[use] Fix halant detection

Before, we were just checking the use_category().  This detects as
halant a ligature that had the halant as first glyph (as seen in
NotoSansBalinese.)  Change that to use the is_ligated() glyph prop
bit.  The font is forming this ligature in ccmp, which is before
the rphf / pref tests.  So we need to make sure the "ligated" bit
survives those tests.  Since those only check the "substituted" bit,
we now only clear that bit for them and "ligated" survives.

Fixes https://github.com/behdad/harfbuzz/issues/180

src/hb-ot-layout-private.hh

@@ -517,11 +517,9 @@ _hb_glyph_info_clear_ligated_and_multiplied (hb_glyph_info_t *info)
 }
 
 static inline void
-_hb_glyph_info_clear_substituted_and_ligated_and_multiplied (hb_glyph_info_t *info)
+_hb_glyph_info_clear_substituted (hb_glyph_info_t *info)
 {
-  info->glyph_props() &= ~(HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED |
-			   HB_OT_LAYOUT_GLYPH_PROPS_LIGATED |
-			   HB_OT_LAYOUT_GLYPH_PROPS_MULTIPLIED);
+  info->glyph_props() &= ~(HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED);
 }
 
 

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

@@ -360,7 +360,7 @@ clear_substitution_flags (const hb_ot_shape_plan_t *plan,
   hb_glyph_info_t *info = buffer->info;
   unsigned int count = buffer->len;
   for (unsigned int i = 0; i < count; i++)
-    _hb_glyph_info_clear_substituted_and_ligated_and_multiplied (&info[i]);
+    _hb_glyph_info_clear_substituted (&info[i]);
 }
 
 static void
@@ -405,6 +405,12 @@ record_pref (const hb_ot_shape_plan_t *plan,
   }
 }
 
+static inline bool
+is_halant (const hb_glyph_info_t &info)
+{
+  return info.use_category() == USE_H && !_hb_glyph_info_ligated (&info);
+}
+
 static void
 reorder_syllable (hb_buffer_t *buffer, unsigned int start, unsigned int end)
 {
@@ -420,7 +426,6 @@ reorder_syllable (hb_buffer_t *buffer, unsigned int start, unsigned int end)
 
   hb_glyph_info_t *info = buffer->info;
 
-#define HALANT_FLAGS FLAG(USE_H)
 #define BASE_FLAGS (FLAG (USE_B) | FLAG (USE_GB) | FLAG (USE_IV))
 
   /* Move things forward. */
@@ -428,12 +433,12 @@ reorder_syllable (hb_buffer_t *buffer, unsigned int start, unsigned int end)
   {
     /* Got a repha.  Reorder it to after first base, before first halant. */
     for (unsigned int i = start + 1; i < end; i++)
-      if (FLAG_UNSAFE (info[i].use_category()) & (HALANT_FLAGS | BASE_FLAGS))
+      if ((FLAG_UNSAFE (info[i].use_category()) & (BASE_FLAGS)) || is_halant (info[i]))
       {
 	/* If we hit a halant, move before it; otherwise it's a base: move to it's
 	 * place, and shift things in between backward. */
 
-	if (info[i].use_category() == USE_H)
+	if (is_halant (info[i]))
 	  i--;
 
 	buffer->merge_clusters (start, i + 1);
@@ -450,11 +455,11 @@ reorder_syllable (hb_buffer_t *buffer, unsigned int start, unsigned int end)
   for (unsigned int i = start; i < end; i++)
   {
     uint32_t flag = FLAG_UNSAFE (info[i].use_category());
-    if (flag & (HALANT_FLAGS | BASE_FLAGS))
+    if ((flag & (BASE_FLAGS)) || is_halant (info[i]))
     {
-      /* If we hit a halant, move before it; otherwise it's a base: move to it's
+      /* If we hit a halant, move after it; otherwise it's a base: move to it's
        * place, and shift things in between backward. */
-      if (info[i].use_category() == USE_H)
+      if (is_halant (info[i]))
 	j = i + 1;
       else
 	j = i;

test/shaping/Makefile.am

@@ -55,6 +55,7 @@ TESTS = \
 	tests/mongolian-variation-selector.tests \
 	tests/spaces.tests \
 	tests/simple.tests \
+	tests/use.tests \
 	tests/vertical.tests \
 	tests/zero-width-marks.tests \
 	$(NULL)

test/shaping/fonts/sha1sum/MANIFEST

@@ -36,3 +36,4 @@ e207635780b42f898d58654b65098763e340f5c7.ttf
 ef86fe710cfea877bbe0dbb6946a1f88d0661031.ttf
 f499fbc23865022234775c43503bba2e63978fe1.ttf
 fab39d60d758cb586db5a504f218442cd1395725.ttf
+fbb6c84c9e1fe0c39e152fbe845e51fd81f6748e.ttf

test/shaping/tests/MANIFEST

@@ -13,5 +13,6 @@ indic-pref-blocking.tests
 mongolian-variation-selector.tests
 simple.tests
 spaces.tests
+use.tests
 vertical.tests
 zero-width-marks.tests

test/shaping/tests/use.tests

@@ -0,0 +1 @@
+fonts/sha1sum/fbb6c84c9e1fe0c39e152fbe845e51fd81f6748e.ttf::U+1B1B,U+1B44,U+1B13,U+1B3E:[gid3=0+990|gid7=0+2473|gid5=0@-293,-400+0]