Texture support (#217)

Author: pchampio

application.go

@@ -100,6 +100,11 @@ func (a *Application) Run() error {
 		return errors.Errorf("invalid window mode %T", a.config.windowMode)
 	}
 
+	glfw.WindowHint(glfw.ContextVersionMajor, 4)
+	glfw.WindowHint(glfw.ContextVersionMinor, 1)
+	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
+	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
+  
 	if a.config.windowInitialLocations.xpos != 0 {
 		// To create the window at a specific position, make it initially invisible
 		// using the Visible window hint, set its position and then show it.
@@ -217,6 +222,11 @@ func (a *Application) Run() error {
 
 	a.engine.PlatfromMessage = messenger.handlePlatformMessage
 
+	texturer := newRegistry(a.engine, a.window)
+	a.engine.GLExternalTextureFrameCallback = texturer.handleExternalTexture
+
+	texturer.init()
+
 	// Not very nice, but we can only really fix this when there's a pluggable
 	// renderer.
 	defaultTextinputPlugin.keyboardLayout = a.config.keyboardLayout
@@ -254,6 +264,16 @@ func (a *Application) Run() error {
 	// platfrom message can be corectly handled by ui.Window.onPlatformMessage.
 	glfw.WaitEvents()
 
+	for _, p := range a.config.plugins {
+		// Extra init call for plugins that satisfy the PluginTexture interface.
+		if glfwPlugin, ok := p.(PluginTexture); ok {
+			err = glfwPlugin.InitPluginTexture(texturer)
+			if err != nil {
+				return errors.Wrap(err, "failed to initialize texture plugin"+fmt.Sprintf("%T", p))
+			}
+		}
+	}
+
 	a.window.SetKeyCallback(
 		func(window *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
 			defaultTextinputPlugin.glfwKeyCallback(window, key, scancode, action, mods)

embedder/embedder.go

@@ -53,6 +53,16 @@ const (
 	ResultEngineNotRunning      Result = -1
 )
 
+// FlutterOpenGLTexture corresponds to the C.FlutterOpenGLTexture struct.
+type FlutterOpenGLTexture struct {
+	// Target texture of the active texture unit (example GL_TEXTURE_2D)
+	Target uint32
+	// The name of the texture
+	Name uint32
+	// The texture format (example GL_RGBA8)
+	Format uint32
+}
+
 // FlutterEngine corresponds to the C.FlutterEngine with his associated callback's method.
 type FlutterEngine struct {
 	// Flutter Engine.
@@ -65,12 +75,13 @@ type FlutterEngine struct {
 	index int
 
 	// GL callback functions
-	GLMakeCurrent         func() bool
-	GLClearCurrent        func() bool
-	GLPresent             func() bool
-	GLFboCallback         func() int32
-	GLMakeResourceCurrent func() bool
-	GLProcResolver        func(procName string) unsafe.Pointer
+	GLMakeCurrent                  func() bool
+	GLClearCurrent                 func() bool
+	GLPresent                      func() bool
+	GLFboCallback                  func() int32
+	GLMakeResourceCurrent          func() bool
+	GLProcResolver                 func(procName string) unsafe.Pointer
+	GLExternalTextureFrameCallback func(textureID int64, width int, height int) *FlutterOpenGLTexture
 
 	// platform message callback function
 	PlatfromMessage func(message *PlatformMessage)
@@ -299,6 +310,40 @@ func (flu *FlutterEngine) SendPlatformMessageResponse(
 	return (Result)(res)
 }
 
+// RegisterExternalTexture registers an external texture with a unique identifier.
+func (flu *FlutterEngine) RegisterExternalTexture(textureID int64) Result {
+	flu.sync.Lock()
+	defer flu.sync.Unlock()
+	if flu.closed {
+		return ResultEngineNotRunning
+	}
+	res := C.FlutterEngineRegisterExternalTexture(flu.Engine, C.int64_t(textureID))
+	return (Result)(res)
+}
+
+// UnregisterExternalTexture unregisters a previous texture registration.
+func (flu *FlutterEngine) UnregisterExternalTexture(textureID int64) Result {
+	flu.sync.Lock()
+	defer flu.sync.Unlock()
+	if flu.closed {
+		return ResultEngineNotRunning
+	}
+	res := C.FlutterEngineUnregisterExternalTexture(flu.Engine, C.int64_t(textureID))
+	return (Result)(res)
+}
+
+// MarkExternalTextureFrameAvailable marks that a new texture frame is
+// available for a given texture identifier.
+func (flu *FlutterEngine) MarkExternalTextureFrameAvailable(textureID int64) Result {
+	flu.sync.Lock()
+	defer flu.sync.Unlock()
+	if flu.closed {
+		return ResultEngineNotRunning
+	}
+	res := C.FlutterEngineMarkExternalTextureFrameAvailable(flu.Engine, C.int64_t(textureID))
+	return (Result)(res)
+}
+
 // FlutterEngineFlushPendingTasksNow flush tasks on a  message loop not
 // controlled by the Flutter engine.
 //