Dragger (adapted from Betwixt)

.flexLibProperties

@@ -76,6 +76,7 @@
     <classEntry path="flashbang.input.MouseInput"/>
     <classEntry path="flashbang.input.MouseReactor"/>
     <classEntry path="flashbang.util.SignalAndEventConnections"/>
+    <classEntry path="flashbang.objects.Dragger"/>
   </includeClasses>
   <includeResources/>
   <namespaceManifests/>

src/main/as/flashbang/objects/Dragger.as

@@ -0,0 +1,129 @@
+//
+// Flashbang - a framework for creating Flash games
+// Copyright (C) 2008-2012 Three Rings Design, Inc., All Rights Reserved
+// http://github.com/threerings/flashbang
+//
+// This library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+package flashbang.objects {
+
+import com.threerings.util.Preconditions;
+import com.threerings.util.Registration;
+
+import flash.events.MouseEvent;
+import flash.geom.Point;
+
+import flashbang.GameObject;
+import flashbang.input.MouseListener;
+
+public class Dragger extends GameObject
+{
+    public function get dragging () :Boolean
+    {
+        return _dragReg != null;
+    }
+
+    public function startDrag (e :MouseEvent) :void
+    {
+        Preconditions.checkState(!this.dragging, "already dragging");
+        _listener = new DragListener(new Point(e.stageX, e.stageY), this.onDragged,
+            function (current :Point, start :Point) :void {
+                // stop the drag before calling onDragEnd, to allow safe destruction of the
+                // dragger from within onDragEnd
+                stopDrag(true);
+                onDragEnd(current, start);
+            });
+        _dragReg = this.mode.mouseInput.registerListener(_listener);
+    }
+
+    public function cancelDrag () :void
+    {
+        stopDrag(false);
+    }
+
+    override protected function removedFromMode () :void
+    {
+        cancelDrag();
+        super.removedFromMode();
+    }
+
+    protected function stopDrag (dragCompleted :Boolean) :void
+    {
+        if (_dragReg != null) {
+            _dragReg.cancel();
+            _dragReg = null;
+            if (!dragCompleted) {
+                var start :Point = _listener.start;
+                var current :Point = _listener.current;
+                _listener = null;
+                onDragCanceled(current != null ? current : start, start);
+            }
+        }
+    }
+
+    protected function onDragStart (start :Point) :void {}
+    protected function onDragged (current :Point, start :Point) :void {}
+    protected function onDragEnd (current :Point, start :Point) :void {}
+    protected function onDragCanceled (last :Point, start :Point) :void {}
+
+    protected var _listener :DragListener;
+    protected var _dragReg :Registration;
+}
+}
+
+import flash.events.MouseEvent;
+import flash.geom.Point;
+
+import flashbang.input.MouseReactor;
+import flashbang.objects.Dragger;
+
+class DragListener extends MouseReactor
+{
+    public function DragListener (start :Point, onMouseMove :Function, onMouseUp :Function)
+    {
+        _start = start;
+        _onMouseMove = onMouseMove;
+        _onMouseUp = onMouseUp;
+    }
+
+    public function get start () :Point
+    {
+        return _start;
+    }
+
+    public function get current () :Point
+    {
+        return _current;
+    }
+
+    override public function onMouseMove (e :MouseEvent) :Boolean
+    {
+        _current = new Point(e.stageX, e.stageY);
+        _onMouseMove(_current, _start);
+        return true;
+    }
+
+    override public function onMouseUp (e :MouseEvent) :Boolean
+    {
+        _current = new Point(e.stageX, e.stageY);
+        _onMouseUp(_current, _start);
+        return true;
+    }
+
+    protected var _start :Point;
+    protected var _current :Point;
+
+    protected var _onMouseMove :Function;
+    protected var _onMouseUp :Function;
+}