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| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version

## radial-line-box-intersection

Arguments: point box &optional pos-to-return &key margin

Returns 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 argument is a position object for the arbitrary point, and the second argument is a box object. Returns a position object or `nil`.

If pos-to-return is `nil` or unspecified, then a new position object is created and returned. Otherwise pos-to-return should be a position object, which will be modified and returned.

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.) If you specify a value for margin, you must also specify a value for the pos-to-return optional argument. Specify `nil` if you do not want to specify a position.

As usual, position and box objects should contain integers. See make-position and make-box. See also radial-line-box-intersection-x-y and radial-line-circle-intersection.

Copyright (c) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.

|  | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version