Wrote non-working code to get Windows to have Window sizes not count window decoration. Technically it does work, but it doesn't seem to fix Area scrollbars... which reminds me, the default configuration for the keyboard test exhibits the "last pixel" but mentioned in one of the TODOs in area_windows.go on both scrollbars, so let's fix that first anyway. I'll move the TODO for window decoration to the future plans after I get a definite answer about GTK+'s behavior.

experiments/winclientsize.go

@@ -0,0 +1,47 @@
+func (s *sysData) setWindowSize(width int, height int) error {
+	var rect _RECT
+
+	ret := make(chan uiret)
+	defer close(ret)
+	// we need the size to cover only the client rect
+	// unfortunately, Windows only provides general client->window rect conversion functions (AdjustWindowRect()/AdjustWindowRectEx()), not any that can pull from an existing window
+	// so as long as we don't change the window styles during execution we're good
+	// now we tell it to adjust (0,0)..(width,height); this will give us the approrpiate rect to get the proper width/height from
+	// then we call SetWindowPos() to set the size without moving the window
+	// see also: http://blogs.msdn.com/b/oldnewthing/archive/2003/09/11/54885.aspx
+	// TODO do the WM_NCCALCSIZE stuff on that post when adding menus
+	rect.Right = int32(width)
+	rect.Bottom = int32(height)
+	uitask <- &uimsg{
+		call:		_adjustWindowRectEx,
+		p:		[]uintptr{
+			uintptr(unsafe.Pointer(&rect)),
+			uintptr(classTypes[c_window].style),
+			uintptr(_FALSE),		// TODO change this when adding menus
+			uintptr(classTypes[c_window].xstyle),
+		},
+		ret:		ret,
+	}
+	r := <-ret
+	if r.ret == 0 {		// failure
+		panic(fmt.Errorf("error computing window rect from client rect for resize: %v", r.err))
+	}
+	uitask <- &uimsg{
+		call:		_setWindowPos,
+		p:		[]uintptr{
+			uintptr(s.hwnd),
+			uintptr(_NULL),			// not changing the Z-order
+			uintptr(0),
+			uintptr(0),
+			uintptr(rect.Right - rect.Left),
+			uintptr(rect.Bottom - rect.Top),
+			uintptr(_SWP_NOMOVE | _SWP_NOZORDER),
+		},
+		ret:		ret,
+	}
+	r = <-ret
+	if r.ret == 0 {		// failure
+		return fmt.Errorf("error actually resizing window: %v", r.err)
+	}
+	return nil
+}

windows_windows.go

@@ -166,6 +166,7 @@ const (
 )
 
 var (
+	_adjustWindowRectEx = user32.NewProc("AdjustWindowRectEx")
 	_createWindowEx = user32.NewProc("CreateWindowExW")
 	_getClientRect = user32.NewProc("GetClientRect")
 	_moveWindow = user32.NewProc("MoveWindow")