We need a simple way of zeroing online spectra, using the roody viewer to
select which spectra are to be zeroed.

   We would also like the histogram view to be unaffected by refreshing. 
Currently the y axis is autoscaled after a refresh.

  We would also like a quicker way of manipulating the histogram display, than
by the awkward, particularly for canvases containing multiple histograms, axis
manipulation currently available.  This could be a toolbar similar to the view
editor that already exists - are the contents of this customisable, or would a
separate toolbar be needed?, and would ideally contain the following ...
   4 buttons, which could each be labelled with a single arrow, for shifting the
histogram left/right/up/down (e.g. by half the corresponding axis's range).  4
buttons, which could each be labelled with double arrows, for scaling the x/y
axes (scaling by factors of 2 and 0.5, about the axis's initial position).  3
buttons for toggling linear/log scale on each axis (these are in the current
view editor).  3 more buttons, for resetting the view to default, for retaining
the current view and for reverting to a previously retained view.
  We would also like to be able to attach markers to a histogram (requiring
another button to remove markers).  markers would be placed using mouse clicks
on the histogram, *and* by a text entry box for typing channel numbers.  Markers
would be labelled with x,y.  There would then be a button to expand an axis
between the last 2 placed markers.  The markers would also be used for analysis
such as integral and peakfind/fitting.
  The view manipulation toolbar would be one per canvas, so there would also
need to be a toggle button to apply the view manipulation commands to all the
histograms on that canvas, or to just the currently selected histogram[s] (a way
to select several, rather than just one, histograms would be useful)

   This would be very much quicker and easier to use than selecting items from
long menus, which themselves need to be called by selecting specific, often very
small, regions of a canvas.

Chris