[Emacs-diffs] emacs-26 b081ec9: Fix backward scrolling in buffers with header-line

[Eli Zaretskii]

branch: emacs-26
commit b081ec9dd7e4575b82872e16e598566fabf77cb1
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    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)
---
 src/window.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/window.c b/src/window.c
index 7f47252..504dcd3 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,