title: How to set a fixed width for CheckboxModel column in GridPanel?
body: <p>I needed checkbox selection mode in my gridpanel, so i use <code>Ext.selection.CheckboxModel</code> component, but my problem is about the column (checkbox column) which this component will append to my grid. I want to set a fixed width for it, because this column's width may vary when i resize the browser window. I use the code below, but it doesn't work:</p>
  
  <pre><code>constructor: function() {
      var me = this;
          me.selModel = Ext.create('Ext.selection.CheckboxModel', {width: 16});
      me.callParent(arguments);
  }
  </code></pre>
  
  <p>This is code snippet and snapshot of my users table:</p>
  
  <pre><code>Ext.define('VDOA.view.users.Table', {
      extend: 'Ext.grid.GridPanel',
      alias: 'widget.usersgrid',
      forceFit: true,
      selType: 'checkboxmodel',
      //selType: 'rowmodel',
      //selModel: Ext.create('Ext.selection.CheckboxModel'),
      title: '',
      initComponent: function() {
          ...
      }
  });
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/3MzrL.png" alt="snapshot of my panel"></p>