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[autofit] Avoid excessive stem length rounding (#25392).

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* src/autofit/aflatin.c (af_latin_compute_stem_width): Add argument
to pass difference between hinted and unhinted position of base
point; use this to adjust the stem width depending on the PPEM so
that it doesn't become too large under certain circumstances.
Update all callers using value 0 for this argument except...
(af_latin_align_linked_edge): Pass position delta of base point to
`af_latin_compute_stem_width'.
This commit is contained in:
Werner Lemberg 2016-03-05 19:47:07 +01:00
parent 1fd2bc8c37
commit caa48b0db1
2 changed files with 57 additions and 8 deletions
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12
ChangeLog
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@ -1,3 +1,15 @@
2016-03-05 Werner Lemberg <wl@gnu.org>
[autofit] Avoid excessive stem length rounding (#25392).
* src/autofit/aflatin.c (af_latin_compute_stem_width): Add argument
to pass difference between hinted and unhinted position of base
point; use this to adjust the stem width depending on the PPEM so
that it doesn't become too large under certain circumstances.
Update all callers using value 0 for this argument except...
(af_latin_align_linked_edge): Pass position delta of base point to
`af_latin_compute_stem_width'.
2016-03-05 J Raynor <jxraynor@gmail.com>
Make FreeType compile on AIX out of the box.

53
src/autofit/aflatin.c
View File

@ -2504,12 +2504,14 @@
af_latin_compute_stem_width( AF_GlyphHints hints,
AF_Dimension dim,
FT_Pos width,
FT_Pos base_delta,
FT_UInt base_flags,
FT_UInt stem_flags )
{
AF_LatinMetrics metrics = (AF_LatinMetrics)hints->metrics;
AF_LatinAxis axis = &metrics->axis[dim];
FT_Pos dist = width;
FT_Pos bdelta = 0;
FT_Int sign = 0;
FT_Int vertical = ( dim == AF_DIMENSION_VERT );
@ -2524,6 +2526,32 @@
sign = 1;
}
/* A stem's end position depends on two values: the start position */
/* and the stem length. The former gets usually rounded to the grid, */
/* while the latter gets rounded also if it exceeds a certain length */
/* (see below in this function). This `double rounding' can lead to */
/* a great difference to the original, unhinted position; this */
/* normally doesn't matter for large PPEM values, but for small sizes */
/* it can easily make outlines collide. For this reason, we adjust */
/* the stem length by a small amount depending on the PPEM value in */
/* case the former and latter rounding both point into the same */
/* direction. */
if ( ( ( width > 0 ) && ( base_delta > 0 ) ) ||
( ( width < 0 ) && ( base_delta < 0 ) ) )
{
FT_UInt ppem = metrics->root.scaler.face->size->metrics.x_ppem;
if ( ppem < 10 )
bdelta = base_delta;
else if ( ppem < 30 )
bdelta = ( base_delta * (FT_Pos)( 30 - ppem ) ) / 20;
if ( bdelta < 0 )
bdelta = -bdelta;
}
if ( ( vertical && !AF_LATIN_HINTS_DO_VERT_SNAP( hints ) ) ||
( !vertical && !AF_LATIN_HINTS_DO_HORZ_SNAP( hints ) ) )
{
@ -2581,7 +2609,7 @@
dist += delta;
}
else
dist = ( dist + 32 ) & ~63;
dist = ( dist - bdelta + 32 ) & ~63;
}
}
else
@ -2670,11 +2698,17 @@
AF_Edge base_edge,
AF_Edge stem_edge )
{
FT_Pos dist = stem_edge->opos - base_edge->opos;
FT_Pos dist, base_delta;
FT_Pos fitted_width;
FT_Pos fitted_width = af_latin_compute_stem_width( hints, dim, dist,
base_edge->flags,
stem_edge->flags );
dist = stem_edge->opos - base_edge->opos;
base_delta = base_edge->pos - base_edge->opos;
fitted_width = af_latin_compute_stem_width( hints, dim,
dist, base_delta,
base_edge->flags,
stem_edge->flags );
stem_edge->pos = base_edge->pos + fitted_width;
@ -2878,7 +2912,8 @@
org_len = edge2->opos - edge->opos;
cur_len = af_latin_compute_stem_width( hints, dim, org_len,
cur_len = af_latin_compute_stem_width( hints, dim,
org_len, 0,
edge->flags,
edge2->flags );
@ -2947,7 +2982,8 @@
org_len = edge2->opos - edge->opos;
org_center = org_pos + ( org_len >> 1 );
cur_len = af_latin_compute_stem_width( hints, dim, org_len,
cur_len = af_latin_compute_stem_width( hints, dim,
org_len, 0,
edge->flags,
edge2->flags );
@ -3007,7 +3043,8 @@
org_len = edge2->opos - edge->opos;
org_center = org_pos + ( org_len >> 1 );
cur_len = af_latin_compute_stem_width( hints, dim, org_len,
cur_len = af_latin_compute_stem_width( hints, dim,
org_len, 0,
edge->flags,
edge2->flags );