[Fontconfig] Trouble forcing rescanning of font dirs

[Behdad Esfahbod]

Hi Diego,

I committed a modified version of your patch to my tree.

Thanks,
behdad

PS. Here's the patch:

diff --git a/src/fccache.c b/src/fccache.c
index 53df860..f35304a 100644
--- a/src/fccache.c
+++ b/src/fccache.c
@@ -538,7 +538,13 @@ FcDirCacheMapFd (int fd, struct stat *fd_stat, struct stat
        return NULL;
     cache = FcCacheFindByStat (fd_stat);
     if (cache)
-       return cache;
+    {
+       if (FcCacheTimeValid (cache, dir_stat))
+           return cache;
+       FcDirCacheUnload (cache);
+       cache = NULL;
+    }
+
     /*
      * Lage cache files are mmap'ed, smaller cache files are read. This
      * balances the system cost of mmap against per-process memory usage.



Diego Santa Cruz wrote:
> Hello,
> 
>  
> 
> We are using fontconfig in our project for font matching and it works
> well. However at certain times we need to check if the user has
> installed new fonts or removed others and make sure that fontconfig
> stays current with those changes.
> 
>  
> 
> Thus we try to force fontconfig to validate all its caches and we do
> this by doing something like
> 
>  
> 
> if ( ! FcConfigUptoDate (0) )
> 
>         FcInitReinitialize ();
> 
>  
> 
> at appropriate times (i.e. just before reloading content).
> 
>  
> 
> Although FcConfigUptoDate() correctly reports a change when something is
> added or removed from the font directories FcInitReinitialize() does not
> produce the intended effect (revalidating the font directories).
> 
>  
> 
> We tracked a bit the code in fontconfig  and when the list of fonts is
> being rebuilt via FcConfigBuildFonts() the function FcDirCacheRead() is
> called but with its force argument to false (which appears correct to
> me).  Thus the call chain to load the cache file is FcDirCacheRead() ->
> FcDirCacheLoad() -> FcDirCacheProcess() -> FcDirCacheMapHelper() ->
> FcDirCacheMapFd(). But when FcDirCacheMapFd() finds the cache file
> already loaded through FcCacheFindByStat() it does not verify that the
> font directory  stat data matches the one in the cache file, happily
> returning an outdated cache.
> 
>  
> 
> I think that FcDirCacheMapFd() should call FcCacheTimeValid() if
> FcCacheFindByStat() returns a cache. Would this be  the correct fix or
> should I go through some other mechanism to force fontconfig to validate
> all its caches?
> 
>  
> 
> I would greatly appreciate some feedback on this.
> 
>  
> 
> Sincerely,
> 
>  
> 
> Diego
> 
> --
> Diego Santa Cruz, PhD
> Technology Architect
> _________________________________
> SpinetiX S.A.
> Rue des Terreaux 17
> 1003, Lausanne, Switzerland
> T +41 21 341 15 50
> F +41 21 311 19 56
> diego.santacruz at spinetix.com
> http://www.spinetix.com
> _________________________________
> 
>  
> 
> 
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> 
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