[font] Remove division when scaling
Yoohoo. This seems to be precise enough! Let's see if it sticks.
I'm asking Dominik to run this in Chrome test suite and report.
Fixes https://github.com/harfbuzz/harfbuzz/issues/1801
diff --git a/src/hb-font.hh b/src/hb-font.hh
index e379f12..4adf6ae 100644
--- a/src/hb-font.hh
+++ b/src/hb-font.hh
@@ -129,16 +129,16 @@
/* Convert from font-space to user-space */
- int dir_scale (hb_direction_t direction)
- { return HB_DIRECTION_IS_VERTICAL(direction) ? y_scale : x_scale; }
- hb_position_t em_scale_x (int16_t v) { return em_scale (v, x_scale); }
- hb_position_t em_scale_y (int16_t v) { return em_scale (v, y_scale); }
- hb_position_t em_scalef_x (float v) { return em_scalef (v, this->x_scale); }
- hb_position_t em_scalef_y (float v) { return em_scalef (v, this->y_scale); }
+ int64_t dir_mult (hb_direction_t direction)
+ { return HB_DIRECTION_IS_VERTICAL(direction) ? y_mult : x_mult; }
+ hb_position_t em_scale_x (int16_t v) { return em_mult (v, x_mult); }
+ hb_position_t em_scale_y (int16_t v) { return em_mult (v, y_mult); }
+ hb_position_t em_scalef_x (float v) { return em_scalef (v, x_scale); }
+ hb_position_t em_scalef_y (float v) { return em_scalef (v, y_scale); }
float em_fscale_x (int16_t v) { return em_fscale (v, x_scale); }
float em_fscale_y (int16_t v) { return em_fscale (v, y_scale); }
hb_position_t em_scale_dir (int16_t v, hb_direction_t direction)
- { return em_scale (v, dir_scale (direction)); }
+ { return em_mult (v, dir_mult (direction)); }
/* Convert from parent-font user-space to our user-space */
hb_position_t parent_scale_x_distance (hb_position_t v)
@@ -616,14 +616,9 @@
y_mult = ((int64_t) y_scale << 16) / upem;
}
- hb_position_t em_scale (int16_t v, int scale)
+ hb_position_t em_mult (int16_t v, int64_t mult)
{
- signed upem = face->get_upem ();
- signed upem2 = upem >> 1;
- int64_t scaled = v * (int64_t) scale;
-
- scaled += scaled >= 0 ? upem2 : -upem2; /* Round. */
- return (hb_position_t) (scaled / upem);
+ return (hb_position_t) ((v * mult) >> 16);
}
hb_position_t em_scalef (float v, int scale)
{ return (hb_position_t) roundf (v * scale / face->get_upem ()); }
