The source code

    /**
     @class Ext.util.ClickRepeater
     @extends Ext.util.Observable

     A wrapper class which can be applied to any element. Fires a "click" event while the
     mouse is pressed. The interval between firings may be specified in the config but
     defaults to 20 milliseconds.

     Optionally, a CSS class may be applied to the element during the time it is pressed.

     @cfg {Mixed} el The element to act as a button.
     @cfg {Number} delay The initial delay before the repeating event begins firing.
     Similar to an autorepeat key delay.
     @cfg {Number} interval The interval between firings of the "click" event. Default 20 ms.
     @cfg {String} pressClass A CSS class name to be applied to the element while pressed.
     @cfg {Boolean} accelerate True if autorepeating should start slowly and accelerate.
               "interval" and "delay" are ignored.
     @cfg {Boolean} preventDefault True to prevent the default click event
     @cfg {Boolean} stopDefault True to stop the default click event

     @history
        2007-02-02 jvs Original code contributed by Nige "Animal" White
        2007-02-02 jvs Renamed to ClickRepeater
        2007-02-03 jvs Modifications for FF Mac and Safari

     @constructor
     @param {Mixed} el The element to listen on
     @param {Object} config
     */
    Ext.util.ClickRepeater = function(el, config)
    {
        this.el = Ext.get(el);
        this.el.unselectable();

        Ext.apply(this, config);

        this.addEvents(
        /**
         * @event mousedown
         * Fires when the mouse button is depressed.
         * @param {Ext.util.ClickRepeater} this
         */
            "mousedown",
        /**
         * @event click
         * Fires on a specified interval during the time the element is pressed.
         * @param {Ext.util.ClickRepeater} this
         */
            "click",
        /**
         * @event mouseup
         * Fires when the mouse key is released.
         * @param {Ext.util.ClickRepeater} this
         */
            "mouseup"
        );

        if(!this.disabled){
            this.disabled = true;
            this.enable();
        }

        // allow inline handler
        if(this.handler){
            this.on("click", this.handler,  this.scope || this);
        }

        Ext.util.ClickRepeater.superclass.constructor.call(this);
    };

    Ext.extend(Ext.util.ClickRepeater, Ext.util.Observable, {
        interval : 20,
        delay: 250,
        preventDefault : true,
        stopDefault : false,
        timer : 0,

        /**
         * Enables the repeater and allows events to fire.
         */
        enable: function(){
            if(this.disabled){
                this.el.on('mousedown', this.handleMouseDown, this);
                if(this.preventDefault || this.stopDefault){
                    this.el.on('click', this.eventOptions, this);
                }
            }
            this.disabled = false;
        },

        /**
         * Disables the repeater and stops events from firing.
         */
        disable: function(/* private */ force){
            if(force || !this.disabled){
                clearTimeout(this.timer);
                if(this.pressClass){
                    this.el.removeClass(this.pressClass);
                }
                Ext.getDoc().un('mouseup', this.handleMouseUp, this);
                this.el.removeAllListeners();
            }
            this.disabled = true;
        },

        /**
         * Convenience function for setting disabled/enabled by boolean.
         * @param {Boolean} disabled
         */
        setDisabled: function(disabled){
            this[disabled ? 'disable' : 'enable']();
        },

        eventOptions: function(e){
            if(this.preventDefault){
                e.preventDefault();
            }
            if(this.stopDefault){
                e.stopEvent();
            }
        },

        // private
        destroy : function() {
            this.disable(true);
            Ext.destroy(this.el);
            this.purgeListeners();
        },

        // private
        handleMouseDown : function(){
            clearTimeout(this.timer);
            this.el.blur();
            if(this.pressClass){
                this.el.addClass(this.pressClass);
            }
            this.mousedownTime = new Date();

            Ext.getDoc().on("mouseup", this.handleMouseUp, this);
            this.el.on("mouseout", this.handleMouseOut, this);

            this.fireEvent("mousedown", this);
            this.fireEvent("click", this);

    //      Do not honor delay or interval if acceleration wanted.
            if (this.accelerate) {
                this.delay = 400;
    	    }
            this.timer = this.click.defer(this.delay || this.interval, this);
        },

        // private
        click : function(){
            this.fireEvent("click", this);
            this.timer = this.click.defer(this.accelerate ?
                this.easeOutExpo(this.mousedownTime.getElapsed(),
                    400,
                    -390,
                    12000) :
                this.interval, this);
        },

        easeOutExpo : function (t, b, c, d) {
            return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
        },

        // private
        handleMouseOut : function(){
            clearTimeout(this.timer);
            if(this.pressClass){
                this.el.removeClass(this.pressClass);
            }
            this.el.on("mouseover", this.handleMouseReturn, this);
        },

        // private
        handleMouseReturn : function(){
            this.el.un("mouseover", this.handleMouseReturn, this);
            if(this.pressClass){
                this.el.addClass(this.pressClass);
            }
            this.click();
        },

        // private
        handleMouseUp : function(){
            clearTimeout(this.timer);
            this.el.un("mouseover", this.handleMouseReturn, this);
            this.el.un("mouseout", this.handleMouseOut, this);
            Ext.getDoc().un("mouseup", this.handleMouseUp, this);
            this.el.removeClass(this.pressClass);
            this.fireEvent("mouseup", this);
        }
    });