Steps to Reproduce

https://zkfiddle.org/sample/1fk5tle/2-missing-listbox-size-event-CE

Run in a CE context

Click button

Current Result

Listbox adds the new rows, but doesn't resize (not flexing). The listbox grows outside of the screen incorectly.

Expected Result

Listbox just normally trigger a flex sync and flex calculation is applied

Debug Information

The interval_added internal event need to trigger partial invalidate

https://github.com/zkoss/zk/blob/678daef08e6005f7e1acb4036679868e8c2898fa/zul/src/org/zkoss/zul/impl/ListboxDataLoader.java#L118

This only happen if there is no other even triggering a full invalidate in the execution, and if the added rows are > invalidate threshold of the listbox, and if the original listbox wasn't empty

Workaround

<script><![CDATA[ 
        zk.afterLoad("zk", function () {
            var _xcmd1 = {};
            zk.override(zAu.cmd1, _xcmd1, {
                outerPartial: function(a, b, c) {
                    var result = _xcmd1.outerPartial.apply(this, arguments);
                    var target = a;
                    setTimeout(function(){
                        zUtl.fireSized(zk.$(a.uuid));
                    },0);
                    return result;
                }
             });
        });
    ]]></script>