Improve efficiency of operations involving font interpreter scale

* src/sfnt.c (sfnt_mul_f26dot6_fixed): Correct rounding
constant.
(sfnt_make_interpreter, SSW, WCVTF, sfnt_compute_phantom_points)
(sfnt_interpret_simple_glyph, sfnt_interpret_compound_glyph_1)
(sfnt_vary_interpreter, sfnt_check_ssw): Account for the
fractional bits in a f26dot6 when computing the interpreter
scale factor.

1 files changed, 21 insertions, 20 deletions

diff --git a/src/sfnt.c b/src/sfnt.c
index c33f21215a6..eb3add7390e 100644
--- a/src/sfnt.c
+++ b/src/sfnt.c
@@ -6456,7 +6456,8 @@ sfnt_mul_f26dot6_fixed (sfnt_f26dot6 x, sfnt_fixed y)
   product = (uint64_t) y * (uint64_t) x;
 
   /* This can be done quickly with int64_t.  */
-  return ((int64_t) (product + 32676) / (int64_t) 65536) * sign;
+  return ((int64_t) (product + 32768)
+          / (int64_t) 65536) * sign;
 #else
   struct sfnt_large_integer temp;
   int sign;
@@ -6685,7 +6686,7 @@ sfnt_make_interpreter (struct sfnt_maxp_table *maxp,
   /* Now compute the scale.  Then, scale up the control value table
      values.  */
   interpreter->scale
-    = sfnt_div_fixed (pixel_size, head->units_per_em);
+    = sfnt_div_fixed (pixel_size * 64, head->units_per_em);
 
   /* Set the PPEM.  */
   interpreter->ppem = pixel_size;
@@ -6701,7 +6702,7 @@ sfnt_make_interpreter (struct sfnt_maxp_table *maxp,
   /* Load the control value table.  */
   for (i = 0; i < interpreter->cvt_size; ++i)
     interpreter->cvt[i]
-      = sfnt_mul_f26dot6_fixed (cvt->values[i] * 64,
+      = sfnt_mul_f26dot6_fixed (cvt->values[i],
                                 interpreter->scale);
 
   /* Fill in the default values for phase, period and threshold.  */
@@ -7016,8 +7017,8 @@ sfnt_interpret_trap (struct sfnt_interpreter *interpreter,
     single_width = POP ();                      \
                                                 \
     interpreter->state.single_width_value       \
-      = (interpreter->scale * single_width      \
-         / 1024);                               \
+      = sfnt_mul_fixed (single_width,           \
+                        interpreter->scale);    \
   }
 
 #define DUP()                                   \
@@ -7545,8 +7546,8 @@ sfnt_interpret_trap (struct sfnt_interpreter *interpreter,
       TRAP ("WCVTF out of bounds");             \
                                                 \
     interpreter->cvt[location]                  \
-      = (interpreter->scale * value             \
-         / 1024);                               \
+      = sfnt_mul_fixed (value,                  \
+                        interpreter->scale);    \
   }
 
 #define JROT()                                  \
@@ -12258,8 +12259,8 @@ sfnt_compute_phantom_points (struct sfnt_glyph *glyph,
   f2 += glyph->advance_distortion;
 
   /* Next, scale both up.  */
-  *s1 = sfnt_mul_f26dot6_fixed (f1 * 64, scale);
-  *s2 = sfnt_mul_f26dot6_fixed (f2 * 64, scale);
+  *s1 = sfnt_mul_f26dot6_fixed (f1, scale);
+  *s2 = sfnt_mul_f26dot6_fixed (f2, scale);
 
   /* While not expressly provided in the manual, the phantom points
      (at times termed the advance and origin points) represent pixel
@@ -12343,7 +12344,7 @@ sfnt_interpret_simple_glyph (struct sfnt_glyph *glyph,
       tem = glyph->simple->x_coordinates[i];
 
       /* Scale that fword.  */
-      tem = sfnt_mul_f26dot6_fixed (tem * 64, interpreter->scale);
+      tem = sfnt_mul_f26dot6_fixed (tem, interpreter->scale);
 
       /* Set x_points and x_current.  */
       zone->x_points[i] = tem;
@@ -12371,7 +12372,7 @@ sfnt_interpret_simple_glyph (struct sfnt_glyph *glyph,
 
       /* Scale that fword.  Make sure not to round Y, as this could
          lead to Y spilling over to the next line.  */
-      tem = sfnt_mul_fixed (tem * 64, interpreter->scale);
+      tem = sfnt_mul_f26dot6_fixed (tem, interpreter->scale);
 
       /* Set y_points and y_current.  */
       zone->y_points[i] = tem;
@@ -12824,14 +12825,14 @@ sfnt_interpret_compound_glyph_1 (struct sfnt_glyph *glyph,
           if (!(component->flags & 01)) /* ARG_1_AND_2_ARE_WORDS */
             {
               /* X and Y are signed bytes.  */
-              x = component->argument1.b * 64;
-              y = component->argument2.b * 64;
+              x = component->argument1.b;
+              y = component->argument2.b;
             }
           else
             {
               /* X and Y are signed words.  */
-              x = component->argument1.d * 64;
-              y = component->argument2.d * 64;
+              x = component->argument1.d;
+              y = component->argument2.d;
             }
 
           /* Now convert X and Y into device coordinates.  */
@@ -16335,7 +16336,7 @@ sfnt_vary_interpreter (struct sfnt_interpreter *interpreter,
 
           /* Multiply the delta by the interpreter scale factor and
              then the tuple scale factor.  */
-          delta = sfnt_mul_f26dot6_fixed (variation->deltas[j] * 64,
+          delta = sfnt_mul_f26dot6_fixed (variation->deltas[j],
                                           interpreter->scale);
           delta = sfnt_mul_fixed_round (delta, scale);
 
@@ -17352,13 +17353,13 @@ sfnt_check_ssw (struct sfnt_interpreter *interpreter,
     }
 
   if (interpreter->state.single_width_value
-      != sfnt_mul_f26dot6_fixed (-64, interpreter->scale))
+      != sfnt_mul_f26dot6_fixed (-1, interpreter->scale))
     {
       fprintf (stderr, "failed, got %d at scale %d,"
                " expected %d\n",
                interpreter->state.single_width_value,
                interpreter->scale,
-               sfnt_mul_f26dot6_fixed (-64, interpreter->scale));
+               sfnt_mul_f26dot6_fixed (-1, interpreter->scale));
       return;
     }
 
@@ -20532,8 +20533,8 @@ main (int argc, char **argv)
       return 1;
     }
 
-#define FANCY_PPEM 14
-#define EASY_PPEM  14
+#define FANCY_PPEM 12
+#define EASY_PPEM  12
 
   interpreter = NULL;
   head = sfnt_read_head_table (fd, font);