type
  TCard = class(TGraphicControl)
  private
    // the following message will be performed when the common Text property changes
    procedure CMFontChanged(var AMessage: TMessage); message CM_FONTCHANGED;
    // the following message will be performed when the common Font property changes
    procedure CMTextChanged(var AMessage: TMessage); message CM_TEXTCHANGED;
  protected
    procedure Paint; override;
  published
    // this will add to your control Font and Text properties (like e.g. TEdit has)
    property Font;
    property Text;
  end;

implementation

{ TCard }

procedure TCard.CMFontChanged(var AMessage: TMessage);
begin
  inherited;
  // ask to repaint the control because the Font has changed
  Invalidate;
end;

procedure TCard.CMTextChanged(var AMessage: TMessage);
begin
  inherited;
  // ask to repaint the control because the Text has changed
  Invalidate;
end;

procedure TCard.Paint;
var
  R: TRect;
  S: string;
begin
  // the S variable is needed here just because the Text parameter of the following TextRect method call
  // needs a declared variable, so let's have one and assign our common Text property value to it
  S := Text;
  // build the rectangle into which you want to render the text
  R := Rect(100, 100, 200, 200);
  // assign the font you want to use to the Canvas.Font before the text drawing; let's use the one from
  // our common Font property
  Canvas.Font := Font;
  // and draw the text
  Canvas.TextRect(R, S, [tfWordBreak]);
end;