[Lazarus] TThread.Synchronize

LacaK lacak at zoznam.sk
Tue Oct 25 14:07:25 CEST 2016

>> My understanding is that, Synchronize schedules execution of 
>> MyForm.MyMethod to main thread, so method is not executed until 
>> control is returned from event handler in MyForm. Right?
> TThread.Synchronze pushes the procedure that is given as a parameter 
> (including it's Self pointer) to the event queue and then the Therad 
> that called TThread.Synchronize is stalled.

> Some time later the main (GUI) thread will execute the scheduled 
> procedure. When this call returns, the thread that called 
> TThread.Synchronize is activated.

but what is relation between "main thread" and this "sheduled procedure" 
? Can "sheduled procedure" jump into execution while main thread is 
still executing prior called form method ?

> There also is TThread.Queue that works identically, only without 
> stalling the thread.
yes, but I do not want this

>> But in my case happens, that method is executed while execution of 
>> event handler does not finished yet ... is it expected behavior ?
> What is "that method"? If same is called by the thread after 
> TThread.Synchronize, IMHO this can't be correct.

Yes this can happen.
MyForm.MyMethod is called also from event handler and also is used in 
How can this happen/play role?

I have suspection that somewhere in Win32 widgetset is called 
CheckSynchronize as reaction on some message or so, which releases 
execution of MyForm.MyMethod ... but it is inappropriate, does not ?


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