XDamage extension over-reports window damage

[Owen Taylor]

On Sat, 2005-01-29 at 11:27 -0500, Jonathan Lennox wrote:
> On Thursday, January 27 2005, "Owen Taylor" wrote to "Jonathan Lennox, Keith Packard, xorg at lists.freedesktop.org" saying:
> 
> > Any impetus for action here is decreased by the move to  Composite that
> > is under way. Once we are keeping full contents for all toplevel
> > windows, they will never be covered, so tracking that isn't very
> > interesting.
> 
> For application sharing, there is (potentially) a motivation to keep track
> of what the user can actually *see* -- the idea is that if the user covers
> up part of a window with another one, the application sharing server
> shouldn't send that window part, for privacy reasons.

Sounds a bit annoying ... like having two people confined to work 
on a 1 ft square desk. "Hey, move your paper, I'm looking at that!" :-)

> As Joel Dice mentioned, with the current X protocol, it's possible for a
> client to manually track the positions and stacking of all top-level windows
> and so compute which parts of the windows of interest are visible to the
> user.
> 
> Is this possible with the composite extension?  I'm not very familiar with
> the details of that.

Is a window visible if another translucent window is on top?
Is a window visible if it is on a different desktop with a live
thumbnail?
Is a window visible if it is turned in 3d at an extreme angle from the
viewer?

All of these things have been done already with the composite extension.
The compositing manager / window manager could give hints to the
application about what is visible via properties, but I don't think the
concept makes sense at the base window system level.

Regards,
						Owen

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