Merge branch 'abort-redisplay'

This allows abandoning the redisplay of a window
that takes too long to complete.  Bug#45898
* src/xdisp.c (update_redisplay_ticks): New function.
(init_iterator, set_iterator_to_next): Call
'update_redisplay_ticks'.
(syms_of_xdisp) <max_redisplay_ticks>: New variable.
<list_of_error>: Remove 'void-variable': it is no longer needed,
since 'calc_pixel_width_or_height' can no longer signal a
void-variable error, and it gets in the way of aborting
redisplay via 'redisplay_window_error'.
* src/keyboard.c (command_loop_1): Reinitialize the tick count
before executing each command in the loop.
* src/syntax.c (scan_sexps_forward): Call 'update_redisplay_ticks'
after finishing the loop.
* src/dispnew.c (make_current): Make sure enabled rows of the
current matrix have a valid hash, even if redisplay of a window
was aborted due to slowness.  This avoids assertion violations in
'scrolling_window' due to the wrong hash value.
* src/xdisp.c (display_working_on_window_p): New global variable.
(unwind_display_working_on_window): New function.
* src/keyboard.c (command_loop_1): Reset
'display_working_on_window_p' before and after executing commands.
* src/window.c (Frecenter, window_scroll, displayed_window_lines):
* src/indent.c (Fvertical_motion): Set
'display_working_on_window_p' before calling 'start_display'.
* src/syntax.c (scan_sexps_forward): Call 'update_redisplay_ticks'
after finishing the loop.
* src/regex-emacs.c (re_match_2_internal):
* src/bidi.c (bidi_find_bracket_pairs, bidi_fetch_char)
(bidi_paragraph_init, bidi_find_other_level_edge): Update the
redisplay tick count as appropriate, when moving the iterator by
one character position actually requires to examine many more
positions.
* src/xdisp.c (redisplay_window_error): Show messages about
aborted redisplay of a window as delayed-warnings.

* doc/emacs/trouble.texi (DEL Does Not Delete): Move to the end of
the chapter.  This issue is no longer frequent or important as it
was back in Emacs 20 days.
(Long Lines): Document 'max-redisplay-ticks'.
* doc/emacs/emacs.texi (Top): Update the detailed menu.

* etc/NEWS: Announce 'max-redisplay-ticks'.

1 files changed, 15 insertions, 1 deletions

diff --git a/src/window.c b/src/window.c
index ad7a85cf550..ad03a02758e 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5568,7 +5568,11 @@ window_scroll (Lisp_Object window, EMACS_INT n, bool whole, bool noerror)
   /* On GUI frames, use the pixel-based version which is much slower
      than the line-based one but can handle varying line heights.  */
   if (FRAME_WINDOW_P (XFRAME (XWINDOW (window)->frame)))
-    window_scroll_pixel_based (window, n, whole, noerror);
+    {
+      record_unwind_protect_void (unwind_display_working_on_window);
+      display_working_on_window_p = true;
+      window_scroll_pixel_based (window, n, whole, noerror);
+    }
   else
     window_scroll_line_based (window, n, whole, noerror);
 
@@ -6496,9 +6500,14 @@ displayed_window_lines (struct window *w)
   CLIP_TEXT_POS_FROM_MARKER (start, w->start);
 
   itdata = bidi_shelve_cache ();
+
+  specpdl_ref count = SPECPDL_INDEX ();
+  record_unwind_protect_void (unwind_display_working_on_window);
+  display_working_on_window_p = true;
   start_display (&it, w, start);
   move_it_vertically (&it, height);
   bottom_y = line_bottom_y (&it);
+  unbind_to (count, Qnil);
   bidi_unshelve_cache (itdata, false);
 
   /* Add in empty lines at the bottom of the window.  */
@@ -6592,6 +6601,10 @@ and redisplay normally--don't erase and redraw the frame.  */)
      data structures might not be set up yet then.  */
   if (!FRAME_INITIAL_P (XFRAME (w->frame)))
     {
+      specpdl_ref count = SPECPDL_INDEX ();
+
+      record_unwind_protect_void (unwind_display_working_on_window);
+      display_working_on_window_p = true;
       if (center_p)
 	{
 	  struct it it;
@@ -6708,6 +6721,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
 
 	  bidi_unshelve_cache (itdata, false);
 	}
+      unbind_to (count, Qnil);
     }
   else
     {