refactor: Split init call of Plugin & PluginGLFW

Plugin interface doesn't need a glfw.Window to be instantiated.
Calling the init function of the Plugin interface improves the
flexibility. #137

Author: Drakirus

application.go

@@ -62,6 +62,16 @@ func (a *Application) Run() error {
 	}
 	defer glfw.Terminate()
 
+	a.engine = embedder.NewFlutterEngine()
+
+	messenger := newMessenger(a.engine)
+	for _, p := range a.config.plugins {
+		err = p.InitPlugin(messenger)
+		if err != nil {
+			return errors.Wrap(err, "failed to initialize plugin "+fmt.Sprintf("%T", p))
+		}
+	}
+
 	a.window, err = glfw.CreateWindow(a.config.windowInitialDimensions.x, a.config.windowInitialDimensions.y, "Loading..", nil, nil)
 	if err != nil {
 		return errors.Wrap(err, "creating glfw window")
@@ -83,15 +93,7 @@ func (a *Application) Run() error {
 		}
 	}
 
-	a.engine = embedder.NewFlutterEngine()
-
-	messenger := newMessenger(a.engine)
 	for _, p := range a.config.plugins {
-		err = p.InitPlugin(messenger)
-		if err != nil {
-			return errors.Wrap(err, "failed to initialize plugin "+fmt.Sprintf("%T", p))
-		}
-
 		// Extra init call for plugins that satisfy the PluginGLFW interface.
 		if glfwPlugin, ok := p.(PluginGLFW); ok {
 			err = glfwPlugin.InitPluginGLFW(a.window)

plugin.go

@@ -13,9 +13,10 @@ import (
 // The BinaryMessenger is passed to allow the plugin to register channels.
 // A plugin may optionally implement PluginGLFW.
 type Plugin interface {
-	// InitPlugin is called during the startup of the flutter application. The
-	// plugin is responsible for setting up channels using the BinaryMessenger.
-	// If an error is returned it is printend the application is stopped.
+	// InitPlugin is called before creating the GLFW window of the flutter
+	// application. The plugin is responsible for setting up channels using the
+	// BinaryMessenger.
+	// If an error is returned it is printed the application is stopped.
 	InitPlugin(messenger plugin.BinaryMessenger) error
 }
 
@@ -26,14 +27,15 @@ type Plugin interface {
 //
 // PluginGLFW is separated because not all plugins need to know about glfw,
 // Adding glfw.Window to the InitPlugin call would add glfw as dependency to
-// every plugin implementation. Also, this helps in a scenarion where glfw is
+// every plugin implementation. Also, this helps in a scenario where glfw is
 // moved into a separate renderer/glfw package.
 //
 // The PluginGLFW interface is not stable and may change at any time.
 type PluginGLFW interface {
-	// Any type inmplementing PluginGLFW must also implement Plugin.
+	// Any type implementing PluginGLFW must also implement Plugin.
 	Plugin
-	// InitPluginGLFW is called after the call to InitPlugin. When an error is
-	// returned it is printend the application is stopped.
+	// InitPluginGLFW is called after the flutter engine is linked to the GLFW
+	// window. When an error is returned it is printed the application is
+	// stopped.
 	InitPluginGLFW(window *glfw.Window) error
 }