Fix handling of window-specific overlays in buffer iteration for display

* src/xdisp.c (compute_display_string_pos): Pay attention to
'display' properties that come from overlays, in case the overlays
are window-specific.  Call 'handle_display_prop' with the argument
OVERLAY non-nil, if the property is from an overlay.
(compute_display_string_end): Accept an additional argument, a
pointer to the window; all callers changed.  Pay attention to
'display' properties that come from overlays, in case the overlays
are window-specific.  In particular, if the property comes from an
overlay, use that overlay's end position as the next place where
the 'display' property changes, effectively disregarding any
properties on buffer text that is replaced by this overlay's
'display' property.
(handle_single_display_spec): Always use the end position of the
overlay which determined the 'display' property as the end of the
property, to make sure we obey windows-specific overlays.
* src/bidi.c (bidi_fetch_char): Adapt to the above change.
* src/dispextern.h: Adjust prototype of 'compute_display_string_end'.
(Bug#80255)

src/bidi.c

@@ -1335,7 +1335,7 @@ bidi_fetch_char (ptrdiff_t charpos, ptrdiff_t bytepos, ptrdiff_t *disp_pos,
 	     Replacement Character.  */
 	  ch = OBJECT_REPLACEMENT_CHARACTER;
 	}
-      disp_end_pos = compute_display_string_end (*disp_pos, string);
+      disp_end_pos = compute_display_string_end (*disp_pos, string, w);
       if (disp_end_pos < 0)
 	{
 	  /* Somebody removed the display string from the buffer

src/dispextern.h

@@ -3581,7 +3581,8 @@ extern ptrdiff_t compute_display_string_pos (struct text_pos *,
 					     struct bidi_string_data *,
 					     struct window *, bool, int *);
 extern ptrdiff_t compute_display_string_end (ptrdiff_t,
-					     struct bidi_string_data *);
+					     struct bidi_string_data *,
+					     struct window *);
 extern void produce_stretch_glyph (struct it *);
 extern int merge_glyphless_glyph_face (struct it *);
 extern void forget_escape_and_glyphless_faces (void);

src/xdisp.c

@@ -4497,6 +4497,7 @@ compute_display_string_pos (struct text_pos *position,
     (charpos < eob - MAX_DISP_SCAN) ? charpos + MAX_DISP_SCAN : eob;
   struct text_pos tpos;
   int rv = 0;
+  Lisp_Object overlay = Qnil, ov1 = Qnil;
 
