# CheckboxSelectionModel.js

    /**
     * @class Ext.grid.CheckboxSelectionModel
     * @extends Ext.grid.RowSelectionModel
     * A custom selection model that renders a column of checkboxes that can be toggled to select or deselect rows.
     * @constructor
     * @param {Object} config The configuration options
     */
    Ext.grid.CheckboxSelectionModel = Ext.extend(Ext.grid.RowSelectionModel, {
        /**
         * @cfg {String} header Any valid text or HTML fragment to display in the header cell for the checkbox column
         * (defaults to '&lt;div class="x-grid3-hd-checker">&#160;&lt;/div>').  The default CSS class of 'x-grid3-hd-checker'
         * displays a checkbox in the header and provides support for automatic check all/none behavior on header click.
         * This string can be replaced by any valid HTML fragment, including a simple text string (e.g., 'Select Rows'), but
         * the automatic check all/none behavior will only work if the 'x-grid3-hd-checker' class is supplied.
         */
        header: '<div class="x-grid3-hd-checker">&#160;</div>',
        /**
         * @cfg {Number} width The default width in pixels of the checkbox column (defaults to 20).
         */
        width: 20,
        /**
         * @cfg {Boolean} sortable True if the checkbox column is sortable (defaults to false).
         */
        sortable: false,

        // private
        menuDisabled:true,
        fixed:true,
        dataIndex: '',
        id: 'checker',

        // private
        initEvents : function(){
            Ext.grid.CheckboxSelectionModel.superclass.initEvents.call(this);
            this.grid.on('render', function(){
                var view = this.grid.getView();
                view.mainBody.on('mousedown', this.onMouseDown, this);
                Ext.fly(view.innerHd).on('mousedown', this.onHdMouseDown, this);

            }, this);
        },

        // private
        onMouseDown : function(e, t){
            if(e.button === 0 && t.className == 'x-grid3-row-checker'){ // Only fire if left-click
                e.stopEvent();
                var row = e.getTarget('.x-grid3-row');
                if(row){
                    var index = row.rowIndex;
                    if(this.isSelected(index)){
                        this.deselectRow(index);
                    }else{
                        this.selectRow(index, true);
                    }
                }
            }
        },

        // private
        onHdMouseDown : function(e, t){
            if(t.className == 'x-grid3-hd-checker'){
                e.stopEvent();
                var hd = Ext.fly(t.parentNode);
                var isChecked = hd.hasClass('x-grid3-hd-checker-on');
                if(isChecked){
                    hd.removeClass('x-grid3-hd-checker-on');
                    this.clearSelections();
                }else{
                    hd.addClass('x-grid3-hd-checker-on');
                    this.selectAll();
                }
            }
        },

        // private
        renderer : function(v, p, record){
            return '<div class="x-grid3-row-checker">&#160;</div>';
        }
    });

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