I'm looking at the beforecut, beforecopy and beforepaste events. I
don't entirely understand their intent, it seems even more obscure
than I expected..
Nothing in the official MSDN documentation [1] really explains the
interaction between beforecopy and copy (given that you can control
the data put on the clipboard from the copy event without handling
beforecopy at all, the demo labelled "this example uses the
onbeforecopy event to customize copy behavior" doesn't really make
sense to me either.)
I was under the impression that you could handle the before* events to
control the state of copy/cut/paste UI like menu entries. However,
when tweaking a local copy of the MSDN code sample [2], I don't see
any difference in IE8's UI whether the event.returnValue is set to
true or false in the beforecopy listener.
Another problem with using before* event to control the state of
copy/cut/paste UI is that it only works for UI that is shown/hidden on
demand (like menus) and not for UI that is always present (like
toolbar buttons). I'm not aware of web browsers that have UI with
copy/cut/paste buttons by default, but some browsers are customizable
and some might have toolbar buttons for this.
I'm wondering if specifying something like
navigator.setCommandState('copy', false); // any "copy" UI is now
disabled until app calls setCommandState('copy', true) or user
navigates away from page
would be more usable? A site/app could call that at will depending on
its internal state. Or, if we want to handle the data type stuff, we
could say
navigator.setCommandState('paste', true, {types:['text/plain','text/html']});
to enable any "paste plain text" and "paste rich text" UI in the browser?
-Hallvord
[1] http://msdn.microsoft.com/en-us/library/ms536901(VS.85).aspx
[2]
http://samples.msdn.microsoft.com/workshop/samples/author/dhtml/refs/onbeforecopyEX.htm
