I'm getting an exception in an OnTimer event handler (TTimer) that when executed increments an integer variable in the parent form. The timers need to be able to access an incremented integer used as an id.
My first question is: How can I tell in Delphi 2007 which code is running in which thread? Is there a way in debug mode to inspect this so I can determine for sure?
Secondly, if I need to access and modify variables in a parent form from another thread, what is the best way to do that? It seems like sometimes Delphi allows me to access these variables "incorrectly" without giving an exception and other times it does give an exception.
Just to be sure: On one hand you are talking about a timer event, on the other about multithreading. Those are two totally different ways of running code in parallel.
A timer will always be run in the main thread. It should be safe there to access everything that was created and is being used in the main thread. In fact, a timer event can only occur, when no other main thread code is running, because it needs the application's message handler to process the timer message. So it is either outside of any event handling code or when one of your event handlers calls Application.ProcessMessages.
A thread is very different from this. In this case, the code in different threads runs independently from each other. If running on a multi-processor machine (or multi core), it is even possible they truly run in parallel. There are quite a few issues you may have this way, in particular the Delphi VCL (up and including Delphi XE) is not thread save, so calls to any VCL class must only be done from the main thread (there are a few exceptions to this rule).
So, please first clarify whether you are talking about timers or true multithreading, before expecting any useful answers.