# Create a Unit Describing a Grob Boundary Location

### Description

These functions create a unit object describing a location somewhere on the boundary of a grob. They are generic.

### Usage

1 2 |

### Arguments

`x` |
A grob, or gList, or gTree, or gPath. |

`theta` |
An angle indicating where the location is
on the grob boundary. Can be one of |

### Details

The angle is anti-clockwise with zero corresponding to a line with an origin centred between the extreme points of the shape, and pointing at 3 o'clock.

If the grob describes a single shape, the boundary value should correspond to the exact edge of the shape.

If the grob describes multiple shapes, the boundary value will either correspond to the edge of a bounding box around all of the shapes described by the grob (for multiple rectangles, circles, xsplines, or text), or to a convex hull around all vertices of all shapes described by the grob (for multiple polygons, points, lines, polylines, and segments).

Points grobs are currently a special case because the convex hull
is based on the data symbol *locations* and does not take
into account the extent of the data symbols themselves.

The extents of any arrow heads are currently *not* taken into account.

### Value

A unit object.

### Author(s)

Paul Murrell

### See Also

`unit`

and
`grobWidth`

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