[PATCH 14/19] present: Add window flip mode

Michel Dänzer michel at daenzer.net
Fri Feb 2 11:08:23 UTC 2018

On 2018-02-02 10:42 AM, Roman Gilg wrote:
> It's because of what you made me aware of in the previous patch set:
> the window original pixmap needs to have the updated content from the
> flip Pixmap, otherwise for example screenshot applications won't work
> anymore. I tested it with xwd.

FWIW, my concerns were about using sub-surfaces in cases where the
presented pixmap dimensions don't match the window pixmap dimensions.

> I also tried to not copy, but set the window pixmap to the flip
> pixmap. The problem I encountered here, is that the window original
> pixmap can be controlled by the client.


> And when unflipping and restoring the original pixmap, this already
> might have been deleted by the client.

A pixmap is only destroyed when its refcnt member drops to 0, so that
shouldn't be an issue.

> There might be ways to circumvent this problem, I have a few ideas,
> but I decided to first go for a simple implementation by just copying
> the pixmap content in order to decrease the overall complexity of the
> patch set.

I'm not sure it would significantly increase the complexity, but fair
enough I guess.

The inability to queue a presentation to the next MSC is more of a step
back compared to the status quo.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

More information about the xorg-devel mailing list