Fix backward scrolling in buffers with header-line

* src/window.c (window_scroll_pixel_based): Account for the
header-line when comparing Y coordinate with the last_visible_y.
(Bug#29325)

1 files changed, 9 insertions, 3 deletions

diff --git a/src/window.c b/src/window.c
index 7f472523b49..504dcd38357 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5355,6 +5355,9 @@ window_scroll_pixel_based (Lisp_Object window, int n, bool whole, bool noerror)
       /* We moved the window start towards BEGV, so PT may be now
          in the scroll margin at the bottom.  */
       move_it_to (&it, PT, -1,
+                  /* We subtract WINDOW_HEADER_LINE_HEIGHT because
+                     it.y is relative to the bottom of the header
+                     line, see above.  */
                   (it.last_visible_y - WINDOW_HEADER_LINE_HEIGHT (w)
                    - partial_line_height (&it) - this_scroll_margin - 1),
                   -1,
@@ -5392,11 +5395,14 @@ window_scroll_pixel_based (Lisp_Object window, int n, bool whole, bool noerror)
 
       /* See if point is on a partially visible line at the end.  */
       if (it.what == IT_EOB)
-        partial_p = it.current_y + it.ascent + it.descent > it.last_visible_y;
+        partial_p =
+          it.current_y + it.ascent + it.descent
+          > it.last_visible_y - WINDOW_HEADER_LINE_HEIGHT (w);
       else
         {
           move_it_by_lines (&it, 1);
-          partial_p = it.current_y > it.last_visible_y;
+          partial_p =
+            it.current_y > it.last_visible_y - WINDOW_HEADER_LINE_HEIGHT (w);
         }
 
       if (charpos == PT && !partial_p
@@ -5415,7 +5421,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, bool whole, bool noerror)
             goal_y = this_scroll_margin;
           SET_TEXT_POS_FROM_MARKER (start, w->start);
           start_display (&it, w, start);
-          /* It would be wrong to subtract CURRENT_HEADER_LINE_HEIGHT
+          /* It would be wrong to subtract WINDOW_HEADER_LINE_HEIGHT
              here because we called start_display again and did not
              alter it.current_y this time.  */
           move_it_to (&it, -1, window_scroll_pixel_based_preserve_x,