Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!agate!spam!lippin
From: lippin@spam.berkeley.edu (The Apathist)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Simulating a Menu Bar with Pop-Up Menus
Message-ID: <1989Nov28.053644.28100@agate.berkeley.edu>
Date: 28 Nov 89 05:36:44 GMT
References: <9095@hoptoad.uucp>
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Reply-To: lippin@math.berkeley.edu
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I don't think there's a good way to do this; Apple either doesn't want
it to be easy or is just being lazy.  But I've also hacked a menu bar
with PopupMenuSelect; I don't know that my way is any better than
Tim's, but here are the differences anyway:

First, I don't think that calling the MDEFs directly should be
overlooked as a possibility.  It has the advantage of being less of a
hack.  On the other hand, it is difficult and it raises some
compatibility questions (future MDEFs; drawing into the desktop).

But I didn't use this approach; instead, I put a hack into my MDEF.  I
pass it an address using a high-numbered message, up where they've
been reserved for applications.  The address lets me communicate back
and forth.  Before going into PopupMenuSelect, I tell it where the
menu bar is, and where the menu's title is.  If the MDEF finds the
mouse in the menu bar, but not in the title area and the mouse is
StillDown(), it posts a fake mouse-up-mouse-down, and sets a flag
indicating the fakeness.  PopupMenuSelect senses this, and returns to
the caller, which then grabs the mouse-down with GetNextEvent if it
was faking, and goes back to tracking the menu bar.  (The mouse down
may not be necessary, but I prefer to post mouse events in pairs, so
that the event queue will have less chance of getting out of sync with
the mouse button.)

Now, using a hacked MDEF instead of a MenuHook is a dubious advantage;
it won't suffer when low memory globals go away, but if MDEF 0 changes
in the future, my menus won't.  This is fine for me -- these menus are
nonstandard anyway, but it's a point that should be considered.

I like posting events better than patching Button, but it's a close
call.  BTW, the patch Tim describes may not be a tail patch by a
strict definition, but it suffers from the tail patch problem -- it
blocks come-from patches.  On the other hand, it blocks them only
during PopupMenuSelect, and only there on rare occasions.

Finally, I agree that longjumping out of a trap is a very bad idea
(although my code does do it in some emergencies).  It'll get you back
to your application ok, but it may leave some global resources (the
screen in this example) in an inconsistent state.

					--Tom Lippincott
					  lippin@math.berkeley.edu

 "Ask a fish head anything you want to.  It won't answer you; they can't talk."
					--"Fish Heads"