feature/long-lines-and-font-locking 57a978fd74: Optimize 'set_vertical_scroll_bar' for long lines

[Eli Zaretskii]

branch: feature/long-lines-and-font-locking
commit 57a978fd74454392a041ac65a5abba8d012b88cc
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Optimize 'set_vertical_scroll_bar' for long lines
    
    * src/xdisp.c (set_vertical_scroll_bar): Don't bother
    being accurate about window_end_pos if long-line shortcuts
    are in effect in the current buffer.
---
 src/xdisp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index c507d0caf2..c73958854c 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -18968,8 +18968,9 @@ set_vertical_scroll_bar (struct window *w)
       ptrdiff_t window_end_pos = w->window_end_pos;
 
       /* If w->window_end_pos cannot be trusted, recompute it "the
-        hard way".  */
-      if (!w->window_end_valid)
+        hard way".  But don't bother to be too accurate when
+        long-line shortcuts are in effect.  */
+      if (!w->window_end_valid && !buf->long_line_optimizations_p)
        {
          struct it it;
          struct text_pos start_pos;