I thought overriding CreateParams as in Delphi might be enough. Thank you for your answer and clarifying my doubts.
Summarize:
- If you are a component writer, plz feel free to use CreateParams, you need it...But you need a whole lot more... And you allow for testing, etc, overriding paint, add your message handling etc.. Object Pascal, not only Delphi but also Lazarus/fpc can help a little.
- If you just want it ad-hoc in a program, don't...