skins2: fix animated image flickering

Switch the layout activity to true before actually displaying the layout. This
gives controls a chance to reinitialize before any real drawing occurs, and
thus a clean animation gets displayed without any unwanted stray image.

This fixes trac #12083

modules/gui/skins2/src/top_window.cpp

@@ -361,13 +361,14 @@ void TopWindow::setActiveLayout( GenericLayout *pLayout )
     // Get the size of the layout and resize the window
     resize( pLayout->getWidth(), pLayout->getHeight() );
 
+    // The new layout is active
+    pLayout->getActiveVar().set( true );
+
     if( isVisible )
     {
         pLayout->onShow();
     }
 
-    // The new layout is active
-    pLayout->getActiveVar().set( true );
 }