okay ... shadow_range sets a limit for the range which
dynamic shadows are displayed ..

set this value so that the shadow wil not
be displayed when it is out of range of a dynamic
light , the engine would determine the distance
calculations for you .

use a trace and if you find the shadow in there ,it
would mean to apply brightness to your view entity,
else set it dark .
I do not know if it would work for only decal shadows
or what .

view_to_light is another option to access ,the
variables of the closest to furthest 8 lights .

not a problem I would like to make my own , good luck