Ext.ns('Ext.ux.form.HtmlEditor');Ext.ux.form.HtmlEditor.HR =Ext.extend(Ext.util.Observable,{
init:function(cmp){this.cmp = cmp;this.cmp.on('render',this.onRender,this);},
onRender:function(){this.cmp.getToolbar().addButton([{
iconCls:'x-edit-custom',//your iconCls here
handler:function(){this.cmp.insertAtCursor('<hr>');},
scope:this,
tooltip:'horizontal ruler',
overflowText:'horizontal ruler'}]);}});var w =newExt.Window({
550,
layout:'fit',
items:[{
xtype:'htmleditor',
plugins:[newExt.ux.form.HtmlEditor.HR()]}]});
w.show();