How to access the jQuery event object in a Seaside callback
To serialize the x mouse coordinate of the event use the following code:
html div onClick: (html jQuery ajax callback: [ :x | x inspect ] value: JQEvent new pageX); with: 'Click'.There are other properties in the event object that you might be interested in, just serialize them with the same AJAX request by adding multiple callback:value: constructs in a cascade.
In the very latest JQuery code you can use html jQuery event to create the event object. This was missing up to now.