opengl: Add Resume() and Pause()

graphicscontext.go

@@ -96,10 +96,12 @@ func (c *graphicsContext) Pause() error {
 	if err := graphics.Finalize(ui.GLContext()); err != nil {
 		return err
 	}
+	ui.GLContext().Pause()
 	return nil
 }
 
 func (c *graphicsContext) Resume() error {
+	ui.GLContext().Resume()
 	if !c.imageTasksDone {
 		return nil
 	}

internal/graphics/opengl/context_desktop.go

@@ -104,6 +104,19 @@ func (c *Context) Init() error {
 	return nil
 }
 
+func (c *Context) Pause() {
+	c.locationCache = newLocationCache()
+	c.lastFramebuffer = ZeroFramebuffer
+	c.lastViewportWidth = 0
+	c.lastViewportHeight = 0
+	c.lastCompositeMode = CompositeModeUnknown
+}
+
+func (c *Context) Resume() {
+	gl.Enable(gl.BLEND)
+	c.BlendFunc(CompositeModeSourceOver)
+}
+
 func (c *Context) BlendFunc(mode CompositeMode) {
 	c.RunOnContextThread(func() error {
 		if c.lastCompositeMode == mode {

internal/graphics/opengl/context_js.go

@@ -118,6 +118,20 @@ func (c *Context) init() {
 	c.BlendFunc(CompositeModeSourceOver)
 }
 
+func (c *Context) Pause() {
+	c.locationCache = newLocationCache()
+	c.lastFramebuffer = ZeroFramebuffer
+	c.lastViewportWidth = 0
+	c.lastViewportHeight = 0
+	c.lastCompositeMode = CompositeModeUnknown
+}
+
+func (c *Context) Resume() {
+	gl := c.gl
+	gl.Enable(gl.BLEND)
+	c.BlendFunc(CompositeModeSourceOver)
+}
+
 func (c *Context) BlendFunc(mode CompositeMode) {
 	if c.lastCompositeMode == mode {
 		return

internal/graphics/opengl/context_mobile.go

@@ -80,6 +80,19 @@ func NewContext() (*Context, error) {
 	return c, nil
 }
 
+func (c *Context) Pause() {
+	c.locationCache = newLocationCache()
+	c.lastFramebuffer = ZeroFramebuffer
+	c.lastViewportWidth = 0
+	c.lastViewportHeight = 0
+	c.lastCompositeMode = CompositeModeUnknown
+}
+
+func (c *Context) Resume() {
+	c.gl.Enable(mgl.BLEND)
+	c.BlendFunc(CompositeModeSourceOver)
+}
+
 func (c *Context) WaitUntilInitializingDone() {
 	// TODO: Call this function at an approriate place
 	<-c.initialized