examples/contextlost: Enable to build on non-JS environments

examples/contextlost/context_js.go

@@ -0,0 +1,63 @@
+// Copyright 2020 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build example
+
+package main
+
+import (
+	"fmt"
+	"syscall/js"
+	"time"
+)
+
+func (g *Game) loseAndRestoreContext() {
+	doc := js.Global().Get("document")
+	canvas := doc.Call("getElementsByTagName", "canvas").Index(0)
+	context := canvas.Call("getContext", "webgl2")
+	if !context.Truthy() {
+		context = canvas.Call("getContext", "webgl")
+		if !context.Truthy() {
+			context = canvas.Call("getContext", "experimental-webgl")
+		}
+	}
+
+	if g.lost {
+		return
+	}
+
+	// Edge might not support the extension. See
+	// https://developer.mozilla.org/en-US/docs/Web/API/WEBGL_lose_context
+	ext := context.Call("getExtension", "WEBGL_lose_context")
+	if !ext.Truthy() {
+		fmt.Println("Fail to force context lost. Edge might not support the extension yet.")
+		return
+	}
+
+	ext.Call("loseContext")
+	fmt.Println("Lost the context!")
+	fmt.Println("The context is automatically restored after 3 seconds.")
+	g.lost = true
+
+	// If and only if the context is lost by loseContext, you need to call restoreContext. Note that in usual
+	// case of context lost, you cannot call restoreContext but the context should be restored automatically.
+	//
+	// After the context is lost, update will not be called. Instead, fire the goroutine to restore the context.
+	go func() {
+		time.Sleep(3 * time.Second)
+		ext.Call("restoreContext")
+		fmt.Println("Restored the context!")
+		g.lost = false
+	}()
+}

examples/contextlost/context_notjs.go

@@ -0,0 +1,26 @@
+// Copyright 2020 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build example
+// +build !js
+
+package main
+
+import (
+	"fmt"
+)
+
+func (g *Game) loseAndRestoreContext() {
+	fmt.Println("Losing context lost works only on browsers.")
+}

examples/contextlost/main.go

@@ -18,13 +18,10 @@ package main
 
 import (
 	"bytes"
-	"fmt"
 	"image"
 	_ "image/jpeg"
 	"log"
 	"math"
-	"syscall/js"
-	"time"
 
 	"github.com/hajimehoshi/ebiten/v2"
 	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
@@ -33,8 +30,8 @@ import (
 )
 
 const (
-	screenWidth  = 320
+	screenWidth  = 640
-	screenHeight = 240
+	screenHeight = 480
 )
 
 var (
@@ -47,48 +44,9 @@ type Game struct {
 	lost  bool
 }
 
-func (g *Game) loseAndRestoreContext(context js.Value) {
-	if g.lost {
-		return
-	}
-
-	// Edge might not support the extension. See
-	// https://developer.mozilla.org/en-US/docs/Web/API/WEBGL_lose_context
-	ext := context.Call("getExtension", "WEBGL_lose_context")
-	if !ext.Truthy() {
-		fmt.Println("Fail to force context lost. Edge might not support the extension yet.")
-		return
-	}
-
-	ext.Call("loseContext")
-	fmt.Println("Lost the context!")
-	fmt.Println("The context is automatically restored after 3 seconds.")
-	g.lost = true
-
-	// If and only if the context is lost by loseContext, you need to call restoreContext. Note that in usual
-	// case of context lost, you cannot call restoreContext but the context should be restored automatically.
-	//
-	// After the context is lost, update will not be called. Instead, fire the goroutine to restore the context.
-	go func() {
-		time.Sleep(3 * time.Second)
-		ext.Call("restoreContext")
-		fmt.Println("Restored the context!")
-		g.lost = false
-	}()
-}
-
 func (g *Game) Update() error {
 	if inpututil.IsKeyJustPressed(ebiten.KeySpace) {
-		doc := js.Global().Get("document")
+		g.loseAndRestoreContext()
-		canvas := doc.Call("getElementsByTagName", "canvas").Index(0)
-		context := canvas.Call("getContext", "webgl2")
-		if !context.Truthy() {
-			context = canvas.Call("getContext", "webgl")
-			if !context.Truthy() {
-				context = canvas.Call("getContext", "experimental-webgl")
-			}
-		}
-		g.loseAndRestoreContext(context)
 		return nil
 	}
 
@@ -151,7 +109,7 @@ func main() {
 		extraImages = append(extraImages, eimg)
 	}
 
-	ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
+	ebiten.SetWindowSize(screenWidth, screenHeight)
 	ebiten.SetWindowTitle("Context Lost (Ebiten Demo)")
 	if err := ebiten.RunGame(&Game{}); err != nil {
 		log.Fatal(err)