#### 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 full directory path is stored in $subjtmpdir
(and can be reset to any writable directory in a
tcl script).

GOTO then finds and marks (with a cyan cursor)
the vertex with the nearest (Euclidean distance)
"original surface" coordinates to the edit.dat
point on the current surface (N.B.: the currently
displayed surface might be a different surface
than orig such as inflated, etc, but "original
surface" coordinates are always used).

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

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

If the edit.dat surface coordinate point was
written by tksurfer "SEND", then it is guaranteed
to correspond exactly 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 correspond exactly to an
$origcoords surface vertex, or may not even be on
the surface.  In that case, the nearest
$origcoords surface vertex is found and marked.

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.

