Add initial implementation for system navigator pop event

Author: GeertJohan

application.go

@@ -36,13 +36,15 @@ func NewApplication(opt ...Option) *Application {
 		config: defaultApplicationConfig,
 	}
 
-	// The platformPlugin and textinputPlugin are currently hardcoded as we have
-	// a hard link with GLFW. The plugins must be singleton and are accessed
-	// directly from the flutter package to wire up with glfw. If there's going
-	// to be a renderer interface, it's init would replace this configuration.
+	// The platformPlugin, textinputPlugin, etc. are currently hardcoded as we
+	// have a hard link with GLFW. The plugins must be singleton and are
+	// accessed directly from the flutter package to wire up with glfw. If
+	// there's going to be a renderer interface, it's init would replace this
+	// configuration.
 	opt = append(opt, AddPlugin(defaultNavigationPlugin))
 	opt = append(opt, AddPlugin(defaultPlatformPlugin))
 	opt = append(opt, AddPlugin(defaultTextinputPlugin))
+	opt = append(opt, AddPlugin(defaultLifecyclePlugin))
 
 	// apply all configs
 	for _, o := range opt {
@@ -180,6 +182,8 @@ func (a *Application) Run() error {
 	a.window.SetKeyCallback(defaultTextinputPlugin.glfwKeyCallback)
 	a.window.SetCharCallback(defaultTextinputPlugin.glfwCharCallback)
 
+	a.window.SetIconifyCallback(defaultLifecyclePlugin.glfwIconifyCallback)
+
 	a.window.SetCursorEnterCallback(m.glfwCursorEnterCallback)
 	a.window.SetCursorPosCallback(m.glfwCursorPosCallback)
 	a.window.SetMouseButtonCallback(m.glfwMouseButtonCallback)

lifecycle.go

@@ -0,0 +1,40 @@
+package flutter
+
+import (
+	"fmt"
+
+	"github.com/go-flutter-desktop/go-flutter/plugin"
+	"github.com/go-gl/glfw/v3.2/glfw"
+)
+
+const lifecycleChannelName = "flutter/lifecycle"
+
+// lifecyclePlugin implements flutter.Plugin and handles method calls to the
+// flutter/lifecycle channel.
+type lifecyclePlugin struct {
+	channel *plugin.BasicMessageChannel
+}
+
+// all hardcoded because theres not pluggable renderer system.
+var defaultLifecyclePlugin = &lifecyclePlugin{}
+
+var _ Plugin = &lifecyclePlugin{} // compile-time type check
+
+func (p *lifecyclePlugin) InitPlugin(messenger plugin.BinaryMessenger) error {
+	p.channel = plugin.NewBasicMessageChannel(messenger, lifecycleChannelName, plugin.StringCodec{})
+	return nil
+}
+
+func (p *lifecyclePlugin) glfwIconifyCallback(w *glfw.Window, iconified bool) {
+	var state string
+	switch iconified {
+	case true:
+		state = "AppLifecycleState.paused"
+	case false:
+		state = "AppLifecycleState.resumed"
+	}
+	_, err := p.channel.Send(state)
+	if err != nil {
+		fmt.Printf("go-flutter: Failed to send lifecycle event %s: %v\n", state, err)
+	}
+}

navigation.go

@@ -7,7 +7,7 @@ import (
 const navigationChannelName = "flutter/navigation"
 
 // navigationPlugin implements flutter.Plugin and handles method calls to the
-// flutter/platform channel.
+// flutter/navigation channel.
 type navigationPlugin struct {
 	channel *plugin.MethodChannel
 }

platform.go

@@ -13,14 +13,18 @@ import (
 // platformPlugin implements flutter.Plugin and handles method calls to the
 // flutter/platform channel.
 type platformPlugin struct {
+	popBehavior PopBehaviorKind
+
 	messenger  plugin.BinaryMessenger
 	glfwTasker *tasker.Tasker
 	window     *glfw.Window
 	channel    *plugin.MethodChannel
 }
 
