Add the `scroll-command' property.

* window.c: Add Qscroll_command.
Remove Vscroll_preserve_screen_position_commands.
(window_scroll_pixel_based, window_scroll_line_based): Check the
`scroll-command' property on the last command instead of searching
the last command in Vscroll_preserve_screen_position_commands.
(syms_of_window): Initialize and staticpro `Qscroll_command'.
Put Qscroll_command property on Qscroll_up and Qscroll_down.
(scroll-preserve-screen-position): Doc fix.
(Vscroll_preserve_screen_position_commands): Remove variable.

* simple.el (scroll-up-command, scroll-down-command)
(scroll-up-line, scroll-down-line): Put `scroll-command'
property on the these symbols.  Remove them from
`scroll-preserve-screen-position-commands'.

* mwheel.el (mwheel-scroll): Put `scroll-command' and
`isearch-scroll' properties on the `mwheel-scroll' symbol.
Remove it from `scroll-preserve-screen-position-commands'.

* isearch.el (isearch-allow-scroll): Doc fix.

1 files changed, 15 insertions, 20 deletions

diff --git a/src/window.c b/src/window.c
index b9683fbbca8..882f76d9758 100644
--- a/src/window.c
+++ b/src/window.c
@@ -54,7 +54,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 Lisp_Object Qwindowp, Qwindow_live_p, Qwindow_configuration_p;
 Lisp_Object Qdisplay_buffer;
-Lisp_Object Qscroll_up, Qscroll_down;
+Lisp_Object Qscroll_up, Qscroll_down, Qscroll_command;
 Lisp_Object Qwindow_size_fixed;
 
 extern Lisp_Object Qleft_margin, Qright_margin;
@@ -168,10 +168,6 @@ static Lisp_Object Vwindow_configuration_change_hook;
 
 Lisp_Object Vscroll_preserve_screen_position;
 
-/* List of commands affected by `Vscroll_preserve_screen_position'.  */
-
-Lisp_Object Vscroll_preserve_screen_position_commands;
-
 /* Non-nil means that text is inserted before window's markers.  */
 
 Lisp_Object Vwindow_point_insertion_type;
@@ -4946,12 +4942,13 @@ window_scroll_pixel_based (window, n, whole, noerror)
   if (!NILP (Vscroll_preserve_screen_position))
     {
       /* We preserve the goal pixel coordinate across consecutive
-         calls to scroll-up or scroll-down.  This avoids the
+         calls to scroll-up, scroll-down and other commands that
+         have the `scroll-command' property.  This avoids the
          possibility of point becoming "stuck" on a tall line when
          scrolling by one line.  */
       if (window_scroll_pixel_based_preserve_y < 0
-          || NILP (Fmemq (current_kboard->Vlast_command,
-                          Vscroll_preserve_screen_position_commands)))
+          || !SYMBOLP (current_kboard->Vlast_command)
+          || NILP (Fget (current_kboard->Vlast_command, Qscroll_command)))
         {
           start_display (&it, w, start);
           move_it_to (&it, PT, -1, -1, -1, MOVE_TO_POS);
@@ -5211,8 +5208,8 @@ window_scroll_line_based (window, n, whole, noerror)
   if (!NILP (Vscroll_preserve_screen_position))
     {
       if (window_scroll_preserve_vpos <= 0
-          || NILP (Fmemq (current_kboard->Vlast_command,
-                          Vscroll_preserve_screen_position_commands)))
+          || !SYMBOLP (current_kboard->Vlast_command)
+          || NILP (Fget (current_kboard->Vlast_command, Qscroll_command)))
         {
           struct position posit
             = *compute_motion (startpos, 0, 0, 0,
@@ -7180,6 +7177,12 @@ syms_of_window ()
   Qscroll_down = intern_c_string ("scroll-down");
   staticpro (&Qscroll_down);
 
+  Qscroll_command = intern_c_string ("scroll-command");
+  staticpro (&Qscroll_command);
+
+  Fput (Qscroll_up, Qscroll_command, Qt);
+  Fput (Qscroll_down, Qscroll_command, Qt);
+
   Qwindow_size_fixed = intern_c_string ("window-size-fixed");
   staticpro (&Qwindow_size_fixed);
   Fset (Qwindow_size_fixed, Qnil);
@@ -7270,18 +7273,10 @@ A value of t means point keeps its screen position if the scroll
 command moved it vertically out of the window, e.g. when scrolling
 by full screens.
 Any other value means point always keeps its screen position.
-Scroll commands are defined by the variable
-`scroll-preserve-screen-position-commands'.  */);
+Scroll commands should have the `scroll-command' property
+on their symbols to be controlled by this variable.  */);
   Vscroll_preserve_screen_position = Qnil;
 
-  DEFVAR_LISP ("scroll-preserve-screen-position-commands",
-               &Vscroll_preserve_screen_position_commands,
-               doc: /* A list of commands whose scrolling should keep screen position unchanged.
-This list defines the names of scroll commands affected by the variable
-`scroll-preserve-screen-position'.  */);
-  Vscroll_preserve_screen_position_commands =
-    Fcons (Qscroll_down, Fcons (Qscroll_up, Qnil));
-
   DEFVAR_LISP ("window-point-insertion-type", &Vwindow_point_insertion_type,
                doc: /* Type of marker to use for `window-point'.  */);
   Vwindow_point_insertion_type = Qnil;