Unconstrained margins in `sf::plot()`?

[courtiol]

The "simple" plot() function in sf does not seem to let the user define margins.
This is hard-coded here:

sf/R/plot.R

Lines 304 to 309 in a3de3df

	if (!isTRUE(dots$add)) {
	mar = c(1, 1, 1.2, 1)
	if (isTRUE(dots$axes))
	mar[1:2] = 2.1
	par(mar = mar)
	}

So unless I am wrong, any attempt to define par(mar = c(...)) beforehand, or to define mar = c(...) when calling plot(), will fail.

This can be problematic even in simple cases, e.g.:

library(sf)
#> Linking to GEOS 3.14.1, GDAL 3.11.5, PROJ 9.6.2; sf_use_s2() is TRUE
nc <- st_read(system.file("gpkg/nc.gpkg", package="sf"), quiet = TRUE)
plot(nc["SID74"], graticule = TRUE, axes = TRUE, las = 1, main = "A double line\ntitle")

One can use grid "black magic" to get around the constraint, but it is not quite user friendly...

plot(nc["SID74"], graticule = TRUE, axes = TRUE, las = 1, main = "")
p <- recordPlot()
gridGraphics::grid.echo() # needed (for side effect)
a <- grid::grid.grab()
grid::grid.newpage()
a <- grid::editGrob(a, vp = grid::viewport(width = 0.8, height = 0.9))
grid::grid.draw(a)
grid::grid.text("A double line\ntitle", y = grid::unit(0.95, "npc"))

^{Created on 2025-11-30 with reprex v2.1.1}

Of course, there is always the ggplot way out, but passing a mar argument to plot would be a very welcome addition to plot().

[courtiol]

(note that the workaround above does not seem to be compatible with writing plots into files, i.e. using pdf() and so forth)