Plot elements appear outside plot region with cairo_pdf() but not pdf()

Question

I don't know much about graphic devices etc. All I want to do is to save plots to PDF and to embed fonts.

I use cairo_pdf() for this, but I noticed that sometimes plot elements are printed outside of the box/plot region (see screenshots of the PDFs). I can reproduce the issue on different Windows machines, different R versions, using packages cairoDevice or Cairo, and with for example lines(). But plots saved via pdf() look fine.

My questions are:

• Is this reproducible? If yes, is this a bug and where?
• Are there any other situations were cairo_pdf()-plots look different compared to pdf()-plots? Are there any other disadvantages of using cairo_pdf()?

Below are screenshots from details of the whole PDFs illustrating the differences. Note that, in the left image, the axis overlap with some points.

capabilities("cairo")
#> cairo 
#>  TRUE
set.seed(123456)
N <- 10000
v1 <- rnorm(N)
v2 <- rnorm(N)
v3 <- ifelse(v1 > 1.02 | v2 > 1.02 | v1 < -.02 | v2 < -.02, 2, 1)

cairo_pdf("plot1.pdf")
plot(v1, v2, xlim = 0:1, ylim = 0:1, col = v3, pch = 16)
dev.off()
#> null device 
#>           1

pdf("plot2.pdf")
plot(v1, v2, xlim = 0:1, ylim = 0:1, col = v3, pch = 16)
dev.off()
#> null device 
#>           1

devtools::session_info()
#> Session info ------------------------------------------------------------------
#>  setting  value                       
#>  version  R version 3.4.2 (2017-09-28)
#>  system   x86_64, mingw32             
#>  ui       Rgui                        
#>  language (EN)                        
#>  collate  German_Germany.1252         
#>  tz       Europe/Berlin               
#>  date     2018-03-09                  
#> 
#> Packages ----------------------------------------------------------------------
#>  package   * version date       source        
#>  base      * 3.4.2   2017-09-28 local         
#>  compiler    3.4.2   2017-09-28 local         
#>  datasets  * 3.4.2   2017-09-28 local         
#>  devtools    1.13.5  2018-02-18 CRAN (R 3.4.3)
#>  digest      0.6.15  2018-01-28 CRAN (R 3.4.3)
#>  graphics  * 3.4.2   2017-09-28 local         
#>  grDevices * 3.4.2   2017-09-28 local         
#>  memoise     1.1.0   2017-04-21 CRAN (R 3.4.1)
#>  methods   * 3.4.2   2017-09-28 local         
#>  stats     * 3.4.2   2017-09-28 local         
#>  utils     * 3.4.2   2017-09-28 local         
#>  withr       2.1.1   2017-12-19 CRAN (R 3.4.3)

Answer 1

This bug is fixed in R 3.6.0.

From the NEWS:

The cairo_pdf graphics device (and other Cairo-based devices) now clip correctly to the right and bottom border.
There was an off-by-one-pixel bug, reported by Lee Kelvin.