Added provisions for proper window redraw on Window.SetParent() and implemented them on Mac OS X; still untested.

redo/controls_darwin.go

@@ -11,7 +11,7 @@ import "C"
 
 type widgetbase struct {
 	id		C.id
-	parentw	*window
+	notnew	bool		// to prevent unparenting a new control
 	floating	bool
 }
 
@@ -24,17 +24,18 @@ func newWidget(id C.id) *widgetbase {
 // these few methods are embedded by all the various Controls since they all will do the same thing
 
 func (w *widgetbase) unparent() {
-	if w.parentw != nil {
+	if w.notnew {
+		// redrawing the old window handled by C.unparent()
 		C.unparent(w.id)
 		w.floating = true
-		w.parentw = nil
 	}
 }
 
 func (w *widgetbase) parent(win *window) {
+	// redrawing the new window handled by C.parent()
 	C.parent(w.id, win.id, toBOOL(w.floating))
 	w.floating = false
-	w.parentw = win
+	w.notnew = true
 }
 
 type button struct {

redo/controls_darwin.m

@@ -11,8 +11,13 @@
 
 void unparent(id control)
 {
+	NSWindow *old;
+
 	[toNSView(control) retain];		// save from being freed when released by the removal selector below
+	old = [toNSView(control) window];
 	[toNSView(control) removeFromSuperview];
+	// redraw since we changed controls
+	windowRedraw((id) old);
 }
 
 void parent(id control, id parentid, BOOL floating)
@@ -20,6 +25,8 @@ void parent(id control, id parentid, BOOL floating)
 	[[toNSWindow(parentid) contentView] addSubview:toNSView(control)];
 	if (floating)		// previously unparented
 		[toNSView(control) release];
+	// redraw since we changed controls
+	windowRedraw(parentid);
 }
 
 static inline void setStandardControlFont(id control)

redo/window.go

@@ -45,6 +45,5 @@ func (w *window) SetControl(control Control) {
 	control.unparent()
 	control.parent(w)
 	w.child = control
-	// TODO trigger a resize to let the new control actually be shown
-	// TODO do the same with control's old parent, if any
+	// each call to unparent() and parent() will cause the old/new parents to be redrawn; we don't have to worry about that here
 }

redo/window_darwin.m

@@ -65,12 +65,9 @@ void windowSetTitle(id win, const char * title)
 
 void windowShow(id win)
 {
-	goWindowDelegate *d;
-
 	[toNSWindow(win) makeKeyAndOrderFront:toNSWindow(win)];
 	// calling the above the first time won't emit a size changed event (unlike on Windows and GTK+), so fake one to get the controls laid out properly
-	d = [toNSWindow(win) delegate];
-	[d doWindowResize:win];
+	windowRedraw(win);
 }
 
 void windowHide(id win)
@@ -82,3 +79,12 @@ void windowClose(id win)
 {
 	[toNSWindow(win) close];
 }
+
+// fake a resize event under certain conditions; see each invocation for details
+void windowRedraw(id win)
+{
+	goWindowDelegate *d;
+
+	d = [toNSWindow(win) delegate];
+	[d doWindowResize:win];
+}