Implement some preparation code for go2cpp

Updates #744

internal/devicescale/impl_js.go

@@ -19,7 +19,11 @@ import (
 )
 
 func impl(x, y int) float64 {
-	ratio := js.Global().Get("window").Get("devicePixelRatio").Float()
+	window := js.Global().Get("window")
+	if !window.Truthy() {
+		return 1
+	}
+	ratio := window.Get("devicePixelRatio").Float()
 	if ratio == 0 {
 		ratio = 1
 	}

internal/graphicsdriver/opengl/context_js.go

@@ -85,6 +85,7 @@ const (
 
 var (
 	isWebGL2Available = !forceWebGL1 && js.Global().Get("WebGL2RenderingContext").Truthy()
+	needsRestoring_   = !web.IsMobileBrowser() && !js.Global().Get("go2cpp").Truthy()
 )
 
 type contextImpl struct {
@@ -95,27 +96,28 @@ type contextImpl struct {
 func (c *context) initGL() {
 	c.gl = js.Value{}
 
-	// TODO: Define id?
-	doc := js.Global().Get("document")
-	if !doc.Truthy() {
-		return
-	}
-	canvas := doc.Call("querySelector", "canvas")
-	attr := js.Global().Get("Object").New()
-	attr.Set("alpha", true)
-	attr.Set("premultipliedAlpha", true)
-
 	var gl js.Value
-	if isWebGL2Available {
-		gl = canvas.Call("getContext", "webgl2", attr)
-	} else {
-		gl = canvas.Call("getContext", "webgl", attr)
-		if jsutil.Equal(gl, js.Null()) {
-			gl = canvas.Call("getContext", "experimental-webgl", attr)
+
+	// TODO: Define id?
+	if doc := js.Global().Get("document"); doc.Truthy() {
+		canvas := doc.Call("querySelector", "canvas")
+		attr := js.Global().Get("Object").New()
+		attr.Set("alpha", true)
+		attr.Set("premultipliedAlpha", true)
+
+		if isWebGL2Available {
+			gl = canvas.Call("getContext", "webgl2", attr)
+		} else {
+			gl = canvas.Call("getContext", "webgl", attr)
 			if jsutil.Equal(gl, js.Null()) {
-				panic("opengl: getContext failed")
+				gl = canvas.Call("getContext", "experimental-webgl", attr)
+				if jsutil.Equal(gl, js.Null()) {
+					panic("opengl: getContext failed")
+				}
 			}
 		}
+	} else if go2cpp := js.Global().Get("go2cpp"); go2cpp.Truthy() {
+		gl = go2cpp.Get("gl")
 	}
 
 	c.gl = gl
@@ -493,7 +495,7 @@ func (c *context) flush() {
 }
 
 func (c *context) needsRestoring() bool {
-	return !web.IsMobileBrowser()
+	return needsRestoring_
 }
 
 func (c *context) canUsePBO() bool {

internal/uidriver/js/input_js.go

@@ -244,6 +244,9 @@ func (i *Input) setMouseCursor(x, y int) {
 
 func (i *Input) UpdateGamepads() {
 	nav := js.Global().Get("navigator")
+	if !nav.Truthy() {
+		return
+	}
 	if !nav.Get("getGamepads").Truthy() {
 		return
 	}

internal/uidriver/js/ui_js.go

@@ -60,8 +60,8 @@ var (
 	window                = js.Global().Get("window")
 	document              = js.Global().Get("document")
 	canvas                js.Value
-	requestAnimationFrame = window.Get("requestAnimationFrame")
-	setTimeout            = window.Get("setTimeout")
+	requestAnimationFrame = js.Global().Get("requestAnimationFrame")
+	setTimeout            = js.Global().Get("setTimeout")
 )
 
 func (u *UserInterface) ScreenSizeInFullscreen() (int, int) {
@@ -134,10 +134,14 @@ func (u *UserInterface) updateSize() {
 
 	if u.sizeChanged {
 		u.sizeChanged = false
-		body := document.Get("body")
-		bw := body.Get("clientWidth").Float()
-		bh := body.Get("clientHeight").Float()
-		u.context.Layout(bw, bh)
+		if document.Truthy() {
+			body := document.Get("body")
+			bw := body.Get("clientWidth").Float()
+			bh := body.Get("clientHeight").Float()
+			u.context.Layout(bw, bh)
+		} else {
+			u.context.Layout(640, 480)
+		}
 	}
 }
 
@@ -250,7 +254,12 @@ func (u *UserInterface) loop(context driver.UIContext) <-chan error {
 }
 
 func init() {
-	if jsutil.Equal(document.Get("body"), js.Null()) {
+	// docuemnt is undefined on node.js
+	if !document.Truthy() {
+		return
+	}
+
+	if !document.Get("body").Truthy() {
 		ch := make(chan struct{})
 		window.Call("addEventListener", "load", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 			close(ch)
@@ -400,7 +409,7 @@ func init() {
 }
 
 func (u *UserInterface) Run(context driver.UIContext) error {
-	if u.initFocused {
+	if u.initFocused && window.Truthy() {
 		// Do not focus the canvas when the current document is in an iframe.
 		// Otherwise, the parent page tries to focus the iframe on every loading, which is annoying (#1373).
 		isInIframe := !jsutil.Equal(window.Get("location"), window.Get("parent").Get("location"))
@@ -417,11 +426,13 @@ func (u *UserInterface) RunWithoutMainLoop(context driver.UIContext) {
 }
 
 func (u *UserInterface) updateScreenSize() {
-	body := document.Get("body")
-	bw := int(body.Get("clientWidth").Float() * u.DeviceScaleFactor())
-	bh := int(body.Get("clientHeight").Float() * u.DeviceScaleFactor())
-	canvas.Set("width", bw)
-	canvas.Set("height", bh)
+	if document.Truthy() {
+		body := document.Get("body")
+		bw := int(body.Get("clientWidth").Float() * u.DeviceScaleFactor())
+		bh := int(body.Get("clientHeight").Float() * u.DeviceScaleFactor())
+		canvas.Set("width", bw)
+		canvas.Set("height", bh)
+	}
 	u.sizeChanged = true
 }
 

internal/web/web_js.go

@@ -29,7 +29,11 @@ var (
 )
 
 func init() {
-	userAgent := js.Global().Get("navigator").Get("userAgent").String()
+	nav := js.Global().Get("navigator")
+	if !nav.Truthy() {
+		return
+	}
+	userAgent := nav.Get("userAgent").String()
 	isIOSSafari = strings.Contains(userAgent, "iPhone") || strings.Contains(userAgent, "iPad")
 	isAndroidChrome = strings.Contains(userAgent, "Android") && strings.Contains(userAgent, "Chrome")
 }