Data file UX improvements

[alexdewar]

Description

@jonemurray has pointed out that it isn't currently obvious whether or not recording is taking place, so it is easy to forget to start recording before e.g. running a measure script.

I've tried to remedy this in two ways:

1. Make it more obvious when recording is happening by flashing a red LED and displaying some red text in a QLabel
2. Prompt the user to start data recording if they try to run a measure script when recording is not happening

Widget when recording is stopped:

Widget when recording is running (with flashing LED):

Suggestions on how to improve the appearance of the widget are welcome! (In particular, it looks a little odd the way the controls move around when the user starts/stops recording.) That said, I think it's perfectly usable as is :smile:

Fixes #526.

I've broken tests (hence why this is a draft PR), but I'll fix them up if everyone is happy with this solution.

Type of change

• [x] New feature (non-breaking change which adds functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Documentation (non-breaking change that adds or improves the documentation)
• [ ] Optimisation (non-breaking, back-end change that speeds up the code)

Key checklist

• [x] Pre-commit hooks run successfully (pre-commit run -a)
• [ ] All tests pass (pytest)
• [ ] The documentation builds without warnings (mkdocs build -s)
• [x] Check the GUI still works (if relevant)
• [ ] Check the code works with actual hardware (if relevant)
• [ ] Check the pyinstaller-built executable works (if relevant)

Further checks

• [x] Code is commented, particularly in hard-to-understand areas
• [ ] Tests have been added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[jonemurray]

Hi Alex, this is a good solution thank you.

[alexdewar]

A red light is often used to mean "recording in progress" though, e.g. on camcorders, so that was my logic. It's also more eye-catching than green IMO. That's the same reason I made the light blink, to draw the user's attention to it. I take your point that it might make more sense to sync the blinking with when data is actually recorded, though.

[dc2917]

Ah yes, fair point!

[alexdewar]

I've finished adding all the tests now, so we have 100% coverage for the changed files.

I also followed Dan's suggestion of flashing the LED when the data is actually being written.