New parameter to control the face extension..

* src/xdisp.c (handle_face_prop_general): New function to specialize
handle_face_prop with ATTR_FILTER.
* src/dispextern.h (face_at_buffer_position): Added
LFACE_ATTRIBUTE_INDEX.
* src/xfaces.c (merge_face_ref): Added LFACE_ATTRIBUTE_INDEX to merge
conditionally.

4 files changed, 82 insertions, 46 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 519cc36345c..5db3ae88bf8 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3554,8 +3554,8 @@ int lookup_derived_face (struct window *, struct frame *,
 void init_frame_faces (struct frame *);
 void free_frame_faces (struct frame *);
 void recompute_basic_faces (struct frame *);
-int face_at_buffer_position (struct window *, ptrdiff_t, ptrdiff_t *, ptrdiff_t,
-                             bool, int);
+int face_at_buffer_position (struct window *, ptrdiff_t, ptrdiff_t *,
+                             ptrdiff_t, bool, int, enum lface_attribute_index);
 int face_for_overlay_string (struct window *, ptrdiff_t, ptrdiff_t *, ptrdiff_t,
                              bool, Lisp_Object);
 int face_at_string_position (struct window *, Lisp_Object, ptrdiff_t, ptrdiff_t,
diff --git a/src/font.c b/src/font.c
index 6bc977fd68e..e1e33ab8b22 100644
--- a/src/font.c
+++ b/src/font.c
@@ -3785,10 +3785,10 @@ font_at (int c, ptrdiff_t pos, struct face *face, struct window *w,
 
       if (STRINGP (string))
         face_id = face_at_string_position (w, string, pos, 0, &endptr,
-                                           DEFAULT_FACE_ID, false);
+                                           DEFAULT_FACE_ID, 0);
       else
         face_id = face_at_buffer_position (w, pos, &endptr,
-                                           pos + 100, false, -1);
+                                           pos + 100, false, -1, 0);
       face = FACE_FROM_ID (f, face_id);
     }
   if (multibyte)
@@ -3832,7 +3832,7 @@ font_range (ptrdiff_t pos, ptrdiff_t pos_byte, ptrdiff_t *limit,
 
       if (NILP (string))
           face_id = face_at_buffer_position (w, pos, &ignore, *limit,
-                                             false, -1);
+                                             false, -1, 0);
       else
         {
           face_id =
@@ -4618,7 +4618,7 @@ DEFUN ("internal-char-font", Finternal_char_font, Sinternal_char_font, 1, 2, 0,
       w = XWINDOW (window);
       f = XFRAME (w->frame);
       face_id = face_at_buffer_position (w, pos, &dummy,
-                                         pos + 100, false, -1);
+                                         pos + 100, false, -1, 0);
     }
   if (! CHAR_VALID_P (c))
     return Qnil;
diff --git a/src/xdisp.c b/src/xdisp.c
index 38a2ff66c5b..07ff4c7da7d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4148,15 +4148,18 @@ handle_fontified_prop (struct it *it)
                                 Faces
  ***********************************************************************/
 
-/* Set up iterator IT from face properties at its current position.
-   Called from handle_stop.  */
-
 static enum prop_handled
-handle_face_prop (struct it *it)
+handle_face_prop_general (struct it *it,
+                          enum lface_attribute_index attr_filter)
 {
-  int new_face_id;
+  int new_face_id, *face_id_ptr;
   ptrdiff_t next_stop;
 
+  if (attr_filter == LFACE_EXTEND_INDEX)
+    face_id_ptr = &(it->extend_face_id);
+  else
+    face_id_ptr = &(it->face_id);
+
   if (!STRINGP (it->string))
     {
       new_face_id
@@ -4165,7 +4168,7 @@ handle_face_prop (struct it *it)
                                    &next_stop,
                                    (IT_CHARPOS (*it)
                                     + TEXT_PROP_DISTANCE_LIMIT),
-                                   false, it->base_face_id);
+                                   false, it->base_face_id, attr_filter);
 
       /* Is this a start of a run of characters with box face?
          Caveat: this can be called for a freshly initialized
@@ -4173,13 +4176,13 @@ handle_face_prop (struct it *it)
          face will not change until limit, i.e. if the new face has a
          box, all characters up to limit will have one.  But, as
          usual, we don't know whether limit is really the end.  */
-      if (new_face_id != it->face_id)
+      if (new_face_id != *face_id_ptr)
         {
           struct face *new_face = FACE_FROM_ID (it->f, new_face_id);
           /* If it->face_id is -1, old_face below will be NULL, see
              the definition of FACE_FROM_ID_OR_NULL.  This will happen
              if this is the initial call that gets the face.  */
-          struct face *old_face = FACE_FROM_ID_OR_NULL (it->f, it->face_id);
+          struct face *old_face = FACE_FROM_ID_OR_NULL (it->f, *face_id_ptr);
 
