")
+	}
 }
 
 func (bridge *wasmBridge) callCanvasFunc(funcName string, args ...any) {
@@ -103,7 +106,7 @@ func (bridge *wasmBridge) callCanvasFunc(funcName string, args ...any) {
 				for k, x := range array {
 					arr[k] = x
 				}
-				args[i] = js.ValueOf(array)
+				args[i] = js.ValueOf(arr)
 			}
 		}
 
@@ -142,17 +145,53 @@ func (bridge *wasmBridge) updateCanvasProperty(property string, value any) {
 }
 
 func (bridge *wasmBridge) cavnasFinish() {
+	if !bridge.canvas.IsNull() {
+		bridge.canvas.Call("restore")
+	}
 }
 
 func (bridge *wasmBridge) canvasTextMetrics(htmlID, font, text string) TextMetrics {
-	result := js.Global().Call("canvasTextMetrics", 0, htmlID, font, text).String()
-	DebugLog(result)
 
-	// TODO
-	return TextMetrics{}
+	result := TextMetrics{}
+
+	canvas := js.Global().Get("document").Call("getElementById", htmlID)
+	if !canvas.IsUndefined() && !canvas.IsNull() {
+		context := canvas.Call("getContext", "2d")
+		if !context.IsUndefined() && !context.IsNull() {
+			context.Call("save")
+			context.Set("font", font)
+			context.Set("textBaseline", "alphabetic")
+			context.Set("textAlign", "start")
+
+			metrics := context.Call("measureText", text)
+			if !metrics.IsUndefined() && !metrics.IsNull() {
+				metricsValue := func(name string) float64 {
+					value := metrics.Get(name)
+					if !value.IsUndefined() && !value.IsNull() && value.Type() == js.TypeNumber {
+						return value.Float()
+					}
+					return 0
+				}
+
+				result.Width = metricsValue("width")
+				result.Ascent = metricsValue("actualBoundingBoxAscent")
+				result.Descent = metricsValue("actualBoundingBoxDescent")
+				result.Left = metricsValue("actualBoundingBoxLeft")
+				result.Right = metricsValue("actualBoundingBoxRight")
+			}
+			context.Call("restore")
+		}
+	}
+
+	return result
 }
 
 func (bridge *wasmBridge) htmlPropertyValue(htmlID, name string) string {
+	element := js.Global().Get("document").Call("getElementById", htmlID)
+	if !element.IsUndefined() && !element.IsNull() {
+		return element.Get(name).String()
+	}
+
 	return ""
 }