Avoid unnecessary PlatformMessage copies in plugin callback loop (#25)

* Implement system UI Clipboard

* Avoid unnecessary PlatformMessage copies in plugin callback loop

Author: pas2k

example/simpleDemo/main.go

@@ -57,7 +57,7 @@ func setIcon(window *glfw.Window) error {
 
 // Plugin that read the stdin and send the number to the dart side
 func ownPlugin(
-	platMessage flutter.PlatformMessage,
+	platMessage *flutter.PlatformMessage,
 	flutterEngine *flutter.EngineOpenGL,
 	window *glfw.Window,
 ) bool {

flutter/flutter.go

@@ -48,7 +48,7 @@ type EngineOpenGL struct {
 	FMakeResourceCurrent func(v unsafe.Pointer) bool
 
 	// platform message callback.
-	FPlatfromMessage func(message PlatformMessage, window unsafe.Pointer) bool
+	FPlatfromMessage func(message *PlatformMessage, window unsafe.Pointer) bool
 
 	// Engine arguments
 	PixelRatio  float64
@@ -163,9 +163,9 @@ type Message struct {
 }
 
 // SendPlatformMessage is used to send a PlatformMessage to the Flutter engine.
-func (flu *EngineOpenGL) SendPlatformMessage(Message PlatformMessage) Result {
+func (flu *EngineOpenGL) SendPlatformMessage(Message *PlatformMessage) Result {
 
-	marshalled, err := json.Marshal(Message.Message)
+	marshalled, err := json.Marshal(&Message.Message)
 	if err != nil {
 		panic("Cound not send a message to the flutter engine: Error while creating the JSON")
 	}
@@ -189,7 +189,7 @@ func (flu *EngineOpenGL) SendPlatformMessage(Message PlatformMessage) Result {
 
 // SendPlatformMessageResponse is used to send a message to the Flutter side using the correct ResponseHandle!
 func (flu *EngineOpenGL) SendPlatformMessageResponse(
-	responseTo PlatformMessage,
+	responseTo *PlatformMessage,
 	data []byte,
 ) Result {
 

flutter/flutter_proxy_glfw.go

@@ -22,15 +22,14 @@ func proxy_on_platform_message(message *C.FlutterPlatformMessage, userPointer un
 	if message.message != nil {
 		str := C.GoStringN(C.c_str(message.message), C.int(message.message_size))
 
-		FlutterPlatformMessage := PlatformMessage{}
-
 		messageContent := Message{}
 		json.Unmarshal([]byte(str), &messageContent)
 
-		FlutterPlatformMessage.Message = messageContent
-		FlutterPlatformMessage.Channel = C.GoString(message.channel)
-		FlutterPlatformMessage.ResponseHandle = message.response_handle
-
+		FlutterPlatformMessage := &PlatformMessage{
+			Message:        messageContent,
+			Channel:        C.GoString(message.channel),
+			ResponseHandle: message.response_handle,
+		}
 		return C.bool(flutterEngines[0].FPlatfromMessage(FlutterPlatformMessage, userPointer))
 	}
 	return C.bool(false)

gutter.go

@@ -21,6 +21,7 @@ func Run(options ...Option) (err error) {
 	// The Windows Title Handler and the TextInput handler come by default
 	options = append(options, addHandlerWindowTitle())
 	options = append(options, addHandlerTextInput())
+	options = append(options, addHandlerClipboard())
 
 	c = c.merge(options...)
 
@@ -203,7 +204,7 @@ func runFlutter(window *glfw.Window, c config) *flutter.EngineOpenGL {
 	}
 
 	// PlatformMessage
-	flutterOGL.FPlatfromMessage = func(platMessage flutter.PlatformMessage, window unsafe.Pointer) bool {
+	flutterOGL.FPlatfromMessage = func(platMessage *flutter.PlatformMessage, window unsafe.Pointer) bool {
 		windows := glfw.GoWindow(window)
 
 		hasDispatched := false
@@ -262,7 +263,7 @@ func updateEditingState(window *glfw.Window) {
 		Method: textUpdateStateMethod,
 	}
 
-	var mess = flutter.PlatformMessage{
+	var mess = &flutter.PlatformMessage{
 		Channel: textInputChannel,
 		Message: message,
 	}

plugin_receiver.go

@@ -8,7 +8,7 @@ import (
 // PluginReceivers do stuff when receiving Message from the Engine,
 // send result with `flutterEngine.SendPlatformMessageResponse`
 type PluginReceivers func(
-	message flutter.PlatformMessage,
+	message *flutter.PlatformMessage,
 	flutterEngine *flutter.EngineOpenGL,
 	window *glfw.Window,
 ) bool

system_plugins.go

@@ -20,6 +20,9 @@ const (
 	platformChannel = "flutter/platform"
 	// Args -> struct ArgsAppSwitcherDescription
 	setDescriptionMethod = "SystemChrome.setApplicationSwitcherDescription"
+
+	clipboardSetData = "Clipboard.setData"
+	clipboardGetData = "Clipboard.getData"
 )
 
 // ArgsAppSwitcherDescription Args content
@@ -31,11 +34,11 @@ type ArgsAppSwitcherDescription struct {
 func addHandlerWindowTitle() Option {
 
 	var handler PluginReceivers = func(
-		platMessage flutter.PlatformMessage,
+		platMessage *flutter.PlatformMessage,
 		flutterEngine *flutter.EngineOpenGL,
 		window *glfw.Window,
 	) bool {
-		message := platMessage.Message
+		message := &platMessage.Message
 
 		if message.Method == setDescriptionMethod {
 			msgBody := ArgsAppSwitcherDescription{}
@@ -50,6 +53,44 @@ func addHandlerWindowTitle() Option {
 
 }
 
+func addHandlerClipboard() Option {
+	handler := func(platMessage *flutter.PlatformMessage,
+		flutterEngine *flutter.EngineOpenGL,
+		window *glfw.Window) bool {
+
+		message := &platMessage.Message
+		switch message.Method {
+		case clipboardSetData:
+			newClipboard := struct {
+				Text string `json:"text"`
+			}{}
+			json.Unmarshal(message.Args, &newClipboard)
+			window.SetClipboardString(newClipboard.Text)
+		case clipboardGetData:
+			requestedMime := ""
+			json.Unmarshal(message.Args, &requestedMime)
+			if requestedMime == "text/plain" {
+				clipText, _ := window.GetClipboardString()
+
+				retBytes, _ := json.Marshal([]struct {
+					Text string `json:"text"`
+				}{{clipText}})
+
+				flutterEngine.SendPlatformMessageResponse(platMessage, retBytes)
+				return true
+			} else {
+				// log.Printf("Don't know how to acquire type #v from the clipboard", requestedMime)
+			}
+
+		default:
+			// log.Printf("unhandled platform method: %#v\n", platMessage.Message)
+		}
+		return false
+
+	}
+	return OptionAddPluginReceiver(handler, platformChannel)
+}
+
 /////////////////
 //  TextInput  //
 /////////////////
@@ -83,12 +124,12 @@ type argsEditingState struct {
 func addHandlerTextInput() Option {
 
 	var handler PluginReceivers = func(
-		platMessage flutter.PlatformMessage,
+		platMessage *flutter.PlatformMessage,
 		flutterEngine *flutter.EngineOpenGL,
 		window *glfw.Window,
 	) bool {
 
-		message := platMessage.Message
+		message := &platMessage.Message
 
 		switch message.Method {
 		case textInputClientClear: