Update metR for incoming ggplot2 version

[teunbrand]

Hi Elio,

We have been preparing a new release of ggplot2 and during a reverse dependency check, it became apparent that the prospective ggplot2 3.5.0 would break metR.

In a sense, this PR is a follow-up on #177 in that it aims to make metR compatible with both the old an new versions of ggplot2. A few things of note:

• makeContent.labelgrob was removed from ggplot2, so this PR provides a facsimile for rendering metR's labels.
• Scales no longer censor out-of-bounds breaks. This responsibility falls now on guides, which is what the changes to guide_colorstrip() deal with.
• The changes in guide_vector() are in lockstep with changes to guides in ggplot2 since Guide methods #177.
• The scale_name field in scales is deprecated, so geom_arrow() now checks the transformation's name for detecting date scales.

To test the code changes with the release candidate, you can install it with the code below:

remotes::install_github("tidyverse/ggplot2", ref = remotes::github_pull("5592"))

The release of ggplot2 3.5.0 is scheduled for the 12th of February. The progress of the release can be tracked in tidyverse/ggplot2#5588. We hope that this PR might help metR get out a fix if necessary.

[eliocamp]

Thank you! Looks good.

What is the best source to learn about the guide system? I had to fumble around the source code before and now that things are changing, I probably don't understand half of what's going on.

[teunbrand]

Yeah there still isn't good guide to guides. I suppose the Guides section of the ggproto documentation is the closest thing, which you can find here. There is also this WIP blog post that talks about it a little bit.

The currently tricky bit about the guides in metR is that they maintain compatibility with both old and new versions of ggplot2, so it is a bit of a Frankenstein's monster between the S3 and ggproto systems. If you at some point decide to bump the required version of ggplot2 to >= 3.5.0, you wouldn't have to deal with the S3 part anymore.

[eliocamp]

If you at some point decide to bump the required version of ggplot2 to >= 3.5.0, you wouldn't have to deal with the S3 part anymore.

Yes. What I actually need to do is to move all the ggplo2-extension stuff to another package and have that package follow ggplot2, while the other functionality can be agnostic to ggplot2 versions.

[teunbrand]

That makes sense to me. This is just friendly reminder that the release is due soon.

[eliocamp]

New version of metR is now on CRAN 🎉