* qscreen.[Ch]:

* qscreen.[Ch]:
  - Cursor handing is done on the server -> *cursor are
    QPixmap
  - Use new drawScreen and copyScreen methods.
* QWorkArea.[Ch]:
  - Pixel manipulation is done on the client -> paint_device_ is a
    QImage
  - an intermediate Screen device is updated whenever expose is called
    -> sreen_device_ is a QPixmap. This screen_device is the one that is
    painted on screen in QWorkArea::repaintEvent().
  - new update, drawScreen and copyScreen methods.
* QLPainter.C: use the new paintDevice interface.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@13428 a592a061-630c-0410-9148-cb99ea01b6c8