MysterX documents are interactive. You can trap mouse and keyboard events in documents, and use Scheme code to respond to the events.
Each HTML element in a document may have its own event handler, which is a procedure of one argument. An event handler needs to be registered with the document, as in
(send doc register-event-handler button (lambda (event) ...))
You also need to call
(send doc handle-events)
to begin event processing.
When an event occurs in an element, the event handler is
called, passing an instance of the mx-event% class.
You can test what kind of event occurred with the follow method
(lambda (event) (when (send event dblclick?) (do-something)))
For a given event, at most one of these predicates returns #t. All the other predicates return #f for that event.
Events also have attributes, that give you information about how the event occurred. Like the predicates, the attributes are methods associated with mx-event%. Some of the attributes are
We could extend the event handler above to print the coordinates of double-clicks:
(lambda (event) (when (send event dblclick?) (printf "Double-click at x = ~a, y = ~a~n" (send event x) (send event y))))