Hintergrundform abdunkeln, wenn andere Form Modal geöffnet wird?

[Bodenseematze]

Zitat von peterbelow:

Try a handler for the Screen.OnActiveFormchange event, that may work for your purpose.

I tried this - but it has two problems...

Code:

procedure   TMyForm.ScreenActiveFormChange(
                                    sender_              : TObject );
var
   frmActive         : TCustomForm;
   bIsModal          : Boolean;
   ctrlForeground    : TWinControl;
begin
   ctrlForeground          := FindControl(
                                    Windows.GetForegroundWindow() );

   frmActive               := nil;
   bIsModal                := false;
   if ( Assigned(ctrlForeground) and
        (ctrlForeground is TCustomForm) ) then begin
      frmActive            := TCustomForm( ctrlForeground );
      bIsModal             := ( fsModal in frmActive.FormState );
   end;
...

1.) how do I get if the foreground window is modal?
I find the correct foreground Form in the above code snippet but the FormState never contains fsModal - only fsVisible...
2.) the procedure will not be called if a dialog pops up (e.g. a TPrinterSetupDialog)

EDIT: I even tried to use Screen.OnActiveControlChange - with same result (will also not be called if the modal foreground dialog e.g. is a TPrinterSetupDialog).