   if (string && STRINGP (string->lstring))
     object1 = object = string->lstring;
@@ -4529,13 +4530,15 @@ compute_display_string_pos (struct text_pos *position,
   else
     bufpos = charpos;
   tpos = *position;
-  if (!NILP (spec = Fget_char_property (pos, Qdisplay, object))
+  if (!NILP (spec = get_char_property_and_overlay (pos, Qdisplay, object,
+						   &overlay))
       && (charpos <= begb
-	  || !EQ (Fget_char_property (make_fixnum (charpos - 1), Qdisplay,
-				      object),
-		  spec))
-      && (rv = handle_display_spec (NULL, spec, object1, Qnil, &tpos, bufpos,
-				    frame_window_p)))
+	  || !EQ (get_char_property_and_overlay (make_fixnum (charpos - 1),
+						 Qdisplay, object, &ov1),
+		  spec)
+	  || !BASE_EQ (overlay, ov1))
+      && (rv = handle_display_spec (NULL, spec, object1, overlay, &tpos,
+				    bufpos, frame_window_p)))
     {
       if (rv == 2)
 	*disp_prop = 2;
@@ -4557,11 +4560,11 @@ compute_display_string_pos (struct text_pos *position,
       BYTEPOS (tpos) = string_char_to_byte (object, CHARPOS (tpos));
     else
       BYTEPOS (tpos) = CHAR_TO_BYTE (CHARPOS (tpos));
-    spec = Fget_char_property (pos, Qdisplay, object);
+    spec = get_char_property_and_overlay (pos, Qdisplay, object, &overlay);
     if (!STRINGP (object))
       bufpos = CHARPOS (tpos);
   } while (NILP (spec)
-	   || !(rv = handle_display_spec (NULL, spec, object1, Qnil, &tpos,
+	   || !(rv = handle_display_spec (NULL, spec, object1, overlay, &tpos,
 					  bufpos, frame_window_p)));
   if (rv == 2)
     *disp_prop = 2;
@@ -4575,11 +4578,19 @@ compute_display_string_pos (struct text_pos *position,
    property whose value is a string or a `display' text property whose
    value is a string.  */
 ptrdiff_t
-compute_display_string_end (ptrdiff_t charpos, struct bidi_string_data *string)
+compute_display_string_end (ptrdiff_t charpos, struct bidi_string_data *string,
+			    struct window *w)
 {
+  Lisp_Object window = Qnil;
+  if (w)
+    XSETWINDOW (window, w);
+
   /* OBJECT = nil means current buffer.  */
-  Lisp_Object object =
-    (string && STRINGP (string->lstring)) ? string->lstring : Qnil;
+  Lisp_Object object = (string && STRINGP (string->lstring))
+		       ? string->lstring
+		       : WINDOWP (window)
+			 ? window
+			 : Qnil;
   Lisp_Object pos = make_fixnum (charpos);
   ptrdiff_t eob =
     (STRINGP (object) || (string && string->s)) ? string->schars : ZV;
@@ -4601,11 +4612,18 @@ compute_display_string_end (ptrdiff_t charpos, struct bidi_string_data *string)
      it->stop_charpos.  But neither compute_display_string_pos nor
      bidi_fetch_char that calls it know or care where the next
      stop_charpos is.  */
-  if (NILP (Fget_char_property (pos, Qdisplay, object)))
+  Lisp_Object overlay = Qnil;
+  if (NILP (get_char_property_and_overlay (pos, Qdisplay, object, &overlay)))
     return -1;
 
   /* Look forward for the first character where the `display' property
      changes.  */
+  if (OVERLAYP (overlay))
+    return OVERLAY_END (overlay);
+
+  /* next-char-property-change doesn't support window OBJECTs.  */
+  if (WINDOWP (object))
+    object = w->contents;
   pos = Fnext_single_char_property_change (pos, Qdisplay, object, Qnil);
 
   return XFIXNAT (pos);
@@ -6286,14 +6304,14 @@ handle_single_display_spec (struct it *it, Lisp_Object spec, Lisp_Object object,
   if (it)
     {
       start_pos = *position;
-      *position = display_prop_end (it, object, start_pos);
-      /* If the display property comes from an overlay, don't consider
-	 any potential stop_charpos values before the end of that
-	 overlay.  Since display_prop_end will happily find another
-	 'display' property coming from some other overlay or text
-	 property on buffer positions before this overlay's end, we
-	 need to ignore them, or else we risk displaying this
-	 overlay's display string/image twice.  */
+      /* If the display property comes from an overlay, always use the
+	 end of that overlay as the end of the property.  Since
+	 display_prop_end will happily find another 'display' property
+	 coming from some other overlay or text property on buffer
+	 positions before this overlay's end, or overlays not specific
+	 to this window, we need to ignore them, or else we risk
+	 displaying this overlay's display string/image twice, or fail
+	 to display text that should be.  */
       if (!NILP (overlay))
 	{
 	  ptrdiff_t ovendpos = OVERLAY_END (overlay);
@@ -6306,9 +6324,10 @@ handle_single_display_spec (struct it *it, Lisp_Object spec, Lisp_Object object,
 	     set below.  Prevent that.  */
 	  ovendpos = clip_to_bounds (BEGV, ovendpos, ZV);
 
-	  if (ovendpos > CHARPOS (*position))
-	    SET_TEXT_POS (*position, ovendpos, CHAR_TO_BYTE (ovendpos));
+	  SET_TEXT_POS (*position, ovendpos, CHAR_TO_BYTE (ovendpos));
 	}
+      else
+	*position = display_prop_end (it, object, start_pos);
     }
   value = Qnil;