SRW: add calculation of "degree of coherence"

[bruhwiler]

This is possible in SRW.
It should be accessible from Sirepo.

[bruhwiler]

Some update of SRW is required first.

[bnash]

What needs to be changed in SRW for this?
It looks like the mutual coherence function is already available in the python interface in srwlib via the function
srwl_wfr_emit_prop_multi_e with options:
2- Mutual Intensity Cut vs X;
3- Mutual Intensity Cut vs Y;
4- Mutual Intensity Cuts and Degree of Coherence vs X & Y;

See also this issue from the SRW repository
ochubar/SRW#12

[bruhwiler]

Maybe the necessary capabilities are present in SRW now.
This would be a good feature to have in Sirepo.

[bnash]

I guess the question is whether its available in the virtual beamline API . It is available from the low level python API.
The parameter wm_ch does seem to allow it:
['wm_ch', 'i', 0, 'type of a characteristic to be extracted after calculation of multi-electron wavefront propagation: #0- intensity (s0); 1- four Stokes components; 2- mutual intensity cut vs x; 3- mutual intensity cut vs y'],