graphcis: Bug fix: Can't dispose textures/framebuffers after the context is lost (fixing #305)

graphicscontext.go

@@ -36,6 +36,7 @@ type graphicsContext struct {
 	screen      *Image
 	screenScale float64
 	initialized int32
+	invalidated bool
 }
 
 func (c *graphicsContext) GLContext() *opengl.Context {
@@ -45,6 +46,14 @@ func (c *graphicsContext) GLContext() *opengl.Context {
 	return ui.GLContext()
 }
 
+func (c *graphicsContext) Invalidate() {
+	// Note that this is called only on browsers so far.
+	// TODO: On mobiles, this function is not called and instead IsTexture is called
+	// to detect if the context is lost. This is simple but might not work on some platforms.
+	// Should Invalidate be called explicitly?
+	c.invalidated = true
+}
+
 func (c *graphicsContext) SetSize(screenWidth, screenHeight int, screenScale float64) error {
 	if c.screen != nil {
 		if err := c.screen.Dispose(); err != nil {
@@ -91,6 +100,9 @@ func (c *graphicsContext) SetSize(screenWidth, screenHeight int, screenScale flo
 }
 
 func (c *graphicsContext) needsRestoring(context *opengl.Context) (bool, error) {
+	if c.invalidated {
+		return true, nil
+	}
 	// FlushCommands is required because c.offscreen.impl might not have an actual texture.
 	if err := graphics.FlushCommands(context); err != nil {
 		return false, err
@@ -178,5 +190,6 @@ func (c *graphicsContext) restore(context *opengl.Context) error {
 	if err := theImagesForRestoring.restore(context); err != nil {
 		return err
 	}
+	c.invalidated = false
 	return nil
 }

image.go

@@ -94,17 +94,8 @@ func (i *images) resetPixelsIfDependingOn(target *Image, context *opengl.Context
 func (i *images) restore(context *opengl.Context) error {
 	i.m.Lock()
 	defer i.m.Unlock()
-	// Dispose all images first because framebuffer/texture numbers can be reused.
-	// If framebuffers/textures are not disposed here, a newly created framebuffer/texture
-	// number can be a same number as existing one.
-	for img := range i.images {
-		if img.isDisposed() {
-			continue
-		}
-		if err := img.restorable.DisposeOnlyImage(); err != nil {
-			return err
-		}
-	}
+	// Framebuffers/textures cannot be disposed since framebuffers/textures that
+	// don't belong to the current context.
 	imagesWithoutDependency := []*imageImpl{}
 	imagesWithDependency := []*imageImpl{}
 	for img := range i.images {

internal/loop/run.go

@@ -77,6 +77,7 @@ func (c *runContext) updateFPS(fps float64) {
 type GraphicsContext interface {
 	SetSize(width, height int, scale float64) error
 	UpdateAndDraw(context *opengl.Context, updateCount int) error
+	Invalidate()
 }
 
 type loopGraphicsContext struct {
@@ -92,6 +93,10 @@ func (g *loopGraphicsContext) Update() error {
 	return g.runContext.render(g.graphicsContext)
 }
 
+func (g *loopGraphicsContext) Invalidate() {
+	g.graphicsContext.Invalidate()
+}
+
 func Run(g GraphicsContext, width, height int, scale float64, title string, fps int) (err error) {
 	if currentRunContext != nil {
 		return errors.New("loop: The game is already running")

internal/opengl/context_js.go

@@ -220,7 +220,8 @@ func (c *Context) DeleteTexture(t Texture) {
 
 func (c *Context) IsTexture(t Texture) bool {
 	gl := c.gl
-	return gl.IsTexture(t.Object)
+	b := gl.IsTexture(t.Object)
+	return b
 }
 
 func (c *Context) TexSubImage2D(p []uint8, width, height int) {

internal/restorable/image.go

@@ -304,13 +304,6 @@ func (p *Image) Dispose() error {
 	return nil
 }
 
-func (p *Image) DisposeOnlyImage() error {
-	if err := p.image.Dispose(); err != nil {
-		return err
-	}
-	return nil
-}
-
 func (p *Image) IsInvalidated(context *opengl.Context) bool {
 	return p.image.IsInvalidated(context)
 }

internal/ui/ui.go

@@ -17,6 +17,7 @@ package ui
 type GraphicsContext interface {
 	SetSize(width, height int, scale float64) error
 	Update() error
+	Invalidate()
 }
 
 type RegularTermination struct {

internal/ui/ui_js.go

@@ -74,6 +74,7 @@ func (u *userInterface) update(g GraphicsContext) error {
 	}
 	if glContext.IsContextLost() {
 		glContext.RestoreContext()
+		g.Invalidate()
 	}
 	currentInput.updateGamepads()
 	if u.sizeChanged {