t_wの輪郭

/
* Add an event listener to one of the elements inserted in the canvasFrame
* native anonymous container.
* Like other methods in this helper, this requires the ID of the element to
* be passed in.
*
* Note that if the content page navigates, the event listeners won't be
* added again.
*
* Also note that unlike traditional DOM events, the events handled by
* listeners added here will propagate through the document only through
* bubbling phase, so the useCapture parameter isn't supported.
* It is possible however to call e.stopPropagation() to stop the bubbling.
*
* IMPORTANT: the chrome-only canvasFrame insertion API takes great care of
* not leaking references to inserted elements to chrome JS code. That's
* because otherwise, chrome JS code could freely modify native anon elements
* inside the canvasFrame and probably change things that are assumed not to
* change by the C++ code managing this frame.
* See https://wiki.mozilla.org/DevTools/Highlighter#The_AnonymousContent_API
* Unfortunately, the inserted nodes are still available via
* event.originalTarget, and that's what the event handler here uses to check
* that the event actually occured on the right element, but that also means
* consumers of this code would be able to access the inserted elements.
* Therefore, the originalTarget property will be nullified before the event
* is passed to your handler.
*
* IMPL DETAIL: A single event listener is added per event types only, at
* browser level and if the event originalTarget is found to have the provided
* ID, the callback is executed (and then IDs of parent nodes of the
* originalTarget are checked too).
*
* @param String id
* @param String type
* @param Function handler
*/