Switch to PyQt v2 API for QString and QVariant

[Russell Taylor]

This is required in order for us to be able to bring in IPython as the interpreter window. In this API, QString & QVariant are mapped to equivalent Python types instead of being wrapped objects as they are with the v1 API. There are other types that have a v2 API (see ​here), but these are the only ones we must move so that's as far as I will go.

Effecting the switch itself is easy, it's hunting down the places that break when we do it that's the hard part. It's no longer possible to instantiate these types on the Python side (easier to find), or to use methods of those types on returned objects (harder to find).

[Russell Taylor]

Re #7950. Fix usage of QString method.

Changeset: c0121b27257d52f9a73b32e945cdf6c5e0ebc6af

[Russell Taylor]

Hmmm... none of yesterday's commits showed up here.

[Russell Taylor]

Tester: The branch is feature/7950_pyqt_v2_api_for_qstring_qvariant. It has 10 commits, all but one of which didn't make it to here.

The main place this impacts is the PyQt reduction interfaces (ORNL SANS, DGS Reduction, REFM/L & SNS Powder Diffration). The creators of all these interfaces were asked to check them at the start of this week so have had ample time to do so. As this should have been checked (and I attempted to do so as well) I suggest just a little exploratory testing. Any problems will manifest themselves as Python errors that will abort the script.

The change could also theoretically affect the mantidplot(.)py code, though I couldn't find anywhere that it did. It's also possible, though unlikely I would think, that it could affect user scripts that deal with graphical outputs.

[Alex Buts]

Can not test it properly untill #8038 is fixed

[Russell Taylor]

It transpires that things are broken on RHEL6. There's apparently some difference there compared to the Mac (where the work was done). I thought python was supposed to be completely portable....

[Russell Taylor]

Re #7950. Make sure variable is converted to the right type.

It seems that the settings are stored differently on different platforms and on linux this was reading in as a string instead of a boolean.

Changeset: 3bc3d43aabcb36ea85ec4dd9bab3f643a5bdc220

[Russell Taylor]

Re #7950. Make sure empty list is loaded back correctly.

An empty list of recent files is saved to the QSettings as "@Invalid". Reading this back in sets the variable to 'None', which causes problems. Change it back to an empty list.

Changeset: 88889ae7c16ced215a0d570c75573bbf08f28193

[Russell Taylor]

Re #7950. Remove barrier to starting reduction gui outside MantidPlot.

There are other places with an unguarded import of MantidPlot, but this one is trivial to fix.

Changeset: 3bb0f093bc5e974572578fd8576f6915c7da7dee

[Russell Taylor]

Re #7950. Set PyQt API version for stand-alone running.

If running in Mantid, this setting is done within the C++ code. I'm adding it here to make sure things work if running outside of MantidPlot (which doesn't work at the moment, but could cause confusion later if that's fixed). Note that this has to be done before the first import of PyQt.

Changeset: 6bf36880a7baab19219c488bacf92c1e016d7780

[Russell Taylor]

Re #7950. More changes for PyQt API change.

This is exactly the same change in several places. Previously the toPyObject() turned the returned QVariant into the desired type. Now the actual type is returned in the first place.

Changeset: 0d502b776166d0ad9930813c70b41817bbefe635

[Russell Taylor]

Tester: See comment:3. This is probably best tested by someone familiar with at least one of the python-based reduction interfaces, but the more important thing is that it gets tested soon!

Several more changes were required because it turned out that the the settings (QSettings) behaved differently on the Mac (where I did the initial work) to elsewhere. I'd also missed some things in the reflectometery GUI code. I've now checked again that simple reductions work for each interface on my branch and with mantidplotunstable. Of course there's no way I've executed all code paths. It seems unavoidable that some of the testing will effectively be by users after it's on master, but this needs to be merged to allow IPython to proceed.

[Owen Arnold]

The code changes look fine to me, but I'm not familiar enough with any of the interfaces that have been changed to say with any confidence that they have not been broken.

[Michael Reuter]

Things seem to be working OK, but there's an annoying print statement left in line 274 in the reduction_application.py file. Please remove it.

[Russell Taylor]

Re #7950. Remove debug print statement left in by mistake.

Changeset: 3da90953facab114d5edcad1a5b03e9e1b84c0bb

[Michael Reuter]

Looks like the automatic closure on commit forgot this one.

[Russell Taylor]

Adding a link to the full changeset for possible future reference: ​https://github.com/mantidproject/mantid/commit/a7e6cdd03f92d7d7e9413228231e0781893f0576

[Stuart Campbell]

This ticket has been transferred to github issue ​8795