Steps to Reproduce

Run fiddle: https://zkfiddle.org/sample/1955k98/5-Another-new-ZK-fiddle

Scroll down a little, drag image to page

Current Result

The dropupload anchor position is shifted by the browser scroll position

Expected Result

Drop upload anchor position matches the anchor

Debug Information

Dropupload _dragShow() function finds anchor position using

ofs = $anchor.offset()

Which includes the scroll position of the browser into the offset.

However, the dropupload sets the the CSS position:static property on the component, so it doesn't need to also be offset by browser scroll position

Workaround

Do not scroll browser, instead have a window containing the whole UI with the data-scrollable attribute:

<zk xmlns:ca="client/attribute">
<window title="bug drop upload" border="normal" vflex="1" contentStyle="overflow:auto;" ca:data-scrollable="true">

UI CONTENT HERE

</window>
</zk>

alternatively, use JS workaround in attached fiddle.

(JS workaround is overriding a lot of functions, so only use if necessary)