 // hardcoded because there is no swappable renderer interface.
-var defaultPlatformPlugin = &platformPlugin{}
+var defaultPlatformPlugin = &platformPlugin{
+	popBehavior: PopBehaviorNone,
+}
 
 var _ Plugin = &platformPlugin{}     // compile-time type check
 var _ PluginGLFW = &platformPlugin{} // compile-time type check
@@ -37,6 +41,7 @@ func (p *platformPlugin) InitPluginGLFW(window *glfw.Window) (err error) {
 	p.channel.HandleFunc("Clipboard.setData", p.handleClipboardSetData)
 	p.channel.HandleFunc("Clipboard.getData", p.handleClipboardGetData)
 	p.channel.HandleFunc("SystemChrome.setApplicationSwitcherDescription", p.handleWindowSetTitle)
+	p.channel.HandleFunc("SystemNavigator.pop", p.handleSystemNavigatorPop)
 
 	return nil
 }

plugin/method-channel.go

@@ -55,10 +55,13 @@ func (m *MethodChannel) InvokeMethod(name string, arguments interface{}) (result
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to send methodcall")
 	}
+	// TODO(GeertJohan): InvokeMethod may not return any JSON. In Java this is
+	// handled by not having a callback handler, which means no reponse is
+	// expected and reponse is never unmarshalled. We should perhaps define
+	// InvokeMethod(..) and InovkeMethodNoResponse(..) to avoid errors when no
+	// response is given.
+	// https://github.com/go-flutter-desktop/go-flutter/issues/141
 	result, err = m.methodCodec.DecodeEnvelope(encodedReply)
-	if flutterError, ok := err.(*FlutterError); ok {
-		return nil, flutterError
-	}
 	if err != nil {
 		return nil, err
 	}

pop.go

@@ -0,0 +1,67 @@
+package flutter
+
+import (
+	"fmt"
+
+	"github.com/pkg/errors"
+)
+
+// PopBehaviorKind defines how an application should handle the navigation pop
+// event from the flutter side.
+type PopBehaviorKind int
+
+const (
+	// PopBehaviorNone means the system navigation pop event is ignored.
+	PopBehaviorNone PopBehaviorKind = iota
+	// PopBehaviorHide hides the application window on a system navigation pop
+	// event.
+	PopBehaviorHide
+	// PopBehaviorIconify iconifies the application window on a system
+	// navigation pop event.
+	PopBehaviorIconify
+	// PopBehaviorClose closes the application on a system navigation pop event.
+	PopBehaviorClose
+)
+
+// PopBehavior sets the PopBehavior on the application
+func PopBehavior(popBehavior PopBehaviorKind) Option {
+	return func(c *config) {
+		// TODO: this is a workarround because there is no renderer interface
+		// yet. We rely on a platform plugin singleton to handle events from the
+		// flutter side. Should go via Application and renderer abstraction
+		// layer.
+		//
+		// Downside of this workarround is that it will configure the pop
+		// behavior for all Application's within the same Go process.
+		defaultPlatformPlugin.popBehavior = popBehavior
+	}
+}
+
+func (p *platformPlugin) handleSystemNavigatorPop(arguments interface{}) (reply interface{}, err error) {
+	switch p.popBehavior {
+	case PopBehaviorNone:
+		return nil, nil
+	case PopBehaviorHide:
+		p.glfwTasker.Do(func() {
+			p.window.Hide()
+		})
+		return nil, nil
+	case PopBehaviorIconify:
+		var err error
+		p.glfwTasker.Do(func() {
+			err = p.window.Iconify()
+		})
+		if err != nil {
+			fmt.Printf("go-flutter: error on iconifying window: %v\n", err)
+			return nil, errors.Wrap(err, "failed to iconify window")
+		}
+		return nil, nil
+	case PopBehaviorClose:
+		p.glfwTasker.Do(func() {
+			p.window.SetShouldClose(true)
+		})
+		return nil, nil
+	default:
+		return nil, errors.Errorf("unknown pop behavior %T not implemented by platform handler", p.popBehavior)
+	}
+}