[Fontconfig] some bitmap fonts are discovered by fc-cache, some are not

[Weiwu Zhang]

I've installed all XFree86-ISO8859-2-1 fonts

# ls /usr/share/fonts/X11/100dpi/lutRS18*
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-10.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-13.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-14.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-15.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-2.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-3.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-4.pcf.gz
/usr/share/fonts/X11/100dpi/lutRS18-ISO8859-9.pcf.gz

But 0 fonts are found with fc-cache

# fc-cache -f -v /usr/share/fonts/X11/100dpi
/usr/share/fonts/X11/100dpi: caching, new cache contents: 0 fonts, 0 dirs

To experiment, I copied a font over to the same directory:

# cd /usr/share/fonts/X11/100dpi
# wget https://github.com/ifax/HylaFAX/raw/master/etc/lutRS18.pcf
# fc-cache -f -v /usr/share/fonts/X11/100dpi
/usr/share/fonts/X11/100dpi: caching, new cache contents: 1 fonts, 0 dirs

In order to be sure the single newly found font is the one I just downloaded:

# fc-list | grep 100dpi
/usr/share/fonts/X11/100dpi/lutRS18.pcf: LucidaTypewriter:style=Sans

Yes, it is.

The question is of course why the fonts I installed is not recongised
but the one I downloaded is.

I installed it on Ubuntu 18.04 through:

# apt-get install xfonts-100dpi-transcoded

whose content is here:
https://packages.ubuntu.com/bionic/all/xfonts-100dpi-transcoded/filelist

Thanks!