           /* If the value of face_id of the iterator is -1, we have to
              look in front of IT's position and see whether there is a
@@ -4285,10 +4288,10 @@ handle_face_prop (struct it *it)
          box, all characters up to that position will have a
          box.  But, as usual, we don't know whether that position
          is really the end.  */
-      if (new_face_id != it->face_id)
+      if (new_face_id != *face_id_ptr)
         {
           struct face *new_face = FACE_FROM_ID (it->f, new_face_id);
-          struct face *old_face = FACE_FROM_ID_OR_NULL (it->f, it->face_id);
+          struct face *old_face = FACE_FROM_ID_OR_NULL (it->f, *face_id_ptr);
 
           /* If new face has a box but old face hasn't, this is the
              start of a run of characters with box, i.e. it has a
@@ -4299,11 +4302,21 @@ handle_face_prop (struct it *it)
         }
     }
 
-  it->face_id = new_face_id;
+  *face_id_ptr = new_face_id;
   return HANDLED_NORMALLY;
 }
 
 
+/* Set up iterator IT from face properties at its current position.
+   Called from handle_stop.  */
+
+static enum prop_handled
+handle_face_prop (struct it *it)
+{
+  return handle_face_prop_general (it, 0);
+}
+
+
 /* Return the ID of the face ``underlying'' IT's current position,
    which is in a string.  If the iterator is associated with a
    buffer, return the face at IT's current buffer position.
@@ -4527,7 +4540,7 @@ face_before_or_after_it_pos (struct it *it, bool before_p)
       face_id = face_at_buffer_position (it->w,
                                          CHARPOS (pos),
                                          &next_check_charpos,
-                                         limit, false, -1);
+                                         limit, false, -1, 0);
 
       /* Correct the face for charsets different from ASCII.  Do it
          for the multibyte case only.  The face returned above is
@@ -7649,10 +7662,11 @@ get_next_display_element (struct it *it)
                   else
                     {
                       next_face_id =
-                        face_at_buffer_position (it->w, CHARPOS (pos), &ignore,
+                        face_at_buffer_position (it->w, CHARPOS (pos),
+                                                 &ignore,
                                                  CHARPOS (pos)
                                                  + TEXT_PROP_DISTANCE_LIMIT,
-                                                 false, -1);
+                                                 false, -1, 0);
                       it->end_of_box_run_p
                         = (FACE_FROM_ID (it->f, next_face_id)->box
                            == FACE_NO_BOX);
@@ -32068,7 +32082,7 @@ mouse_face_from_buffer_pos (Lisp_Object window,
   hlinfo->mouse_face_face_id
     = face_at_buffer_position (w, mouse_charpos, &ignore,
                                mouse_charpos + 1,
-                               !hlinfo->mouse_face_hidden, -1);
+                               !hlinfo->mouse_face_hidden, -1, 0);
   show_mouse_face (hlinfo, DRAW_MOUSE_FACE);
 }
 
diff --git a/src/xfaces.c b/src/xfaces.c
index 889bf83561c..189ba1e7678 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -347,7 +347,8 @@ static struct face_cache *make_face_cache (struct frame *);
 static void free_face_cache (struct face_cache *);
 static bool merge_face_ref (struct window *w,
                             struct frame *, Lisp_Object, Lisp_Object *,
-                            bool, struct named_merge_point *);
+                            bool, struct named_merge_point *,
+                            enum lface_attribute_index);
 static int color_distance (Emacs_Color *x, Emacs_Color *y);
 
 #ifdef HAVE_WINDOW_SYSTEM
@@ -1910,7 +1911,8 @@ get_lface_attributes (struct window *w,
             attrs[i] = Qunspecified;
 
           return merge_face_ref (w, f, XCDR (face_remapping), attrs,
-                                 signal_p, named_merge_points);
+                                 signal_p, named_merge_points,
+                                 0);
         }
     }
 
@@ -2065,7 +2067,8 @@ merge_face_vectors (struct window *w,
   if (!UNSPECIFIEDP (from[LFACE_INHERIT_INDEX])
       && !NILP (from[LFACE_INHERIT_INDEX]))
     merge_face_ref (w, f, from[LFACE_INHERIT_INDEX],
-                    to, false, named_merge_points);
+                    to, false, named_merge_points,
+                    0);
 
   if (FONT_SPEC_P (from[LFACE_FONT_INDEX]))
     {
@@ -2131,7 +2134,8 @@ merge_face_vectors (struct window *w,
 static bool
 merge_named_face (struct window *w,
                   struct frame *f, Lisp_Object face_name, Lisp_Object *to,
-                  struct named_merge_point *named_merge_points)
+                  struct named_merge_point *named_merge_points,
+                  enum lface_attribute_index attr_filter)
 {
   struct named_merge_point named_merge_point;
 
