constants.py cleanup and improvement

manimlib/media_dir.txt is deprecated and should be removed, and the constants.py file should be brushed up as well.

Most notably the constant MEDIA_DIR currently gets completely ignored due to always being overwritten by this part of the code:

        if config["media_dir"]:
            MEDIA_DIR = config["media_dir"]
        else:
            MEDIA_DIR = os.path.join(
                os.path.expanduser('~'),
                "Dropbox (3Blue1Brown)/3Blue1Brown Team Folder"

This causes manim to always create a media folder in the location of the executed py file containing the rendered scenes. Just removing the else statement is enough.

The original DIR lines might also be changed to immediately imply raw text input for obvious reasons (you know, with \ being used for win folders, but also escape characters).

MEDIA_DIR = ""

↓

MEDIA_DIR = r""

Adding a 4K rendering constant might be prudent, although linking it to an argument would happen in some other file I don’t know out of my head.

I’ve also spotted at least two text issues:

1. Two times ‘both’ in a sentence that triggers when media_dir is redundantly specified in the terminal.
2. -p referring to low quality output, even though it’s only triggering a preview, that is firing the mp4 into its assigned program.

And the file could use some serious commenting to make it easier for others to get into what’s going on. I’m willing to work on that and submit a PR for that.

[XorUnison]

Oh right, we might also want to get the review and merge on #26 done first if we do the whole .cfg business here.

[PgBiel]

Any PR takers?

I’d be willing to help on this one