Path: utzoo!attcan!uunet!nih-csl!lhc!ncifcrf!haven!purdue!decwrl!adobe!heaven!glenn
From: glenn@heaven.woodside.ca.us (Glenn Reid)
Newsgroups: comp.sys.next
Subject: Re: How do I interrupt my App?
Message-ID: <313@heaven.woodside.ca.us>
Date: 5 Nov 90 23:00:14 GMT
References: <1614@libra.cs.nps.navy.mil>
Reply-To: glenn@heaven.woodside.ca.us (Glenn Reid)
Organization: RightBrain Software, Woodside, CA
Lines: 71

In article <1614@libra.cs.nps.navy.mil> sisk@cs.nps.navy.mil (Tamara Sisk) writes:
>I'm polishing up a nifty App to submit to the sites, but I'm stuck on
>one thing.
>
>Part of the App involves creating a (very) long list in a ScrollView.
>I want to be able to stop the listing without crashing my App, once
>I'm happy with how long the list is.  Currently, there is a "Start" button
>that starts the listing.  I'd like to make it so that this button
>turns into a "Stop" button while the list is going, so that if
>I push it again, the method creating the list just stops, just like
>ScorePlayer, for example, whose start button turns into a stop button.

This turns out to be a little more complicated than you might think,
but below is some code that does the trick, thanks to some pointers from
NeXT people a long time ago.

The basic idea is this:
	* start a "modal session" for the active window
	* enter your busy loop in which you create the long
	  list in the scrollview
	* periodically within the loop you call a method to see
	  if the modal dialog has been stopped, and exit the loop if so
	* end the modal session and clean up

Here are some code fragments; assume that you have a button that triggers
a method called "stop" in your object, and that the object itself has a
outlet to the button called "stopButton" so it can disable it.  My code
does not make the same button into the STOP button, but you can figure
out that part.


/****************************** yourMethod */
- yourMethod:sender
{
    NXModalSession session;
    short whatever = TRUE;

    [NXApp beginModalSession: &session for: window];
    [stopButton setEnabled:TRUE];
    while ( whatever ) {
	if ( [NXApp runModalSession: &session] != NX_RUNCONTINUES ) {
	    // stop button was hit
	    // clean up and exit while loop
	    break;
	}
    }
    [NXApp endModalSession: &session];
    [stopButton setEnabled:FALSE];
    return self;

} // yourMethod


/****************************** stop */
- stop:sender
{

    [NXApp stopModal];
    NXBeep();
    NXRunAlertPanel ( "Stopped",
	"Stopped at your request.", NULL, NULL, NULL
    );
    return self;
    
} // stop


-- 
 Glenn Reid				RightBrain Software
 glenn@heaven.woodside.ca.us		PostScript/NeXT developers
 ..{adobe,next}!heaven!glenn		415-851-1785