Hi,

I've implemented an ATL ActiveX control for handling telephony methods and
events asynchronously.
One of the control's methods (OpenChannel) creates a worker thread to poll
for telephony events passing the 'this' pointer as the thread's function
parameter. Instead of marshaling the interface pointer before I create the
thread, I just implemented my connection points from IConnectionPointImplMT
(it's a class provided by Microsoft to enable firing events from worker
thread, as shown in this article:
http://www.*-*-*.com/ ;en-us;Q280512).
Another method enables the client to play a simple message file (Play) and
returns immediately. When the worker thread gets a notification from the
telephony card driver that the message has finished playing, it fires an
event (OnPlayFinished) to notify the client about that. It works very fine.
My problem now is, if I call the Play method just inside the OnPlayFinished
event, an access violation occurs (it has been noted in VB clients).
So, I ask: can I call COM methods inside a COM event when this event is
fired from other thread than the main thread ? How can I accomplish this ?

Thanks in advance for any help,

--
[]'s

Raul M. Fragoso

I suspect the problem is not on the COM side, but on the driver
side. Your callback has not returned yet (waiting for the client to
process the event on the other thread) when you call the Play
method. This may be causing the crash. The solution is not to fire
the event from within the driver callback. Post yourself a message
and raise the event from the message handler. This also makes
the whole sink marshaling ringmarole unnecessary (since your
hidden window will reside on your object's STA thread anyway).
You create the hidden window in FinalConstruct (also see the
CContainedWindow class and ALT_MSG_MAP) and DestroyWindow
it in FinalRelease.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD

MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================

Hi Alexander,

You was right, the problem was calling a driver function while the callback
is busy. The message pump solution you suggested is working nice now.
Thank you very much for your help.

--
[]'s

Raul M. Fragoso

I suspect the problem is not on the COM side, but on the driver
side. Your callback has not returned yet (waiting for the client to
process the event on the other thread) when you call the Play
method. This may be causing the crash. The solution is not to fire
the event from within the driver callback. Post yourself a message
and raise the event from the message handler. This also makes
the whole sink marshaling ringmarole unnecessary (since your
hidden window will reside on your object's STA thread anyway).
You create the hidden window in FinalConstruct (also see the
CContainedWindow class and ALT_MSG_MAP) and DestroyWindow
it in FinalRelease.