ApplicationHandleException variable in Delphi 5?

Question

I am trying to use AsyncCalls which suppose to work for Delphi 5 also.

Everything compiles and runs fine, if I comment the lines that call/use ApplicationHandleException classes variable which Delphi 5 does not have (I'm not sure when it was introduced either).

procedure TThreadPool.MainThreadWndProc(var Msg: TMessage);
begin
  try
    ...
  except
    if Assigned(ApplicationHandleException) then
      ApplicationHandleException(Self); 
  end;
end;

I'm almost sure that in Delphi 5 the above should be:

  try
    ...
  except
      Application.HandleException(Self); 
  end;

But not sure what to do about this code:

destructor TInternalAsyncCall.Destroy;
begin
  ...
  // TAsyncCall.Destroy either already called Sync() or we are a "forgotten" async call
  // and we need to handle the exception ourself by trying to throw it in the main thread
  // or just ignoring it.
  if FFatalException <> nil then
  begin
    if Assigned(ApplicationHandleException) and // <---
       (ThreadPool.FMainThreadVclHandle <> 0) and IsWindow(ThreadPool.FMainThreadVclHandle) then
      PostMessage(ThreadPool.FMainThreadVclHandle, WM_RAISEEXCEPTION, WPARAM(FFatalErrorAddr), LPARAM(FFatalException))
    else
      FFatalException.Free;
  end;
  inherited Destroy;
end;

What could be the correct "translation" in Delphi 5? Should I simply ignore this variable since it does not exists? please advice.

"I'm not sure when it was introduced" - the ApplicationHandleException callback was introduced in Delphi 6, as part of the re-organization of the VCL to support CLX in Kylix. — Remy Lebeau
– Remy Lebeau, Commented Apr 3, 2017 at 15:47

David Heffernan · Accepted Answer · 2017-04-03 14:08:11Z

2

In TApplication.Create there is this code which assigns to the ApplicationHandleException variable.

if not Assigned(System.Classes.ApplicationHandleException) then
  System.Classes.ApplicationHandleException := HandleException;

Now HandleException is really Self.HandleException, when you allow for the implicit Self target.

So yes, you can replace:

if Assigned(ApplicationHandleException) then
  ApplicationHandleException(Self);

with

if Assigned(Application) then
  Application.HandleException(Self);

In general then, for Delphi 5, you would replace

Assigned(ApplicationHandleException)

with

Assigned(Application)

Almost always it will be the case that Assigned(Application) evaluates to True, but you might be working in a non VCL setting, or perhaps the code executes before the global Application object is created, or after it is destroyed.

answered Apr 3, 2017 at 14:08

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

zig Over a year ago

Thank you so much. your knowledge is outstanding!

zig Over a year ago

BTW, do you know where else the ApplicationHandleException could be assigned by the framework? I mean, is it assigned differently for a service application for example? (just guessing...)

David Heffernan Over a year ago

FMX application, TIdHTTPWebBrokerBridgeRequestHandler.Create, TSockWebRequestHandler.Create, TApacheApplication.Create, TCGIFactory.Create, TWebApplication.Create, TISAPIApplication.Create, TAppletApplication.Run. But not service applications it seems.

zig Over a year ago

So it seems that Application in some cases will not work as designed. never mind I'll think about it when I get there :-P

David Heffernan Over a year ago

You probably need to look at how exceptions are handled in those other application types in D5. Quite a few won't exist I suspect.

Collectives™ on Stack Overflow

ApplicationHandleException variable in Delphi 5?

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related