public void CircleEquality(string center, double radius)
{
var cp = Point2D.Parse(center);
Circle2D c = new Circle2D(cp, radius);
Circle2D c2 = new Circle2D(cp, radius);
Assert.True(c == c2);
Assert.True(c.Equals(c2));
}
/// <summary>
/// Provides information about the intersection of two circles.
/// </summary>
/// <param name="circle1">circle 1</param>
/// <param name="circle2">circle 2</param>
/// <returns>
/// <see cref="Kanji.DesktopApp.Interfaces.AreaCode.Unknown"/> if status is unknown.
/// <see cref="Kanji.DesktopApp.Interfaces.AreaCode.Disjoint"/> if the circles don't touch anywhere.
/// <see cref="Kanji.DesktopApp.Interfaces.AreaCode.Overlap"/> if there is an overlapping area.
/// Additionally to Overlap: <see cref="Kanji.DesktopApp.Interfaces.AreaCode.AEnclosesB"/> if circle2 lies completely inside circle1 and doesn't intersect.
/// Additionally to Overlap: <see cref="Kanji.DesktopApp.Interfaces.AreaCode.BEnclosesA"/> if circle1 lies completely inside circle2 and doesn't intersect.
/// Additionally to Overlap and AEnclosesB/BEnclosesA: <see cref="Kanji.DesktopApp.Interfaces.AreaCode.Identical"/> if the centre points are equal and the radius is equal.
/// <see cref="Kanji.DesktopApp.Interfaces.AreaCode.Tangents"/> if the outer edge of circle1 touches the outer edge of circle2.
/// </returns>
public static AreaCode Intersect(Circle2D circle1, Circle2D circle2)
{
AreaCode retval = AreaCode.Unknown;
// the circles are identical
if (circle1.Equals(circle2))
{
retval =
AreaCode.AEnclosesB |
AreaCode.BEnclosesA |
AreaCode.Identical |
AreaCode.Intersect;
}
// the circles are not identical
else
{
double distance = circle1.Centre.Distance(circle2.Centre);
// the distance between the centres equals the sum of the radii
// so the circles are tangents of each other
if (distance == circle1.Radius + circle2.Radius)
retval = AreaCode.Tangents;
// the distance between the centres is greater than the sum of the radii
// therefore the circles must be disjoint
else if (distance > circle1.Radius + circle2.Radius)
retval = AreaCode.Disjoint;
// the distance between the centres is lower than the sum of the radii
// therefore they must overlap in some way
else if (distance < circle1.Radius + circle2.Radius)
{
retval = AreaCode.Overlap;
// the sum of the distance and radius B is lower than radius A
// therefore: A encloses B
if (distance + circle2.Radius < circle1.Radius)
retval = retval | AreaCode.AEnclosesB;
// the sum of the distance and radius A is lower than radius B
// therefore: B encloses A
else if (distance + circle1.Radius < circle2.Radius)
retval = retval | AreaCode.BEnclosesA;
// no other possibility holds, the circles intersect
else
retval = retval | AreaCode.Intersect;
}
}
return retval;
}