TScrollingPaintBox = class(TScrollingWinControl)

private
  FCanvas: TCanvas;
public
  constructor Create(aOwner: TComponent); override;
  destructor Destroy; override;
  property Canvas: TCanvas read FCanvas;
end;

constructor TScrollingPaintBox.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FCanvas := TControlCanvas.Create;
  TControlCanvas(FCanvas).Control := Self;
end;

destructor TScrollingPaintBox.Destroy;
begin
  FCanvas.Free;
  inherited Destroy;
end;