Thus spake Bill Medland: [...]
I added a couple of MessageBox calls in the source of the control's code. While the OCX was loading the "before" and "after" message boxes were displayed as expected. However once the OCX was up and I pulled down the dropdown list the "before" message box popped up TWICE and you had to say OK to them in the correct order to get the pair of "after" boxes. So I included GetCurrentThreadID in the message they displayed, thinking that we now had two threads. But both had (or appeared to have) the same thread ID. So I turned on the dialog warnings and, yes, the second call to MessageBox was occurring while the first was still executing.
Anyone know what is going on there?
I suspect you are calling MessageBox() during processing of a message sent via SendMessage() during processing of another message posted to the control's queue. That is typically a recipe for confusion or worse; one way to avoid it, though it might not make MessageBox() debugging very useful, is to call MessageBox() only when InSendMessage() returns FALSE.
-
John K. Hohm