Reference TSurfaceForm

  TSurfaceForm = class(TForm)
  protected
    { Allow controls direct access to draw state }
    FDrawState: TDrawState;
    { Override ThemeAware and return true to subscribe to global theme changes }
    function ThemeAware: Boolean; virtual;
    { Invoked when the theme is changed }
    procedure ThemeChanged; virtual;
    { Allow the form to be drawn at design time }
    procedure PaintWindow(DC: HDC); override;
    { Paint is now final, so use Draw to access Surface }
    procedure Paint; override; final;
    { While Draw is executing Surface refers to a valid ISurface }
    procedure Draw; virtual;
    { Surface is only valid while Draw is executing }
    property Surface: ISurface read GetSurface;
    { Visual representation of the control. Is it pressed, hot, checked, etc }
    property DrawState: TDrawState read FDrawState write SetDrawState;
  public
    { Create a new form without loading a form resource }
    constructor CreateNew(AOwner: TComponent; Num: Integer = 0); override;
    destructor Destroy; override;
  published
    { Draw event handler }
    property OnRender: TDrawEvent read FOnRender write FOnRender;
    { Theme name determines the styling for a control }
    property ThemeName: string read FThemeName write SetThemeName;
  end;