Avoid calling 'current_column' in buffers with long lines.

* src/xdisp.c (decode_mode_spec, redisplay_window)
(mode_line_update_needed):
* src/indent.c (Fcurrent_column): In a buffer with long-line
optimizations enabled, avoid calling 'current_column', which is
very slow in that case.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/indent.c b/src/indent.c
index d4ef075f001..e90e3fde203 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -306,6 +306,8 @@ and point (e.g., control characters will have a width of 2 or 4, tabs
 will have a variable width).
 Ignores finite width of frame, which means that this function may return
 values greater than (frame-width).
+In a buffer with very long lines, the value can be zero, because calculating
+the exact number is very expensive.
 Whether the line is visible (if `selective-display' is t) has no effect;
 however, ^M is treated as end of line when `selective-display' is t.
 Text that has an invisible property is considered as having width 0, unless
@@ -313,6 +315,9 @@ Text that has an invisible property is considered as having width 0, unless
   (void)
 {
   Lisp_Object temp;
+
+  if (current_buffer->long_line_optimizations_p)
+    return make_fixnum (0);
   XSETFASTINT (temp, current_column ());
   return temp;
 }