Provide native touchpad scrolling on macOS

* etc/NEWS: Describe changes.
* lisp/term/ns-win.el (mouse-wheel-scroll-amount,
mouse-wheel-progressive-speed): Set to smarter values for macOS
touchpads.
* src/nsterm.m (emacsView::mouseDown): Use precise scrolling deltas to
calculate scrolling for touchpads and mouse wheels.
(syms_of_nsterm): Add variables 'ns-use-system-mwheel-acceleration',
'ns-touchpad-scroll-line-height' and 'ns-touchpad-use-momentum'.
* src/keyboard.c (make_lispy_event): Pass on .arg when relevant.
* src/termhooks.h (event_kind): Update comments re. WHEEL_EVENT.
* lisp/mwheel.el (mwheel-scroll): Use line count.
* lisp/subr.el (event-line-count): New function.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index 4db50be855c..e8701b88708 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -5925,7 +5925,10 @@ make_lispy_event (struct input_event *event)
                                       ASIZE (wheel_syms));
         }
 
-        if (event->modifiers & (double_modifier | triple_modifier))
+        if (NUMBERP (event->arg))
+          return list4 (head, position, make_number (double_click_count),
+                        event->arg);
+        else if (event->modifiers & (double_modifier | triple_modifier))
           return list3 (head, position, make_number (double_click_count));
         else
           return list2 (head, position);