Added Post() and implemented it on Windows.

stdwndclass_windows.go

@@ -108,6 +108,10 @@ func stdWndProc(hwnd _HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) _LRESUL
 		return storeSysData(hwnd, uMsg, wParam, lParam)
 	}
 	switch uMsg {
+	case msgPost:
+		data := (*interface{})(unsafe.Pointer(lParam))
+		s.post(*data)
+		return 0
 	case _WM_COMMAND:
 		id := _HMENU(wParam.LOWORD())
 		s.childrenLock.Lock()

sysdata.go

@@ -9,8 +9,9 @@ type cSysData struct {
 	spaced	bool
 	alternate bool        // editable for Combobox, multi-select for listbox, password for lineedit
 	handler   AreaHandler // for Areas; TODO rename to areahandler
-	close	func() bool	// provided by each Window
-	event	func()		// provided by each control
+	close	func() bool		// provided by each Window
+	post		func(interface{})	// provided by each Window
+	event	func()			// provided by each control
 }
 
 // this interface is used to make sure all sysDatas are synced

test/main.go

@@ -249,12 +249,13 @@ func areaTest() {
 	layout.SetStretchy(0)
 	w := NewWindow("Area Test", 100, 100)
 	w.Closing = die
+	w.Posted = func(data interface{}) {
+		timedisp.SetText(data.(string))
+	}
 	w.Open(layout)
 	go func() {
 		for t := range timechan {
-			// TODO
-			_ = t
-//			timedisp.SetText(t.String())
+			Post(w, t.String())
 		}
 	}()
 }

uitask.go

@@ -26,6 +26,14 @@ func Go(start func()) error {
 	return nil
 }
 
+// Post issues a request to the given Window to do something on the main thread.
+// Note the name of the function: there is no guarantee that the request will be handled immediately.
+// Because this can be safely called from any goroutine, it is a package-level function, and not a method on Window.
+// TODO garbage collection
+func Post(w *Window, data interface{}) {
+	uipost(w, data)
+}
+
 // TODO this needs to be replaced with a function
 // Stop should be pulsed when you are ready for Go() to return.
 // Pulsing Stop will cause Go() to return immediately; the programmer is responsible for cleaning up (for instance, hiding open Windows) beforehand.

uitask_windows.go

@@ -29,6 +29,7 @@ const (
 	msgQuit = _WM_APP + iota + 1			// + 1 just to be safe
 	msgSetAreaSize
 	msgRepaintAll
+	msgPost
 )
 
 func uiinit() error {
@@ -66,6 +67,15 @@ func ui() {
 	msgloop()
 }
 
+// we'll use SendMessage() here, which will do a thread switch, call the function immediately, and wait for it to return, so we don't have to worry about the garbage collector collecting data
+func uipost(w *Window, data interface{}) {
+	_sendMessage.Call(
+		uintptr(w.sysData.hwnd),		// note: we pass this directly to the window
+		msgPost,
+		0,
+		uintptr(unsafe.Pointer(&data)))
+}
+
 var (
 	_dispatchMessage  = user32.NewProc("DispatchMessageW")
 	_getActiveWindow		= user32.NewProc("GetActiveWindow")

window.go

@@ -15,6 +15,11 @@ type Window struct {
 	// If Closing is nil, a default which rejects the close will be used.
 	Closing		func() bool
 
+	// Posted is called when Post() is called with the given Window as an argument.
+	// It receives the data passed to Post() as an argument.
+	// If Posted is nil, a default handler which does nothing will be used.
+	Posted		func(data interface{})
+
 	created    bool
 	sysData    *sysData
 	initTitle  string
@@ -87,6 +92,10 @@ func (w *Window) Create(control Control) {
 			return false
 		}
 	}
+	w.sysData.post = w.Posted
+	if w.sysData.post == nil {
+		w.sysData.post = func(data interface{}) {}
+	}
 	err := w.sysData.make(nil)
 	if err != nil {
 		panic(fmt.Errorf("error opening window: %v", err))