COMmunism: Sharing your Apartment

re: COMmunism: Sharing your Apartment

Arno Schoedl — Sat, 08 Oct 2005 15:45:24 GMT

Hello Marc,

CoGetCallContext and IContextCallback are virtually undocumented, so I am not sure whether they are a solution to my problem. I have a COM interface (on a non-creatable object) which gets handed to another process to be called in the MTA.

But the interface gets sent to the other process by a call from my app's main STA. And marshalling the interface there would marshal it as STA. So I created a separate COM MTA worker thread, which does nothing else but marshalling interfaces whenever the STA needs to send a MTA-marshalled interface off to another process.

It seems to work fine: the call-backs arrive on separate threads as they should. Unfortunately, the profiler says this frequent thread switching is very slow. Is there a better way?

Thank you for your help,

Arno

re: COMmunism: Sharing your Apartment

marcmill — Mon, 10 Oct 2005 09:33:35 GMT

Arno:

The short answer is: I don't know.

The long answer is: trying using the neutral apartment instead. The context callback stuff is virtually undocumented, but the interface is very straightforward, except for the bit about the IID and method number: I just pass IID_IContextCallback and "3" to get default context. Seems to work fine so far, and seems to be what other places in the Windows source code does (shh!).

-marc

re: COMmunism: Sharing your Apartment

Arno Schoedl — Mon, 10 Oct 2005 13:45:16 GMT

Thanks for your reply. I am a little reluctant to create the object in the neutral apartment, because as far as I understand, I can only do this via a registry entry and CoCreateInstance, and the object is currently non-creatable. I tried the IContextCallback::ContextCallback route, but found that IID_IEnterActivityWithNoLock is nowhere defined:-(

Arno