inside-polygon-p

Arguments: position position-vector-or-list

Returns whether position is inside the polygon that is defined by position-vector-or-list. position should be a position instance (as created with make-position), and position-vector-or-list should be either a vector or a list of positions that define a polygon, just as you would pass to draw-polygon or fill-polygon.

The beginning position should not be repeated at the end of the vector or list to "close" the polygon, and so a vector or list of three positions would specify a triangle. A position that is exactly on a line segment is considered to be "inside" the polygon.

This function is used internally by polygonal hotspots (see hotspot-region), but can be used by itself if desired.

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Created 2010.1.21.