[Fontconfig] Application startup performance

[u-pnrz at aetey.se]

On Mon, Jan 11, 2016 at 07:28:44PM -0800, Keith Packard wrote:
> > I still think we should have only single process to update caches to
> > keep consistency. though you disagree with that idea.
> 
> Keeping that invariant would require locking, which means either only
> updating caches when the user runs fc-cache, or doing locking within
> processes. The former means missing some font updates unless fc-cache is
> always run, the latter means risking locking up the desktop if some
> application fails.

I would rather postulate fc-cache to be run and risk ignoring some fonts
until this is done. Is the risk really significant? Distros run fc-cache,
users who add fonts on their own would know they have to run fc-cache.

What makes me unconfortable is applications doing huge i/o operation at
startup just because of a certain library being used. Then neither
the application developer nor the user have some real power over the
behaviour.

I would be even more uncomfortable if there will be some locks involved
or some daemons would be expected to run just to be able to rely on
fontconfig. Explicit cache creation looks like the cleanest solution.

My 2c
Rune