Steps to Reproduce

https://zkfiddle.org/sample/33tupp1/2-async-combobox-popup#source-2

run fiddle

open combobox popup

the combobox is empty at first, then is populated in a serverpush activation

Current Result

popup sizes based on content without any height limit, cause scrollbar on browser window

Expected Result

popup size is recalculated after adding new items

Debug Information

onResponse: function(ctl, opts) {
 if ((opts.rtags.onOpen || opts.rtags.onChanging) && this.isOpen())

Size calculation is only triggered if the response contains ((onOpen or onChanging) + popup currently open).

Since the serverpush response doesn't contain rtags, it never trigger this recalculation.

Workaround