How to resize a TPanel at runtime

Problem/Question/Abstract:

How to resize a TPanel at runtime

Answer:

You should add a SIZEBOX constant to the your panel window style:

TMyNewPanel = class(TPanel)
  { ... }
  procedure CreateParams(var Params: TCreateParams); override;
  { ... }

  procedure TMyNewPanel.CreateParams(var Params: TCreateParams);
  begin
    inherited CreateParams(Params);
    Params.Style := Params.Style or WS_SIZEBOX;
  end;