Fix scrolling under scroll-preserve-screen-position on TTY

* src/window.c (window_scroll_line_based): When setting point to
preserve screen coordinates, don't let cursor enter either of the
two scroll margins.  (Bug#22395)

1 files changed, 19 insertions, 2 deletions

diff --git a/src/window.c b/src/window.c
index 1a75342471f..2eacc3a2647 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5212,6 +5212,7 @@ window_scroll_line_based (Lisp_Object window, int n, bool whole, bool noerror)
       w->force_start = true;
 
       if (!NILP (Vscroll_preserve_screen_position)
+          && this_scroll_margin == 0
           && (whole || !EQ (Vscroll_preserve_screen_position, Qt)))
         {
           SET_PT_BOTH (pos, pos_byte);
@@ -5237,8 +5238,16 @@ window_scroll_line_based (Lisp_Object window, int n, bool whole, bool noerror)
                          marker_byte_position (opoint_marker));
           else if (!NILP (Vscroll_preserve_screen_position))
             {
+              int nlines = window_scroll_preserve_vpos;
+
               SET_PT_BOTH (pos, pos_byte);
-              Fvertical_motion (original_pos, window, Qnil);
+              if (window_scroll_preserve_vpos < this_scroll_margin)
+                nlines = this_scroll_margin;
+              else if (window_scroll_preserve_vpos
+                       >= w->total_lines - this_scroll_margin)
+                nlines = w->total_lines - this_scroll_margin - 1;
+              Fvertical_motion (Fcons (make_number (window_scroll_preserve_hpos),
+                                       make_number (nlines)), window, Qnil);
             }
           else
             SET_PT (top_margin);
@@ -5264,8 +5273,16 @@ window_scroll_line_based (Lisp_Object window, int n, bool whole, bool noerror)
             {
               if (!NILP (Vscroll_preserve_screen_position))
                 {
+                  int nlines = window_scroll_preserve_vpos;
+
                   SET_PT_BOTH (pos, pos_byte);
-                  Fvertical_motion (original_pos, window, Qnil);
+                  if (window_scroll_preserve_vpos < this_scroll_margin)
+                    nlines = this_scroll_margin;
+                  else if (window_scroll_preserve_vpos
+                           >= ht - this_scroll_margin)
+                    nlines = ht - this_scroll_margin - 1;
+                  Fvertical_motion (Fcons (make_number (window_scroll_preserve_hpos),
+                                           make_number (nlines)), window, Qnil);
                 }
               else
                 Fvertical_motion (make_number (-1), window, Qnil);