[font] Optimize font scaling further

src/hb-font.cc

@@ -1649,8 +1649,8 @@ DEFINE_NULL_INSTANCE (hb_font_t) =
   1000, /* y_scale */
   0., /* slant */
   0., /* slant_xy; */
-  1000, /* upem */
-  0.001f, /* upem_inv */
+  1.f, /* x_multf */
+  1.f, /* y_multf */
   1<<16, /* x_mult */
   1<<16, /* y_mult */
 
@@ -1683,9 +1683,8 @@ _hb_font_create (hb_face_t *face)
   font->face = hb_face_reference (face);
   font->klass = hb_font_funcs_get_empty ();
   font->data.init0 (font);
-  font->x_scale = font->y_scale = hb_face_get_upem (face);
-  font->upem = face->get_upem ();
-  font->upem_inv = 1.f / font->upem;
+  font->x_scale = font->y_scale = face->get_upem ();
+  font->x_multf = font->y_multf = 1.f;
   font->x_mult = font->y_mult = 1 << 16;
 
   return font;

src/hb-font.hh

@@ -114,8 +114,8 @@ struct hb_font_t
   int32_t y_scale;
   float slant;
   float slant_xy;
-  unsigned upem;
-  float upem_inv;
+  float x_multf;
+  float y_multf;
   int64_t x_mult;
   int64_t y_mult;
 
@@ -141,12 +141,12 @@ struct hb_font_t
   { 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); }
-  float em_fscalef_x (float v) { return em_fscalef (v, x_scale); }
-  float em_fscalef_y (float v) { return em_fscalef (v, y_scale); }
+  hb_position_t em_scalef_x (float v) { return em_multf (v, x_multf); }
+  hb_position_t em_scalef_y (float v) { return em_multf (v, y_multf); }
+  float em_fscale_x (int16_t v) { return em_fmult (v, x_multf); }
+  float em_fscale_y (int16_t v) { return em_fmult (v, y_multf); }
+  float em_fscalef_x (float v) { return em_fmultf (v, x_multf); }
+  float em_fscalef_y (float v) { return em_fmultf (v, y_multf); }
   hb_position_t em_scale_dir (int16_t v, hb_direction_t direction)
   { return em_mult (v, dir_mult (direction)); }
 
@@ -631,23 +631,24 @@ struct hb_font_t
 
   void mults_changed ()
   {
-    upem = face->get_upem ();
-    upem_inv = 1.f / upem;
+    float upem = face->get_upem ();
+    x_multf = x_scale / upem;
+    y_multf = y_scale / upem;
     bool x_neg = x_scale < 0;
-    x_mult = (x_neg ? -((int64_t) -x_scale << 16) : ((int64_t) x_scale << 16)) * upem_inv;
+    x_mult = (x_neg ? -((int64_t) -x_scale << 16) : ((int64_t) x_scale << 16)) / upem;
     bool y_neg = y_scale < 0;
-    y_mult = (y_neg ? -((int64_t) -y_scale << 16) : ((int64_t) y_scale << 16)) * upem_inv;
+    y_mult = (y_neg ? -((int64_t) -y_scale << 16) : ((int64_t) y_scale << 16)) / upem;
     slant_xy = y_scale ? slant * x_scale / y_scale : 0.f;
   }
 
   hb_position_t em_mult (int16_t v, int64_t mult)
   { return (hb_position_t) ((v * mult + 32768) >> 16); }
-  hb_position_t em_scalef (float v, int scale)
-  { return (hb_position_t) roundf (em_fscalef (v, scale)); }
-  float em_fscalef (float v, int scale)
-  { return v * scale * upem_inv; }
-  float em_fscale (int16_t v, int scale)
-  { return (float) v * scale * upem_inv; }
+  hb_position_t em_multf (float v, float mult)
+  { return (hb_position_t) roundf (em_fmultf (v, mult)); }
+  float em_fmultf (float v, float mult)
+  { return v * mult; }
+  float em_fmult (int16_t v, float mult)
+  { return (float) v * mult; }
 };
 DECLARE_NULL_INSTANCE (hb_font_t);
 

test/api/test-draw.c

@@ -479,7 +479,7 @@ test_hb_draw_font_kit_glyphs_tests (void)
     char expected[] = "M581,274L443,274Q409,274 384,259Q359,243 348,219Q336,194 340,166"
 		      "Q343,138 365,111L468,-13Q470,-10 473,-6Q475,-3 477,0L253,0Q225,0 203,8"
 		      "Q180,15 168,32Q155,48 155,73L155,269L50,269L50,73Q50,24 69,-10"
-		      "Q88,-44 118,-65Q147,-85 181,-95Q214,-104 243,-104L473,-104"
+		      "Q88,-44 118,-64Q147,-85 181,-94Q214,-104 243,-104L473,-104"
 		      "Q501,-104 525,-91Q549,-78 564,-56Q578,-34 578,-8Q578,18 557,43"
 		      "L442,182Q439,179 437,176Q435,173 432,170L581,170L581,274ZM184,-194"
 		      "Q184,-216 199,-231Q214,-246 236,-246Q258,-246 273,-231Q288,-216 288,-194"