Re: Awfull rendering of fonts in KDE terminal with nouveau 1.0.3 drivers

[Thomas Lübking]

On Montag, 5. November 2012 11:19:00 CEST, Łukasz Maśko wrote:

> $ xrandr
> Screen 0: minimum 320 x 200, current 1600 x 1200, maximum 8192 x 8192
> DVI-I-1 connected 1600x1200+0+0 (normal left inverted right x 
> axis y axis) 352mm x 264mm
>    1600x1200      85.0*+   75.0     70.0     65.0     60.0     
> 1280x1024      85.0 +   75.0     60.0  [...]
> DVI-I-2 disconnected (normal left inverted right x axis y axis)
>
> So the card works in 1600x1200. BUT if I execute this:
>
> xrandr --output DVI-I-1 --mode 1600x1200 --scale 0.8x0.8533, 
> xrandr gives this (just a part again):
>
> $ xrandr
> Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
> DVI-I-1 connected 1600x1200+0+0 (normal left inverted right x 
> axis y axis) 352mm x 264mm
>    1600x1200      85.0*+   75.0     70.0     65.0     60.0     
> 1280x1024      85.0 +   75.0     60.0  [...]
>
> and fonts are rendered in a much better (i.e. readable) way.

> What may be even more important, if I just use 1280x1024 mode 
> directly (xrandr --output DVI-I-1 --mode 1280x1024), fonts are 
> crisp and perfectly rendered. This is why I suppose, that 
> somehow internally, font rendering either works with a wrong 
> DPI, or wrong resolution. By the way, I'm using internal font 
> renderer of Xorg, not the external xfs.

If the fonts were actually rendered wrong, that would be notable on screenshots. "Wrong" DPI would cause tiny or large, but not blurry fonts.

Since there's also no relation to the compositor or the ARGB state of the window, yet the problem is (is it?) restricted to konsole, i'm out of ideas.

Observation:
you're running 1600x1200 at 85Hz while basic Single Link DVI has it's maximum at 1600x1200 at 60Hz

To run higher resolutions or frequency, the entire chain has to support reduced blanking capabilities and there's recently been a mail which suggested this was broken in "older" versions of "something" (worked in some recent ubuntu, but not debian)

This would impact _everything_ but might be only notable in the bright-on-black context of konsole.

So you should either absolutely ensure that the entire HW chain (output, cable, input) is Dual Link DVI (full pins, no gap the the plug) or try the outcome of 1600x1200 at 60Hz (yes, 60Hz on crts suck) or try a vga connection.

xrandr --output DVI-I-1 --mode 1600x1200 --rate 60

If this is crisp (but flickers.. that's normal) there's your problem.

I'd nearly bet your right arm, that the nouveau driver version does somehow fail on reduced blanking while the nvidia blob does not.

Cheers,
Thomas