1 files changed, 37 insertions, 12 deletions
diff --git a/uitask_windows.go b/uitask_windows.go
index 772403f..1075b5b 100644
--- a/uitask_windows.go
+++ b/uitask_windows.go
@@ -22,15 +22,17 @@ the only recourse, and the one both Microsoft (http://support.microsoft.com/kb/1
 yay.
 */
 
-var uimsgwin _HWND
+var uitask chan interface{}
 
-// works from any thread; waits for the function to finish before returning
-func uitask(f func()) {
-	_sendMessage.Call(
-		uintptr(uimsgwin),
-		msgRequested,
-		uintptr(0),
-		uintptr(unsafe.Pointer(&f)))
+type uimsg struct {
+	call *syscall.LazyProc
+	p    []uintptr
+	ret  chan uiret
+}
+
+type uiret struct {
+	ret uintptr
+	err error
 }
 
 const (
@@ -47,20 +49,34 @@ var (
 func ui(main func()) error {
 	runtime.LockOSThread()
 
+	uitask = make(chan interface{})
 	err := doWindowsInit()
 	if err != nil {
 		return fmt.Errorf("error doing general Windows initialization: %v", err)
 	}
 
-	uimsgwin, err = makeMessageHandler()
+	hwnd, err := makeMessageHandler()
 	if err != nil {
 		return fmt.Errorf("error making invisible window for handling events: %v", err)
 	}
 
 	go func() {
+		for m := range uitask {
+			r1, _, err := _postMessage.Call(
+				uintptr(hwnd),
+				msgRequested,
+				uintptr(0),
+				uintptr(unsafe.Pointer(&m)))
+			if r1 == 0 { // failure
+				panic("error sending message to message loop to call function: " + err.Error())
+			}
+		}
+	}()
+
+	go func() {
 		main()
 		r1, _, err := _postMessage.Call(
-			uintptr(uimsgwin),
+			uintptr(hwnd),
 			msgQuit,
 			uintptr(0),
 			uintptr(0))
@@ -162,8 +178,17 @@ func makeMessageHandler() (hwnd _HWND, err error) {
 func messageHandlerWndProc(hwnd _HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) _LRESULT {
 	switch uMsg {
 	case msgRequested:
-		f := (*func())(unsafe.Pointer(lParam))
-		(*f)()
+		mt := (*interface{})(unsafe.Pointer(lParam))
+		switch m := (*mt).(type) {
+		case *uimsg:
+			r1, _, err := m.call.Call(m.p...)
+			m.ret <- uiret{
+				ret: r1,
+				err: err,
+			}
+		case func():
+			m()
+		}
 		return 0
 	case msgQuit:
 		// does not return a value according to MSDN