Inconsistent kerning when using `ggsave()` with `device = cairo_pdf`

[archavan]

When saving a plot with ggsave() with device = cairo_pdf, the kerning appears to be inconsistent for text. This is not a problem with the default pdf device or when using the Cairo::CairoPDF() directly.

Below is code to reproduce the issue, and attached is a picture illustrating an example of the problem.

library(ggplot2)
library(Cairo)

df <- data.frame(
  x = "a",
  y = "avoid awkward spacing issues between sequences of letters"
)

p <- ggplot(df, aes(x, y)) +
  geom_point()

ww <- 4
hh <- 1

# this has inconsistent kerning
ggsave("kerning_ggsave_cairopdf.pdf", plot = p, device = cairo_pdf, width = ww, height = hh)

# this has no issues
ggsave("kerning_ggsave_default.pdf", plot = p, width = ww, height = hh)

# this has no issues either
CairoPDF("kerning_CairoPDF.pdf", width = ww, height = hh)
print(p)
dev.off()

sessionInfo()
#> R version 4.5.1 (2025-06-13)
#> Platform: aarch64-apple-darwin20
#> Running under: macOS Sequoia 15.6.1
#> 
#> Matrix products: default
#> BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib 
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1
#> 
#> locale:
#> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
#> 
#> time zone: America/New_York
#> tzcode source: internal
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] Cairo_1.6-5   ggplot2_3.5.2
#> 
#> loaded via a namespace (and not attached):
#>  [1] vctrs_0.6.5        knitr_1.50         cli_3.6.5          xfun_0.53          rlang_1.1.6       
#>  [6] processx_3.8.6     generics_0.1.4     textshaping_1.0.3  glue_1.8.0         labeling_0.4.3    
#> [11] clipr_0.8.0        htmltools_0.5.8.1  ps_1.9.1           ragg_1.5.0         rmarkdown_2.29    
#> [16] scales_1.4.0       grid_4.5.1         evaluate_1.0.5     tibble_3.3.0       fastmap_1.2.0     
#> [21] yaml_2.3.10        lifecycle_1.0.4    compiler_4.5.1     dplyr_1.1.4        fs_1.6.6          
#> [26] RColorBrewer_1.1-3 pkgconfig_2.0.3    rstudioapi_0.17.1  digest_0.6.37      systemfonts_1.2.3 
#> [31] farver_2.1.2       R6_2.6.1           reprex_2.1.1       tidyselect_1.2.1   pillar_1.11.0     
#> [36] callr_3.7.6        magrittr_2.0.3     tools_4.5.1        withr_3.0.2        gtable_0.3.6

[thomasp85]

ggplot2 is not in control of how the graphics device choose to render text. Since you have already identified a graphics device that satisfies your need I'm going to close it