Handle W = NULL in 'update_redisplay_ticks'

* src/xdisp.c (update_redisplay_ticks): If W == NULL, assume we
are iterating the current buffer.

1 files changed, 10 insertions, 4 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index ae428f4b404..d14955af415 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -17179,7 +17179,11 @@ redisplay_window_1 (Lisp_Object window)
    means to initialize the tick count to zero.
 
    W can be NULL if TICKS is zero: that means unconditionally
-   re-initialize the current tick count to zero.   */
+   re-initialize the current tick count to zero.
+
+   W can also be NULL if the caller doesn't know which window is being
+   processed by the display code.  In that case, if TICKS is non-zero,
+   we assume it's the last window that shows the current buffer.  */
 void
 update_redisplay_ticks (int ticks, struct window *w)
 {
@@ -17204,9 +17208,11 @@ update_redisplay_ticks (int ticks, struct window *w)
          the one used for the native tool bar).  */
       Lisp_Object contents = w ? w->contents : Qnil;
       char *bufname =
-        BUFFERP (contents)
-        ? SSDATA (BVAR (XBUFFER (contents), name))
-        : (char *) "<none>";
+        NILP (contents)
+        ? SSDATA (BVAR (current_buffer, name))
+        : (BUFFERP (contents)
+           ? SSDATA (BVAR (XBUFFER (contents), name))
+           : (char *) "<unknown>");
 
       windows_or_buffers_changed = 177;
       error ("Window showing buffer %s takes too long to redisplay", bufname);