refactor to break Run into register and native loop

example/main.go

@@ -6,8 +6,6 @@ import (
 	"io/ioutil"
 	"time"
 
-	"github.com/lxn/walk"
-
 	"github.com/getlantern/systray"
 	"github.com/getlantern/systray/example/icon"
 	"github.com/skratchdot/open-golang/open"
@@ -25,26 +23,8 @@ func main() {
 	}
 
 	if *webview {
-		systray.Register(onExit)
-		onReady()
-		mainWindow, err := walk.NewMainWindow()
-		if err != nil {
-			panic(fmt.Sprintf("Failed to create main window: %v\n", err))
-		}
-		mainWindow.SetTitle("Webview")
-		mainWindow.SetWidth(800)
-		mainWindow.SetHeight(600)
-		layout := walk.NewVBoxLayout()
-		if err := mainWindow.SetLayout(layout); err != nil {
-			panic(fmt.Sprintf("Failed to set layout: %v\n", err))
-		}
-		webView, err := walk.NewWebView(mainWindow)
-		if err != nil {
-			panic(fmt.Sprintf("Failed to create webview window: %v\n", err))
-		}
-		webView.SetURL("https://www.getlantern.org")
-		mainWindow.SetVisible(true)
-		mainWindow.Run()
+		systray.Register(onReady, onExit)
+		showWebviewOnWindows()
 	} else {
 		systray.Run(onReady, onExit)
 	}

example/webview_nonwindows.go

@@ -0,0 +1,7 @@
+//+build !windows
+
+package main
+
+func showWebviewOnWindows() {
+	panic("not implemented")
+}

example/webview_windows.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"github.com/lxn/walk"
+)
+
+func showWebviewOnWindows() {
+	mainWindow, err := walk.NewMainWindow()
+	if err != nil {
+		panic(fmt.Sprintf("Failed to create main window: %v\n", err))
+	}
+	mainWindow.SetTitle("Webview")
+	mainWindow.SetWidth(800)
+	mainWindow.SetHeight(600)
+	layout := walk.NewVBoxLayout()
+	if err := mainWindow.SetLayout(layout); err != nil {
+		panic(fmt.Sprintf("Failed to set layout: %v\n", err))
+	}
+	webView, err := walk.NewWebView(mainWindow)
+	if err != nil {
+		panic(fmt.Sprintf("Failed to create webview window: %v\n", err))
+	}
+	webView.SetURL("https://www.getlantern.org")
+	mainWindow.SetVisible(true)
+	mainWindow.Run()
+}

systray.go

@@ -1,8 +1,5 @@
 /*
 Package systray is a cross-platform Go library to place an icon and menu in the notification area.
-
-Methods can be called from any goroutine except Run(), which should be called
-at the very beginning of main() to lock at main thread.
 */
 package systray
 
@@ -16,11 +13,22 @@ import (
 )
 
 var (
-	hasStarted = int64(0)
-	hasQuit    = int64(0)
+	log = golog.LoggerFor("systray")
+
+	systrayReady  func()
+	systrayExit   func()
+	menuItems     = make(map[int32]*MenuItem)
+	menuItemsLock sync.RWMutex
+
+	currentID = int32(-1)
+	quitOnce  sync.Once
 )
 
-// MenuItem is used to keep track each menu item of systray
+func init() {
+	runtime.LockOSThread()
+}
+
+// MenuItem is used to keep track each menu item of systray.
 // Don't create it directly, use the one systray.AddMenuItem() returned
 type MenuItem struct {
 	// ClickedCh is the channel which will be notified when the menu item is clicked
@@ -60,25 +68,17 @@ func newMenuItem(title string, tooltip string, parent *MenuItem) *MenuItem {
 	}
 }
 
-var (
-	log = golog.LoggerFor("systray")
-
-	systrayReady  func()
-	systrayExit   func()
-	menuItems     = make(map[int32]*MenuItem)
-	menuItemsLock sync.RWMutex
-
-	currentID = int32(-1)
-)
-
 // Run initializes GUI and starts the event loop, then invokes the onReady
-// callback.
-// It blocks until systray.Quit() is called.
-// Should be called at the very beginning of main() to lock at main thread.
+// callback. It blocks until systray.Quit() is called.
 func Run(onReady func(), onExit func()) {
-	runtime.LockOSThread()
-	atomic.StoreInt64(&hasStarted, 1)
+	Register(onReady, onExit)
+	nativeLoop()
+}
 
