Edge windows

           |
           |
           | <- copy gets rendered here
           |
+----window+
|          |
|          |
|          |
|          |
+----------+
     ^
  Viewport

-------------------------------------

non-edge windows

        |          |
        |          |
copy -> |          | <- copy
        |          |
        +--window--+
        |          |
        |          |
        |          |
        |          |
        +----------+
              ^
          Viewport