The Brush-Edit Menu Option

This dialog allows you to edit the current brush.  You can 
set the @ref("brush cell attributes",xgre/brushatt.def) for each brush cell and you can 
specify which brush cell is to be the @ref("brush hotspot.",xgre/brushhot.def) 

Setting a Brush-cell's Attributes

When you choose the Brush-Edit menu option you will be presented 
with a dialog that consists of a matrix of brush-cell buttons, 
and below this three panels: a brush-cell information panel, 
a brush-cell operation-list panel and a brush-cell input-list panel.

Before you can do anything you must select one of the brush-cells
by clicking on its button.  When you click on a brush-cell button,
you will see a number of things happen: the brush-cell button will
be highlighted by a thicker border, the brush-cell's position and
value will appear in the information panel, the brush-cell's
operation parameter will appear in the operation-list panel, and
the brush-cell's input parameter will appear in  the input-list
panel.

If you would like to change the brush-cell's value, just type in
a new value in the appropriate text field of the information panel.
If you would like to change the brush-cell's input parameter, just
select an alternate input paramter from the input-list.  

Setting the Brush Hotspot

If you are using a 1x1 brush then the brush will effect only
the one raster map cell to which it is applied.  However, if
you are using a larger brush then you will have to specify a
one brush-cell as the brush "hot-spot."  The brush hot-spot
is the brush-cell that is applied to the raster map cell over
which the brush cursor cross-hair is positioned.  The other
brush-cells will be applied to the raster map cells around the
cross-hairs position according to their position relative to
the brush hot-spot.

If you would like to set the currently selected brush-cell to be 
the brush hot-spot, just click on the information-panel button
labelled "Set Current Brush-Cell as Brush Hot-Spot."

