Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!Greg@AppleLink.Apple.Com
From: Greg@AppleLink.Apple.Com (Greg Marriott)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Gestalt Bug?
Message-ID: <11839@goofy.Apple.COM>
Date: 24 Jan 91 12:07:16 GMT
References: <1991Jan21.221130.2061@athena.mit.edu> <1991Jan23.170829.2793@waikato.ac.nz>
Sender: usenet@Apple.COM
Distribution: usa
Organization: Apple Computer, Inc.
Lines: 60

In article <1991Jan23.170829.2793@waikato.ac.nz>, ldo@waikato.ac.nz
 (Lawrence D'Oliveiro, Waikato University) wonders about the
"sound input hardware present" bit:

Okay, I talked to a sound engineer, and here's what he told me:

NOBODY is suppose to change any of the SoundMgr Gestalt selectors!
If a developer wants to determine if a Sound Input driver is available,
then call the SPBGetIndexedDevice call (as shown below).
The Gestalt selectors for sound will only report if the machine has
"built-in sound input hardware". 

In System 7, we've added a new bit in the sound selector and changed
a previous one to a name that is more descriptive.  The new selector,
gestaltHasSoundInputDevice, will call SPBGetIndexedDevice for you, but
this only happens in System 7.  If you are running under System 6.0.7,
then you have to call SPBGetIndexedDevice directly.  Also, if you are
running under older Systems then you'll have to test if _SoundDispatch
is implemented before calling SPBGetIndexedDevice.  Here's some code that
developers should be using.  This issue is documented in the
new Sound Manager chapter of Inside Mac 6.

{is the new Sound Manager running?}

IF NGetTrapAddress(_Unimplemented, ToolTrap)
<> NGetTrapAddress(_SoundDispatch, ToolTrap) THEN
   gNewSndMgr:= SndSoundManagerVersion > 0
ELSE
   gNewSndMgr:= FALSE;

{is the Sound Input Manager available?}

gHasSndInput:= FALSE;
IF gNewSndMgr THEN BEGIN
   IF SPBVersion > 0 THEN BEGIN
      IF SPBGetIndexedDevice(1, devName, devIconHandle) = noErr THEN BEGIN
         DisposHandle(devIconHandle);
         gHasSndInput:= TRUE;
      END;
   END;
END;


Here are the latest versions of the Gestalt bit for sound.
"gestaltHasSoundInputDevice" only will be valid for System 7.

gestaltSoundAttr = 'snd ';         { sound attributes }
gestaltStereoCapability = 0;       { sound hardware has stereo capability }
gestaltStereoMixing = 1;           { stereo mixing on external speaker }
gestaltSoundIOMgrPresent = 3;      { The Sound I/O Manager is present  }
gestaltBuiltInSoundInput = 4;      { built-in Sound Input hardware is present }
gestaltHasSoundInputDevice = 5;    { Sound Input device available }

Jim Reekes E.O., Macintosh Toolbox Engineering
---------------------
So, there you have it.

Greg Marriott
Blue Meanie
Apple Computer, Inc.