A better fix for extension of overlay string's faces

* src/xdisp.c (face_at_pos): Revert previous change that
rejected the underlying face if it failed the filtering
criteria.
* src/xfaces.c (face_at_string_position): Reset the base face's
attribute used for filtering faces if the attribute is t.
(Bug#38563)

2 files changed, 9 insertions, 20 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index bb370bbb78f..4ddde1be717 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4243,26 +4243,11 @@ face_at_pos (const struct it *it, enum lface_attribute_index attr_filter)
              the display string do.  This sounds like a design bug,
              but Emacs always did that since v21.1, so changing that
              might be a big deal.  */
-          bool use_default = (it->string_from_prefix_prop_p != 0);
-          base_face_id = DEFAULT_FACE_ID;
-          if (!use_default)
-            {
-              base_face_id = underlying_face_id (it);
-              /* Reject the underlying face, if that face is different
-                 from the iterator face, and we filter by attr_filter,
-                 and that face's value of the filter attribute is nil
-                 or unspecified; use the default face instead.  */
-              struct face *bf = FACE_FROM_ID_OR_NULL (it->f, base_face_id);
-              if (base_face_id != it->base_face_id
-                  && attr_filter > 0
-                  && (NILP (bf->lface[attr_filter])
-                      || EQ (bf->lface[attr_filter], Qunspecified)))
-                use_default = true;
-            }
-          if (use_default)
-            base_face_id = (!NILP (Vface_remapping_alist)
-                            ? lookup_basic_face (it->w, it->f, DEFAULT_FACE_ID)
-                            : DEFAULT_FACE_ID);
+          base_face_id = it->string_from_display_prop_p
+            ? (!NILP (Vface_remapping_alist)
+               ? lookup_basic_face (it->w, it->f, DEFAULT_FACE_ID)
+               : DEFAULT_FACE_ID)
+            : underlying_face_id (it);
         }
 
       return face_at_string_position (it->w,
diff --git a/src/xfaces.c b/src/xfaces.c
index 54b5f4a94a4..5c347d41e30 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6445,6 +6445,10 @@ face_at_string_position (struct window *w, Lisp_Object string,
 
   /* Begin with attributes from the base face.  */
   memcpy (attrs, base_face->lface, sizeof attrs);
+  /* Reset the attribute of the base face used as the filter, because
+     otherwise there's no way for faces to be merged to countermand that.  */
+  if (EQ (attrs[attr_filter], Qt))
+    attrs[attr_filter] = Qnil;
 
   /* Merge in attributes specified via text properties.  */
   if (!NILP (prop))