Top-most windows

[Soeren Sandmann]

Keith Packard wrote:

>No, in the compositing world, grabbing the server isn't really that
>nasty -- you can't see any changes unless the compositing manager paints
>them in any case, so it hardly matters if the compositing manager has
>the server grabbed. In fact, you might well get better performance
>overall as this will tend to 'batch' other application window updates
>when the compositing manager is especially busy.
>
>I agree that grabbing the server is generally an ugly idea, but at least
>for now I suggest we give this a try as it *requires no X server
>changes*.
>  
>
For what it's worth, the metacity compositor works with no semantic changes
or extensions to the X server. What it does is:

- RedirectSubwindows on root window
- Create screensized output window that is a child of the root
- Unredirect this window
- Set empty input shape
- before drawing, raise the window to the top of the stack

It doesn't grab the server, although it probably should. The changes I 
need to the X server
are just bug fixes, although they are fairly bad bugs  - see 5272 - 5276.

The output window has background None so that raising it on top of other 
windows doesn't
cause ugly flickers. But this is just a workaround for another bug: 
restacking redirected
windows below a non-redirected window should not cause 
expose/background-painting for
the \non-redirected window.

I haven't yet thought much about input redirection, although my 
impression was that Xevie
would be adequate.


Soren