Subpixel averaging

Subpixel averaging

[Chong Yidong]

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Although Emacs now performs anti-aliasing, it doesn't seem to perform
subpixel averaging.  I, for one, find the anti-aliased text in Emacs
blurry and very uncomfortable to read, especially when using
bright-on-dark color schemes.  As a result, I'm forced to use the old
fonts.

The attached screenshot shows the difference between gedit (top) and
Emacs 23 (bottom).


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I don't know how easy it is to add subpixel averaging.  Could someone
who has been working on this part of the code enlighten me?  Even if you
are too busy to work on this yourself, I'd appreciate it if you could
point me to the right starting place for adding this feature.

Re: Subpixel averaging

[Tom Rauchenwald]

Chong Yidong <cyd@stupidchicken.com> writes:

> Although Emacs now performs anti-aliasing, it doesn't seem to perform
> subpixel averaging.  I, for one, find the anti-aliased text in Emacs
> blurry and very uncomfortable to read, especially when using
> bright-on-dark color schemes.  As a result, I'm forced to use the old
> fonts.
>
> The attached screenshot shows the difference between gedit (top) and
> Emacs 23 (bottom).
>
> I don't know how easy it is to add subpixel averaging.  Could someone
> who has been working on this part of the code enlighten me?  Even if you
> are too busy to work on this yourself, I'd appreciate it if you could
> point me to the right starting place for adding this feature.

I don't know it that is the issue, but I have the following in my
.Xresources for that:

Xft.dpi:                96
Xft.hinting:            true
Xft.hintstyle:          hintfull
Xft.antialias:          rgba
Xft.rgba:               rgb

Tom

-- 
Then I drew in a breath, and my renewed will with it, lifted the rod
in my right hand, murmured a phrase in a language I didn't know, and
blew the tires off his fucking truck.
        -- Harry Dresden

Re: Subpixel averaging

[Chong Yidong]

Tom Rauchenwald <sehnsucht.nach.unendlichkeit@quantentunnel.de> writes:

>> Although Emacs now performs anti-aliasing, it doesn't seem to perform
>> subpixel averaging.  I, for one, find the anti-aliased text in Emacs
>> blurry and very uncomfortable to read, especially when using
>> bright-on-dark color schemes.  As a result, I'm forced to use the old
>> fonts.
>
> I don't know it that is the issue, but I have the following in my
> .Xresources for that:
>
> Xft.dpi:                96
> Xft.hinting:            true
> Xft.hintstyle:          hintfull
> Xft.antialias:          rgba
> Xft.rgba:               rgb

That does indeed work.  Many thanks.

But none of the other applications on the Gnome desktop seem to need
these tweaking.  Why is Emacs the only one?

Re: Subpixel averaging

[Andreas Schwab]

Chong Yidong <cyd@stupidchicken.com> writes:

> But none of the other applications on the Gnome desktop seem to need
> these tweaking.  Why is Emacs the only one?

Works for me without the tweaking.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Subpixel averaging

[James Cloos]

>>>>> "Chong" == Chong Yidong <cyd@stupidchicken.com> writes:

Chong> But none of the other applications on the Gnome desktop seem to
Chong> need these tweaking.  Why is Emacs the only one?

Gnome uses gconf for configuration rather than xrm resources.

The following is all I have in xrm related to Emacs, and -- when
combined with my fonts.conf config -- does generate subpixel fonts:

,----[ .Xdefaults excerpt ]
|       Xft.rgba: rgb
|
| Emacs.toolBar: off
| Emacs.menuBar: off
| *FontBackend: xft
| emacs.font: DejaVu Sans Mono:pixelsize=14
`----

,----[ .fonts.conf excerpt ]
| <?xml version="1.0"?>
| <fontconfig>
|
|  <match target="font" >
|   <edit mode="assign" name="hinting" >
|    <bool>true</bool>
|   </edit>
|  </match>
| 
|  <match target="font" >
|   <edit mode="assign" name="hintstyle" >
|    <const>hintfull</const>
|   </edit>
|  </match>
| 
|  <match target="font" >
|   <edit mode="assign" name="rgba" >
|    <const>rgb</const>
|   </edit>
|  </match>
|
| </fontconfig>
`----

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6

Re: Subpixel averaging

[Chong Yidong]

Andreas Schwab <schwab@suse.de> writes:

> Chong Yidong <cyd@stupidchicken.com> writes:
>
>> But none of the other applications on the Gnome desktop seem to need
>> these tweaking.  Why is Emacs the only one?
>
> Works for me without the tweaking.

Well, it's strange.  I just tried it on my laptop, and the fonts look OK
there.  To be precise, Xft.hinting defaults to true (though
Xft.hintstyle is not hintfull).  On my desktop, Xft.hinting defaults to
false.

The funny thing is that both are running Ubuntu gutsy, though the laptop
is a fresh install whereas the desktop was upgraded from Ubuntu feisty.
I suppose it's simply a matter of the OS neglecting to set the
appropriate default Xresources.  And, and James Cloos pointed out, the
Gnome applications are not affected because they don't use xrm.

Maybe we should provide Lisp variables to allow setting the hintstyle
from within Emacs.

Re: Subpixel averaging

[Stephen J. Turnbull]

Chong Yidong writes:

 > Maybe we should provide Lisp variables to allow setting the hintstyle
 > from within Emacs.

FWIW, in XEmacs we simply exposed the whole fontconfig API to Lisp,
except for stuff like memory management which are done by Lisp
automatically.  I haven't heard of this particular problem, but if we
see it and fontconfig APIs are insufficient (which IMO would be
considered a bug in fontconfig or Xft), I think we would probably do
the same thing for Xft APIs we need.

I would think that hintstyle is probably accessible via fontconfig.

Re: Subpixel averaging

[Andreas Schwab]

Chong Yidong <cyd@stupidchicken.com> writes:

> Andreas Schwab <schwab@suse.de> writes:
>
>> Chong Yidong <cyd@stupidchicken.com> writes:
>>
>>> But none of the other applications on the Gnome desktop seem to need
>>> these tweaking.  Why is Emacs the only one?
>>
>> Works for me without the tweaking.
>
> Well, it's strange.  I just tried it on my laptop, and the fonts look OK
> there.  To be precise, Xft.hinting defaults to true (though
> Xft.hintstyle is not hintfull).  On my desktop, Xft.hinting defaults to
> false.

On my system, KDE creates a suitable fonts.conf.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."