[arabic] Adjust feature order again

Fixes https://github.com/behdad/harfbuzz/issues/505

src/hb-ot-shape-complex-arabic.cc

@@ -199,6 +199,9 @@ collect_features_arabic (hb_ot_shape_planner_t *plan)
    * work.  However, testing shows that rlig and calt are applied
    * together for Mongolian in Uniscribe.  As such, we only add a
    * pause for Arabic, not other scripts.
+   *
+   * A pause after calt is required to make KFGQPC Uthmanic Script HAFS
+   * work correctly.  See https://github.com/behdad/harfbuzz/issues/505
    */
 
   map->add_gsub_pause (nuke_joiners);
@@ -222,7 +225,10 @@ collect_features_arabic (hb_ot_shape_planner_t *plan)
   if (plan->props.script == HB_SCRIPT_ARABIC)
     map->add_gsub_pause (arabic_fallback_shape);
 
+  /* No pause after rclt.  See 98460779bae19e4d64d29461ff154b3527bf8420. */
+  map->add_global_bool_feature (HB_TAG('r','c','l','t'));
   map->add_global_bool_feature (HB_TAG('c','a','l','t'));
+  map->add_gsub_pause (NULL);
 
   /* The spec includes 'cswh'.  Earlier versions of Windows
    * used to enable this by default, but testing suggests
@@ -232,7 +238,6 @@ collect_features_arabic (hb_ot_shape_planner_t *plan)
    * Note that IranNastaliq uses this feature extensively
    * to fixup broken glyph sequences.  Oh well...
    * Test case: U+0643,U+0640,U+0631. */
-  //map->add_gsub_pause (NULL);
   //map->add_global_bool_feature (HB_TAG('c','s','w','h'));
   map->add_global_bool_feature (HB_TAG('m','s','e','t'));
 }

test/shaping/tests/arabic-feature-order.tests

 fonts/sha1sum/813c2f8e5512187fd982417a7fb4286728e6f4a8.ttf::U+1820,U+180B:[uni2048.E81A=0+1550]
 fonts/sha1sum/8a9fea2a7384f2116e5b84a9b31f83be7850ce21.ttf::U+1820,U+180B:[uni2048.E81A=0+1550]
 fonts/sha1sum/a919b33197965846f21074b24e30250d67277bce.ttf::U+0644,U+0644,U+0647:[Lellah=0+1503]
+fonts/sha1sum/bf39b0e91ef9807f15a9e283a21a14a209fd2cfc.ttf::U+0644,U+064E,U+0670,U+0653,U+0626:[afii57414.zz04=4+1202|uni0670_uni0653=0@50,350+0|afii57454=0@550,1425+0|afii57444.calt=0+1065]