| Calling CTAPI directly from an Active X
control in Citect will cause a deadlock. The CTAPI has been
designed for high performance asynchronous operation and has many
functions which will block the caller. These operations cannot be
called from an Active X control or you will block the primary
Citect animation thread. When CTAPI blocks the primary Citect
thread, this will cause a deadlock condition. This is because
Citect is calling the Active X control and then the Active X
control is calling back into Citect.
You may work around this problem by creating another thread in
you Active X control which calls CTAPI. This way the secondary
thread does all the blocking calls to the CTAPI and stores the
results in global memory. The normal Active X draw code can pick up
the results from global memory and display them in its control. By
separating the slower, I/O bound operations into another thread, it
keeps the animation of graphics pages fast.
This problem can also occur if you call CTAPI via the DLLCall()
function
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