Re: Syncing the guest display resolution with the host in fullscreen

[Jakob Bohm]

On 2024-07-08 08:00, Thomas Huth wrote:
> On 06/07/2024 00.46, Anton Shepelev wrote:
> > Thomas Huth:
> >
> > > I had a quick look, but if I got this right, 1366x768 is
> > > not a mode that fits into the standard EDID information,
> > > since 1366 is not dividable by 8.
> >
> > Thank you very much Thomas.  That also explains why get-
> > edid(1) does not work on this laptop.
> >
> > > See also
> > > https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#Limitations 
> > >
> > > for some more information.
> >
> > It says:
> >
> >     For 1366x768 pixel Wide XGA panels the nearest resolution
> >     expressible in the EDID standard timing descriptor syntax
> >     is 1360x765 pixels, typically leading to 3 pixel thin
> >     black bars.
> >
> > I can live with 3-pixel black bars, if QEMU will only enter
> > a corresponding full-screen mode.  What I cannot live with,
> > is a scaled image with intepolative blur or other artefacts.
>
> QEMU already enables 1360x768 in the EDID information, see:
>
>
> https://gitlab.com/qemu-project/qemu/-/blob/master/hw/display/edid-generate.c#L18 
>
>
> ... but I've got no clue why guests don't offer that screen resolution 
> ... I still assume this resolution is something special that the 
> driver in the guest has to support explicitly.
1366x768 is a very common display size in real hardware, as it is the
closestapproximation to 16:9 at 768p, see the discussion at

 https://en.wikipedia.org/wiki/Display_resolution_standards#1366x768

Commercial display drivers are likely to have it as a tested use case,
possiblywith some non-EDID detection method.Maybe the DisplayID data
format allows returning 1366 pixels as width even when delivered over
an EDID connection.

Duckducking for 1366x768 EDID returns some troubleshooting conversations
about making various drivers (including the X11 nVidia driver) use it,
but no explanation of what such monitors typically return in their EDID
messages to drivers.

Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
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