title: Qt drag/drop: cannot move when copy is enabled (Ubuntu Gnome)
body: <p>I'm implementing a view and a model where I want to support both moving items internally (by dragging), and copying items (by pressing Ctrl while dragging). I've done everything I need to do according to the instructions. I've set up the mime functions, I've implemented removeRows(), and flags(). The problem is when I drag, it defaults to a copy operation (I get the arrow cursor with a plus sign, and it indeed copies the item by creating a new one in the model).</p>
  
  <p>The only difference I can see is this: If I return only Qt::MoveAction in supportedDropActions(), it only moves. If I return (Qt::CopyAction | Qt::MoveAction), it only copies.</p>
  
  <p>Any ideas? I want it to work like files in Nautilus (Gnome) or Windows file Explorer: drag moves icons around, ctrl+drag copies them.</p>