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

Michel Dänzer michel at daenzer.net
Mon Feb 5 11:53:06 UTC 2018

On 2018-02-02 09:56 PM, Keith Packard wrote:
> Michel Dänzer <michel at daenzer.net> writes:
>> 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.
> And this is the main reason I didn't really worry about flipping window
> pixmaps -- the application window was generally contained within a
> window manager frame, which (typically) also contains window management
> decorations. So the application window is generally smaller than the
> frame, so the pixmap can't just be flipped. With client-side
> decorations, or other techniques that make the client geometry match
> that of the redirected window, figuring out how to do this makes good
> sense.

The motivation for this work is fullscreen applications with Xwayland.

>>> 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.
>> How?
> If it's a DRM buffer passed to the server, then the client has a direct
> handle to the object?

Above, Roman wrote the client can control *the original window pixmap*.
I'm asking how it can do that.

>> The inability to queue a presentation to the next MSC is more of a step
>> back compared to the status quo.
> I'm about to go write up some ideas I'm working on that will make it
> possible to more regularly display redirected windows at the target MSC,
> and to reliably report which MSC the window contents were displayed at.
> I mention this because I think there are some parallels between that
> work and this.

Not really seeing that. Composite isn't involved with Xwayland.

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

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