Q: Xserver / Composite behavior

[Russell Shaw]

Carsten Haitzler (The Rasterman) wrote:
> On Sun, 08 Jan 2006 12:34:05 +1100 Russell Shaw <rjshaw at netspace.net.au>
> babbled:
> 
>>Keith Packard wrote:
>>
>>>On Sun, 2006-01-08 at 01:46 +0100, Amir Bukhari wrote:
>>>
>>>>What happend when application move it's top level window out side root
>>>>window. Example: screen is 1200x1024 and a window is moved to 1600,512 which
>>>>out side screen. Does Xserver will not alow it or it will only not be
>>>>visable?
>>>>does Xcomposite will stil render to off-screen pixmap?
>>>
>>>The entire contents of the redirected window are always available,
>>>independent of position or stacking.
>>
>>Isn't that a bit inefficient? If you had a 1000x1000 window scrolled
>>outside the root, it'd be wasting 4MB in a useless pixmap. No wonder
>>X is so slow;)
> 
> then dont use compositing! :) seriously - the contents are NEEDED! without them
> you cannto do loive pager/icon thumbnails - things like "expose" in osx are not
> possible etc. etc. etc.

I haven't got into great detail into the internals of the X server yet.
Can't you read and composite using the data from the video memory instead
of having another duplicating pixmap of the entire window, even if most of
it is clipped?

A slight bit of flicker happening while a menu is redrawn is a small price
for something that can work well in small hardware.

If full double buffering is required, it should remain as a Window attribute
that can be enabled or disabled.