Present extension changes needed for GL/Vulkan vblank modes

[Michel Dänzer]

On 17/10/17 10:48 AM, Michel Dänzer wrote:
> On 17/10/17 06:52 AM, Keith Packard wrote:
>>
>> PresentOptionRelative
>>
>>         If 'options' contains PresentOptionRelative, then the most
>>         recent actual MSC for a PresentPixmap request to the same
>>         drawable (i.e., the MSC value that would have been reported in
>>         the associated PresentCompleteNotify event) will be added to
>> [apparent copy-paste accident snipped]
>>         target-msc.
>>
>>         If no PresentPixmap request has been made to this drawable, then
>>         the current MSC value for the drawable will be added to
>>         target-msc.
> 
> I see an issue with basing the relative target on the last effective
> MSC: Imagine that the application misses a large number of frames, e.g.
> because the user hit Ctrl-Z. This means that the target MSC values will
> trail the drawable's current MSC, and the application's presentation
> timing may be "different" until it catches up.
> 
> 
> How about this instead: If there are pending PresentPixmap requests for
> the window, the relative target will be added to the latest target MSC
> of the pending requests.

Or maybe actual MSC instead of target MSC.

> Otherwise, it will be added to the drawable's current MSC.


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

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