Chiebot-Mirror
/
freetype
mirror of https://github.com/freetype/freetype.git
8
0
Fork 0
Code Issues Projects Releases Wiki Activity

[sfnt] Use typo metrics if OS/2 fsSelection USE_TYPO_METRICS bit is set.

Browse Source 
If the OS/2 table exists and fsSelection bit 7 (USE_TYPO_METRICS) is set,
use the sTypo* set of values to compute the FT_Face's ascender, descender
and height. Otherwise, fall back to old behavior.

* src/sfnt/sfobjs.c (sfnt_load_face): Implement.
cmakelists-updates
Nikolaus Waxweiler 6 years ago
parent f686ad46a3
commit f72b00746c
2 changed files with 75 additions and 51 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 12
      ChangeLog
  2. 114
      src/sfnt/sfobjs.c

12
ChangeLog
Unescape View File

@ -1,3 +1,13 @@
2019-02-02 Nikolaus Waxweiler <madigens@gmail.com>
[sfnt] Use typo metrics if OS/2 fsSelection USE_TYPO_METRICS bit is set.
If the OS/2 table exists and fsSelection bit 7 (USE_TYPO_METRICS) is set,
use the sTypo* set of values to compute the FT_Face's ascender, descender
and height. Otherwise, fall back to old behavior.
* src/sfnt/sfobjs.c (sfnt_load_face): Implement.
2019-01-18 John Tytgat <John.Tytgat@esko.com>
[sfnt] Handle TT fonts having two PostScript font names (#55471).
@ -420,7 +430,7 @@
* src/base/ftobjs.c (ft_glyphslot_preset_bimap): Another tweak.
This one should be clearer. When the rounded monochrome bbox collapses
we add a pixel that covers most if not all original cbox.
we add a pixel that covers most if not all original cbox.
2018-09-21 Alexei Podtelezhnikov <apodtele@gmail.com>

114
src/sfnt/sfobjs.c
Unescape View File

@ -1641,59 +1641,73 @@
root->units_per_EM = face->header.Units_Per_EM;
/* XXX: Computing the ascender/descender/height is very different */
/* from what the specification tells you. Apparently, we */
/* must be careful because */
/* */
/* - not all fonts have an OS/2 table; in this case, we take */
/* the values in the horizontal header. However, these */
/* values very often are not reliable. */
/* */
/* - otherwise, the correct typographic values are in the */
/* sTypoAscender, sTypoDescender & sTypoLineGap fields. */
/* */
/* However, certain fonts have these fields set to 0. */
/* Rather, they have usWinAscent & usWinDescent correctly */
/* set (but with different values). */
/* */
/* As an example, Arial Narrow is implemented through four */
/* files ARIALN.TTF, ARIALNI.TTF, ARIALNB.TTF & ARIALNBI.TTF */
/* */
/* Strangely, all fonts have the same values in their */
/* sTypoXXX fields, except ARIALNB which sets them to 0. */
/* */
/* On the other hand, they all have different */
/* usWinAscent/Descent values -- as a conclusion, the OS/2 */
/* table cannot be used to compute the text height reliably! */
/* */
/* The ascender and descender are taken from the `hhea' table. */
/* If zero, they are taken from the `OS/2' table. */
root->ascender = face->horizontal.Ascender;
root->descender = face->horizontal.Descender;
root->height = root->ascender - root->descender +
face->horizontal.Line_Gap;
if ( !( root->ascender || root->descender ) )
/*
* Computing the ascender/descender/height is tricky.
*
* The OpenType specification v1.8.3 says:
*
* [OS/2's] sTypoAscender, sTypoDescender and sTypoLineGap fields
* are intended to allow applications to lay out documents in a
* typographically-correct and portable fashion.
*
* This is somewhat at odds with the decades of backwards
* compatibility, operating systems and applications doing whatever
* they want, not to mention broken fonts.
*
* Not all fonts have an OS/2 table; in this case, we take the values
* in the horizontal header, although there is nothing stopping the
* values from being unreliable. Even with a OS/2 table, certain fonts
* set the sTypoAscender, sTypoDescender and sTypoLineGap fields to 0
* and instead correctly set usWinAscent and usWinDescent.
*
* As an example, Arial Narrow is shipped as four files ARIALN.TTF,
* ARIALNI.TTF, ARIALNB.TTF and ARIALNBI.TTF. Strangely, all fonts have
* the same values in their sTypo* fields, except ARIALNB.ttf which
* sets them to 0. All of them have different usWinAscent/Descent
* values. The OS/2 table therefore cannot be trusted for computing the
* text height reliably.
*
* As a compromise, do the following:
*
* 1. If the OS/2 table exists and the fsSelection bit 7 is set
* (USE_TYPO_METRICS), trust the font and use the sTypo* metrics.
* 2. Otherwise, use the `hhea' table's metrics.
* 3. If they are zero and the OS/2 table exists,
* 1. use the OS/2 table's sTypo* metrics if they are non-zero.
* 2. Otherwise, use the OS/2 table's usWin* metrics.
*/
if ( face->os2.version != 0xFFFFU && face->os2.fsSelection & 128 )
{
if ( face->os2.version != 0xFFFFU )
{
if ( face->os2.sTypoAscender || face->os2.sTypoDescender )
{
root->ascender = face->os2.sTypoAscender;
root->descender = face->os2.sTypoDescender;
root->ascender = face->os2.sTypoAscender;
root->descender = face->os2.sTypoDescender;
root->height = root->ascender - root->descender +
face->os2.sTypoLineGap;
}
else
{
root->ascender = face->horizontal.Ascender;
root->descender = face->horizontal.Descender;
root->height = root->ascender - root->descender +
face->horizontal.Line_Gap;
root->height = root->ascender - root->descender +
face->os2.sTypoLineGap;
}
else
if ( !( root->ascender || root->descender ) )
{
if ( face->os2.version != 0xFFFFU )
{
root->ascender = (FT_Short)face->os2.usWinAscent;
root->descender = -(FT_Short)face->os2.usWinDescent;
root->height = root->ascender - root->descender;
if ( face->os2.sTypoAscender || face->os2.sTypoDescender )
{
root->ascender = face->os2.sTypoAscender;
root->descender = face->os2.sTypoDescender;
root->height = root->ascender - root->descender +
face->os2.sTypoLineGap;
}
else
{
root->ascender = (FT_Short)face->os2.usWinAscent;
root->descender = -(FT_Short)face->os2.usWinDescent;
root->height = root->ascender - root->descender;
}
}
}
}

Write Preview
Loading…
Cancel
Save