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[sfnt] Sanitize bitmap strike glyph height.

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Problem reported by Nikolay Sivov <bunglehead@gmail.com>.

* src/sfnt/ttsbit.c (tt_face_load_strike_metrics): Avoid zero value
for `metrics->height' by applying some heuristics.
2.6.5
Werner Lemberg 9 years ago
parent e93d326c8b
commit 6f09011fe6
2 changed files with 68 additions and 1 deletions
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  1. 9
      ChangeLog
  2. 60
      src/sfnt/ttsbit.c

9
ChangeLog
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@ -1,3 +1,12 @@
2015-10-24 Werner Lemberg <wl@gnu.org>
[sfnt] Sanitize bitmap strike glyph height.
Problem reported by Nikolay Sivov <bunglehead@gmail.com>.
* src/sfnt/ttsbit.c (tt_face_load_strike_metrics): Avoid zero value
for `metrics->height' by applying some heuristics.
2015-10-22 Werner Lemberg <wl@gnu.org>
[sfnt, type42] Fix clang compiler warnings.

60
src/sfnt/ttsbit.c
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@ -247,6 +247,8 @@
case TT_SBIT_TABLE_TYPE_CBLC:
{
FT_Byte* strike;
FT_Char max_before_bl;
FT_Char min_after_bl;
strike = face->sbit_table + 8 + strike_index * 48;
@ -256,7 +258,63 @@
metrics->ascender = (FT_Char)strike[16] * 64; /* hori.ascender */
metrics->descender = (FT_Char)strike[17] * 64; /* hori.descender */
metrics->height = metrics->ascender - metrics->descender;
/* Due to fuzzy wording in the EBLC documentation, we find both */
/* positive and negative values for `descender'. Additionally, */
/* many fonts have both `ascender' and `descender' set to zero */
/* (which is definitely wrong). MS Windows simply ignores all */
/* those values... For these reasons we apply some heuristics */
/* to get a reasonable, non-zero value for the height. */
max_before_bl = (FT_Char)strike[24];
min_after_bl = (FT_Char)strike[25];
if ( metrics->descender > 0 )
{
/* compare sign of descender with `min_after_bl' */
if ( min_after_bl < 0 )
metrics->descender = -metrics->descender;
}
else if ( metrics->descender == 0 )
{
if ( metrics->ascender == 0 )
{
FT_TRACE2(( "tt_face_load_strike_metrics:"
" sanitizing invalid ascender and descender\n"
" "
" values for strike (%d, %d)\n",
metrics->x_ppem, metrics->y_ppem ));
/* sanitize buggy ascender and descender values */
if ( max_before_bl || min_after_bl )
{
metrics->ascender = max_before_bl;
metrics->descender = min_after_bl;
}
else
{
metrics->ascender = metrics->y_ppem;
metrics->descender = 0;
}
}
}
#if 0
else
; /* if we have a negative descender, simply use it */
#endif
metrics->height = metrics->ascender - metrics->descender;
if ( metrics->height == 0 )
{
FT_TRACE2(( "tt_face_load_strike_metrics:"
" sanitizing invalid height value\n"
" "
" for strike (%d, %d)\n",
metrics->x_ppem, metrics->y_ppem ));
metrics->height = metrics->y_ppem;
}
/* Is this correct? */
metrics->max_advance = ( (FT_Char)strike[22] + /* min_origin_SB */

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