Polygons

A polygon is drawn as a set of ordered vertices relative to the shape's x,y coordinate.

The following contains an example that will add a star polygon to a canvas. The blue lines represent the x and y axes, and show through since an alpha value of 0.9 is used.

Star shaped polygon drawn by example code below

void add_polygon_star( Papyrus::Canvas::pointer canvas ) {
  // Create a filled polygon that will form a star
  Papyrus::Polygon::pointer polygon = Papyrus::Polygon::create();

  // Add the polygon to the canvas
  canvas->add( polygon );

  // Set the fill color to red, with an alpha value of 0.9
  polygon->set_fill( Papyrus::RGBA(0.0, 0.0, 1.0, 0.9) );

  // To color the lines of a polygon shape, set the stroke paint
  polygon->set_stroke( Papyrus::RGBA(1.0, 0.0, 0.0, 0.9) );
  
  // Set a line width
  polygon->stroke()->set_width(10);

  // Add the 10 points of the star
  for (double angle=-M_PI_2; angle < 1.5*M_PI; angle += M_PI/2.5) {
    polygon->add_vertex( cos(angle)*80, sin(angle)*80);
    polygon->add_vertex( cos(angle+M_PI/5.0)*40, sin(angle+M_PI/5.0)*40);
  }

Note that the major difference between a polygon and a polyline is that a polygon will close the surface on the stroke, while a polyline will not. Below is the image generated from a polyline with vertices in the shape of a U, and following is a polygon with the same vertices.

Filled Polyline with U vertices

Polygon with U vertices

void add_polygon_u( Papyrus::Canvas::pointer canvas ) {
  // Create a filled polygon that will form a U
  Papyrus::Polygon::pointer polygon = Papyrus::Polygon::create();

  // Add the polygon to the canvas
  canvas->add( polygon );

  // Set the fill color to red, with an alpha value of 0.9
  polygon->set_fill( Papyrus::RGBA(0.0, 1.0, 1.0, 0.9) );

  // To color the lines of a polygon shape, set the stroke paint
  polygon->set_stroke( Papyrus::RGBA(0.0, 0.0, 0.0, 0.9) );
  
  // Set a line width
  polygon->stroke()->set_width(10);

  // Add the four points of the U (upper left, lower left, lower right, upper right)
  polygon->add_vertex( -50, -50 );
  polygon->add_vertex( -50,  50 );
  polygon->add_vertex(  50,  50 );
  polygon->add_vertex(  50, -50 );
}