Split sysData.show() into separate show() and firstShow() to accomodate Windows's differing rules for first-time window show; this will also allow me to remove the error returns from sysData.show() and sysData.hide() (later).

sysdata.go

@@ -22,6 +22,9 @@ type cSysData struct {
 func (c *cSysData) make(initText string, window *sysData) error {
 	panic(runtime.GOOS + " sysData does not define make()")
 }
+func (c *cSysData) firstShow() error {
+	panic(runtime.GOOS + " sysData does not define firstShow()")
+}
 func (c *cSysData) show() error {
 	panic(runtime.GOOS + " sysData does not define show()")
 }

sysdata_darwin.go

@@ -314,6 +314,12 @@ func (s *sysData) make(initText string, window *sysData) error {
 	return nil
 }
 
+// used for Windows; nothing special needed elsewhere
+func (s *sysData) firstShow() error {
+	s.show()
+	return nil
+}
+
 func (s *sysData) show() error {
 	ret := make(chan struct{})
 	defer close(ret)

sysdata_unix.go

@@ -156,6 +156,12 @@ func (s *sysData) make(initText string, window *sysData) error {
 	return nil
 }
 
+// used for Windows; nothing special needed elsewhere
+func (s *sysData) firstShow() error {
+	s.show()
+	return nil
+}
+
 func (s *sysData) show() error {
 	ret := make(chan struct{})
 	defer close(ret)

sysdata_windows.go

@@ -15,7 +15,6 @@ type sysData struct {
 	children			map[_HMENU]*sysData
 	nextChildID		_HMENU
 	childrenLock		sync.Mutex
-	shownAlready		bool
 }
 
 type classData struct {
@@ -190,25 +189,18 @@ var (
 // if the object is a window, we need to do the following the first time
 // 	ShowWindow(hwnd, nCmdShow);
 // 	UpdateWindow(hwnd);
-// otherwise we go ahead and show the object normally with SW_SHOW
-func (s *sysData) show() (err error) {
-	if s.ctype != c_window {		// don't do the init ShowWindow/UpdateWindow chain on non-windows
-		s.shownAlready = true
-	}
-	show := uintptr(_SW_SHOW)
-	if !s.shownAlready {
-		show = uintptr(nCmdShow)
-	}
+func (s *sysData) firstShow() error {
 	ret := make(chan uiret)
 	defer close(ret)
-	// TODO figure out how to handle error
 	uitask <- &uimsg{
 		call:		_showWindow,
-		p:		[]uintptr{uintptr(s.hwnd), show},
+		p:		[]uintptr{
+			uintptr(s.hwnd),
+			uintptr(nCmdShow),
+		},
 		ret:		ret,
 	}
 	<-ret
-	if !s.shownAlready {
 	uitask <- &uimsg{
 		call:		_updateWindow,
 		p:		[]uintptr{uintptr(s.hwnd)},
@@ -218,8 +210,21 @@ func (s *sysData) show() (err error) {
 	if r.ret == 0 {		// failure
 		return fmt.Errorf("error updating window for the first time: %v", r.err)
 	}
-		s.shownAlready = true
+	return nil
+}
+
+func (s *sysData) show() (err error) {
+	ret := make(chan uiret)
+	defer close(ret)
+	uitask <- &uimsg{
+		call:		_showWindow,
+		p:		[]uintptr{
+			uintptr(s.hwnd),
+			uintptr(_SW_SHOW),
+		},
+		ret:		ret,
 	}
+	<-ret
 	return nil
 }
 

window.go

@@ -90,7 +90,7 @@ func (w *Window) Open(control Control) (err error) {
 		return fmt.Errorf("error setting window size (in Window.Open()): %v", err)
 	}
 	// TODO separate showing?
-	err = w.sysData.show()
+	err = w.sysData.firstShow()
 	if err != nil {
 		return fmt.Errorf("error showing window (in Window.Open()): %v", err)
 	}