Re: COM objects and instance creation in Lispworks

The first thing you need to do is generate FLI definitions from the .idl files
(not from the .h files).  See
https://www.lispworks.com/documentation/lw81/com/com-com-using-2.htm#1.2.2%20Generating%20FLI%20definitions%20from%20COM%20definitions-2

Microsoft provides these .idl files in this case (probably as part of the
Windows SDK):

IMMDeviceEnumerator is in mmdeviceapi.idl

IAudioSessionManager and IAudioSessionNotification are in audiopolicy.idl

I assume that you don't have to implement IMMDeviceEnumerator etc -- they are
implemented by Microsoft, so you just need to call their implementations.  You
will need to implement IAudioSessionNotification with
define-com-implementation.

There is an example of implementing and calling COM methods here:

https://www.lispworks.com/documentation/lw81/com/com-examples-ug-1.htm

The example just calls the methods in args-calling.lisp that it implements in
args-impl.lisp, but the same approach using com:call-com-interface works for
methods implemented by someone else.

The example contains args.idl, but :type :midl-file in defsystem can also be
used with files from the Windows SDK.  It should detect the path of the SDK
automatically (see "Import paths" in
https://www.lispworks.com/documentation/lw81/com/com-com-ref-34.htm).

-- 
Martin Simmons
LispWorks Ltd
http://www.lispworks.com/



>>>>> On Tue, 04 Nov 2025 23:25:47 +0100, david (as david at bundgaard dot se) said:
> 
> Hello all,
> I am fairly new to Lispworks.
> I am trying to grok the COM library.
> In this case, I want to build an audio session monitoring for Windows, which to requires me to implement the IAudioSessionNotification in Lisp.
> 
> The interface is fairly simple
> 
> MIDL_INTERFACE("641DD20B-4D41-49CC-ABA3-174B9477BB08")
> 
> IAudioSessionNotification : public IUnknown
> 
> {
> 
> public:
>     virtual HRESULT STDMETHODCALLTYPE OnSessionCreated( 
>         /* [in] */ IAudioSessionControl *NewSession) = 0;
> 
> };
> 
> To get access to use this event, I need to instantiate IMMDeviceEnumerator, from there we go get the GetDefaultEndpoint(eRender, eConsole, &device).
> 
> Then we do some more magic, the process is the same, and we end up with an IAudioSessionManager, with which we can register our callback class (IAudioSessionNotification).
> 
> Do I need to replicate all the methods and types to be able to call the various methods on each COM class?
> 
> I started by creating a .idl file, that would mirror the IAudioSessionNotification and  IAudioSessionControl.
> 
> I assume I should continue creating all the types (IMMDeviceEnumerator, IMMDevice, IAudioSessionEnumerator, etc), should I also implement their interfaces (define-com-implementation).
> 
> All the best
> David
> 
> 

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