add 'snap' option when reading in a raster with a window?

[dfriend21]

When cropping you can use the snap parameter to control how the provided extent aligns to the geometry of the raster being cropped. It'd be nice if a similar option was available when reading in a raster with a set window (via the win parameter). In my particular use case I want to read in only the extent defined by a polygon, and as it's currently implemented it's likely that not all cells touched by the polygon will be included in the window.

Example:

library(terra)
#> terra 1.7.18

r <- rast(matrix(runif(100), nrow = 10, ncol = 10))
poly_mat <- rbind(
  c(1.7, 1.3),
  c(4.2, 8.2),
  c(6.2, 8.2),
  c(8.2, 1.1),
  c(1.7, 1.3)
)
poly <- vect(poly_mat, type = "polygons")

tf <- tempfile(fileext = ".tif")
writeRaster(r, tf)

r2 <- rast(tf, win = ext(poly))

plot_ext <- ext(poly) + .5
plot(r2, xlim = plot_ext[1:2], ylim = plot_ext[3:4])
plot(poly, add = TRUE, lwd = 2)

^{Created on 2023-04-03 with reprex v2.0.2}

[rhijmans]

Thanks. You can now do

r2 <- rast(tf, win = poly, snap="out")
plot(r2)
lines(poly, lwd=2)