Be more careful if selected window shows the buffer other than current,

use window_outdated only if this is not so.  This change should also
address some weird issues discussed in Bug#13012.
* window.h (window_outdated): New prototype.
* window.c (window_outdated): Now here.  Convert from static and
always assume window's buffer.
(Fwindow_end, Fwindow_line_height): Use it.
* xdisp.c (reconsider_clip_changes): Remove prototype, drop 2nd arg
and always assume window's buffer.
(redisplay_window): Adjust user.
(redisplay_internal): Call to reconsider_clip_change once and
check whether mode line should be updated only if selected window
shows current buffer.
(run_window_scroll_functions): Use eassert for debugging check.
(Fmove_point_visually, note_mouse_highlight): Use window_outdated.

1 files changed, 13 insertions, 4 deletions

diff --git a/src/window.c b/src/window.c
index 33d7dab7ec0..dff449072f5 100644
--- a/src/window.c
+++ b/src/window.c
@@ -239,6 +239,17 @@ wset_combination (struct window *w, bool horflag, Lisp_Object val)
     w->horizontal = horflag;
 }
 
+/* Nonzero if leaf window W doesn't reflect the actual state
+   of displayed buffer due to its text or overlays change.  */
+
+bool
+window_outdated (struct window *w)
+{
+  struct buffer *b = XBUFFER (w->contents);
+  return (w->last_modified < BUF_MODIFF (b)
+          || w->last_overlay_modified < BUF_OVERLAY_MODIFF (b));
+}
+
 struct window *
 decode_live_window (register Lisp_Object window)
 {
@@ -1506,8 +1517,7 @@ if it isn't already recorded.  */)
           || !w->window_end_valid
           || b->clip_changed
           || b->prevent_redisplay_optimizations_p
-          || w->last_modified < BUF_MODIFF (b)
-          || w->last_overlay_modified < BUF_OVERLAY_MODIFF (b))
+          || window_outdated (w))
       && !noninteractive)
     {
       struct text_pos startp;
@@ -1720,8 +1730,7 @@ Return nil if window display is not up-to-date.  In that case, use
       || windows_or_buffers_changed
       || b->clip_changed
       || b->prevent_redisplay_optimizations_p
-      || w->last_modified < BUF_MODIFF (b)
-      || w->last_overlay_modified < BUF_OVERLAY_MODIFF (b))
+      || window_outdated (w))
     return Qnil;
 
   if (NILP (line))