Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!snorkelwacker!bloom-beacon!LARRY.MCRCIM.MCGILL.EDU!mouse
From: mouse@LARRY.MCRCIM.MCGILL.EDU (der Mouse)
Newsgroups: comp.windows.x
Subject: Re:  Single/Double Click
Message-ID: <9004080623.AA02917@Larry.McRCIM.McGill.EDU>
Date: 8 Apr 90 06:23:02 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 39

> I need to be able to cause two different actions depending on whether
> I click once or twice on a mouse button.  My translation table looks
> (in part) like this:

> <Btn1Down>(2):		action_one\n\
> <Btn1Down>,<Btn1Up>:	action_two\n\

> With this table, a single click calls action_two as required, but a
> double click calls action_two followed by action_one.  How can I
> ensure action_two is not called from a double click?

I think you can't.

You see, X does not have mouse clicks.  All it has is button presses
and releases.  (And motion events, but those are irrelevant to the
discussion at hand.)  Xt tries to fake clicks with this, but the lack
of a mouse timeout event makes it difficult, and the result therefore
has problems, not surprisingly.  In particular, if you want to do <foo>
on a single click and <bar> on a double click, you have to make sure
either that <foo> is a subset of <bar> or that <foo> is undoable.  This
is because <foo> is done after the first click regardless of whether
it's the first click of a double-click or not.

I think X should have mouse timeout events of some sort, that is, some
sort of event that can be requested saying that "the mouse hasn't
changed state in <time>", where <time> is settable somehow, either
globally, per-client, per-window, or per-<client,window>-pair.
(Ideally all four, of course.)  This would allow multiple clicks to be
done reliably.  (Clicks could also be made into events in their own
right, but "mechanism not policy"; someone may want pointer-idle events
for something else.)

Perhaps if nobody else does I'll put together an extension and see how
it goes.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu