Method to detect whether a user has set a global theme

[jack-davison]

Hello folks,

Correct me if I'm wrong, but I don't believe there is a way to detect whether a user has a global ggplot2 theme set. The closest I can get, I think, is something like:

user_has_set_theme <- function() {
  !identical(ggplot2::get_theme(), ggplot2::theme_gray())
}

This covers almost all cases, except where the user specifically wants theme_gray()!

My use case is writing a package which produces ggplot2 figures. By default we choose a nice theme that is appropriate for each plot type, but I'm keen that advanced users can escape this default theming if they do have a global theme set. The above user_has_theme_set() function does the job in all cases - e.g., if they set theme_minimal() or some other theme as their global theme - except that where the user really wants to use that default gray theme.

The only discussion I can find on this topic is https://forum.posit.co/t/how-to-check-if-the-user-has-set-a-global-ggplot-theme-with-theme-set-or-not/129162/4 where this "check against theme_grey" is advised.

Cheers!

[teunbrand]

Hi there! I don't think ggplot2 tracks this at all. I think your proposal is probably the best you can get without ggplot2 artificially starting to track this. If you are returning plots/patchwork from your functions, can't these advanced users manually set + theme_gray() themselves?

[teunbrand]

@jack-davison just to clarify: is this a feature request to track this somewhere, or is this seeking advice within the means of current capabilities?

[jack-davison]

Hi Teun - it was initially a question, but I think it could be a useful feature (albeit low priority in the grand scheme of things as it is incredibly niche).

In my specific case there are certain themes I want to hard-code for my specific plot types, so having a user just do function_output + theme_grey() themselves would override them. I want to ideally catch the user's global theme before my package applies its necessary theme overrides.

I fully appreciate this is pretty niche though, and is only a problem if someone wants to globally set theme_grey(), which is probably very unlikely in the wild!

[teunbrand]

Thanks for elaborating! I think the main reason somebody would want to set theme_grey() globally is if they want to revert to the default to undo any global theme changes they or their loaded packages have made (using e.g. reset_theme_settings()). So even if they set theme_grey() it does not 100% indicate the intent to draw a plot using that theme and I imagine they still want your overrides applied to their plots.