Polymer paper-dropdown-menu not resized when dynamically add/remove elements to it

[Xiao Cao]

Hi everyone

I met an UI problem when developing website with dart polymer. I have the following paper-dropdown-menu code

<paper-dropdown-menu>

 <paper-dropdown>

   <core-menu>

     <template repeat="{{enumerator in enumeratorList}}">

       <paper-item name="{{enumerator}}"> {{enumerator}} </paper-item>

     </template>

   </core-menu>

 </paper-dropdown>

</paper-dropdown-menu>

, where enumeratorList is an observable list defined in dart. 

Here is the problem, If I toggle the dropdown menu first,  add several elements to the enumeratorList dynamically through dart, and at last open the dropdown menu again, the dropdown would have a wrong display. It would be like this

If I don't toggle the dropdown menu at first, the dropdown menu display would be correct, like this

It seems to me that the dropdown menu can not dynamically detect added/removed paper-item content. I went through the dart APIs of all these element paper-dropdown-menu, paper-dropdown and core-menu but didn't see any method called resize or update. Anyone has ideas how to fix the problem?

Thanks very much!!!

[Günter Zöchbauer]

Looks similar to https://github.com/Polymer/paper-dropdown/issues/2#issuecomment-76155635

[Günter Zöchbauer]

It seems here a `sizingTarget` was added but I couldn't find it in the docs. 

Setting `paper-dropdown`s `sizingTarget` to `core-menu` might be worth a try.

[Xiao Cao]

Could you please explain it in more details. Where should I modify the sizingTarget attribute.  Is it possible to do it in the html file. Or do I have to query all dropdown element and set their attribute in dart. Can I set the value directly?

Thank you very much!!!