Merge pull request #23681 from Cwiiis/bug1062321-notifications-not-sc…

…rollable

Bug 1062321 - Fix notification overflow not being scrollable. r=mhenretty

apps/system/js/notifications.js

@@ -8,10 +8,12 @@ var NotificationScreen = {
   TOASTER_TIMEOUT: 5000,
   TRANSITION_FRACTION: 0.30,
   TAP_THRESHOLD: 10,
+  SCROLL_THRESHOLD: 10,
 
   _notification: null,
   _containerWidth: null,
   _touchStartX: 0,
+  _touchStartY: 0,
   _touchPosX: 0,
   _touching: false,
   _isTap: false,
@@ -230,10 +232,10 @@ var NotificationScreen = {
     if (!target.dataset.notificationId)
       return;
 
-    evt.preventDefault();
     this._notification = target;
     this._containerWidth = this.container.clientWidth;
     this._touchStartX = evt.touches[0].pageX;
+    this._touchStartY = evt.touches[0].pageY;
     this._touchPosX = 0;
     this._touching = true;
     this._isTap = true;
@@ -244,13 +246,16 @@ var NotificationScreen = {
       return;
     }
 
-    if (evt.touches.length !== 1) {
+    var touchDiffY = Math.abs(evt.touches[0].pageY - this._touchStartY);
+    if (evt.touches.length !== 1 ||
+        (this._isTap && touchDiffY >= this.SCROLL_THRESHOLD)) {
       this._touching = false;
       this.cancelSwipe();
       return;
     }
 
     evt.preventDefault();
+
     this._touchPosX = evt.touches[0].pageX - this._touchStartX;
     if (this._touchPosX >= this.TAP_THRESHOLD) {
       this._isTap = false;