These generic functions are used to determine a location on the boundary of a grid grob.

1 2 |

`x` |
A grid grob. |

`theta` |
A numeric angle, in degrees, measured
anti-clockwise from the 3 o'clock |

The location on the grob boundary is determined by taking
a line from the centre of the grob at the angle `theta`

and intersecting it with the convex hull of the grob
(for the basic
grob primitives, the centre is
determined as half way between the minimum and maximum values
in x and y directions).

These functions are called in the calculation of
`"grobx"`

and `"groby"`

units as produced by
the `grobX`

and `grobY`

functions.
Methods should be written for classes derived from grob or gTree
where the boundary of the grob can be determined.

A unit object.

Paul Murrell

`grobX`

,
`grobY`

.

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