Revert "Remove unneeded buffer clear_output / remove_output calls"

This reverts commit 06175b7143.

One of the sanitizers is failing. Pushing again as PR to debug.
I have suspicions.

src/hb-buffer.cc

@@ -281,6 +281,16 @@ hb_buffer_t::add_info (const hb_glyph_info_t &glyph_info)
 }
 
 
+void
+hb_buffer_t::remove_output ()
+{
+  have_output = false;
+  have_positions = false;
+
+  out_len = 0;
+  out_info = info;
+}
+
 void
 hb_buffer_t::clear_output ()
 {

src/hb-buffer.hh

@@ -209,6 +209,7 @@ struct hb_buffer_t
   HB_INTERNAL void guess_segment_properties ();
 
   HB_INTERNAL void swap_buffers ();
+  HB_INTERNAL void remove_output ();
   HB_INTERNAL void clear_output ();
   HB_INTERNAL void clear_positions ();
 

src/hb-ot-layout.cc

@@ -1857,9 +1857,8 @@ apply_string (OT::hb_ot_apply_context_t *c,
   if (likely (!lookup.is_reverse ()))
   {
     /* in/out forward substitution/positioning */
-    if (!Proxy::inplace)
+    if (Proxy::table_index == 0u)
       buffer->clear_output ();
-
     buffer->idx = 0;
 
     bool ret;
@@ -1875,7 +1874,10 @@ apply_string (OT::hb_ot_apply_context_t *c,
   else
   {
     /* in-place backward substitution/positioning */
+    if (Proxy::table_index == 0u)
+      buffer->remove_output ();
     buffer->idx = buffer->len - 1;
+
     apply_backward (c, accel);
   }
 }
@@ -1891,8 +1893,7 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
   OT::hb_ot_apply_context_t c (table_index, font, buffer);
   c.set_recurse_func (Proxy::Lookup::apply_recurse_func);
 
-  for (unsigned int stage_index = 0; stage_index < stages[table_index].length; stage_index++)
+  for (unsigned int stage_index = 0; stage_index < stages[table_index].length; stage_index++) {
-  {
     const stage_map_t *stage = &stages[table_index][stage_index];
     for (; i < stage->last_lookup; i++)
     {
@@ -1914,7 +1915,10 @@ inline void hb_ot_map_t::apply (const Proxy &proxy,
     }
 
     if (stage->pause_func)
+    {
+      buffer->clear_output ();
       stage->pause_func (plan, font, buffer);
+    }
   }
 }
 

src/hb-ot-shape.cc

@@ -551,7 +551,6 @@ hb_insert_dotted_circle (hb_buffer_t *buffer, hb_font_t *font)
   info.cluster = buffer->cur().cluster;
   info.mask = buffer->cur().mask;
   (void) buffer->output_info (info);
-
   buffer->swap_buffers ();
 }
 
@@ -1128,6 +1127,8 @@ hb_ot_shape_internal (hb_ot_shape_context_t *c)
 
   _hb_buffer_allocate_unicode_vars (c->buffer);
 
+  c->buffer->clear_output ();
+
   hb_ot_shape_initialize_masks (c);
   hb_set_unicode_props (c->buffer);
   hb_insert_dotted_circle (c->buffer, c->font);