Manager.js

define([
	"../_base/array",  "../_base/declare", "../_base/lang", "../_base/window",
	"../dom-class", "../Evented", "../has", "../keys", "../on", "../topic", "../touch",
	"./common", "./autoscroll", "./Avatar"
], function(array, declare, lang, win, domClass, Evented, has, keys, on, topic, touch,
	dnd, autoscroll, Avatar){

// module:
//		dojo/dnd/Manager

var Manager = declare("dojo.dnd.Manager", [Evented], {
	// summary:
	//		the manager of DnD operations (usually a singleton)
	constructor: function(){
		this.avatar  = null;
		this.source = null;
		this.nodes = [];
		this.copy  = true;
		this.target = null;
		this.canDropFlag = false;
		this.events = [];
	},

	// avatar's offset from the mouse
	OFFSET_X: has("touch") ? 0 : 16,
	OFFSET_Y: has("touch") ? -64 : 16,

	// methods
	overSource: function(source){
		// summary:
		//		called when a source detected a mouse-over condition
		// source: Object
		//		the reporter
		if(this.avatar){
			this.target = (source && source.targetState != "Disabled") ? source : null;
			this.canDropFlag = Boolean(this.target);
			this.avatar.update();
		}
		topic.publish("/dnd/source/over", source);
	},
	outSource: function(source){
		// summary:
		//		called when a source detected a mouse-out condition
		// source: Object
		//		the reporter
		if(this.avatar){
			if(this.target == source){
				this.target = null;
				this.canDropFlag = false;
				this.avatar.update();
				topic.publish("/dnd/source/over", null);
			}
		}else{
			topic.publish("/dnd/source/over", null);
		}
	},
	startDrag: function(source, nodes, copy){
		// summary:
		//		called to initiate the DnD operation
		// source: Object
		//		the source which provides items
		// nodes: Array
		//		the list of transferred items
		// copy: Boolean
		//		copy items, if true, move items otherwise

		// Tell autoscroll that a drag is starting
		autoscroll.autoScrollStart(win.doc);

		this.source = source;
		this.nodes  = nodes;
		this.copy   = Boolean(copy); // normalizing to true boolean
		this.avatar = this.makeAvatar();
		win.body().appendChild(this.avatar.node);
		topic.publish("/dnd/start", source, nodes, this.copy);

		function stopEvent(e){
			e.preventDefault();
			e.stopPropagation();
		}

		this.events = [
			on(win.doc, touch.move, lang.hitch(this, "onMouseMove")),
			on(win.doc, touch.release,   lang.hitch(this, "onMouseUp")),
			on(win.doc, "keydown",   lang.hitch(this, "onKeyDown")),
			on(win.doc, "keyup",     lang.hitch(this, "onKeyUp")),

			// cancel text selection and text dragging
			on(win.doc, "dragstart",   stopEvent),
			on(win.body(), "selectstart", stopEvent)
		];
		var c = "dojoDnd" + (copy ? "Copy" : "Move");
		domClass.add(win.body(), c);
	},
	canDrop: function(flag){
		// summary:
		//		called to notify if the current target can accept items
		var canDropFlag = Boolean(this.target && flag);
		if(this.canDropFlag != canDropFlag){
			this.canDropFlag = canDropFlag;
			this.avatar.update();
		}
	},
	stopDrag: function(){
		// summary:
		//		stop the DnD in progress
		domClass.remove(win.body(), ["dojoDndCopy", "dojoDndMove"]);
		array.forEach(this.events, function(handle){ handle.remove(); });
		this.events = [];
		this.avatar.destroy();
		this.avatar = null;
		this.source = this.target = null;
		this.nodes = [];
	},
	makeAvatar: function(){
		// summary:
		//		makes the avatar; it is separate to be overwritten dynamically, if needed
		return new Avatar(this);
	},
	updateAvatar: function(){
		// summary:
		//		updates the avatar; it is separate to be overwritten dynamically, if needed
		this.avatar.update();
	},

	// mouse event processors
	onMouseMove: function(e){
		// summary:
		//		event processor for onmousemove
		// e: Event
		//		mouse event
		var a = this.avatar;
		if(a){
			autoscroll.autoScrollNodes(e);
			//autoscroll.autoScroll(e);
			var s = a.node.style;
			s.left = (e.pageX + this.OFFSET_X) + "px";
			s.top  = (e.pageY + this.OFFSET_Y) + "px";
			var copy = Boolean(this.source.copyState(dnd.getCopyKeyState(e)));
			if(this.copy != copy){
				this._setCopyStatus(copy);
			}
		}
		if(has("touch")){
			// Prevent page from scrolling so that user can drag instead.
			e.preventDefault();
		}
	},
	onMouseUp: function(e){
		// summary:
		//		event processor for onmouseup
		// e: Event
		//		mouse event
		if(this.avatar){
			if(this.target && this.canDropFlag){
				var copy = Boolean(this.source.copyState(dnd.getCopyKeyState(e)));
				topic.publish("/dnd/drop/before", this.source, this.nodes, copy, this.target, e);
				topic.publish("/dnd/drop", this.source, this.nodes, copy, this.target, e);
			}else{
				topic.publish("/dnd/cancel");
			}
			this.stopDrag();
		}
	},

	// keyboard event processors
	onKeyDown: function(e){
		// summary:
		//		event processor for onkeydown:
		//		watching for CTRL for copy/move status, watching for ESCAPE to cancel the drag
		// e: Event
		//		keyboard event
		if(this.avatar){
			switch(e.keyCode){
				case keys.CTRL:
					var copy = Boolean(this.source.copyState(true));
					if(this.copy != copy){
						this._setCopyStatus(copy);
					}
					break;
				case keys.ESCAPE:
					topic.publish("/dnd/cancel");
					this.stopDrag();
					break;
			}
		}
	},
	onKeyUp: function(e){
		// summary:
		//		event processor for onkeyup, watching for CTRL for copy/move status
		// e: Event
		//		keyboard event
		if(this.avatar && e.keyCode == keys.CTRL){
			var copy = Boolean(this.source.copyState(false));
			if(this.copy != copy){
				this._setCopyStatus(copy);
			}
		}
	},

	// utilities
	_setCopyStatus: function(copy){
		// summary:
		//		changes the copy status
		// copy: Boolean
		//		the copy status
		this.copy = copy;
		this.source._markDndStatus(this.copy);
		this.updateAvatar();
		domClass.replace(win.body(),
			"dojoDnd" + (this.copy ? "Copy" : "Move"),
			"dojoDnd" + (this.copy ? "Move" : "Copy"));
	}
});

// dnd._manager:
//		The manager singleton variable. Can be overwritten if needed.
dnd._manager = null;

Manager.manager = dnd.manager = function(){
	// summary:
	//		Returns the current DnD manager.  Creates one if it is not created yet.
	if(!dnd._manager){
		dnd._manager = new Manager();
	}
	return dnd._manager;	// Object
};

// TODO: for 2.0, store _manager and manager in Manager only.   Don't access dnd or dojo.dnd.

return Manager;
});