Clean up the 'js' build tags

Updates #1129

examples/contextlost/main.go

@@ -1,160 +0,0 @@
-// Copyright 2018 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 js
-// +build example
-
-package main
-
-import (
-	"bytes"
-	"fmt"
-	"image"
-	_ "image/jpeg"
-	"log"
-	"math"
-	"syscall/js"
-	"time"
-
-	"github.com/hajimehoshi/ebiten/v2"
-	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
-	"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
-	"github.com/hajimehoshi/ebiten/v2/inpututil"
-)
-
-const (
-	screenWidth  = 320
-	screenHeight = 240
-)
-
-var (
-	gophersImage *ebiten.Image
-	extraImages  []*ebiten.Image
-)
-
-type Game struct {
-	count int
-	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")
-		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
-	}
-
-	if inpututil.IsKeyJustPressed(ebiten.KeyS) {
-		ebiten.SetScreenClearedEveryFrame(!ebiten.IsScreenClearedEveryFrame())
-	}
-
-	g.count++
-	return nil
-}
-
-func (g *Game) Draw(screen *ebiten.Image) {
-	if g.lost {
-		// When the context is lost, skip rendering. Usually this logic should not be required, but when the
-		// context lost happens by the API explicitly, Draw can be called even after the data in GPU
-		// disappered.
-		return
-	}
-
-	w, h := gophersImage.Size()
-	op := &ebiten.DrawImageOptions{}
-
-	// For the details, see examples/rotate.
-	op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
-	op.GeoM.Rotate(float64(g.count%360) * 2 * math.Pi / 360)
-	op.GeoM.Translate(screenWidth/2, screenHeight/2)
-	screen.DrawImage(gophersImage, op)
-
-	msg := `Press Space to force to lose/restore the GL context!
-(Browser only)
-
-Press S to switch clearing the screen
-at the beginning of each frame.`
-	ebitenutil.DebugPrint(screen, msg)
-}
-
-func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
-	return screenWidth, screenHeight
-}
-
-func main() {
-	// Decode image from a byte slice instead of a file so that
-	// this example works in any working directory.
-	// If you want to use a file, there are some options:
-	// 1) Use os.Open and pass the file to the image decoder.
-	//    This is a very regular way, but doesn't work on browsers.
-	// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
-	//    This works even on browsers.
-	// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
-	//    This also works on browsers.
-	img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
-	if err != nil {
-		log.Fatal(err)
-	}
-	gophersImage = ebiten.NewImageFromImage(img)
-
-	// Extend the shared backend GL texture on purpose.
-	for i := 0; i < 20; i++ {
-		eimg := ebiten.NewImageFromImage(img)
-		extraImages = append(extraImages, eimg)
-	}
-
-	ebiten.SetWindowSize(screenWidth*2, screenHeight*2)
-	ebiten.SetWindowTitle("Context Lost (Ebiten Demo)")
-	if err := ebiten.RunGame(&Game{}); err != nil {
-		log.Fatal(err)
-	}
-}