Re: [matplotlib-devel] font problems: fc-list takes up 100% of CPU and runs forever

[Russell E. O. <ro...@uw...>]

In article <524...@st...>,
 Michael Droettboom <md...@st...> 
 wrote:

> On 10/02/2013 01:34 PM, Russell E. Owen wrote:
> > In article <524...@st...>,
> >   Michael Droettboom <md...@st...>
> >   wrote:
> >
> >> I haven't heard of this issue before.
> >>
> >> fc-list comes from the fontconfig project.  It is used to get a list of
> >> all of the fonts installed on the system.  It sounds like there is some
> >> bug there -- the usual culprit is that there is a slightly non-standard
> >> font installed on the system and fontconfig has a hard time parsing it.
> >> You could try updating fc-list (it's in all the major package managers).
> >>
> >> As for a workaround from our end, we could try to set a timeout on
> >> fc-list and just skip it if it takes too long.  We can't rely on it
> >> being there on a Mac at all, so already we gracefully degrade to a less
> >> thorough search for fonts when fc-list can't be found.
> > Thanks for the advice. A defective font is an interesting possibility.
> >
> > I was wrong it's new in 1.3.0; turns out it's seen in much older
> > versions of my application (back to using mpl 1.0.0), but apparently on
> > few machines.
> >
> > The issue showed up when I added some fancy animated strip charts to my
> > application (which may be a coincidence), not when I upgraded mpl.
> >
> > I'm surprised the timeout on fc-list isn't working.
> 
> We don't currently do a timeout -- we make a blocking call to fc-list.  
> I was only suggesting it as a possible fix for this problem.

Sorry. I read too hastily. If it's not too hard to code a time limit, it 
sounds like a good idea.

> >   Maybe something else
> > is also using fc-list, but the fix is to add an ~/.matplotlib dir, which
> > suggests it's an mpl issue.
> 
> When you copy over the .matplotlib dir, you copy over the font cache.  
> When matplotlib finds a font cache, it doesn't need to generate a list 
> of fonts, so thus doesn't need to call fc-list.  But copying font caches 
> from one machine to another is unlikely to work (the set of fonts and 
> their locations is quite likely different). Worse yet, if matplotlib 
> attempts to look up a font and finds that it isn't where the cache says 
> it is, it regenerates the cache again, and thus you could get this 
> hanging anyway.

Thank you for that warning.

As a followup: one of the two computers had 3 copies of fc-list (one 
from darwinports, one in /usr/local/bin and the on provided with Apple's 
X11). Making sure Apple's version ran seems to have cleared up the 
problem, based on one test. So we may have a fix.

I really appreciate the help.

-- Russell