-------------------------------------------
variable: $arrowscale -- gradient arrow scaling
default: 0 (FALSE)
-------------------------------------------
Return -- set $arrowscale
Shift-Return -- set both $arrowscale and $arrowline
-------------------------------------------

This unlabeled entry (at the bottom of the
phasecontour box, "phc") scales the length of
gradient arrows displayed when the "F"
(fieldsign) or "GR" (calculate gradients) buttons
on the "fs:" line are used.  See "F" and "GR"
help for details.  This entry also scales the
length of vertex normal vectors when they are displayed.

The unmarked checkbox immediately to the left of
the entry toggles the normalization gradient
vectors.  If ticked, the units of the value typed
into the entry will be mm.  If not ticked, the
value is multiplied by gradient length to scale
it.  That checkbox can also be used to toggle the
display of vertex normal vectors.

If gradients have been calculated using
phase-encoded data, the gradient arrows (fastest
changing direction of scalar data) will be
appoximately perpendicular to the phase contours
(direction of no change in scalar data).  This is
why these controls have been placed near the
phase contour controls.

Shift-Return -- also set $arrowline

A Shift-Return instead of a default Return in
this entry also sets $arrowline to the current
entry value.  The default is 1.0
