GUI: Specular and DepthProbe scans are broken

Specular and DepthProbe scans stopped working after refactoring scans.

For example, at commit 1004b7f2 specular scan still works, depth probe already doesn't. At 58dab9d1 specular scan doesn't work.

changed milestone to %21 GUI fixes

added GUI bug labels

added release-critical label

assigned to @j.wuttke

Specular simulation still works with Gaussian distributions for lambda and alpha_i, but fails if one distribution is set to None. Which means I failed to adapt GUI to changes in core where there is no more "None" distribution; instead, the case of no distribution is now indicated by a nullptr. Current GUI code is intransparent not least because of the incorrect inheritance of ScanItem from BeamItem, #437 (closed).

hints from Mikhail:

Method SpecularInstrumentItem::createSimulation creates local AlphaScan object, passing wavelength value to it:

AlphaScan scan(beamItem()->wavelength(), *axis_item->createAxis(Units::deg));

Further this scan object is used to create and return new SpecularSimulation object.

To pick up wavelength value from UI the corresponding item is used: BeamWavelengthItem* wavelengthItem() const. For example, BeamWavelengthItem* wavelengthItem() is used in "GUI/View/Instrument/SpecularBeamEditor.cpp" , line 50. It is passed further, to DistributionEditor where it is edited by UI means.But BeamItem::setWavelength() is not used for getting values from the UI, it is done only through BeamWavelengthItem variable BeamItem::m_wavelengthItem.

mentioned in merge request !1322 (merged)

mentioned in commit 5b5e9227

closed with merge request !1322 (merged)