coord_sf() doesn't adjust line size for graticule lines

[clauswilke]

Line sizes in themes are generally provide in units of mm and converted to grid units by multiplication by .pt. However, coord_sf() doesn't do that, it uses the value of size directly. Reprex:

library(ggplot2)

df <- data.frame(x = c(1, 2, 3), y = c(1, 2, 3))
p <- ggplot(df, aes(x, y)) + geom_point()

cowplot::plot_grid(
  p + coord_fixed() + theme(panel.grid.minor = element_blank()) +
    ggtitle("coord_fixed()"),
  p + coord_sf() +
    ggtitle("coord_sf() default"),
  p + coord_sf() + theme(panel.grid = element_line(size = 0.5*.pt)) +
    ggtitle("coord_sf() theme adjusted"),
  nrow = 2
)

^{Created on 2018-11-09 by the reprex package (v0.2.1)}

The offending lines are here:

ggplot2/R/sf.R

Lines 576 to 582 in 6786969

	render_bg = function(self, panel_params, theme) {
	el <- calc_element("panel.grid.major", theme)
	line_gp <- gpar(col = el$colour, lwd = el$size, lty = el$linetype)
	grobs <- c(
	list(element_render(theme, "panel.background")),
	lapply(sf::st_geometry(panel_params$graticule), sf::st_as_grob, gp = line_gp)
	)

The fix is simple, but it would affect the visual appearance of a lot of plots out in the wild.

[thomasp85]

I think this makes sense to change irrespectively of the changes in the wild it may affect... but better wait until the next big(ish) release

[yutannihilation]

+1

[clauswilke]

There's a somewhat related issue that could be fixed at the same time: #2525

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/