Hi,
when I open calendar.zul from calendar live demo (downloaded from zkoss.org), I got an error in ZUL visual editor:
Fail to render : org.xml.sax.SAXParseException: Element type "divarrow" must be followed by either attribute specifications, ">" or "/>".
I have found that it caused by a comma enclosed in apostrophes in the attribute:
<divarrow type="arrow-left" command='cal.previousPage();Events.postEvent("onCreate", label, null);syncModel();'/>
Where's the fault? My code looks exactly like yours, zul visual editor shows the same error.
Well, when I open valid ZUL file in a ZUL editor, I expect it is rendered correctly without any errors. Nor, the ZUL editor is unusable for certain ZUL files.