[ot] Improve shaper selection heuristic

src/hb-ot-shape-complex-private.hh

@@ -253,10 +253,12 @@ hb_ot_shape_complex_categorize (const hb_ot_shape_planner_t *planner)
     case HB_SCRIPT_SINHALA:
 
       /* If the designer designed the font for the 'DFLT' script,
-       * use the default shaper.  Otherwise, use the specific shaper.
+       * (or we ended up arbitrarily pick 'latn'), use the default shaper.
+       * Otherwise, use the specific shaper.
        * Note that for some simple scripts, there may not be *any*
        * GSUB/GPOS needed, so there may be no scripts found! */
-      if (planner->map.chosen_script[0] == HB_TAG ('D','F','L','T'))
+      if (planner->map.chosen_script[0] == HB_TAG ('D','F','L','T') ||
+	  planner->map.chosen_script[0] == HB_TAG ('l','a','t','n'))
 	return &_hb_ot_complex_shaper_default;
       else
 	return &_hb_ot_complex_shaper_indic;
@@ -368,10 +370,12 @@ hb_ot_shape_complex_categorize (const hb_ot_shape_planner_t *planner)
     case HB_SCRIPT_ZANABAZAR_SQUARE:
 
       /* If the designer designed the font for the 'DFLT' script,
-       * use the default shaper.  Otherwise, use the specific shaper.
+       * (or we ended up arbitrarily pick 'latn'), use the default shaper.
+       * Otherwise, use the specific shaper.
        * Note that for some simple scripts, there may not be *any*
        * GSUB/GPOS needed, so there may be no scripts found! */
-      if (planner->map.chosen_script[0] == HB_TAG ('D','F','L','T'))
+      if (planner->map.chosen_script[0] == HB_TAG ('D','F','L','T') ||
+	  planner->map.chosen_script[0] == HB_TAG ('l','a','t','n'))
 	return &_hb_ot_complex_shaper_default;
       else
 	return &_hb_ot_complex_shaper_use;