Prevent infloops in redisplay due to truncate-lines and overlays

* src/xdisp.c (hscroll_window_tree): Avoid inflooping in
redisplay_window when a screen line ends in an overlay string with
a newline.  (Bug#25246)

1 files changed, 11 insertions, 0 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index ad0b9686f04..5de5ecaef0d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13049,6 +13049,17 @@ hscroll_window_tree (Lisp_Object window)
               init_to_row_start (&it, w, cursor_row);
               it.last_visible_x = INFINITY;
               move_it_in_display_line_to (&it, pt, -1, MOVE_TO_POS);
+              /* If the line ends in an overlay string with a newline,
+                 we might infloop, because displaying the window will
+                 want to put the cursor after the overlay, i.e. at X
+                 coordinate of zero on the next screen line.  So we
+                 use the buffer position prior to the overlay string
+                 instead.  */
+              if (it.method == GET_FROM_STRING && pt > 1)
+                {
+                  init_to_row_start (&it, w, cursor_row);
+                  move_it_in_display_line_to (&it, pt - 1, -1, MOVE_TO_POS);
+                }
               current_buffer = saved_current_buffer;
 
               /* Position cursor in window.  */