Created attachment 5272 [details] [review]
Don't copy FcCharSet if we're going to chuck it anyway.

This is just a bit tricky, so I'm sleeping on this patch before committing it.

Good thing I slept on it, I had an extra ! in there...

Copying a charset is cheap, but doing charset union is potentially expensive. 
Not sure how much we save here.  Anyway, I've committed the fixed patch.

Thank you for the fix.  Previously, FcFontSort without trimming was more than 10
times slower than with trimming.  But now they run in almost the same speed.  It
seems that the overhead of building big fontset is compatible with the overhead
of many charset union.

This is the program I used for confirming it.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fontconfig/fontconfig.h>

int
main (int argc, char **argv)
{
  int i;
  FcPattern *pat;
  FcFontSet *fs;
  FcResult result;
  FcBool trim;

  FcInit ();
  pat = FcPatternCreate ();
  FcPatternAddInteger (pat, FC_WEIGHT, FC_WEIGHT_MEDIUM);
  FcPatternAddInteger (pat, FC_SLANT, FC_SLANT_ROMAN);
  FcPatternAddInteger (pat, FC_WIDTH, FC_WIDTH_NORMAL);

  trim = (argc > 1 && strcmp (argv[1], "trim") == 0) ? FcTrue : FcFalse;
  for (i = 0; i < 10; i++)
    {
      fs = FcFontSort (NULL, pat, trim, NULL, &result);
      FcFontSetDestroy (fs);
    }
  exit (0);
}

Thanks!