Hi,
there's a very annoying gotcha in the clipboard events spec: the "default
action" of for example the copy event is to copy any selected text in the page
(and do nothing if there is no selection). This remains the default action even
if you use event.clipboardData.setData() and friends to modify the "payload" -
it's a requirement to also call event.preventDefault() to make what you want to
happen actually happen.
This extra "event.preventDefault()" is something I've personally forgotten to
do several times - which is a bit embarrassing as I should be expected to know
:-p. But worse than that is that regular web developers are likely to run into
this pretty often too. I guess lots of people will struggle a bit here, and few
of them will understand why it is even necessary.
So, is it necessary? IMO we can't change this basic
default-action-of-event-is-copying-content approach, for backwards
compatibility. But I guess we could say that the implementation itself cancels
the default event if
a) The event is script-generated and has a data payload (new
ClipboardEvent('copy', {dataType:'text/plain', data:'Hi World'}))
b) Any event listener calls setData() or modifies the DataTransfer payload some
other way
Thoughts?
-Hallvord
