ragg does not render minus sign in axis title superscript

[weerasuriya]

I have an unusual issue, which I can't isolate the cause of. The ragg png device seems to drop the minus sign in negative exponents, for example, day^-1 or 10^-1.

It seems to work fine with the base png device. Example:

data(mtcars)

# Using base png device
png("/tmp/default_image.png")
plot(data = mtcars, disp ~ mpg, xlab = expression("efficiency" ~ mpg^-1))
dev.off()
#> png 
#>   2

# Using ragg png device
ragg::agg_png("/tmp/ragg_image.png")
plot(data = mtcars, disp ~ mpg, xlab = expression("efficiency" ~ mpg^-1))
dev.off()
#> png 
#>   2

^{Created on 2021-08-22 by the reprex package (v2.0.1)}

Session info

sessionInfo()
#> R version 4.1.1 (2021-08-10)
#> Platform: x86_64-pc-linux-gnu (64-bit)
#> Running under: Arch Linux
#> 
#> Matrix products: default
#> BLAS:   /usr/lib/libopenblasp-r0.3.17.so
#> LAPACK: /usr/lib/liblapack.so.3.10.0
#> 
#> locale:
#>  [1] LC_CTYPE=en_GB.UTF-8    LC_NUMERIC=C            LC_TIME=en_GB.UTF-8    
#>  [4] LC_COLLATE=en_GB.UTF-8  LC_MONETARY=en_GB.UTF-8 LC_MESSAGES=en_GB.UTF-8
#>  [7] LC_PAPER=en_GB.UTF-8    LC_NAME=C               LC_ADDRESS=C           
#> [10] LC_TELEPHONE=C          LC_MEASUREMENT=C        LC_IDENTIFICATION=C    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] ragg_1.1.3
#> 
#> loaded via a namespace (and not attached):
#>  [1] knitr_1.33        magrittr_2.0.1    rlang_0.4.11      fansi_0.5.0      
#>  [5] stringr_1.4.0     styler_1.5.1      highr_0.9         tools_4.1.1      
#>  [9] xfun_0.25         utf8_1.2.2        withr_2.4.2       systemfonts_1.0.2
#> [13] htmltools_0.5.1.1 ellipsis_0.3.2    yaml_2.2.1        digest_0.6.27    
#> [17] tibble_3.1.3      lifecycle_1.0.0   crayon_1.4.1      textshaping_0.3.5
#> [21] purrr_0.3.4       vctrs_0.3.8       fs_1.5.0          glue_1.4.2       
#> [25] evaluate_0.14     rmarkdown_2.10    reprex_2.0.1      stringi_1.7.3    
#> [29] compiler_4.1.1    pillar_1.6.2      backports_1.2.1   pkgconfig_2.0.3

These lead to:

Base png:

ragg png:

I'm unsure how to debug this. Any suggestions would be really appreciate. Thanks.

[weerasuriya]

Interestingly, it seems like forcing the minus sign through unicode works:

data(mtcars)

# Using ragg png device
ragg::agg_png("/tmp/ragg_image.png")
plot(data = mtcars, disp ~ mpg, xlab = expression("efficiency" ~ mpg^{"\u2212"*1}))
dev.off()
#> png 
#>   2

^{Created on 2021-08-22 by the reprex package (v2.0.1)}

Session info

sessionInfo()
#> R version 4.1.1 (2021-08-10)
#> Platform: x86_64-pc-linux-gnu (64-bit)
#> Running under: Arch Linux
#> 
#> Matrix products: default
#> BLAS:   /usr/lib/libopenblasp-r0.3.17.so
#> LAPACK: /usr/lib/liblapack.so.3.10.0
#> 
#> locale:
#>  [1] LC_CTYPE=en_GB.UTF-8    LC_NUMERIC=C            LC_TIME=en_GB.UTF-8    
#>  [4] LC_COLLATE=en_GB.UTF-8  LC_MONETARY=en_GB.UTF-8 LC_MESSAGES=en_GB.UTF-8
#>  [7] LC_PAPER=en_GB.UTF-8    LC_NAME=C               LC_ADDRESS=C           
#> [10] LC_TELEPHONE=C          LC_MEASUREMENT=C        LC_IDENTIFICATION=C    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> loaded via a namespace (and not attached):
#>  [1] knitr_1.33        magrittr_2.0.1    ragg_1.1.3        rlang_0.4.11     
#>  [5] fansi_0.5.0       stringr_1.4.0     styler_1.5.1      highr_0.9        
#>  [9] tools_4.1.1       xfun_0.25         utf8_1.2.2        withr_2.4.2      
#> [13] systemfonts_1.0.2 htmltools_0.5.1.1 ellipsis_0.3.2    yaml_2.2.1       
#> [17] digest_0.6.27     tibble_3.1.3      lifecycle_1.0.0   crayon_1.4.1     
#> [21] textshaping_0.3.5 purrr_0.3.4       vctrs_0.3.8       fs_1.5.0         
#> [25] glue_1.4.2        evaluate_0.14     rmarkdown_2.10    reprex_2.0.1     
#> [29] stringi_1.7.3     compiler_4.1.1    pillar_1.6.2      backports_1.2.1  
#> [33] pkgconfig_2.0.3

[thomasp85]

This issue seems to be unique to your system or maybe Arch Linux... Don't know what to make of it I'm afraid

Will see if I can reproduce in a VM

[remlapmot]

Another way to fix this is like in #136, i.e., the default symbol font on Linux does not display alot of the plotmath expressions correctly under ragg (although it does under grDevices).

So like #136 this can be fixed by choosing a different font, e.g.,

systemfonts::register_variant("symbol", "Liberation Sans")

and then doing your plot.