Implement flutter/mousecursor (#445)

Author: jld3103

application.go

@@ -54,6 +54,7 @@ func NewApplication(opt ...Option) *Application {
 	opt = append(opt, AddPlugin(defaultLifecyclePlugin))
 	opt = append(opt, AddPlugin(defaultKeyeventsPlugin))
 	opt = append(opt, AddPlugin(defaultAccessibilityPlugin))
+	opt = append(opt, AddPlugin(defaultMousecursorPlugin))
 
 	// apply all configs
 	for _, o := range opt {

mousecursor.go

@@ -0,0 +1,60 @@
+package flutter
+
+import (
+	"errors"
+	"fmt"
+	"github.com/go-flutter-desktop/go-flutter/plugin"
+	"github.com/go-gl/glfw/v3.3/glfw"
+)
+
+const mousecursorChannelName = "flutter/mousecursor"
+
+// mousecursorPlugin implements flutter.Plugin and handles method calls to the
+// flutter/mousecursor channel.
+type mousecursorPlugin struct {
+	window     *glfw.Window
+	lastCursor *glfw.Cursor
+}
+
+var defaultMousecursorPlugin = &mousecursorPlugin{}
+
+func (p *mousecursorPlugin) InitPlugin(messenger plugin.BinaryMessenger) error {
+	channel := plugin.NewMethodChannel(messenger, mousecursorChannelName, plugin.StandardMethodCodec{})
+	channel.HandleFuncSync("activateSystemCursor", p.handleActivateSystemCursor)
+	return nil
+}
+func (p *mousecursorPlugin) InitPluginGLFW(window *glfw.Window) error {
+	p.window = window
+	return nil
+}
+
+func (p *mousecursorPlugin) handleActivateSystemCursor(arguments interface{}) (reply interface{}, err error) {
+	args := arguments.(map[interface{}]interface{})
+	var cursor *glfw.Cursor
+	if args["kind"] == "none" {
+		p.window.SetInputMode(glfw.CursorMode, glfw.CursorHidden)
+	} else {
+		p.window.SetInputMode(glfw.CursorMode, glfw.CursorNormal)
+	}
+	switch kind := args["kind"]; {
+	case kind == "none":
+	case kind == "basic" || kind == "forbidden" || kind == "grab" || kind == "grabbing":
+		// go-gl GLFW currently (latest tagged v3.3 version) has no cursors for "forbidden", "grab" and "grabbing"
+		// TODO: Wait for https://github.com/glfw/glfw/commit/7dbdd2e6a5f01d2a4b377a197618948617517b0e to appear in go-gl GLFW and implement the "forbidden" cursor
+		cursor = glfw.CreateStandardCursor(glfw.ArrowCursor)
+	case kind == "click":
+		cursor = glfw.CreateStandardCursor(glfw.HandCursor)
+	case kind == "text":
+		cursor = glfw.CreateStandardCursor(glfw.IBeamCursor)
+	default:
+		return nil, errors.New(fmt.Sprintf("cursor kind %s not implemented", args["kind"]))
+	}
+	if p.lastCursor != nil {
+		p.lastCursor.Destroy()
+	}
+	if cursor != nil {
+		p.window.SetCursor(cursor)
+		p.lastCursor = cursor
+	}
+	return nil, nil
+}