@@ -2141,9 +2145,13 @@ merge_named_face (struct window *w,
     {
       Lisp_Object from[LFACE_VECTOR_SIZE];
       bool ok = get_lface_attributes (w, f, face_name, from, false,
-                                      named_merge_points);
+                                      named_merge_points);
 
-      if (ok)
+      eassert (attr_filter <  LFACE_VECTOR_SIZE);
+
+      if (ok && (attr_filter == 0
+                 || (!NILP (from[attr_filter])
+                     && !UNSPECIFIEDP (from[attr_filter]))))
         merge_face_vectors (w, f, from, to, named_merge_points);
 
       return ok;
@@ -2274,6 +2282,11 @@ filter_face_ref (Lisp_Object face_ref,
    of ERR_MSGS).  Use NAMED_MERGE_POINTS to detect loops in face
    inheritance or list structure; it may be 0 for most callers.
 
+   attr_filter is the index of a parameter that conditions the merging
+   for named faces (case 1) to only the face_ref where
+   lface[merge_face_ref] is non-nil. To merge unconditionally set this
+   value to 0.
+
    FACE_REF may be a single face specification or a list of such
    specifications.  Each face specification can be:
 
@@ -2302,7 +2315,8 @@ filter_face_ref (Lisp_Object face_ref,
 static bool
 merge_face_ref (struct window *w,
                 struct frame *f, Lisp_Object face_ref, Lisp_Object *to,
-                bool err_msgs, struct named_merge_point *named_merge_points)
+                bool err_msgs, struct named_merge_point *named_merge_points,
+                enum lface_attribute_index attr_filter)
 {
   bool ok = true;               /* Succeed without an error? */
   Lisp_Object filtered_face_ref;
@@ -2514,7 +2528,8 @@ merge_face_ref (struct window *w,
                   /* This is not really very useful; it's just like a
                      normal face reference.  */
                   if (! merge_face_ref (w, f, value, to,
-                                        err_msgs, named_merge_points))
+                                        err_msgs, named_merge_points,
+                                        0))
                     err = true;
                 }
               else if (EQ (keyword, QCextend))
@@ -2544,16 +2559,19 @@ merge_face_ref (struct window *w,
           Lisp_Object next = XCDR (face_ref);
 
           if (! NILP (next))
-            ok = merge_face_ref (w, f, next, to, err_msgs, named_merge_points);
+            ok = merge_face_ref (w, f, next, to, err_msgs,
+                                 named_merge_points, 0);
 
-          if (! merge_face_ref (w, f, first, to, err_msgs, named_merge_points))
+          if (! merge_face_ref (w, f, first, to, err_msgs,
+                                named_merge_points, 0))
             ok = false;
         }
     }
   else
     {
       /* FACE_REF ought to be a face name.  */
-      ok = merge_named_face (w, f, face_ref, to, named_merge_points);
+      ok = merge_named_face (w, f, face_ref, to, named_merge_points,
+                             attr_filter);
       if (!ok && err_msgs)
         add_to_log ("Invalid face reference: %s", face_ref);
     }
@@ -4534,7 +4552,8 @@ lookup_face (struct frame *f, Lisp_Object *attr)
    suitable face is found, realize a new one.  */
 
 int
-face_for_font (struct frame *f, Lisp_Object font_object, struct face *base_face)
+face_for_font (struct frame *f, Lisp_Object font_object,
+               struct face *base_face)
 {
   struct face_cache *cache = FRAME_FACE_CACHE (f);
   unsigned hash;
@@ -4769,7 +4788,7 @@ DEFUN ("face-attributes-as-vector", Fface_attributes_as_vector,
   Lisp_Object lface = make_vector (LFACE_VECTOR_SIZE, Qunspecified);
   merge_face_ref (NULL, XFRAME (selected_frame),
                   plist, XVECTOR (lface)->contents,
-                  true, 0);
+                  true, NULL, 0);
   return lface;
 }
 
