Fixed the infinite loop on Tab control dialog message bug(s) on the Windows backend.

redo/container_windows.go

@@ -14,6 +14,7 @@ import "C"
 type container struct {
 	containerbase
 	hwnd		C.HWND
+	nchildren		int
 }
 
 type sizing struct {
@@ -45,12 +46,12 @@ func newContainer(control Control) *container {
 		panic(fmt.Errorf("inconsistency: hwnd returned by CreateWindowEx() (%p) and hwnd stored in container (%p) differ", hwnd, c.hwnd))
 	}
 	c.child = control
-	c.child.setParent(&controlParent{c.hwnd})
+	c.child.setParent(&controlParent{c})
 	return c
 }
 
-func (c *container) setParent(p *controlParent) {
-	C.controlSetParent(c.hwnd, p.hwnd)
+func (c *container) setParent(hwnd C.HWND) {
+	C.controlSetParent(c.hwnd, hwnd)
 }
 
 // this is needed because Windows won't move/resize a child window for us

redo/control_windows.go

@@ -11,11 +11,12 @@ type controlPrivate interface {
 }
 
 type controlParent struct {
-	hwnd	C.HWND
+	c	*container
 }
 
 func basesetParent(c controlPrivate, p *controlParent) {
-	C.controlSetParent(c.hwnd(), p.hwnd)
+	C.controlSetParent(c.hwnd(), p.c.hwnd)
+	p.c.nchildren++
 }
 
 // don't specify basepreferredSize; it is custom on ALL controls

redo/label_windows.go

@@ -57,7 +57,8 @@ func (l *label) settextlen(len C.LONG) {
 }
 
 func (l *label) setParent(p *controlParent) {
-	basesetParent(l, p)
+	C.controlSetParent(l.hwnd(), p.c.hwnd)
+	// don't increment p.c.nchildren here because Labels aren't tab stops
 }
 
 func (l *label) allocate(x int, y int, width int, height int, d *sizing) []*allocation {

redo/tab_windows.c

@@ -25,6 +25,8 @@ static LRESULT CALLBACK tabSubProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM l
 			return 0;
 		}
 		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	case msgTabCurrentTabHasChildren:
+		return (LRESULT) tabTabHasChildren((void *) data, SendMessageW(hwnd, TCM_GETCURSEL, 0, 0));
 	case WM_NCDESTROY:
 		if ((*fv_RemoveWindowSubclass)(hwnd, tabSubProc, id) == FALSE)
 			xpanic("error removing Tab subclass (which was for its own event handler)", GetLastError());

redo/tab_windows.go

@@ -34,7 +34,7 @@ func newTab() Tab {
 
 func (t *tab) Append(name string, control Control) {
 	c := newContainer(control)
-	c.setParent(&controlParent{t._hwnd})
+	c.setParent(t._hwnd)
 	t.tabs = append(t.tabs, c)
 	// initially hide tab 1..n controls; if we don't, they'll appear over other tabs, resulting in weird behavior
 	if len(t.tabs) != 1 {
@@ -55,6 +55,15 @@ func tabChanged(data unsafe.Pointer, new C.LRESULT) {
 	t.tabs[int(new)].show()
 }
 
+//export tabTabHasChildren
+func tabTabHasChildren(data unsafe.Pointer, which C.LRESULT) C.BOOL {
+	t := (*tab)(data)
+	if t.tabs[int(which)].nchildren > 0 {
+		return C.TRUE
+	}
+	return C.FALSE
+}
+
 func (t *tab) hwnd() C.HWND {
 	return t._hwnd
 }

redo/uitask_windows.c

@@ -41,17 +41,19 @@ void uimsgloop(void)
 				if (wcscmp(classchk, areaWindowClass) == 0)
 					dodlgmessage = FALSE;
 				else if (wcscmp(classchk, WC_TABCONTROL) == 0)
-					istab = TRUE;
+					// THIS BIT IS IMPORTANT
+					// if the current tab has no children, then there will be no children left in the dialog to tab to, and IsDialogMessageW() will loop forever
+					istab = (BOOL) SendMessageW(focus, msgTabCurrentTabHasChildren, 0, 0);
 			}
-			if (istab)
-				tabEnterChildren(focus);
-			// TODO this goes into an infinite loop on a blank tab
-			if (dodlgmessage)
+			if (dodlgmessage) {
+				if (istab)
+					tabEnterChildren(focus);
 				idm = IsDialogMessageW(active, &msg);
-			if (istab)
-				tabLeaveChildren(focus);
-			if (idm != 0)
-				continue;
+				if (istab)
+					tabLeaveChildren(focus);
+				if (idm != 0)
+					continue;
+			}
 		}
 		TranslateMessage(&msg);
 		DispatchMessageW(&msg);

redo/winapi_windows.h

@@ -29,6 +29,7 @@ enum {
 	msgNOTIFY,					// WM_NOTIFY proxy
 	msgAreaSizeChanged,
 	msgAreaRepaintAll,
+	msgTabCurrentTabHasChildren,
 };
 
 // uitask_windows.c

redo/window_windows.go

@@ -44,7 +44,7 @@ func newWindow(title string, width int, height int, control Control) *window {
 	if hresult != C.S_OK {
 		panic(fmt.Errorf("error setting tab background texture on Window; HRESULT: 0x%X", hresult))
 	}
-	w.container.setParent(&controlParent{w.hwnd})
+	w.container.setParent(w.hwnd)
 	return w
 }