linearView: Cancel workspace scrolling when the user stops dragging

Currently there is no way for the user to cancel a workspace drag action,
which means the user has to complete the drag action before and move back
to the other workspace manually afterwards.
So cancel the drag action when the user stops.

https://bugzilla.gnome.org/show_bug.cgi?id=618062

diff --git a/js/ui/workspacesView.js b/js/ui/workspacesView.js
index 99f0805522e4192511ccd5176a88a296a183d1a9..b34c222d0498b698ba0ada7b36043bdc9a1b8906 100644 (file)
--- a/js/ui/workspacesView.js
+++ b/js/ui/workspacesView.js
@@ -653,7 +653,7 @@ SingleView.prototype = {
         this._scrolling = false; // dragging scroll bar or desktop
         this._animatingScroll = false; // programatically move the scroll bar
         this._inDrag = false; // dragging a window
-
+        this._lastMotionTime = -1; // used to track "stopping" while dragging workspaces
         let primary = global.get_primary_monitor();
         this._dropGroup = new Clutter.Group({ x: 0, y: 0,
                                               width: primary.width,
@@ -833,11 +833,21 @@ SingleView.prototype = {
                 let activate = this._dragIndex;
                 let last = global.screen.n_workspaces - 1;
 
-                // switch workspaces according to the drag direction
-                if (stageX > this._dragStartX && activate > 0)
-                    activate--;
-                else if (stageX < this._dragStartX && activate < last)
-                    activate++;
+                // If the user has moved more than half a workspace, we want to "settle"
+                // to the new workspace even if the user stops dragging rather "throws"
+                // by releasing during the drag.
+                let noStop = Math.abs(activate - this._scroll.adjustment.value) > 0.5;
+
+                // We detect if the user is stopped by comparing the timestamp of the button
+                // release with the timestamp of the last motion. Experimentally, a difference
+                // of 0 or 1 millisecond indicates that the mouse is in motion, a larger
+                // difference indicates that the mouse is stopped.
+                if ((this._lastMotionTime > 0 && this._lastMotionTime > event.get_time() - 2) || noStop) {
+                    if (stageX > this._dragStartX && activate > 0)
+                        activate--;
+                    else if (stageX < this._dragStartX && activate < last)
+                        activate++;
+                }
 
                 if (activate != active) {
                     let workspace = this._workspaces[activate].metaWorkspace;
@@ -859,6 +869,7 @@ SingleView.prototype = {
 
                 this._scroll.adjustment.value += (dx / primary.width);
                 this._dragX = stageX;
+                this._lastMotionTime = event.get_time();
 
                 return true;
         }