[Pkg-cups-devel] Bug#662660: Bug#662660: cups-filters: Please drop ttf-freefonts and use fontconfig to find the best-matching similar font

[Fabian Greffrath]

Hi Till and Martin,

please find my improved patch attached.

If direct loading of the TTF font file passed to font_load() fails, 
turn the file name into a fontconfig "pattern" (see below!) and use it 
to receive a list of similar fonts from fontconfig that somehow match 
this pattern. Then iterate through this list to find the first 
candidate that is both in TrueType format and monospaced. If none is 
found, fontname will still point to NULL and the function returns NULL 
just as before.

With this patch, texttopdf should work whether ttf-freefonts is 
installed or not, whether the symlinks are there or not, whether they 
are dangling or not - it just shouldn't matter, *as long as at least 
on monospaced TrueType font is installed on the system*. This may be 
provided by fonts-liberation, ttf-dejavu, fonts-consolidata or 
whatever. However, if ttf-freefonts is installed, the symlinks will 
point to these fonts and they take preference over all the others. I 
think this still makes sense, because ttf-freefonts may still have the 
widest unicode coverage of them all. I think this fact should also get 
reflected in the package dependencies, which could get changed from 
"Depends: ttf-freefonts" to "Depends: ttf-freefonts | fonts-liberation 
| ttf-dejavu" or similar. This would close #662660 and #495598. ;)

There is one drawback with this patch (but I think the net win 
overweights): The file names passed to font_load() are in fact no 
valid fontconfig patterns, even with their .ttf extensions removed. 
That is, fontconfig cannot know that "FreeMonoBold"  means that we 
want the bold face of the FreeMono or any other valid monospaced font. 
I should be called "FreeMono:Bold" to achieve this, but this in turn 
is incompatible with the file names found in ttf-freefonts. I think it 
still works well enough as a fallback as it is now, but in the long 
term one should consider switching from actual font file names to 
fontconfig patterns in pdf.utf-8.* altogether!

Another warning: This is my very first encounter with fontconfig, so I 
suggest someone with a bit more fontconfig-fu should have a look at it 
before applying it upstream. ;)

Regards,
  - Fabian


PS: The cups-filters package currently FTBFS if built twice in a row, 
because there are object files left in pdftoopvp/oprs/ and 
filter/fontembed/. Maybe those two directories should get added to the 
DIRS variable in the top-level Makefile.
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