-------------------------------------------
entry variable: $oneidnum ("an:") -- show only 1 annot
default: -1 (show all annot idnums/regions)
-------------------------------------------
entry variable: $curv -- curv filename (surface)
default: ~/surf/$hemi.curv
-------------------------------------------
entry variable: $fs -- fieldsign filename (surface)
default: */fs/$hemi.fs
-------------------------------------------
entry variable: $anlabel -- annotation filename (surf)
default: ~/label/$hemi.HCP-MMP1.annot
-------------------------------------------

N.B.: only visible in tkmedit [fn-]F4 panel.

The lower right "curv:", "fs:", and "annot:"
entries and corresponding "R" (read) buttons
display data as colors along the surface ribbon.

All three require first loading a surface using
the tkmedit "surf:" dropdown.

Loading one kind of data toggles off the other
two.

Since the curvature ($hemi.{curv,sulc}) and the
MGH annotation files ($hemi.*.annot) are stored
in the subject's directory (in $SUBJECTS_DIR),
these will always be accessible when opening a
subject from either the VOLUME button or the
VOLUME-STATS button.  The "annot:" dropdown will
contain all .annot files in the subject's label
directory.

The fieldsign data, by contrast, is stored in a
scandir within a session directory (in
$FUNCTIONALS_DIR).  To display fieldsign data on
the surface ribbon, first select a fieldsign
scandir in View Functional Data and open it with
VOLUME-STATS.  Then do [fn-]F4, load a surface,
and load surface-color data onto it.

Show only one MGH annotation region/idnum

The entry "an:" (just right of SURFPAINT), allows
displaying only one annotation region (picked by
its idnum) at a time.  To find the idnum of an
annotation region: (1) display all the regions on
the surface in tksurfer and double-middle-click
one region to get a pop-up, or (2) consult the
complete table of idnums (and their names and
colors) printed in the tkmedit log when the
annotation file is first read.

The cursor will move to the average position of
surface vertices in this annotation region.

The default is -1, which means, show all regions.
Region 0 is Unknown.  Requesting an out of range
idnum shows all regions.
