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funct: find_orig_vertex_coordinates -- save vertex location
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keyboard equivalent: <Cmd/Alt-f>

The "SEND" button (upper right) writes the
freesurfer orig surface coordinates of the last
selected vertex location (last left-click) to the
file:

  edit.dat

in the standard per-subject tmp dir:

  $SUBJECTS_DIR/<subject>/tmp

This directory path is stored in the tcl 
variable, $subjtmpdir, and can be reset to any
(writable) directory in a tcl script.

The surface coordinates are found by looking them
up for the same-numbered vertex in the
$origcoords surface file, which by default is set
to:

  $SUBJECTS_DIR/<subject>/surf/$hemi.orig

If $normdsampsearchflag is ticked, the midpoint
of the current search range along the vertex
normal is first added to the coordinates from the
clicked vertex on the orig surface before writing
the edit.dat file.

Note that this uses the *currently* specified
search policy, which may differ from the policy
in effect when the currently displayed surface
vertex overlay data file was generated.  To see
or change the current policy, use popup from a
left click on the bold "label:" text at the upper
left.

The orig coords in the edit.dat file can be read
by tkregister and tkmedit to find and mark the
position of this surface vertex in a 3D data set
-- after adding the midpoint of the search range
along the surface normal.  It can also be read
back into tksurfer to (re)locate/select the same
vertex.

If a Talairach matrix has been loaded, the MNI
305 Talairach x,y,z's is be written as the second
line of the edit.dat file (or MNI 152 coordinates
if the upper left "ta" button is selected and 152
chosen from the popup).  The edit/dat Talairach
coordinates are currently ignored by tkmedit,
tkregister, and tksurfer.

N.B.: the Save/Goto Views buttons in the
TRANSLATE panel (tcl functions: write_view_matrix
and read_view_matrix) also use $subjtmpdir.
