libxrandr XRRGetCrtcInfo() misinterpretation by nouveau or NVIDIA?

Aaron Plattner aplattner at
Fri Jun 19 13:50:58 PDT 2015

On 06/19/2015 03:49 AM, Thomas Richter wrote:
> Am 19.06.2015 um 12:38 schrieb Chris Wilson:
>> Why is it that in the presence of randr1.3 XRRGetCrtcInfo()  returns
>> semantically(!) different information
>> than XRRGetCrtcInfo() with randr1.2 only? In the former case, it returns
>> the entire panning area. In the latter case,
>> it returns only the visible monitor size.
>> RR1.3 introduced panning. Without panning, the visible area of the CRTC
>> is exactly defined by the mode, rotation, transformation and offset.
>> Basically nvidia have only implemented half of the extension. They allow
>> you to set panning, but don't report it back to the application.
>> -Chris
> Thank you, now that makes sense! IOW, the panning I have with randr1.2
> here on NVIDIA is a proprietary extension
>  to randr1.2 that is not officially present and was added "on top"
> without implementing the 1.3 interface that actually
> communicates panning information.

Yes, the panning support there has been around for many, many years and
certainly predates RandR 1.2.  Getting the semantics of that wired up to
what RandR 1.3 expects was a little tricky, but it should have been
implemented in the 319.* driver series.  I'll see if I can find some
time to reproduce the problem and get a bug filed.

> Ok, so source of the bug identified. NVIDIA. If I only had a chance to
> talk to some engineer there and not just the
> average "support" people...
> Thanks for your patience!
> Thomas


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