Passing control away and back again

Peter Haworth pete at
Sun Feb 15 13:07:22 EST 2015

The -1 trick is new to me, good to know.

What's the problem with using a modal stack as suggested by Doc Hawkins?
The initial code waits until the modal stack closes before continuing -
isn't that the requirement?

As for where to put the startup code, card 1 of the main stack has always
worked for me.  It executes every time the main stack is opened but not
when other stacks are opened.

On Sun Feb 15 2015 at 8:56:21 AM J. Landman Gay <jacque at>

> On February 15, 2015 10:41:42 AM CST, Paul Dupuis <paul at>
> wrote:
> >On 2/15/2015 10:02 AM, Graham Samuel wrote:
> >> But I do understand Paul's, which was very near the approach I was
> >thinking of taking myself. I suppose I am still worried about the
> >'send'. Sending isn't calling, is it? I mean, in principle, a handler
> >like "dopart2" in Paul's example will be executed, and then control
> >will return to the script that executed the 'send', won't it? So we end
> >up executing "end mouseUp" in the context of the button that was
> >clicked, not the script that was running in the 'startUp' handler.
> >Perhaps this doesn't matter, but this is the issue I'm trying to get my
> >head around. Anyway it's a viable solution and I'm grateful.
> >
> >send <message> to <object> -- is like a call. The handler waits until
> >message is executed before proceeding to the next statement
> >
> >send <message> to <object> in <time> -- places the message in the
> >message queue and the handler continues. The message queue then invokes
> >the message in the allotted time.
> >
> >So,
> >
> >on mouseUp
> >  close this stack
> >  send "doPart2" to <main stack>
> >end mouseUp
> >
> >will not do what you want as the send executes "doPart2" and the
> >completes the mouseUp, but
> >
> >on mouseUp
> >  close this stack
> >send "doPart2" to <main stack> in 10 milliseconds -- or some non-zero
> >time
> >end mouseUp
> >
> >causes doPart2 to execute in the context of the main stack AFTER the
> >mouseUp handler has completed.
> >
> >If I recall correctly, Richard Gaskin produced an excellent short 1 or
> >2
> >page guide on message passing in LiveCode. A *must have* reference if
> >you're still learning all the ins and outs. It looks like he's expanded
> >it from the one I remember as well. See
> >
> >
> >
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> Actually you can send in 0, which will execute right after the handler
> completes, or even in - 1 which pushes the request to the front of the
> queue ahead of all other pending messages. I learned that last trick from
> Dar a while back.
> --
> Jacqueline Landman Gay         |     jacque at
> HyperActive Software           |
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