restorable: Disable restoring on desktops and mobile browsers (#380)

graphicscontext.go

@@ -81,14 +81,7 @@ func (c *graphicsContext) initializeIfNeeded() error {
 		}
 		c.initialized = true
 	}
-	r, err := c.needsRestoring()
-	if err != nil {
-		return err
-	}
-	if !r {
-		return nil
-	}
-	if err := c.restore(); err != nil {
+	if err := c.restoreIfNeeded(); err != nil {
 		return err
 	}
 	return nil
@@ -137,7 +130,17 @@ func (c *graphicsContext) UpdateAndDraw(updateCount int) error {
 	return nil
 }
 
-func (c *graphicsContext) restore() error {
+func (c *graphicsContext) restoreIfNeeded() error {
+	if !restorable.IsRestoringEnabled() {
+		return nil
+	}
+	r, err := c.needsRestoring()
+	if err != nil {
+		return err
+	}
+	if !r {
+		return nil
+	}
 	if err := graphics.Reset(); err != nil {
 		return err
 	}

internal/restorable/enabled_desktop.go

@@ -0,0 +1,26 @@
+// Copyright 2017 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 darwin freebsd linux windows
+// +build !js
+// +build !android
+// +build !ios
+
+package restorable
+
+func init() {
+	// OpenGL (not ES) never causes context lost,
+	// so restorable feature is not needed.
+	restoringEnabled = false
+}

internal/restorable/enabled_js.go

@@ -0,0 +1,48 @@
+// Copyright 2017 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
+
+package restorable
+
+import (
+	"strings"
+
+	"github.com/gopherjs/gopherjs/js"
+)
+
+func isIOS() bool {
+	ua := js.Global.Get("navigator").Get("userAgent").String()
+	if !strings.Contains(ua, "iPhone") {
+		return false
+	}
+	return true
+}
+
+func isAndroidChrome() bool {
+	ua := js.Global.Get("navigator").Get("userAgent").String()
+	if !strings.Contains(ua, "Android") {
+		return false
+	}
+	if !strings.Contains(ua, "Chrome") {
+		return false
+	}
+	return true
+}
+
+func init() {
+	if isIOS() || isAndroidChrome() {
+		restoringEnabled = false
+	}
+}

internal/restorable/image.go

@@ -157,8 +157,7 @@ func (p *Image) ReplacePixels(pixels []uint8) {
 
 func (p *Image) DrawImage(img *Image, vertices []float32, colorm *affine.ColorM, mode opengl.CompositeMode) {
 	theImages.resetPixelsIfDependingOn(p)
-	if img.stale || img.volatile {
-		// TODO: What will happen if there are images depending on p?
+	if img.stale || img.volatile || !IsRestoringEnabled() {
 		p.makeStale()
 	} else {
 		p.appendDrawImageHistory(img, vertices, colorm, mode)
@@ -234,6 +233,9 @@ func (p *Image) readPixelsFromGPU(image *graphics.Image) error {
 }
 
 func (p *Image) resolveStalePixels() error {
+	if !IsRestoringEnabled() {
+		return nil
+	}
 	if p.volatile {
 		return nil
 	}
@@ -339,5 +341,8 @@ func (p *Image) Dispose() {
 }
 
 func (p *Image) IsInvalidated() bool {
+	if !IsRestoringEnabled() {
+		return false
+	}
 	return p.image.IsInvalidated()
 }

internal/restorable/images.go

@@ -18,6 +18,19 @@ import (
 	"github.com/hajimehoshi/ebiten/internal/sync"
 )
 
+// restoringEnabled indicates if restoring happens or not.
+var restoringEnabled = true // This value is overridden at enabled_*.go.
+
+func IsRestoringEnabled() bool {
+	// This value is updated only at init or EnableRestoringForTesting.
+	// No need to lock here.
+	return restoringEnabled
+}
+
+func EnableRestoringForTesting() {
+	restoringEnabled = true
+}
+
 type images struct {
 	images      map[*Image]struct{}
 	lastChecked *Image
@@ -88,6 +101,9 @@ func (i *images) resetPixelsIfDependingOn(target *Image) {
 func (i *images) restore() error {
 	i.m.Lock()
 	defer i.m.Unlock()
+	if !IsRestoringEnabled() {
+		panic("not reached")
+	}
 	// Framebuffers/textures cannot be disposed since framebuffers/textures that
 	// don't belong to the current context.
 

internal/restorable/images_test.go

@@ -28,6 +28,7 @@ import (
 )
 
 func TestMain(m *testing.M) {
+	EnableRestoringForTesting()
 	code := 0
 	regularTermination := errors.New("regular termination")
 	f := func(screen *ebiten.Image) error {