Export tweaked version of `ggplot2::guide_colourbar()`?

[trevorld]

• By default ggplot2::guide_colourbar() (and its guide_colorbar() alias) only supports fill and colour aesthetics but it would be more useful to have a version that that also supports pattern_colour, pattern_fill, and pattern_fill2 aesthetics as well (which can be supported by explicitly adjusting its available_aes argument).
• Simply need a wrapper around guide_colourbar() with an expanded default available_aes.
• Although in general a new function name is desirable perhaps in this case it would be less confusing for users if we exported (and hence override the ggplot2 builtin) a function of the same name guide_colourbar(). Only difference in behavior in function would be that the guide will no longer throw errors when used with the pattern_colour, pattern_fill, or pattern_fill2 aesthetics which doesn't seem to be a huge problem to me.
• Probably makes sense to support color aliases in both function name and aesthetic names...

[trevorld]

• More info upstream on ggplot2::guide_colourbar() not working with 3rd party geoms unless they explicitly call guide_colourbar() with an expanded available_aes argument: https://github.com/tidyverse/ggplot2/issues/4105

[coolbutuseless]

I struggled with this same issue with the ggsvg package - where any named aesthetic could be considered to be a colour (and new aesthetics are created on-the-fly)

My solution was not elegant: I rewrote every single colour/fill scale such that the aesthetics argument no longer had a default, and I would then pass this as the available_aes to guide_colorbar() i.e.

scale_svg_colour_gradient <- function(aesthetics,
                                      ...,
                                      low        = "#132B43",
                                      high       = "#56B1F7",
                                      space      = "Lab",
                                      na.value   = "grey50",
                                      guide      = ggplot2::guide_colorbar(available_aes = aesthetics)) {
  ggplot2::continuous_scale(
    aesthetics,
    scale_name = "gradient",
    palette    = scales::seq_gradient_pal(low, high, space),
    na.value   = na.value,
    guide      = guide,
    ...
  )
}

It may be possible to do with

[trevorld]

Thanks! The {ggpattern} scales should work now after explicitly specifying appropriate available_aes arguments to guide_colourbar() instead of just using "colourbar". Just wondering if we should export a helper guide function in case users wanted to explicitly set a guide since guide_colourbar() isn't intuitive for 3rd-party geoms. Probably not many people using a continuous colour scale AND setting a custom colourbar guide so I guess we can reasonably defer on such a feature for now.