Mac OS: added visibility test necessary after a subwindow-containing group was hidden.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10951 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/Fl_cocoa.mm

@@ -735,7 +735,7 @@ void Fl::remove_timeout(Fl_Timeout_Handler cb, void* data)
   if (!NSEqualRects(rp, [self frame])) {
     [self setFrame:rp display:YES];
   }
-  if (![self parentWindow]) {
+  if (w->visible_r() && ![self parentWindow]) {
     [pxid addChildWindow:self ordered:NSWindowAbove]; // needs OS X 10.2
     [self orderWindow:NSWindowAbove relativeTo:[pxid windowNumber]]; // necessary under 10.3
   }