If the system has a lot of fonts then it can take a long time to scan these,
and we generally cannot use the system font cache so this scan has to be done
when the client starts. The end result is that the first startup of the client takes quite some time (40 seconds has been observed).
Debian and Ubuntu seems to have very large default font sets, whilst Fedora is
more conservative (6-8 seconds scan time).
We added a progress dialog in bug 7159 to give the user some feedback, but the
delay is still very annoying.
Perhaps we can make sure the cache is built before the user tries to start the client? The problem then becomes how to maintain it to make sure it stays up to date.
See also bug 7169 which has the corresponding issue for the server.
Note that we might have issues with a global font cache path on cross compiled environments because of bug 5357. E.g. on ARM it might look for the cache in /usr/arm-linux-gnueabi/sys-root/usr/lib/fontconfig/cache rather than just /usr/lib/fontconfig/cache.