Unit cell tool

[dagewa]

Here are a couple of changes to the unit cell tool of dials.image_viewer.

First, I renamed parameters here to be more consistent with other DIALS programs: spacegroup → space_group and unitcell → unit_cell. I suspect this tool is not used much here (whereas it may get much more use in cctbx.image_viewer). Therefore I don't think this change affects many users' existing work patterns.

The second change introduces a new parameter, show_hkl. This can be used to filter the displayed rings to show only those corresponding to Miller indices in the supplied list. This is helpful because datasheets for diffraction standards usually list only the strongly diffracting rings: https://www.emsdiasum.com/microscopy/technical/datasheet/80044.aspx

With this change only the desired rings are displayed

dials.image_viewer imported.expt \
  calibrate_unit_cell.unit_cell=4.094,4.094,4.094,90,90,90 \
  calibrate_unit_cell.d_min=0.81 \
  show_hkl=1,1,1 show_hkl=2,0,0 show_hkl=2,2,0 \
  show_hkl=3,1,1 show_hkl=2,2,2 show_hkl=4,0,0 \
  show_hkl=3,3,1 show_hkl=4,2,0 show_hkl=4,2,2

which is considerably easier to interpret than viewing all rings up to the specified resolution limit

dials.image_viewer imported.expt \
  calibrate_unit_cell.unit_cell=4.094,4.094,4.094,90,90,90 \
  calibrate_unit_cell.d_min=0.81

[phyy-nx]

Yah we use the unit cell tool a lot at xfels to do silver behenate calibration of distance and beam center. However, a while ago I hardcoded the default unit cell parameters to silver behenate so I wouldn't have to type them on the command line :) So renaming these parameters slightly doesn't actually affect us much!

The show hkl list is nice. Thanks.