From: Eli Zaretskii <eliz@gnu.org>
Date: Thu, 25 Nov 2021 13:06:08 +0000 (+0200)
Subject: Fix 'posn-at-point' near some overlays
X-Git-Tag: emacs-28.0.90~37
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=a22c9a34bd1cc3683b965383a59b4a50e9091776;p=emacs.git

Fix 'posn-at-point' near some overlays

* src/xdisp.c (pos_visible_p): Fix 'posn-at-point' for positions
just after a display property that draws a fringe bitmap.
(Bug#52097)
---

diff --git a/src/xdisp.c b/src/xdisp.c
index 34add807986..4642541823c 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -1992,7 +1992,17 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
 	    }
 
 	  *x = top_x;
-	  *y = max (top_y + max (0, it.max_ascent - it.ascent), window_top_y);
+	  /* The condition below is a heuristic fix for the situation
+	     where move_it_to stops just after finishing the display
+	     of a fringe bitmap, which resets it.ascent to zero, and
+	     thus causes Y to be offset by it.max_ascent.  */
+	  if (it.ascent == 0 && it.what == IT_IMAGE
+	      && it.method != GET_FROM_IMAGE
+	      && it.image_id < 0
+	      && it.max_ascent > 0)
+	    *y = max (top_y, window_top_y);
+	  else
+	    *y = max (top_y + max (0, it.max_ascent - it.ascent), window_top_y);
 	  *rtop = max (0, window_top_y - top_y);
 	  *rbot = max (0, bottom_y - it.last_visible_y);
 	  *rowh = max (0, (min (bottom_y, it.last_visible_y)
@@ -2020,7 +2030,13 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
 	  RESTORE_IT (&it2, &it2, it2data);
 	  move_it_to (&it2, charpos, -1, -1, -1, MOVE_TO_POS);
 	  *x = it2.current_x;
-	  *y = it2.current_y + it2.max_ascent - it2.ascent;
+	  if (it2.ascent == 0 && it2.what == IT_IMAGE
+	      && it2.method != GET_FROM_IMAGE
+	      && it2.image_id < 0
+	      && it2.max_ascent > 0)
+	    *y = it2.current_y;
+	  else
+	    *y = it2.current_y + it2.max_ascent - it2.ascent;
 	  *rtop = max (0, -it2.current_y);
 	  *rbot = max (0, ((it2.current_y + it2.max_ascent + it2.max_descent)
 			   - it.last_visible_y));