+// Register initializes GUI and registers the callbacks but relies on the
+// caller to run the event loop somewhere else. It's useful if the program
+// needs to show other UI elements, for example, webview.
+func Register(onReady func(), onExit func()) {
 	if onReady == nil {
 		systrayReady = func() {}
 	} else {
@@ -92,38 +92,18 @@ func Run(onReady func(), onExit func()) {
 			close(readyCh)
 		}
 	}
-
 	// unlike onReady, onExit runs in the event loop to make sure it has time to
 	// finish before the process terminates
 	if onExit == nil {
 		onExit = func() {}
 	}
 	systrayExit = onExit
-
-	nativeLoop()
-}
-
-func Register(onExit func()) {
-	runtime.LockOSThread()
-	atomic.StoreInt64(&hasStarted, 1)
-	// unlike onReady, onExit runs in the event loop to make sure it has time to
-	// finish before the process terminates
-	if onExit == nil {
-		onExit = func() {}
-	}
-	systrayExit = onExit
-	register()
-}
-
-func Run2() {
-	run()
+	registerSystray()
 }
 
 // Quit the systray
 func Quit() {
-	if atomic.LoadInt64(&hasStarted) == 1 && atomic.CompareAndSwapInt64(&hasQuit, 0, 1) {
-		quit()
-	}
+	quitOnce.Do(quit)
 }
 
 // AddMenuItem adds a menu item with the designated title and tooltip.

systray.h

@@ -3,6 +3,7 @@
 extern void systray_ready();
 extern void systray_on_exit();
 extern void systray_menu_item_selected(int menu_id);
+void registerSystray(void);
 int nativeLoop(void);
 
 void setIcon(const char* iconBytes, int length, bool template);

systray_darwin.m

@@ -209,9 +209,12 @@ NSMenuItem *find_menu_item(NSMenu *ourMenu, NSNumber *menuId) {
 
 @end
 
-int nativeLoop(void) {
+void registerSystray(void) {
   AppDelegate *delegate = [[AppDelegate alloc] init];
   [[NSApplication sharedApplication] setDelegate:delegate];
+}
+
+int nativeLoop(void) {
   [NSApp run];
   return EXIT_SUCCESS;
 }

systray_linux.c

@@ -23,7 +23,7 @@ typedef struct {
 	short checked;
 } MenuItemInfo;
 
-int nativeLoop(void) {
+void registerSystray(void) {
 	gtk_init(0, NULL);
 	global_app_indicator = app_indicator_new("systray", "",
 			APP_INDICATOR_CATEGORY_APPLICATION_STATUS);
@@ -31,6 +31,9 @@ int nativeLoop(void) {
 	global_tray_menu = gtk_menu_new();
 	app_indicator_set_menu(global_app_indicator, GTK_MENU(global_tray_menu));
 	systray_ready();
+}
+
+int nativeLoop(void) {
 	gtk_main();
 	systray_on_exit();
 	return 0;

systray_nonwindows.go

@@ -15,6 +15,10 @@ import (
 	"unsafe"
 )
 
+func registerSystray() {
+	C.registerSystray()
+}
+
 func nativeLoop() {
 	C.nativeLoop()
 }

systray_windows.go

@@ -236,14 +236,17 @@ var wt winTray
 // https://msdn.microsoft.com/en-us/library/windows/desktop/ms633573(v=vs.85).aspx
 func (t *winTray) wndProc(hWnd windows.Handle, message uint32, wParam, lParam uintptr) (lResult uintptr) {
 	const (
-		WM_COMMAND    = 0x0111
-		WM_DESTROY    = 0x0002
-		WM_CLOSE      = 0x0010
-		WM_ENDSESSION = 0x16
 		WM_RBUTTONUP  = 0x0205
 		WM_LBUTTONUP  = 0x0202
+		WM_COMMAND    = 0x0111
+		WM_ENDSESSION = 0x0016
+		WM_CLOSE      = 0x0010
+		WM_DESTROY    = 0x0002
+		WM_CREATE     = 0x0001
 	)
 	switch message {
+	case WM_CREATE:
+		systrayReady()
 	case WM_COMMAND:
 		menuItemId := int32(wParam)
 		// https://docs.microsoft.com/en-us/windows/win32/menurc/wm-command#menus
@@ -712,13 +715,7 @@ func (t *winTray) iconToBitmap(hIcon windows.Handle) (windows.Handle, error) {
 	return windows.Handle(hMemBmp), nil
 }
 
-func nativeLoop() {
-	register()
-	go systrayReady()
-	run()
-}
-
-func register() {
+func registerSystray() {
 	if err := wt.initInstance(); err != nil {
 		log.Errorf("Unable to init instance: %v", err)
 		return
@@ -731,7 +728,7 @@ func register() {
 
 }
 
-func run() {
+func nativeLoop() {
 	// Main message pump.
 	m := &struct {
 		WindowHandle windows.Handle