(mouse-wheel-buttons): Map old-style wheel buttons to actual wheel eventsscratch/mouse-wheel-buttons

Change the handling of the old X11 convention to use mouse-4/5/6/7
events to represent wheel events: instead of asking downstream
packages to use the `mouse-wheel-*-event` variables to know which events
represent wheel events, use new var `mouse-wheel-buttons` to directly
convert those events into the standard `wheel-up/down/left/right` events
used everywhere else.

This will simplify the work of packages which can thus just bind their
commands to `wheel-up/down/left/right`.

* lisp/mouse.el (mouse-wheel-buttons): New custom variable.

* src/keyboard.c (make_lispy_event): Adjust for "wheel-clicks" on the tab-bar.
* src/xterm.c (x_construct_mouse_click): Add `xi2` argument and
obey `mouse-wheel-buttons` variable.
(handle_one_xevent): Adjust calls accordingly.
(syms_of_xterm): Define the `mouse-wheel-buttons` and the
`wheel-up/down/left/right`symbols.

* lisp/xt-mouse.el: Don't require `mwheel` any more.
(xterm-mouse--same-button-p): Delete function.
(xterm-mouse--read-event-sequence): Use `mouse-wheel-buttons`.

* lisp/mwheel.el (mouse-wheel-up-event, mouse-wheel-down-event)
(mouse-wheel-left-event, mouse-wheel-right-event): Make obsolete.
(mouse-wheel-obey-old-style-wheel-buttons): Delete variable.

1 files changed, 11 insertions, 2 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index 91faf4582fa..a06c9116d24 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -6639,8 +6639,17 @@ make_lispy_event (struct input_event *event)
 
         if (CONSP (event->arg))
           return list5 (head, position, make_fixnum (double_click_count),
-                        XCAR (event->arg), Fcons (XCAR (XCDR (event->arg)),
-                                                  XCAR (XCDR (XCDR (event->arg)))));
+                        XCAR (event->arg),
+                        /* FIXME: When a mouse-click on a tab-bar is
+                           converted into a wheel-event we get here something
+                           of an unexpected shape...  */
+                        (CONSP (XCDR (event->arg))
+                         && CONSP (XCDR (XCDR (event->arg))))
+                        ? Fcons (XCAR (XCDR (event->arg)),
+                                 XCAR (XCDR (XCDR (event->arg))))
+                        /* ... not knowing what this "unexpected shape" means,
+                           we just use nil.  */
+                        : Qnil);
         else if (NUMBERP (event->arg))
           return list4 (head, position, make_fixnum (double_click_count),
                         event->arg);