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.Dd December 21, 2022
.Dt M_POLYGON 3
.Os Agar 1.7
.Sh NAME
.Nm M_Polygon
.Nd Agar-Math polygon structure
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
#include <agar/gui.h>
#include <agar/math/m.h>
.Ed
.Sh DESCRIPTION
.\" IMAGE(/widgets/VG_Polygon.png, "A polygon")
The
.Ft M_Polygon
structure describes a simple polygon.
The polygon may be convex or concave.
Self-intersections and holes are not allowed.
.Bd -literal
.\" SYNTAX(c)
typedef struct m_polygon {
	M_Vector2 *v;	/* Vertices */
	Uint n;		/* Vertex count */
} M_Polygon;
.Ed
.Sh INITIALIZATION
.nr nS 1
.Ft void
.Fn M_PolygonInit "M_Polygon *P"
.Pp
.Ft M_Polygon
.Fn M_POLYGON_INITIALIZER "void"
.Pp
.Ft void
.Fn M_PolygonFree "M_Polygon *P"
.Pp
.Ft M_Polygon
.Fn M_PolygonFromPts "Uint n" "const M_Vector2 *v"
.Pp
.Ft M_Polygon
.Fn M_PolygonFromPointSet2 "const M_PointSet2 *ps"
.Pp
.Ft M_Polygon
.Fn M_PolygonFromPointSet2i "const M_PointSet2i *ps"
.Pp
.Ft M_Polygon
.Fn M_PolygonFromLines "Uint n" "const M_Line2 *L"
.Pp
.Ft M_PointSet2
.Fn M_PolygonToPointSet2 "const M_Polygon *P"
.Pp
.Ft M_PointSet2i
.Fn M_PolygonToPointSet2i "const M_Polygon *P" "M_Real w" "M_Real h"
.Pp
.Ft M_Polygon
.Fn M_PolygonRead "AG_DataSource *ds"
.Pp
.Ft void
.Fn M_PolygonWrite "AG_DataSource *ds" "const M_Polygon *P"
.Pp
.nr nS 0
The
.Fn M_PolygonInit
function initializes a
.Ft M_Polygon
structure.
The
.Fn M_POLYGON_INITIALIZER
macro may also be used as a static initializer.
.Pp
The
.Fn M_PolygonFree
function releases the memory allocated for vertices.
.Pp
The
.Fn M_PolygonFromPts
function returns a polygon structure given an array of points.
The
.Fn M_PolygonFromPointSet
variant accepts a
.Xr M_PointSet2 3
argument.
.Fn M_PolygonFromLines
returns a polygon from an array of lines
.Fa L .
.Fa n
is the number of elements in the array.
.Pp
The
.Fn M_PolygonToPointSet2
and
.Fn M_PolygonToPointSet2i
routines convert a
.Nm
to a
.Xr M_PointSet2
or
.Xr M_PointSet2i
structure.
.Pp
The
.Fn M_PolygonRead
and
.Fn M_PolygonWrite
functions read or write a polygon structure from/to an
.Xr AG_DataSource 3 .
.Sh OPERATIONS
.nr nS 1
.Ft int
.Fn M_PolygonAddVertex "M_Polygon *P" "M_Vector2 v"
.Pp
.Ft int
.Fn M_PolygonAddLine "M_Polygon *P" "M_Line2 L"
.Pp
.Ft int
.Fn M_PolygonDelVertex "M_Polygon *P" "int v"
.Pp
.Ft int
.Fn M_PolygonCopy "M_Polygon *Pdst" "const M_Polygon *Psrc"
.Pp
.Ft void
.Fn M_PolygonScale "M_Polygon *P" "M_Real xScale" "M_Real yScale"
.Pp
.Ft void
.Fn M_PolygonOffset "M_Polygon *P" "M_Real xOffs" "M_Real yOffs"
.Pp
.Ft int
.Fn M_PointInPolygon "const M_Polygon *P" "M_Vector2 p"
.Pp
.Ft int
.Fn M_PolygonIsConvex "const M_Polygon *P"
.Pp
.nr nS 0
The
.Fn M_PolygonAddVertex
function adds a new vertex to a polygon.
Returns index of new vertex on success, -1 on failure.
The
.Fn M_PolygonAddLine
variant accepts a
.Xr M_Line 3
argument instead of a vector.
.Pp
.Fn M_PolygonDelVertex
removes the vertex at given index
.Fa v .
.Pp
The
.Fn M_PolygonCopy
function copies the vertices of a source polygon
.Fa Psrc
to a destination polygon
.Fa Pdst .
The destination structure does not need to be initialized.
Any existing vertices in
.Fa Pdst
will be overwritten.
The function returns 0 on success or -1 if insufficient memory is
available.
.Pp
.Fn M_PolygonScale
multiplies all vertices of a polygon with the given scaling factors
.Fa xScale ,
.Fa yScale .
.Fn M_PolygonOffset
translates all vertices against
.Fa xOffs ,
.Fa yOffs .
.Pp
The
.Fn M_PointInPolygon
function returns 1 if the point
.Fa p
lies inside the polygon.
.Pp
.Fn M_PolygonIsConvex
returns 1 if the polygon is convex.
.Sh SEE ALSO
.Xr AG_DataSource 3 ,
.Xr AG_Intro 3 ,
.Xr M_Circle 3 ,
.Xr M_Geometry 3 ,
.Xr M_Plane 3 ,
.Xr M_PointSet 3 ,
.Xr M_Polygon 3 ,
.Xr M_Rectangle 3 ,
.Xr M_Sphere 3 ,
.Xr M_Triangle 3 ,
.Xr M_Vector 3
.Sh HISTORY
The
.Nm
structure first appeared in Agar 1.3.4.