[arabic] Use glyph advance width in apply_stch() instead of extents

That seems to be what Windows is doing, and makes more sense.

diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index 8ab9a02..4da8990 100644 (file)
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -463,10 +463,6 @@ apply_stch (const hb_ot_shape_plan_t *plan,
    * Second pass applies the stretch, copying things to the end of buffer.
    */
 
-  /* 30 = 2048 / 70.
-   * https://www.microsoft.com/typography/cursivescriptguidelines.mspx */
-  hb_position_t overlap = font->x_scale / 30;
-  DEBUG_MSG (ARABIC, NULL, "overlap for stretching is %d", overlap);
   int sign = font->x_scale < 0 ? -1 : +1;
   unsigned int extra_glyphs_needed = 0; // Set during MEASURE, used during CUT
   typedef enum { MEASURE, CUT } step_t;
@@ -504,18 +500,15 @@ apply_stch (const hb_ot_shape_plan_t *plan,
             hb_in_range<unsigned> (info[i - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING))
       {
        i--;
-       hb_glyph_extents_t extents;
-       if (!font->get_glyph_extents (info[i].codepoint, &extents))
-         extents.width = 0;
-       extents.width -= overlap;
+       hb_position_t width = font->get_glyph_h_advance (info[i].codepoint);
        if (info[i].arabic_shaping_action() == STCH_FIXED)
        {
-         w_fixed += extents.width;
+         w_fixed += width;
          n_fixed++;
        }
        else
        {
-         w_repeating += extents.width;
+         w_repeating += width;
          n_repeating++;
        }
       }
@@ -540,7 +533,7 @@ apply_stch (const hb_ot_shape_plan_t *plan,
       /* Number of additional times to repeat each repeating tile. */
       int n_copies = 0;
 
-      hb_position_t w_remaining = w_total - w_fixed - overlap;
+      hb_position_t w_remaining = w_total - w_fixed;
       if (sign * w_remaining > sign * w_repeating && sign * w_repeating > 0)
        n_copies = (sign * w_remaining) / (sign * w_repeating) - 1;
 
@@ -562,13 +555,10 @@ apply_stch (const hb_ot_shape_plan_t *plan,
       }
       else
       {
-        hb_position_t x_offset = -overlap;
+       hb_position_t x_offset = 0;
        for (unsigned int k = end; k > start; k--)
        {
-         hb_glyph_extents_t extents;
-         if (!font->get_glyph_extents (info[k - 1].codepoint, &extents))
-           extents.width = 0;
-         extents.width -= overlap;
+         hb_position_t width = font->get_glyph_h_advance (info[k - 1].codepoint);
 
          unsigned int repeat = 1;
          if (info[k - 1].arabic_shaping_action() == STCH_REPEATING)
@@ -578,7 +568,7 @@ apply_stch (const hb_ot_shape_plan_t *plan,
                     repeat, info[k - 1].codepoint, j);
          for (unsigned int n = 0; n < repeat; n++)
          {
-           x_offset -= extents.width;
+           x_offset -= width;
            if (n > 0)
              x_offset += extra_repeat_overlap;
            pos[k - 1].x_offset = x_offset;