Add minimum rectangle width

[sftse]

If the canvas is not sufficiently proportioned, the svg value written as width can become negative and the rectangles disappear.
This is initially confusing. Adding a catch for such cases ensures that a best effort is made to still render something.
Arguably this check could be done in plotters.

[facorread]

I would suggest closing #6 in favor of #7.

Thanks for contributing.

[shinmili]

No, the issue for #7 is not because of negative width/height, so I think this is another one. Maybe this is a fix for plotters-rs/plotters#300?

[facorread]

🤔 You're right. This means that what's going to happen is a combination of both PRs.

Do you think you would like to contribute an updated version of #7, together with an expanded test?

[shinmili]

I tried the code in plotters-rs/plotters#300 with this patch applied. It generated a histogram of 1-px-wide bins (below), but that's still different from this png provided by the original issue author.

I think this patch is to be considered as a workaround (if this is really for the issue!) and I'm not willing to continue this. Sorry 🙇 The true cause of negative width/height must be searched from the caller side, plotters-rs/plotters.

[AaronErhardt]

I agree, a minimum width shouldn't be implemented by each backend individually but by plotters itself. I appreciate the effort but I'm in favor of closing this PR. (But it seems like I don't have the permission to close it, I don't have write access here).