Colourbar tick and frame linewidths

[teunbrand]

Hello there,

This is just a minor inconsistency, but in case this wasn't noticed yet, here it is. Apparently, guide_colourbar() uses the ticks.linewidth and frame.linewidth parameter as-is, while in the rest of ggplot2 (as far as I can tell), almost every parameter for linewidth is calculated as below:

# Right before handing `supplied_value` to grid
lwd = supplied_value * .pt

Here is a reprex with exaggerated line sizes. You can notice when comparing the width of geom_line() versus the colourbar guide ticks. The lines appear of the same width when you adjust ticks.linewidth = 5 * .pt.

library(ggplot2)

df <- data.frame(x = c(0, 1), y = c(0.5, 0.5))

ggplot(df, aes(x, y)) +
  geom_point(aes(colour = x)) +
  geom_line(size = 5) +
  scale_colour_gradientn(
    colours = c("white", "white"),
    guide = guide_colourbar(ticks.colour = "black", ticks.linewidth = 5)
  )

^{Created on 2021-01-12 by the reprex package (v0.3.0)}

Thanks for reading!

[clauswilke]

The correct comparison is with theme elements. I believe they don't multiply by .pt, but I could misremember.

[teunbrand]

That indeed would be a fairer comparison, though also the theme elements appear to use the * .pt. Seen in the code of element_grob.element_line() here:

ggplot2/R/theme-elements.r

Lines 248 to 256 in 37eb64d

	gp <- gpar(
	col = colour, fill = colour,
	lwd = len0_null(size * .pt), lty = linetype, lineend = lineend
	)
	element_gp <- gpar(
	col = element$colour, fill = element$colour,
	lwd = len0_null(element$size * .pt), lty = element$linetype,
	lineend = element$lineend
	)

[clauswilke]

Then it probably should do so in the color bar also.

[teunbrand]

Thanks so I thought as well. Should I leave a PR for you to consider?

[clauswilke]

Yes, please go ahead.