[gnome-shell] popupMenu: Add smooth scrolling support for sliders

[Jasper St. Pierre <jstpierre src gnome org>]

commit 7d4e14f38455977ffb103acd85239ed6b1a9d816
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sun Nov 4 10:50:11 2012 -0500

    popupMenu: Add smooth scrolling support for sliders
    
    Allowing smooth scrolling on the Y axis to accurately adjust the value
    of the slider.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=687573

 js/ui/popupMenu.js |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)
---
diff --git a/js/ui/popupMenu.js b/js/ui/popupMenu.js
index 239edaf..fd4b928 100644
--- a/js/ui/popupMenu.js
+++ b/js/ui/popupMenu.js
@@ -638,14 +638,23 @@ const PopupSliderMenuItem = new Lang.Class({
 
     _onScrollEvent: function (actor, event) {
         let direction = event.get_scroll_direction();
+        let delta;
+
+        if (event.is_pointer_emulated())
+            return;
 
         if (direction == Clutter.ScrollDirection.DOWN) {
-            this._value = Math.max(0, this._value - SLIDER_SCROLL_STEP);
-        }
-        else if (direction == Clutter.ScrollDirection.UP) {
-            this._value = Math.min(1, this._value + SLIDER_SCROLL_STEP);
+            delta = -SLIDER_SCROLL_STEP;
+        } else if (direction == Clutter.ScrollDirection.UP) {
+            delta = +SLIDER_SCROLL_STEP;
+        } else if (direction == Clutter.ScrollDirection.SMOOTH) {
+            let [dx, dy] = event.get_scroll_delta();
+            // Even though the slider is horizontal, use dy to match
+            // the UP/DOWN above.
+            delta = -dy / 10;
         }
 
+        this._value = Math.min(Math.max(0, this._value + delta), 1);
         this._slider.queue_repaint();
         this.emit('value-changed', this._value);
     },