[vtkusers] vtkScalarBarActor range problem

[John Biddiscombe]

One problem is that it simply doesn't matter what you set your
LookupTableRange to - because Mapper will reset it as soon as it renders
the actor.

LookupTable->SetRange(0,100);

will be overridden if

Mapper->GetScalarRange(...)
returns 0,1 (or similar)

I find this a tadge annoying and it is necessary to set the mapper range to
whatever is desired too.

Unfortunately I frequently want to render some data with a subset of the
whole colours available and have the scalar bar display a fixed set of colours

I propose that a boolean flag is added to vtkMapper
Mapper->UseLookupTableScalarRange

and when enabled, the mapper will fetch the correct range from the
lookuptable - or rather - not reset the lookuptable with its own range.

John B