-------------------------------------------
var,funct (left-click): read patch to cut surface
  set patch <infile>
  read_binary_patch_to_cut
-------------------------------------------

The "C" button on the "patch:" entry line reads a
binary patch from file whose name is current
value of $patch (entry at left) in order to cut
away that part of the current surface (this has a
complementary effect to adjoining "M" button on
the "patch:" line).

This function can be used to create multiple,
non-overlapping/abutting patches.  For example,
if patches for the left and right posterior
cerebellar lobes have been created, those patches
can then be cut off from the full surface to
obtain the non-overlapping anterior cerebellum
remainder.

N.B.: The 3D coords in the patch are ignored so
any folded or flattened patch from the same
original surface can be used to cut away parts of
the current surface.

  1) read surface to be cut
  2) select patch to use as cut by holding down Shift
  3) click "M" button to mask current surface with patch

N.B.: holding down shift during selection blocks
the normal behavior of immediately autoloading
the patch after it is selected.

An alternate way to perform the same operation is
to make labels from the patches, then use them to
cut holes in the surface (middle-click on the
"label:" line "C" button).  The method here
avoids creating extra label files that might get
stale if patches are re-made/modified.

