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Fix scrolling problems with misc-fixed fonts under Cairo

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* src/ftcrfont.c (ftcrfont_glyph_extents): Avoid rounding up the
glyph ascent to a higher value than needed due to floating-point
roundoff errors.  (Bug#44284)
This commit is contained in:
Eli Zaretskii 2020-11-07 10:27:15 +02:00
parent ece1e1da5e
commit 33e2418a7c
1 changed files with 6 additions and 1 deletions
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7
src/ftcrfont.c
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@ -84,7 +84,12 @@ ftcrfont_glyph_extents (struct font *font,
cache->lbearing = floor (extents.x_bearing);
cache->rbearing = ceil (extents.width + extents.x_bearing);
cache->width = lround (extents.x_advance);
cache->ascent = ceil (- extents.y_bearing);
/* The subtraction of a small number is to avoid rounding up due
to floating-point inaccuracies with some fonts, which then
could cause unpleasant effects while scrolling (see bug
#44284), since we then think that a glyph row's ascent is too
small to accommodate a glyph with a higher phys_ascent. */
cache->ascent = ceil (- extents.y_bearing - 1.0 / 256);
cache->descent = ceil (extents.height + extents.y_bearing);
}