[Lazarus] Thread finalization

[Leonardo M. Ramé]

On 2011-09-21 14:55:06 +0200, Sven Barth wrote:
> Am 21.09.2011 14:31, schrieb Leonardo M. Ramé:
> >I'm having a rough time with Threads.
> >
> >When my app starts, it creates an instance of a TThread that loads a
> >bunch of images. That TThread instance can be destroyed in two ways:
> >
> >1) When the loading finishes.
> >2) When the user closes the app while loading.
> >
> >In case 2, I destroy the thread using this code:
> >
> >   if Assigned(FMyThread) then
> >   begin
> >     FMyThread.Terminate;
> >     while not FMyThread.Finished do
> >       CheckSynchronize(100);
> >     FreeAndNil(FMyThread);
> >   end;
> >
> >This works ok.
> >
> >Now, in case 1, I thought that I should assign an OnTerminate event to
> >the thread, then destroy it, but it doesn't work as expected. The app
> >gets locked on my thread destroy event:
> >
> >   procedure TForm1.Createthread;
> >   begin
> >     FMyThread := TMyThread.Create;
> >     FMyThread.OnTerminate := @ThreadDestroyEvent;
> >     FMyThread.Start;
> >   end;
> >
> >   procedure TForm1.ThreadDestroyEvent(Sender: TObject);
> >   begin
> >     FMyThread.Free;
> >   end;
> >
> >   destructor TMyThread.destroy;
> >   begin
> >     // destroy internal objects
> >     inherited destroy; //<-- The app gets locked here!!
> >   end;
> >
> >Why is this happening?, am I doing something wrong?.
> >
> 
> I don't know whether this will solve your error, but two things of which I
> don't know whether they are known to you:
> 1. Calling "Terminate" will not kill the thread, it just sets the
> "Terminated" property to true, so you must check for yourself inside
> "Execute" whether your Thread should stop
> 2. The event you assigned to "OnTerminate" will only be called if you call
> "DoTerminate" inside the thread (the event will be called using
> Synchronize).
> 
> You might also want to take a look at the property "FreeOnTerminate" which
> tells the thread to free itself once "Execute" returns.
> 
> Regards,
> Sven

Sven, the event OnTerminate is called. What's wrong is the destruction
of the thread. 

FreeOnTerminate is False. I don't want the thread to be destroyed
automatically. 

-- 
Leonardo M. Ramé
http://leonardorame.blogspot.com