### Filling Loops and Polygons

Loops and polygons have a Boolean EOFill flag to determine the fill algorithm. A fill algorithm is necessary for loops and polygons because when a polygon or a loop is added to an area, the fill algorithm indicated by the fill flag affects the shape of the area. If portions of the interior of the geometry are not filled, those portions are cut out when the geometry is added to the area. Since only a geometry is passed into an area, the fill flag property belongs to the geometry.

The 2D Graphics framework fills loops and polygons with two different functions controlled by the EOFill flag. If the EOFill flag is true, then the polygon is filled with an Even-Odd rule; otherwise a non-zero rule is used.

The figures show the different fill results:

On Windows GDI device, the EOFill is mapped to ALTERNATE fill mode and the non-zero is mapped to WINDING fill mode.