Prevent incorrect display when 'line-spacing' variable is set

* src/xdisp.c (try_window_id): Give up this optimization if the
buffer has its 'line-spacing' variable set non-nil.

diff --git a/src/xdisp.c b/src/xdisp.c
index 03b03d06b3e49340293e136dbb9daf3678c2d9c3..e45cb8702b2bbc27cf9008c967950454ed44635b 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -17753,7 +17753,7 @@ try_window_id (struct window *w)
 #if false
 #define GIVE_UP(X)                                             \
   do {                                                         \
-    fprintf (stderr, "try_window_id give up %d\n", (X));       \
+    TRACE ((stderr, "try_window_id give up %d\n", (X)));       \
     return 0;                                                  \
   } while (false)
 #else
@@ -17775,7 +17775,7 @@ try_window_id (struct window *w)
      changed in the buffer displayed by the window, so give up if they
      have.  */
   if (w->last_overlay_modified != OVERLAY_MODIFF)
-    GIVE_UP (21);
+    GIVE_UP (200);
 
   /* Verify that narrowing has not changed.
      Also verify that we were not told to prevent redisplay optimizations.
@@ -17835,6 +17835,11 @@ try_window_id (struct window *w)
       && NILP (BVAR (XBUFFER (w->contents), bidi_paragraph_direction)))
     GIVE_UP (22);
 
+  /* Give up if the buffer has line-spacing set, as Lisp-level changes
+     to that variable require thorough redisplay.  */
+  if (!NILP (BVAR (XBUFFER (w->contents), extra_line_spacing)))
+    GIVE_UP (23);
+
   /* Make sure beg_unchanged and end_unchanged are up to date.  Do it
      only if buffer has really changed.  The reason is that the gap is
      initially at Z for freshly visited files.  The code below would