The Step Scan GUI needs to run algorithms asynchronously

[Russell Taylor]

This needs, already mentioned in a TODO, has become more urgent with the changes in #7785 as the whole of MantidPlot will now lock up if you try to start collecting data when outside a run. This locking up would last until a run starts - the logging will not get out and there will be no opportunity to cancel.

[Russell Taylor]

Re #7843. Allow AlgorithmRunner to have a parent set.

This follows Qt conventions.

Changeset: 5b5fba5819ad613dbf728296968272d81bdf8cb9

[Russell Taylor]

Re #7843. Existing uses of AlgorithmRunner were leaked.

Changeset: 4753f18b8702c0c58fceb2506dfe738c5c8db314

[Russell Taylor]

Re #7843. Make variable names more general.

Changeset: 3ea271163c6e9e4134c3489b7cedda870a8387c8

[Russell Taylor]

Re #7843. Fix a memory leak.

Changeset: 2322a88bc2e714d7a874f86333a0eeeb3c847b53

[Russell Taylor]

Re #7843. Disconnect observers if cancelling or deleting.

Because very bad things happen if the handlers are called after the object they live in has been deleted!

Changeset: 9f99d4e7781d83f961d70a38b412f89c5a72b3cf

[Russell Taylor]

Re #7843. Run file and live data loading algorithms asynchronously.

Using the AlgorithmRunner class.

Changeset: 6a7f0b1a0b4cafdb591d2d71d72dd63c6a7116ca

[Russell Taylor]

Re #7843. Cancel any already-running alg if a new one is started.

This avoid the temporal coupling where a user needs to know that they ought to call cancel before starting off an algorithm.

Changeset: 29c566ae3ec0c27d076a7bb255a734cf5bb64fee

[Russell Taylor]

Re #7843. Run StartLiveData asynchronously when start is pressed.

The StepScan algorithm itself is fast so there's no real need to make that asynchronous. The other changes are mainly to trap or avoid possible error conditions.

Changeset: fb4a47b239096be31e49a626bdbe56129dad27de

[Russell Taylor]

Tester: Branch is feature/7843_stepscan_async_alg_running

This really needs to be tested at the SNS. Make SEQUOIA your default instrument - this should mean that the live button will be enabled so that you can test the live stuff.

To test, start the 'Step Scan Analysis' GUI from the Interfaces menu and try to break things while algorithms are running in the background! A good file to test with (you can also test with invalid files) is HYSA_2934.nxs.h5 in the System Test repository. Files are loaded as soon as they are entered. Try closing the interface or clicking other things while things are loading. Note that if SEQUOIA is not in a run, the live option will fail immediately - you'll probably need to try again later. The live aspects also happen asynchronously when 'Start' is pressed - try clicking other things/closing the GUI while that is going on.

My aim here is for a smooth experience, that the user cannot crash or generate an unexpected exception from - no matter what they press and in what order!

As I also made changes to the AlgorithmRunner class, it is important to test the other place that uses it. This is the SliceViewer, when BinMD is run. This happens when 'Dynamic Rebin Mode' is selected in the View menu, or when Live Mode is enabled and dragged-out line is integrated.

[Michael Reuter]

Merge remote-tracking branch 'origin/feature/7843_stepscan_async_alg_running'

[Stuart Campbell]

This ticket has been transferred to github issue ​8688