Combine lig_id and lig_comp into one byte, to free up one for Indic

src/hb-ot-layout-gpos-table.hh

@@ -1105,9 +1105,11 @@ struct MarkLigPosFormat1
      * is identical to the ligature ID of the found ligature.  If yes, we
      * can directly use the component index.  If not, we attach the mark
      * glyph to the last component of the ligature. */
-    if (c->buffer->info[j].lig_id() && c->buffer->info[j].lig_id() == c->buffer->info[c->buffer->idx].lig_id() && c->buffer->info[c->buffer->idx].lig_comp())
+    if (get_lig_id (c->buffer->info[j]) &&
+	get_lig_id (c->buffer->info[j]) == get_lig_id (c->buffer->info[c->buffer->idx]) &&
+	get_lig_comp (c->buffer->info[c->buffer->idx]) > 0)
     {
-      comp_index = c->buffer->info[c->buffer->idx].lig_comp() - 1;
+      comp_index = get_lig_comp (c->buffer->info[c->buffer->idx]) - 1;
       if (comp_index >= comp_count)
 	comp_index = comp_count - 1;
     }
@@ -1208,8 +1210,9 @@ struct MarkMarkPosFormat1
     /* Two marks match only if they belong to the same base, or same component
      * of the same ligature.  That is, the component numbers must match, and
      * if those are non-zero, the ligid number should also match. */
-    if ((c->buffer->info[j].lig_comp() != c->buffer->info[c->buffer->idx].lig_comp()) ||
-	(c->buffer->info[j].lig_comp() && c->buffer->info[j].lig_id() != c->buffer->info[c->buffer->idx].lig_id()))
+    if ((get_lig_comp (c->buffer->info[j]) != get_lig_comp (c->buffer->info[c->buffer->idx])) ||
+	(get_lig_comp (c->buffer->info[j]) > 0 &&
+	 get_lig_id (c->buffer->info[j]) != get_lig_id (c->buffer->info[c->buffer->idx])))
       return false;
 
     unsigned int mark2_index = (this+mark2Coverage) (c->buffer->info[j].codepoint);
@@ -1545,8 +1548,7 @@ GPOS::position_finish (hb_buffer_t *buffer)
   for (unsigned int i = 0; i < len; i++)
     fix_mark_attachment (pos, i, direction);
 
-  HB_BUFFER_DEALLOCATE_VAR (buffer, lig_comp);
-  HB_BUFFER_DEALLOCATE_VAR (buffer, lig_id);
+  HB_BUFFER_DEALLOCATE_VAR (buffer, lig_props);
   HB_BUFFER_DEALLOCATE_VAR (buffer, props_cache);
 }
 

src/hb-ot-layout-gsub-table.hh

@@ -516,8 +516,7 @@ struct Ligature
 
     /* Allocate new ligature id */
     unsigned int lig_id = allocate_lig_id (c->buffer);
-    c->buffer->info[c->buffer->idx].lig_comp() = 0;
-    c->buffer->info[c->buffer->idx].lig_id() = lig_id;
+    set_lig_props (c->buffer->info[c->buffer->idx], lig_id, 0);
 
     if (skippy_iter.idx < c->buffer->idx + count) /* No input glyphs skipped */
     {
@@ -538,8 +537,7 @@ struct Ligature
       {
 	while (c->should_mark_skip_current_glyph ())
 	{
-	  c->buffer->info[c->buffer->idx].lig_comp() = i;
-	  c->buffer->info[c->buffer->idx].lig_id() = lig_id;
+	  set_lig_props (c->buffer->info[c->buffer->idx],  lig_id, i);
 	  c->replace_glyph (c->buffer->info[c->buffer->idx].codepoint);
 	}
 
@@ -1193,12 +1191,11 @@ void
 GSUB::substitute_start (hb_buffer_t *buffer)
 {
   HB_BUFFER_ALLOCATE_VAR (buffer, props_cache);
-  HB_BUFFER_ALLOCATE_VAR (buffer, lig_id);
-  HB_BUFFER_ALLOCATE_VAR (buffer, lig_comp);
+  HB_BUFFER_ALLOCATE_VAR (buffer, lig_props);
 
   unsigned int count = buffer->len;
   for (unsigned int i = 0; i < count; i++)
-    buffer->info[i].props_cache() = buffer->info[i].lig_id() = buffer->info[i].lig_comp() = 0;
+    buffer->info[i].props_cache() = buffer->info[i].lig_props() = 0;
 }
 
 void

src/hb-ot-layout-gsubgpos-private.hh

@@ -35,12 +35,30 @@
 
 
 /* buffer var allocations */
-#define lig_id() var2.u8[2] /* unique ligature id */
-#define lig_comp() var2.u8[3] /* component number in the ligature (0 = base) */
+#define lig_props() var2.u8[3]
+
+/* unique ligature id */
+/* component number in the ligature (0 = base) */
+static inline void
+set_lig_props (hb_glyph_info_t &info, unsigned int lig_id, unsigned int lig_comp)
+{
+  info.lig_props() = (lig_id << 4) | (lig_comp & 0x0F);
+}
+static inline unsigned int
+get_lig_id (hb_glyph_info_t &info)
+{
+  return info.lig_props() >> 4;
+}
+static inline unsigned int
+get_lig_comp (hb_glyph_info_t &info)
+{
+  return info.lig_props() & 0x0F;
+}
 
 static inline uint8_t allocate_lig_id (hb_buffer_t *buffer) {
-  uint8_t lig_id = buffer->next_serial ();
-  if (unlikely (!lig_id)) lig_id = buffer->next_serial (); /* in case of overflow */
+  uint8_t lig_id = buffer->next_serial () & 0x0F;
+  if (unlikely (!lig_id))
+    lig_id = allocate_lig_id (buffer); /* in case of overflow */
   return lig_id;
 }