[Bug 94820] Nearest neighbor scaling?

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94820

--- Comment #7 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to nw9165-3201 from comment #6)
> (In reply to Alex Deucher from comment #5)
> > The randr scale options use the 3D engine.  Picking a non-native mode to
> > display on the panel uses either the scaler in the monitor (default for
> > external monitors) or the scaler on the GPU's display controller (default
> > for fixed laptop panels).
> 
> Thanks for the swift reply. Okay, so first question:
> 
> You said the scaler on the GPU's display controller is only used for fixed
> laptop panels by default.
> 
> Why is that?

Some people prefer the monitor's scaler.  It's not always clear which mode is
the monitors native mode so you could theoretically end up with double scaling
(once on the monitor, once on the GPU).

> 
> And is it possible to use the scaler on the GPU's display controller for
> external monitors as well?
> 
> If yes: How?

Yes:
xrandr --output <output> --set "scaling mode" "<scaling mode>"
Where scaling mode is one of:
None, Full, Center, Full aspect
E.g.,
xrandr --output DVI-0 --set "scaling mode" "Full aspect"

> 
> And, to come back to what Grigori and me were hinting at: Is it possible to
> tell the scaler on the GPU's display controller to use nearest neighbor
> scaling? Is it possible to change the filter of the scaler on the GPU's
> display controller?
> 
> If yes: How?

I'm not sure what algorithm(s) the display scaler uses or can use off hand.  We
just use whatever the default is.

Alex

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