@@ -5126,7 +5145,7 @@ face for italic.  */)
 
   for (i = 0; i < LFACE_VECTOR_SIZE; i++)
     attrs[i] = Qunspecified;
-  merge_face_ref (NULL, f, attributes, attrs, true, 0);
+  merge_face_ref (NULL, f, attributes, attrs, true, NULL, 0);
 
   def_face = FACE_FROM_ID_OR_NULL (f, DEFAULT_FACE_ID);
   if (def_face == NULL)
@@ -6012,7 +6031,7 @@ compute_char_face (struct frame *f, int ch, Lisp_Object prop)
       Lisp_Object attrs[LFACE_VECTOR_SIZE];
       struct face *default_face = FACE_FROM_ID (f, DEFAULT_FACE_ID);
       memcpy (attrs, default_face->lface, sizeof attrs);
-      merge_face_ref (NULL, f, prop, attrs, true, 0);
+      merge_face_ref (NULL, f, prop, attrs, true, NULL, 0);
       face_id = lookup_face (f, attrs);
     }
 
@@ -6024,6 +6043,8 @@ compute_char_face (struct frame *f, int ch, Lisp_Object prop)
    which a different face is needed, as far as text properties and
    overlays are concerned.  W is a window displaying current_buffer.
 
+   attr_filter is passed merge_face_ref.
+
    REGION_BEG, REGION_END delimit the region, so it can be
    highlighted.
 
@@ -6043,7 +6064,8 @@ compute_char_face (struct frame *f, int ch, Lisp_Object prop)
 int
 face_at_buffer_position (struct window *w, ptrdiff_t pos,
                          ptrdiff_t *endptr, ptrdiff_t limit,
-                         bool mouse, int base_face_id)
+                         bool mouse, int base_face_id,
+                         enum lface_attribute_index attr_filter)
 {
   struct frame *f = XFRAME (w->frame);
   Lisp_Object attrs[LFACE_VECTOR_SIZE];
@@ -6104,8 +6126,7 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
   }
 
   /* Optimize common cases where we can use the default face.  */
-  if (noverlays == 0
-      && NILP (prop))
+  if (noverlays == 0 && NILP (prop))
     {
       SAFE_FREE ();
       return default_face->id;
@@ -6116,7 +6137,7 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
 
   /* Merge in attributes specified via text properties.  */
   if (!NILP (prop))
-    merge_face_ref (w, f, prop, attrs, true, 0);
+    merge_face_ref (w, f, prop, attrs, true, NULL, 0);
 
   /* Now merge the overlay data.  */
   noverlays = sort_overlays (overlay_vec, noverlays, w);
@@ -6136,7 +6157,7 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
                  so discard the mouse-face text property, if any, and
                  use the overlay property instead.  */
               memcpy (attrs, default_face->lface, sizeof attrs);
-              merge_face_ref (w, f, prop, attrs, true, 0);
+              merge_face_ref (w, f, prop, attrs, true, NULL, attr_filter);
             }
 
           oend = OVERLAY_END (overlay_vec[i]);
@@ -6153,8 +6174,9 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
           ptrdiff_t oendpos;
 
           prop = Foverlay_get (overlay_vec[i], propname);
+
           if (!NILP (prop))
-            merge_face_ref (w, f, prop, attrs, true, 0);
+            merge_face_ref (w, f, prop, attrs, true, NULL, attr_filter);
 
           oend = OVERLAY_END (overlay_vec[i]);
           oendpos = OVERLAY_POSITION (oend);
@@ -6220,7 +6242,7 @@ face_for_overlay_string (struct window *w, ptrdiff_t pos,
 
   /* Merge in attributes specified via text properties.  */
   if (!NILP (prop))
-    merge_face_ref (w, f, prop, attrs, true, 0);
+    merge_face_ref (w, f, prop, attrs, true, NULL, 0);
 
   *endptr = endpos;
 
@@ -6255,7 +6277,7 @@ int
 face_at_string_position (struct window *w, Lisp_Object string,
                          ptrdiff_t pos, ptrdiff_t bufpos,
                          ptrdiff_t *endptr, enum face_id base_face_id,
-                         bool mouse_p)
+                         bool mouse_p)
 {
   Lisp_Object prop, position, end, limit;
   struct frame *f = XFRAME (WINDOW_FRAME (w));
@@ -6299,7 +6321,7 @@ face_at_string_position (struct window *w, Lisp_Object string,
 
   /* Merge in attributes specified via text properties.  */
   if (!NILP (prop))
-    merge_face_ref (w, f, prop, attrs, true, 0);
+    merge_face_ref (w, f, prop, attrs, true, NULL, 0);
 
   /* Look up a realized face with the given face attributes,
      or realize a new one for ASCII characters.  */
@@ -6349,7 +6371,7 @@ merge_faces (struct window *w, Lisp_Object face_name, int face_id,
 
   if (!NILP (face_name))
     {
-      if (!merge_named_face (w, f, face_name, attrs, 0))
+      if (!merge_named_face (w, f, face_name, attrs, NULL, 0))
         return base_face_id;
     }
   else