bug#36028: 26.2; Some faces are ignoring rendering settings in fontconfig pattern

bug#36028: 26.2; Some faces are ignoring rendering settings in fontconfig pattern

[Tetsumi]

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Hi,

Some faces like 'bold, 'italic, or 'bold-italic are ignoring font rendering settings
when setting a font through a font-config pattern.

For example,

    (set-frame-font "Ubuntu Mono-12:antialias=true:lcdfilter=lcddefault" t nil)

The settings antialias and lcdfilter have no effect on the aforementioned faces.
Another more explicit example,

    ; alternating between these two lines turns on/off aliasing for the default face
    (set-face-font 'default "Ubuntu Mono-12:antialias=true:lcdfilter=lcddefault")
    (set-face-font 'default "Ubuntu Mono-12:antialias=false:lcdfilter=lcdnone")

    ; alternating between these two lines has no effect at all.
    (set-face-font 'bold "Ubuntu Mono-12:bold:antialias=true:lcdfilter=lcddefault")
    (set-face-font 'bold "Ubuntu Mono-12:bold:antialias=false:lcdfilter=lcdnone")

It shall be noted that Xresources settings (eg: Xft.antialias) are not ignored by the
aforementioned faces.

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bug#36028: A native module

[Tetsumi]

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To overcome this problem i made a native module to configure Xft from emacs:
https://bitbucket.org/Tetsumi/emacs-xft-config/src/master/

Here a demo (webm video): https://webm.red/3Mr9.webm

Please consider adding two procedures in emacs's xftfont.c to set/get the default pattern of Xft, that would give the user total control on font settings.

To get the current default pattern of Xft:

   FcPattern *pat = FcPatternCreate(); // create an empty Font-Config pattern.
   XftDefaultSubstitute(XDisplay, XScreen, pat); // add current defaults for any options not already present in pat. This also add the current defaults from Font-Config
   FcChar8 *ps = FcNameUnparse(pat); // convert pattern to string
   FcPatternDestroy(pat); // free pat.

The set a new default pattern:

   FcPattern *pat = FcNameParse(buf); // create a Font-Config pattern from a string (eg: ":antialias=false;pixelsize=48")
   XftDefaultSubstitute(XDisplay, XScreen, pat); // see above
   XftDefaultSet(XDisplay, pat); // set pat as the new default pattern
// don't destroy pat! xft takes care ot that.

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bug#36028: A native module

[Eli Zaretskii]

> Date: Tue, 04 Jun 2019 17:45:10 +0000
> From: Tetsumi <tetsumi@protonmail.com>
> 
> To overcome this problem i made a native module to configure Xft from emacs:
> https://bitbucket.org/Tetsumi/emacs-xft-config/src/master/
> 
> Here a demo (webm video): https://webm.red/3Mr9.webm
> 
> Please consider adding two procedures in emacs's xftfont.c to set/get the default pattern of Xft, that would
> give the user total control on font settings.

Thanks.  However, I wonder whether we should invest too much effort in
developing for Xft, as I understand it isn't in active development,
see https://cgit.freedesktop.org/xorg/lib/libXft/.

bug#36028: 26.2; Some faces are ignoring rendering settings in fontconfig pattern

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  However, I wonder whether we should invest too much effort in
> developing for Xft, as I understand it isn't in active development,
> see https://cgit.freedesktop.org/xorg/lib/libXft/.

This was two years ago, and while there does seem to have been some Xft
commits since then, it seems pretty lethargic.

So I think the conclusion here is that we probably don't want to expand
upon Emacs Xft capabilities in-core, so I'm closing this bug report.
But packaging this up as an ELPA package might be useful for somebody.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no