+/* Nonzero if the current window's buffer is shown in more than one
+ window and was modified since last redisplay. */
+
+static int
+buffer_shared_and_changed (void)
+{
+ return (buffer_window_count (current_buffer) > 1
+ && UNCHANGED_MODIFIED < MODIFF);
+}
+
+/* Nonzero if W doesn't reflect the actual state of current buffer due
+ to its text or overlays change. FIXME: this may be called when
+ XBUFFER (w->buffer) != current_buffer, which looks suspicious. */
+
+static int
+window_outdated (struct window *w)
+{
+ return (w->last_modified < MODIFF
+ || w->last_overlay_modified < OVERLAY_MODIFF);
+}
+
+/* Nonzero if W's buffer was changed but not saved or Transient Mark mode
+ is enabled and mark of W's buffer was changed since last W's update. */
+
+static int
+window_buffer_changed (struct window *w)
+{
+ struct buffer *b = XBUFFER (w->buffer);
+
+ eassert (BUFFER_LIVE_P (b));
+
+ return (((BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) != w->last_had_star)
+ || ((!NILP (Vtransient_mark_mode) && !NILP (BVAR (b, mark_active)))
+ != !NILP (w->region_showing)));
+}
+
+/* Nonzero if W has %c in its mode line and mode line should be updated. */
+
+static int
+mode_line_update_needed (struct window *w)
+{
+ return (!NILP (w->column_number_displayed)
+ && !(PT == w->last_point && !window_outdated (w))
+ && (XFASTINT (w->column_number_displayed) != current_column ()));
+}