Re: Question about FcFontSetSort code

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I've done some more digging on this, and I think that this code
has some real problems.

The values contained in nodeps[f]->score[MATCH_LANG_INDEX]
are going to be:

   0 if it was an exact match for the language
   100 if it was a language match, but possible country missmatch
   200 if it was not a match at all.

(The values returned from FcCompareLang are indeed 0, 1, or 2,
but these are multiplied by 100 before entered into score)

This code always does exact matches only up until the number
of languages requested for the set is above 100. (not realistic,
but comparing score to number of languages requested seems
odd anyway)

The basic problem with the entire loop is that if there are no
exact matches, as would be the case with ja_JP locale, then
all of the fonts are rescored to an equally bad 1000 by this
code, and fonts that don't even support the language are being
set as first priority.

Here is the code diffs to fix the problem (fix for 2.3.2 stable release):

732c732
<     int           *patternLangSat;
---
>     FcBool                *patternLangSat;
765c765
<     patternLangSat = (int *) (nodeps + nnodes);
---
>     patternLangSat = (FcBool *) (nodeps + nnodes);
805,810c805,806
<       patternLangSat[i] = 0;
<
<     /*
< * For Solaris, because of ja_JP, en_US, and such locales, exact matches
<      * with font language support is sporatic.
<      */
---
>       patternLangSat[i] = FcFalse;
>
818c814
<       if (nodeps[f]->score[MATCH_LANG_INDEX] <= 100 )
---
>       if (nodeps[f]->score[MATCH_LANG_INDEX] < nPatternLang)
824c820
<               if (patternLangSat[i] != 1 &&
---
>               if (!patternLangSat[i] &&
830c826
< if (compare >= 0 && compare < 2 && ( patternLangSat[i] == 0 || compare + 1 < patternLangSat[i]))
---
>                   if (compare >= 0 && compare < 2)
841c837
<                       patternLangSat[i] = (int)compare + 1;
---
>                       patternLangSat[i] = FcTrue;

This fix basically retains the information about exact vs. close match by using an int instead of a bool, and allows a close match to be stored if no exact match exists. If an exact match shows up later in the list, then store it also.

Jay



Keith Packard wrote:

On Wed, 2006-01-11 at 13:49 -0800, Jay Hobson wrote:
I'm looking at the FcFontSetSort code in fcmatch.c, line 893
in 2.3.93:

if (nodeps[f]->score[MATCH_LANG_INDEX] < nPatternLang)

Isn't this an apples to oranges comparison?

I'm trying to remember what this does; my recollection is that this
comparison allows for exact matches among any of the requested languages
to be equivalent to an exact match for the first language; note that
scores are increased by one each time the match is further along in the
pattern.

This means that a pattern of the form 'en,ja' will exactly match a 'ja'
font.

I don't exactly recall the details though. I do know that locales on
essentially all other systems are of a similar form though, so any
issues you're seeing on Solaris should be present on Linux, BSD and
other systems.

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