support real transparency for controls that return HasTransparentBackground() in wxDFB

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47505 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/dfb/window.cpp

@@ -675,6 +675,7 @@ void wxWindowDFB::PaintWindow(const wxRect& rect)
 
     // FIXME_DFB: don't waste time rendering the area if it's fully covered
     //            by some children, go directly to rendering the children
+    //            (unless some child has HasTransparentBackground()=true!)
 
     // NB: unconditionally send wxEraseEvent, because our implementation of
     //     wxWindow::Refresh() ignores the eraseBack argument

src/univ/winuniv.cpp

@@ -361,6 +361,11 @@ bool wxWindow::DoDrawBackground(wxDC& dc)
     wxWindow * const parent = GetParent();
     if ( HasTransparentBackground() && !UseBgCol() && parent )
     {
+        // DirectFB paints the parent first, then its child windows, so by
+        // the time this code is called, parent's background was already
+        // drawn and there's no point in (imperfectly!) duplicating the work
+        // here:
+#ifndef __WXDFB__
         wxASSERT( !IsTopLevel() );
 
         wxPoint pos = GetPosition();
@@ -383,6 +388,7 @@ bool wxWindow::DoDrawBackground(wxDC& dc)
 
         // Restore DC logical origin
         dc.SetLogicalOrigin( org_x, org_y );
+#endif // !__WXDFB__
     }
     else
     {