Question

I am using TIdHttpServer to process some commands the problem is that some commands are beeing lost my guess is that it’s from the fact that i am updating the vcl inside OnConnect.

How can i use the Synchronize method to safley update the VCL ?

Answer 1

It’s easy enough, just call TThread.Synchronize() with whatever TThreadMethod you want to be called by the GUI thread. TThreadMethod is a parameterless procedure of object, but since the secondary thread making the call is blocked until after the synchronized method has been executed by the GUI thread, you can use TThread members in the synchronized method without any further protection.

Just for completenes, I should mention that there are several alternatives, all of which are better (even those I haven’t tried because nothing could be worse). Indy has TIdSync and TIdNotify classes that you can derive from to carry variables and implement custom methods. Newer Delphi versions have TThread.Queue() and TThread.ForceQueue() that can use anonymous methods to generate closures (with captured variables) that can be executed by the GUI thread without blocking the calling thread. There is also the PostMessage() and PostThreadMessage() APIs – a comms system that has worked without change since D3/W95 and is sure to be available on Windows forever.