[gnome-shell] ScreenShield: constrain vertical movement of the screen lock

[Giovanni Campagna <gcampagna src gnome org>]

commit b53d18fe1cbf113b02e5b4f84b08102e83c31252
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Sat Aug 4 00:14:34 2012 +0200

    ScreenShield: constrain vertical movement of the screen lock
    
    Don't allow dragging the screen lock above and below the screen,
    as in particular dragging below breaks the illusion of the curtain.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=681143

 js/ui/screenShield.js |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/screenShield.js b/js/ui/screenShield.js
index 11cc86a..31355a6 100644
--- a/js/ui/screenShield.js
+++ b/js/ui/screenShield.js
@@ -310,7 +310,11 @@ const ScreenShield = new Lang.Class({
         this._arrow.connect('repaint', Lang.bind(this, this._drawArrow));
         this._lockScreenContents.add_actor(this._arrow);
 
-        let action = new Clutter.DragAction({ drag_axis: Clutter.DragAxis.Y_AXIS });
+        let dragArea = new Clutter.Rect({ origin: new Clutter.Point({ x: 0, y: -global.screen_height, }),
+                                          size: new Clutter.Size({ width: global.screen_width,
+                                                                   height: global.screen_height }) });
+        let action = new Clutter.DragAction({ drag_axis: Clutter.DragAxis.Y_AXIS,
+                                              drag_area: dragArea });
         action.connect('drag-begin', Lang.bind(this, this._onDragBegin));
         action.connect('drag-end', Lang.bind(this, this._onDragEnd));
         this._lockScreenGroup.add_action(action);