Comment 4 for bug 770099

A possible solution:

When user hover a dragged icon onto an app icon at the launcher and stop the mouse motion during a while :

 - If there is no windows for the app:
      Do nothing.
 - If there is one window for the app:
      Raise that window allowing user to drop the dragged icon into the raised window.
 - If there are many windows for the app:
      Spread all windows for the application.
      Then user will move the cursor (and the dragged icon) to a window in the spread, when user stop the mouse motion during a while, that window will be raised and focused, allowing to drop the icon in that window.
      If user drop the icon before spread disappear (no window is raised), but the cursor is over a window, the behaviour should be the same if user drop the icon on the raised window.
      If user drop the icon before spread disappear, but the cursor is NOT over any window, the DnD should be canceled.

When user drop the icon directly in the launcher, the current behavior should be maintained.

For me, that is the dream behavour :) .