Vacuum: Implement TUI for the manual mode

[rnovatorov]

I recently discovered this project and would like to thank you - it is awesome :)

I played with it a bit and noticed that the vacuum manual mode is difficult to use interactively via CLI. One has to enter somewhat lengthy (more than a char) commands and arguments, which might feel clumsy if a real-time response from the device is desired.

This PR adds a tiny curses based TUI to allow for a real-time movement control. I have not thoroughly explored the repo, so the proposed solution might not be optimal.

[rytilahti]

Hi and thanks for the PR! The manual mode is indeed quite cumbersome and this looks like a great addition :-)

I added some comments inline, but it would also be great if you could display the key bindings (either on start as a dialog, or print them out to the screen?).

Also, please update the docs/vacuum.rst to make it easier to find that such feature exists.

[rytilahti]

When can this happen?

[rnovatorov]

What we import here as curses is actually an extension module that must be backed by one of few C implementations of a curses library. ImportError occurs when none of the implementations are available on the system.

I do not think there is much we can do about it except for mentioning in docs/vacuum.rst, that curses lib is a requirement for TUI.

[rytilahti]

Ah, I see. I thought it is part of the standard library and always available.

How about letting it bubble up and doing the import inside the tui() command? It could be caught there to display a user-friendly error message.

[rnovatorov]

Personally, I prefer all the imports to be grouped in one place - at the top of a module. They are easier to manage that way.

If all we want is a prettier error message, I would rather delay the exception until VacuumTUI is instantiated:

try:
    import curses
except ImportError:
    curses = None

...

class VacuumTUI:
    def __new__(cls, *args, **kwargs):
        if curses is None:
            raise ImportError("curses library is not available")
        return super().__new__(cls)

What do you think?

[rytilahti]

So what I want is it not to simply crash silently in any case, so your suggested solution works fine, too! Maybe check for the Noneness inside the __init__ though?

[rnovatorov]

Moved the check to __init__ in a new commit.

[rnovatorov]

Added fixes according to inline comments and usage printing before the main loop. Also updated docs to mention the feature.

[rytilahti]

Looks good to go, thanks again @rnovatorov! 🎉