Fix face extension past EOL in overlay strings

* src/xdisp.c (face_at_pos): Pass ATTR_FILTER to
face_for_overlay_string.
* src/xfaces.c (face_for_overlay_string): Accept an additional
argument ATTR_INDEX and pass it to merge_face_ref for merging the
face at POS.  This ensures a face from buffer text will not be
merged unless it specifies the :extend attribute.  (Bug#42552)
* src/dispextern.h (face_for_overlay_string): Adjust prototype.

3 files changed, 5 insertions, 4 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index e1d6eddc419..311867a0c8c 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3538,7 +3538,7 @@ void recompute_basic_faces (struct frame *);
 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);
+                             bool, Lisp_Object, enum lface_attribute_index);
 int face_at_string_position (struct window *, Lisp_Object, ptrdiff_t, ptrdiff_t,
                              ptrdiff_t *, enum face_id, bool,
                              enum lface_attribute_index);
diff --git a/src/xdisp.c b/src/xdisp.c
index eb7f3e7baa1..fc17014c029 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4339,7 +4339,7 @@ face_at_pos (const struct it *it, enum lface_attribute_index attr_filter)
                                        (IT_CHARPOS (*it)
                                         + TEXT_PROP_DISTANCE_LIMIT),
                                        false,
-                                       from_overlay);
+                                       from_overlay, attr_filter);
         }
       else
         {
diff --git a/src/xfaces.c b/src/xfaces.c
index c4a4e1c94f3..585cfa1cf4a 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6475,7 +6475,8 @@ face_at_buffer_position (struct window *w, ptrdiff_t pos,
 int
 face_for_overlay_string (struct window *w, ptrdiff_t pos,
                          ptrdiff_t *endptr, ptrdiff_t limit,
-                         bool mouse, Lisp_Object overlay)
+                         bool mouse, Lisp_Object overlay,
+                         enum lface_attribute_index attr_filter)
 {
   struct frame *f = XFRAME (w->frame);
   Lisp_Object attrs[LFACE_VECTOR_SIZE];
@@ -6514,7 +6515,7 @@ 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, NULL, 0);
+    merge_face_ref (w, f, prop, attrs, true, NULL, attr_filter);
 
   *endptr = endpos;