Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!han
From: han@Apple.COM (Byron Han, wyl E. coyote )
Newsgroups: comp.sys.mac.programmer
Subject: Re: SoundPlay in Async mode
Message-ID: <28665@apple.Apple.COM>
Date: 9 Apr 89 17:42:45 GMT
References: <1354@ndmath.UUCP>
Organization: Apple R&D - Networking & Communications
Lines: 84

In article <1354@ndmath.UUCP> milo@ndmath.UUCP (Greg Corson) writes:
>
>Would anyone happen to have a code fragment that illustrates how to setup
>the required callback routines so you can have SoundPlay play a sound in the
>background (async) mode?
>
>1. open the channel and specify a callback
>2. play a snd resource
>3. have the callback set a global flag
>4. have my main event loop close the channel when the flag is set.

This is the code I am using.  There is NO guarantee or warranty with this
code.  Use at your own risk!  This is NOT Apple DTS sanctioned code.

1. the main application needs to keep a global variable is a SndChannelPtr.
Initialize it to NIL.

2. Pass in the handle to the snd  resource that you want to play.

This should bootstrap to you greater understanding of the world of the 
Sound Manager.

PROCEDURE PlayIt(VAR chan: SndChannelPtr; theSound: Handle);
VAR
    err: OSErr;
    myWish: SndCommand;

BEGIN
    IF chan <> NIL THEN   {cancel sound in progress}
    BEGIN
        err := SndDisposeChannel(chan, TRUE);  {TRUE means now}
        IF err <> noErr THEN
        BEGIN
            DebugStr('Cannot dispose of old channel');
            Exit(PlayIt);
        END
        ELSE
            chan := NIL;
    END;
  
    err := SndNewChannel(chan, 0, 0, NIL);
    IF err <> noErr THEN
    BEGIN
        DebugStr('Cannot allocate new channel');
        Exit(PlayIt);
    END;
    
    IF theSound <> NIL THEN {we have a handle}
        IF theSound^ <> NIL THEN {and is not a nil handle }
        BEGIN
            err:=SndPlay(chan, theSound, TRUE);     
            IF err <> noErr THEN
            BEGIN
                DebugStr('Cannot play sound');
                Exit(PlayIt);
            END;

            WITH myWish DO   { set up a sound mgr command block }
            BEGIN
               cmd := freeCmd;  {to free self when done }
               param1 := 0;
               param2 := 0;
            END; {with}

            err := SndDoCommand(chan, myWish, FALSE);
 
            IF err <> noErr THEN
            BEGIN
                DebugStr('cannot add command');
                Exit(PlayIt);
            END;
        END;
END;
+-----------------------------------------------------------------------------+
| Disclaimer: Apple has no connection with my postings.                       |
+-----------------------------------------------------------------------------+ 
Byron Han, Communications Architect      Cereal, anyone?  :-)  A1!
Apple Computer, Inc.                     -------------------------------------
20525 Mariani Ave, MS27Y                 Internet: han@apple.COM
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