cairo, xorg-lib-libXft: LCD

[Tomasz Pala]

On Fri, Mar 09, 2007 at 10:43:54PM +0100, Marcin 'Qrczak' Kowalczyk wrote:
> 
> Do you have an LCD monitor (with correctly configured RGB order)?

Yes (LG L1930B), I've checked order with magnyfying glass (it is R-G-B)
and the cairo/Xft is giving almost perfect view; I can barely notice
color fringes in fixed-width 'w' letter (when adding linuxnews comment)
and italic 'N' letter (with background of phpPgAdmin). They apperar only
in extremely small font sizes:

http://www.quarto.pl/~gotar/Xft-without-lcd-tiny.png
fully readable, color fringes visible in letters 'm' and 'j' (rightmost
part rendered redish as seen on zoom in 'więce_j_').

http://www.quarto.pl/~gotar/Xft-without-lcd-small.png
still readable, blue discolours appears in thin letters ('i', 'l' etc).

http://www.quarto.pl/~gotar/Xft-without-lcd-smaller.png
yeah, I can read this too;) Text lost its contrast, but there's no more
bad color placing than before!

http://www.quarto.pl/~gotar/Xft-without-lcd-smallest.png
ok, it's hard to read. But it's even harder to read the zoom!

That's my fontconfig configuration:

10-sub-pixel-rgb.conf
20-fix-globaladvance.conf
20-lohit-gujarati.conf
20-unhint-small-vera.conf
30-amt-aliases.conf
30-urw-aliases.conf
40-generic.conf
49-sansserif.conf
60-latin.conf
65-fonts-persian.conf
65-nonlatin.conf
69-unifont.conf
80-delicious.conf
90-synthetic.conf

> If yes, this is really supposed to look like this.

Well, I can't believe that 'l' letter at this size should be rendered as
yellow-black-blue vertical bars instead of just black... Take a look and
compare 'Digita_l_1' in http://www.quarto.pl/~gotar/cairo-lcd.png and
http://www.quarto.pl/~gotar/cairo-without-lcd.png. It looks like all the
text was shifted left in red phase and right in blue phase. And I do see
it on-screen.

> I was surprised too
> when I zoomed it in. It looks great in the original size, even though
> I'm not sure why.

Probably you're using unhinted font. Please read Keith and David posts
I've given links earlier. Until there's no way to configure this on
system level, please revert the bconds to default (not patched) cairo
and Xft libraries filtering. There's a reason why these patches are
still not incorporated.

-- 
Tom Pala <gotar at pld-linux.org>           http://vfmg.sourceforge.net/
                                         http://tccs.sourceforge.net/