-------------------------------------------
tickbox var: $softtruncphaseflag -- for complex data
-------------------------------------------
default: 0 (FALSE)

The upper middle "sft" tickbox (just to the right
of "truncph", under the "MESH" button) toggles
truncation of a complex-valued data by soft phase
limits.  Ticking the "sft" unticks "truncph" and
vice versa.

This uses same phase limits as $truncphaseflag
(unlabeled entries immediately below tickboxes),
and wraps in the same way, but instead of
truncating to zero (background color) beyond the
phase limits, linearly rolls off to zero over an
additional angular width ($softtruncwidth:
def=0.05) beyond each truncation endpoint.

Ramping to zero reduces the contrast and therfore
the distracting prominence of the (irrelevant)
ragged shape of the color edge at the truncation
endpoint.

-------------------------------------------
entry var: $softtruncwidth -- ramp-to-zero width (0-1)
-------------------------------------------
default: 0.05

The ramp width is controlled by the unlabeled
entry below the truncphase endpoints entries
(immediately right of "invph").  The ramp width
is constrained to be half of the truncated range.

