master 1f0fb1f: Fix rare redisplay glitches when image has been removed from display

[Eli Zaretskii]

branch: master
commit 1f0fb1f6fa50faf67ffaaee0e52d00144883821e
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix rare redisplay glitches when image has been removed from display
    
    * src/dispnew.c (update_window): Make sure all glyph rows below
    the last visible one are marked as invalid, even when the loop
    which "updates the rest of the lines" didn't examine the last
    visible row.  (Bug#47093)
---
 src/dispnew.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/dispnew.c b/src/dispnew.c
index b3e4587..f613f7b 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -3588,6 +3588,7 @@ update_window (struct window *w, bool force_p)
       int yb;
       bool changed_p = 0, mouse_face_overwritten_p = 0;
       int n_updated = 0;
+      bool invisible_rows_marked = false;
 
 #ifdef HAVE_WINDOW_SYSTEM
       gui_update_window_begin (w);
@@ -3679,13 +3680,36 @@ update_window (struct window *w, bool force_p)
               tempted to optimize redisplay based on lines displayed
               in the first redisplay.  */
            if (MATRIX_ROW_BOTTOM_Y (row) >= yb)
-             for (i = vpos + 1; i < w->current_matrix->nrows - 1; ++i)
-               SET_MATRIX_ROW_ENABLED_P (w->current_matrix, i, false);
+             {
+               for (i = vpos + 1; i < w->current_matrix->nrows - 1; ++i)
+                 SET_MATRIX_ROW_ENABLED_P (w->current_matrix, i, false);
+               invisible_rows_marked = true;
+             }
          }
 
       /* Was display preempted?  */
       paused_p = row < end;
 
+      if (!paused_p && !invisible_rows_marked)
+       {
+         /* If we didn't mark the invisible rows in the current
+            matrix as invalid above, do that now.  This can happen if
+            scrolling_window updates the last visible rows of the
+            current matrix, in which case the above loop doesn't get
+            to examine the last visible row.  */
+         int i;
+         for (i = 0; i < w->current_matrix->nrows - 1; ++i)
+           {
+             struct glyph_row *current_row = MATRIX_ROW (w->current_matrix, i);
+             if (current_row->enabled_p
+                 && MATRIX_ROW_BOTTOM_Y (current_row) >= yb)
+               {
+                 for (++i ; i < w->current_matrix->nrows - 1; ++i)
+                   SET_MATRIX_ROW_ENABLED_P (w->current_matrix, i, false);
+               }
+           }
+       }
+
     set_cursor:
 
       /* Update the tab line after scrolling because a new tab