master f3bb2b8: Add `ns-scroll-event-delta-factor'

[Po Lu]

branch: master
commit f3bb2b80b4a347974de3e9da1feb18181ed20cc0
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Add `ns-scroll-event-delta-factor'
    
    * src/nsterm.m (- mouseDown): Take delta factor into account.
    (Vns_scroll_event_delta_factor): New variable.
    
    * lisp/cus-start.el: Add option.
---
 lisp/cus-start.el |  1 +
 src/nsterm.m      | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/lisp/cus-start.el b/lisp/cus-start.el
index 33b861b..53cad99 100644
--- a/lisp/cus-start.el
+++ b/lisp/cus-start.el
@@ -572,6 +572,7 @@ Leaving \"Default\" unchecked is equivalent with specifying 
a default of
             (ns-use-native-fullscreen ns boolean "24.4")
              (ns-use-fullscreen-animation ns boolean "25.1")
              (ns-use-srgb-colorspace ns boolean "24.4")
+             (ns-scroll-event-delta-factor ns float "29.1")
             ;; process.c
             (delete-exited-processes processes-basics boolean)
             ;; syntax.c
diff --git a/src/nsterm.m b/src/nsterm.m
index 78bbae6..f5c2d4d 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -6665,6 +6665,12 @@ not_in_argv (NSString *arg)
           if (lines == 0 && x_coalesce_scroll_events)
             return;
 
+         if (NUMBERP (Vns_scroll_event_delta_factor))
+           {
+             x *= XFLOATINT (Vns_scroll_event_delta_factor);
+             y *= XFLOATINT (Vns_scroll_event_delta_factor);
+           }
+
           emacs_event->kind = horizontal ? HORIZ_WHEEL_EVENT : WHEEL_EVENT;
           emacs_event->arg = list3 (make_fixnum (lines),
                                    make_float (x),
@@ -10037,6 +10043,12 @@ This variable is ignored on macOS < 10.7 and GNUstep.  
Default is t.  */);
 
   DEFSYM (Qx_underline_at_descent_line, "x-underline-at-descent-line");
 
+  DEFVAR_LISP ("ns-scroll-event-delta-factor", Vns_scroll_event_delta_factor,
+              doc: /* A delta to apply to pixel deltas reported in scroll 
events.
+ This is only effective for pixel deltas generated from touch pads or
+ mice with smooth scrolling capability.  */);
+  Vns_scroll_event_delta_factor = make_float (1.0);
+
   /* Tell Emacs about this window system.  */
   Fprovide (Qns, Qnil);