[Lazarus] OSX: Handles and WindowRefs

[Duncan Parsons]

Hi,

I have declared a couple of procedures with the message attribute in a
form class, descended from TForm, like so:

    procedure Log_message(var msg: UserMsg); Message LM_USER;
    procedure Thread_complete(var msg: UserMsg); Message LM_USER+1;

The structure UserMsg has a Cardinal in the first position to hold the
message id. This is always set correctly to one of the two values based
on LM_USER, as above.

The background thread's class, descended from TThread, contains a
pointer to the form that invoked the thread in a field named
Parent_form.

When the background thread comes to post a message to the parent form,
it uses the Dispatch() method of TObject, inherited through TForm to the
form's class. However, the call never returns and the application hangs.
I have also tried the DeliverMessage() function, but the results are
identical.

This looks rather like some sort of deadlock on something like a mutex
semaphore -- but that's just a guess. Is there some "knack" to calling
Dispatch() that avoids this problem?

-- 
Regards,

Dave  [RLU #314465]
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dwnoon at ntlworld.com (David W Noon)
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