Re: fontconfig dpi issue

[Federico Bruni]

Hey Tim

It seems that nobody replied to you.
I hope that some font guru (Werner?) can step in and give some feedback.

I'm interested in this problem, because LilyDev recently switched to 
LXQT.
In which version of LXQT they changed this setting?
I cannot find it on current debian testing:

address@hidden:~# grep -i dpi /etc/fonts/fonts.conf
address@hidden:~#


Il giorno mer 25 gen 2017 alle 23:43, Tim Schellenberg 
<address@hidden> ha scritto:
> Hi everyone,
>
> I ran into an issue with font rendering in Lilypond where text 
> characters
> are far too large. This issue also affected several other users and is
> described here <https://bbs.archlinux.org/viewtopic.php?id=211350>.
>
> It turns out that if the dpi setting is manually set in the fontconfig
> fonts.conf file, Lilypond will adopt that dpi setting (rather than the
> standard setting used in Lilypond, which is 1200) and render all text 
> too
> large.
>
> The desktop environment LXQT sets this to 96 dpi automatically, which 
> is
> what triggered the bug for me. This may not a good idea on their 
> part, but
> I imagine some users may want to or need to adjust this setting and it
> doesn't seem right that this should affect rendering in Lilypond.
>
> To reproduce this bug, edit the following file (or create the file, 
> if it
> doesn't exist):
> $XDG_CONFIG_HOME/fontconfig/fonts.conf
>
> Paste this as the contents of the file (or just add the <match> block 
> with
> the dpi setting):
> <?xml version="1.0"?>
> <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
> <fontconfig>
>   <match target="pattern">
>     <edit name="dpi" mode="assign">
>       <double>96</double>
>     </edit>
>   </match>
> </fontconfig>
>
> Next, compile any .ly file that includes text, for example:
> \version "2.19.49"
> \header {
>   title = "Title"
> }
> \relative c''{
> c
> }

Yep, if I paste that content in ~/.config/fontconfig/fonts.conf I can 
reproduce the problem on my Fedora 25 system.

Before I create an issue on the tracker, some developer should say if 
LilyPond or LXQT must be fixed.
I have no idea about it.


> I also have a proposed patch that fixes the problem described, 
> although I
> don't know if this is the proper way to fix it:
> --- lilypond-2.19.49.orig/lily/pango-font.cc 2016-10-16 
> 07:16:18.000000000
> -0400
> +++ lilypond-2.19.49.new/lily/pango-font.cc 2016-10-29 
> 22:39:02.921622080
> -0400
> @@ -317,7 +317,7 @@
>    pango_fc_font_unlock_face (fcfont);
>    pango_glyph_string_free (pgs);
>    pgs = 0;
> -  PangoFontDescription *descr = pango_font_describe (pa->font);
> +  PangoFontDescription *descr = pango_context_get_font_description
> (context_);
>    Real size = pango_font_description_get_size (descr)
>                / (Real (PANGO_SCALE));
>
>
> I also created a minimal Pango example that reproduces the bug here
> <http://stackoverflow.com/questions/40325159/why-is-the-font-map-resolution-reset-when-using-fontconfig-2-11-94>.
> Thanks!
>
> Tim Schellenberg
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