code: public void strokeLine(double x1, double y1, double x2, double y2) {
  		this.gc.strokeLine(
  				doc2fxX(x1), doc2fxY(y1),
  				doc2fxX(x2), doc2fxY(y2));
  	}
docs: Strokes a line using the current stroke paint.
  
  <p>This method will be affected by any of the
  global common or stroke attributes as specified in the
  Rendering Attributes Table of {@link GraphicsContext}.
  
  @param x1 the X coordinate of the starting point of the line.
  @param y1 the Y coordinate of the starting point of the line.
  @param x2 the X coordinate of the ending point of the line.
  @param y2 the Y coordinate of the ending point of the line.