#### GOTO surface point ####
-------------------------------------------
funct (left-click): goto saved vertex location
  select_orig_vertex_coordinates
  (keyboard equivalent: <Cmd/Alt-g>)
-------------------------------------------
funct (middle-click): goto same point other hemi
  select_opphemi_vertex_coordinates
-------------------------------------------


Detailed Description of "GOTO" Button Actions

-------------------------------------------
funct (left-click): goto saved vertex location
  select_orig_vertex_coordinates 
  (keyboard equivalent: <Cmd/Alt-g>)
-------------------------------------------

A default left-click on the upper right "GOTO"
button reads a point in the individual subject
surface coordinate system from the file:

  edit.dat

in the standard per-subject tmp dir:

  $SUBJECTS_DIR/<subject>/tmp

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

GOTO then finds and marks the vertex with the
same "original surface" coordinates on the
current surface (which may be a different surface
such as inflated, etc).

The "original surface" coordinates are defined by
the $origcoords file, which by default is set to:

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

If the edit.dat surface coordinate location was
written by tksurfer "SEND", then it is guaranteed
to correspond to a vertex on the $origcoords
surface.

However, if the edit.dat surface coordinate
location was written by tkregister or tkmedit
"SEND PNT", it may not lie on the $origcoords
surface.

In that case, the $origcoords vertex nearest in
Euclidean distance to the edit.dat point will be
found and marked with a cyan cursor.

N.B.: if the saved point in edit.dat came from
clicking on a point in the opposite hemisphere in
tkmedit or tkregister, the find-nearest-point
algorithm may produce unanticipated results.  For
example, selecting a point in tkmedit in the
*right* hemisphere, and then using "GOTO" in a
tksurfer that is displaying the *left* hemisphere
of the same subject will usually find a surface
point on the left hemisphere midline.

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

-------------------------------------------
Alt2 funct (middle-click): goto same point other hemi
  select_opphemi_vertex_coordinates
-------------------------------------------

If the "GOTO" button is middle-clicked, it will
instead go to the equivalent point in the
*opposite* hemisphere from the one in which the
point was originally selected/saved using "SEND".

This function is designed to be used on the
fsaverage surface, which provides a standardized
coordinate system with the x-axis perpendicular
to the plane of the midline.

It works by taking the negative of the
x-coordinate of the target point in edit.dat
before finding that surface point on the current
surface.

The easiest way to use this is to open the left
and right hemispheres of fsaverage in two
separate csurf's.

N.B.: using any other single-subject surface
instead of "fsaverage" or appended an version of
fsaverage like "fsaverage-ver17", generates a
warning popup, but then goes to the
(approximately) opposite point.

