# ScrollManager.js

    /**
     * @class Ext.dd.ScrollManager
     * Provides automatic scrolling of overflow regions in the page during drag operations.<br><br>
     * <b>Note: This class uses "Point Mode" and is untested in "Intersect Mode".</b>
     * @singleton
     */
    Ext.dd.ScrollManager = function(){
        var ddm = Ext.dd.DragDropMgr;
        var els = {};
        var dragEl = null;
        var proc = {};

        var onStop = function(e){
            dragEl = null;
            clearProc();
        };

        var triggerRefresh = function(){
            if(ddm.dragCurrent){
                 ddm.refreshCache(ddm.dragCurrent.groups);
            }
        };

        var doScroll = function(){
            if(ddm.dragCurrent){
                var dds = Ext.dd.ScrollManager;
                if(!dds.animate){
                    if(proc.el.scroll(proc.dir, dds.increment)){
                        triggerRefresh();
                    }
                }else{
                    proc.el.scroll(proc.dir, dds.increment, true, dds.animDuration, triggerRefresh);
                }
            }
        };

        var clearProc = function(){
            if(proc.id){
                clearInterval(proc.id);
            }
            proc.id = 0;
            proc.el = null;
            proc.dir = "";
        };

        var startProc = function(el, dir){
            clearProc();
            proc.el = el;
            proc.dir = dir;
            proc.id = setInterval(doScroll, Ext.dd.ScrollManager.frequency);
        };

        var onFire = function(e, isDrop){
            if(isDrop || !ddm.dragCurrent){ return; }
            var dds = Ext.dd.ScrollManager;
            if(!dragEl || dragEl != ddm.dragCurrent){
                dragEl = ddm.dragCurrent;
                // refresh regions on drag start
                dds.refreshCache();
            }

            var xy = Ext.lib.Event.getXY(e);
            var pt = new Ext.lib.Point(xy[0], xy[1]);
            for(var id in els){
                var el = els[id], r = el._region;
                if(r.contains(pt) && el.isScrollable()){
                    if(r.bottom - pt.y <= dds.thresh){
                        if(proc.el != el){
                            startProc(el, "down");
                        }
                        return;
                    }else if(r.right - pt.x <= dds.thresh){
                        if(proc.el != el){
                            startProc(el, "left");
                        }
                        return;
                    }else if(pt.y - r.top <= dds.thresh){
                        if(proc.el != el){
                            startProc(el, "up");
                        }
                        return;
                    }else if(pt.x - r.left <= dds.thresh){
                        if(proc.el != el){
                            startProc(el, "right");
                        }
                        return;
                    }
                }
            }
            clearProc();
        };

        ddm.fireEvents = ddm.fireEvents.createSequence(onFire, ddm);
        ddm.stopDrag = ddm.stopDrag.createSequence(onStop, ddm);

        return {
            /**
             * Registers new overflow element(s) to auto scroll
             * @param {String/HTMLElement/Element/Array} el The id of or the element to be scrolled or an array of either
             */
            register : function(el){
                if(el instanceof Array){
                    for(var i = 0, len = el.length; i < len; i++) {
                    	this.register(el[i]);
                    }
                }else{
                    el = Ext.get(el);
                    els[el.id] = el;
                }
            },

            /**
             * Unregisters overflow element(s) so they are no longer scrolled
             * @param {String/HTMLElement/Element/Array} el The id of or the element to be removed or an array of either
             */
            unregister : function(el){
                if(el instanceof Array){
                    for(var i = 0, len = el.length; i < len; i++) {
                    	this.unregister(el[i]);
                    }
                }else{
                    el = Ext.get(el);
                    delete els[el.id];
                }
            },

            /**
             * The number of pixels from the edge of a container the pointer needs to be to
             * trigger scrolling (defaults to 25)
             * @type Number
             */
            thresh : 25,

            /**
             * The number of pixels to scroll in each scroll increment (defaults to 50)
             * @type Number
             */
            increment : 100,

            /**
             * The frequency of scrolls in milliseconds (defaults to 500)
             * @type Number
             */
            frequency : 500,

            /**
             * True to animate the scroll (defaults to true)
             * @type Boolean
             */
            animate: true,

            /**
             * The animation duration in seconds -
             * MUST BE less than Ext.dd.ScrollManager.frequency! (defaults to .4)
             * @type Number
             */
            animDuration: .4,

            /**
             * Manually trigger a cache refresh.
             */
            refreshCache : function(){
                for(var id in els){
                    if(typeof els[id] == 'object'){ // for people extending the object prototype
                        els[id]._region = els[id].getRegion();
                    }
                }
            }
        };
    }();

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