radial-line-box-intersection-x-y

Arguments: point-x point-y box-left box-top box-right box-bottom &key margin

Returns as multiple values the coordinates of the point on the edge of a box where it is crossed by a line that passes through the center of the box and through an arbitrary point. Returns nil if the box center and the arbitrary point are the same.

The first two arguments are real numbers for the X and Y coordinates of the arbitrary point. The remaining required arguments are real numbers that specify the sides of a box. Returns two real numbers for the X and Y coordinates of the intersection point, or nil.

The margin argument is somewhat obscure. If specified, it should be a real number indicating a distance. If the real intersection point is less than this distance from a corner of the box, then the returned point will be adjusted so that it is this distance from the corner. (This is used by one application to avoid drawing a connecting line to a rounded corner of a rounded box.)

See also radial-line-box-intersection and radial-line-circle-intersection-x-y.

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Created 2015.5.21.