<zk>
   <style>
   .buggy .z-combobox-input {
      background-color: yellow;
   }

   .buggy .z-combobox-input:focus {
      background-color: green;
   }
   </style>
   <label multiline="true">
   1. Combobox's initial background color is yellow.
   2. Click button to open dorp-down list, and Combobox's background color will transform to green.
   3. Select a item, and then Combobox's background color must be still green.
   </label>
   <combobox sclass="buggy">
      <comboitem label="item 1"></comboitem>
      <comboitem label="item 2"></comboitem>
   </combobox>
</zk>