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, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 5aa57a77765..a814c3ec20d 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1882,6 +1882,12 @@ of frame decorations on macOS 10.9+.
 ---
 ** 'process-attributes' on Darwin systems now returns more information.
 
+---
+** Mousewheel and trackpad scrolling on macOS 10.7+ now behaves more
+like the macOS default.  The new variables
+'ns-use-system-mwheel-acceleration', 'ns-touchpad-scroll-line-height'
+and 'ns-touchpad-use-momentum' can be used to customise the behavior.
+
 
 ----------------------------------------------------------------------
 This file is part of GNU Emacs.