[FR] Colorbar properties

[rafaqz]

It would be useful to be able to style additional attributes of colorbars, as discussed recently on slack in plotting

- [ ] tick size
- [ ] tick color

• ticks
• tick scale
• tick font
• tick font size
• tick font color
• border color
• border thickness
• bar width
• bar height
• other things?

My use-case is cleaner map-plotting recipes in GeoData.jl. Currently, if you stray too far from the defaults the colorbar starts to look out of place.

This could start with just GR?

related, but just for ticks: #2308

[mkborregaard]

It's tricky because Plots development aims to keep keywords few(-ish), in order to keep maintainability. In general all new keywords should preferably be applied across all backends to keep interchangeability of backends. One possibility could be to adapt extra_kwargs to be able to pass colorbar kwargs, but this wouldn't work in recipes. I guess this requires a bit of discussion.

@rafaqz do you happen to know how many of these attributes are supported natively by e.g. GR?

[hervasa2]

I think the colorbar should have the same attributes as an axis. For example just like you have xticks and xscale, the colorbar should be able to support cticks and cscale. I came across this limitation while attempting cscale = :log10 (also tried zscale = :log10) on a heatmap.

[rafaqz]

I can see how keeping the keyword scope down would be important! especially given the breadth of use cases Plots.jl has to deal with.

If we can use the same set of attributes as @hervasa2 suggests, (maybe with colorbar_ prefixed?) it would at least add less overhead in terms of new names for things.

I'm not sure what is possible with GR, the colorbar method doesn't have many arguments, but there is lot of global state that is incorporated somehow. It does seem possible to do with matplotlib, plotly, and pgfplots.

[mkborregaard]

So having a new keyword type colorbar in addition to Plot, Subplot, Axis and Series, and reusing Axis keywords while prepending colorbar_? That does sound like a neat design. Thoughts @daschw ?

[rafaqz]

Also I didn't read @hervasa2 comment properly, cticks etc is nice too for where x/y is usually used.

[daschw]

So having a new keyword type colorbar in addition to Plot, Subplot, Axis and Series, and reusing Axis keywords while prepending colorbar_? That does sound like a neat design. Thoughts @daschw ?

I think that sounds like a good approach.

[hervasa2]

Yes colorbar_[keyword] with c[keyword] as an alias would be nice and intuitive. I think a minimal feature in GR (if not all axis attributes can be applied to the colorbar) would be colorbar_ticks, that way the user could manipulate the data behind the scenes and set manual ticks to achieve the desired result.

[isentropic]

There is clims at the moment

[fhagemann]

I would also very much welcome the ability of manipulating colorbar properties. Thanks for bringing this up!

[tbeason]

I'm also looking for this functionality. Asked for exactly this in Slack and was directed here

[bcsj]

I think it would be nice to be able to access the frame/border/axes of the colorbar as well, e.g. colorbar_frame/cframe=:box.

[Gyoshi]

related: #2345

[isentropic]

If anyone is willing to help out with the development of this, please help out with the testing in the PR