Platzieren der Komponente verweigern.

[Mystic]

Zitat von nailor:

Aber ich glaube, du kannst zur Laufzeit noch weitere Instanzen auf dein Form klatschen.

Warum?

Owner war leider ReadOnly, deswegen sieht es jetzt so aus:

Delphi-Quellcode:

constructor TLayeredForm.Create(AOwner: TComponent);
  var i: Word;
begin
  inherited;
  if csDesigning in ComponentState then begin
    if not Owner.InheritsFrom(TForm) then begin
      raise Exception.Create('The LayeredForm component must be put on a form!');
      self.Destroy;
      exit;
    end;
    for i := 0 to Owner.ComponentCount -1 do
      if (Owner.Components[i].InheritsFrom(TLayeredForm)) and (Owner.Components[i] <> self) then begin
        raise Exception.Create('There can be only one LayeredForm component on every form!');
        self.Destroy;
        exit;
      end;
    (Owner as TForm).BorderStyle := bsNone;
  end else begin
    bf^.BlendOp := AC_SRC_OVER;
    bf^.BlendFlags := 0;
    bf^.SourceConstantAlpha := 0;
    bf^.AlphaFormat := AC_SRC_ALPHA;
    setWindowLong((Owner as TForm).Handle, GWL_EXSTYLE, getWindowLong((Owner as TForm).Handle, GWL_EXSTYLE) or WS_EX_LAYERED);
  end;
end;