add fillRectangle helper method

  strokePath(layer, clip, p, style);

}

void fillRectangle(

    Layer* layer,

    const Point& origin,

    double width,

    double height,

    const FillStyle& style) {

  Path p;

  p.moveTo(origin.x, origin.y);

  p.lineTo(origin.x + width, origin.y);

  p.lineTo(origin.x + width, origin.y + height);

  p.lineTo(origin.x, origin.y + height);

  p.lineTo(origin.x, origin.y);

  Rectangle clip(0, 0, layer->width, layer->height);

  fillPath(layer, clip, p, style);

}

} // namespace plotfx

    double height,

    const StrokeStyle& style);

void fillRectangle(

    Layer* layer,

    const Point& origin,

    double width,

    double height,

    const FillStyle& style);

} // namespace plotfx