problem with svg device, expression(), and unicode characters

[richarddmorey]

I am having difficulty using the svg device with math expressions and unicode (in this case, left- and right-quotes). This only occurs on my Windows 10 computer; my osx computer seems unaffected. Consider the following Rmardown document:

---
output: 
  html_document:
      dev: svg
---

```{r echo=FALSE}
plot(1, axes=FALSE, ty='n')

## Line A: 
 mtext(side = 2, text = expression(paste("A")))
## Line B:
 mtext(side = 3, text = expression(paste("“B")))
## Line C: 
 mtext(side = 4, text = expression(paste("C")))

axis(1, at = par()$usr[1:2], lab = c("More", "Less"), tick = FALSE)
```

(Note the left-quote in Line B). Compilation fails with the error:

Quitting from lines 8-18 (testing.Rmd) 
Error in mtext(side = 4, text = expression(paste("C"))) : 
  metric information not available for this device
Calls: <Anonymous> ... withCallingHandlers -> withVisible -> eval -> eval -> mtext
Execution halted

• If I change the device to png I get the output I expect.
• If I comment out lines B and C, I get the output I expect (eg, the output from lines A and the axis)
• If I comment out only line C, I do not get the output I expect. Neither line B works, nor the axis. There appears to be something wrong with line B that causes everything later in the chunk to fail too.
• If I remove the expression() from line B, everything works as expected (including the unicode left-quote)
• I tried installing the development version of knitr as the Issue Guide suggests, but that did not help.

This appears, then, to be an interaction between svg, expression, and unicode.

Windows session info (fails on this computer)

> xfun::session_info('knitr')
R version 3.6.2 (2019-12-12)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363), RStudio 1.2.1335

Locale:
  LC_COLLATE=English_United Kingdom.1252  LC_CTYPE=English_United Kingdom.1252   
  LC_MONETARY=English_United Kingdom.1252 LC_NUMERIC=C                           
  LC_TIME=English_United Kingdom.1252    

Package version:
  evaluate_0.14   glue_1.4.0      graphics_3.6.2  grDevices_3.6.2 highr_0.8       knitr_1.28.3    magrittr_1.5   
  markdown_1.1    methods_3.6.2   mime_0.9        stats_3.6.2     stringi_1.4.6   stringr_1.4.0   tools_3.6.2    
  utils_3.6.2     xfun_0.13       yaml_2.2.1  

OSX session info (no problem on this computer)

> xfun::session_info('knitr')
R version 3.6.1 (2019-07-05)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Catalina 10.15.4, RStudio 1.2.5031

Locale: en_GB.UTF-8 / en_GB.UTF-8 / en_GB.UTF-8 / C / en_GB.UTF-8 / en_GB.UTF-8

Package version:
  evaluate_0.14   glue_1.4.0      graphics_3.6.1  grDevices_3.6.1
  highr_0.8       knitr_1.28.3    magrittr_1.5    markdown_1.1   
  methods_3.6.1   mime_0.9        stats_3.6.1     stringi_1.4.6  
  stringr_1.4.0   tools_3.6.1     utils_3.6.1     xfun_0.12      
  yaml_2.2.1 

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[richarddmorey]

Adding to the mystery, the code works if I change fonts using showtext (apologies for the hard-coded path name to the font):

---
output: 
  html_document:
      dev: svg
---

```{r echo=FALSE, include=FALSE}
  library(showtext)

  ## set chunk options to use showtext
  knitr::opts_chunk$set(fig.showtext=TRUE, dpi=300)

  sysfonts::font_paths( list.dirs("D:/OneDrive - Cardiff University/talks/significance_testing_two_parter/assets/css", recursive = TRUE) )
  
  font_add("roboto_condensed",
           regular = "RobotoCondensed-Regular.ttf", 
           bold = "RobotoCondensed-Bold.ttf",
           italic = "RobotoCondensed-Italic.ttf",
           bolditalic = "RobotoCondensed-BoldItalic.ttf"
  )

  ## Add hooks so that I can choose fonts in the chunk options         
  knitr::knit_hooks$set(
    roboto_condensed = function(before, options, envir)
      if (before) par(family = "roboto_condensed")
  )
  
  knitr::opts_chunk$set(roboto_condensed = TRUE)
  
```

```{r echo=FALSE}
plot(1, axes=FALSE, ty='n')

## Line A: 
 mtext(side = 2, text = expression(paste("A")))
## Line B:
 mtext(side = 3, text = expression(paste("“B")))
## Line C: 
 mtext(side = 4, text = expression(paste("C")))

axis(1, at = par()$usr[1:2], lab = c("More", "Less"), tick = FALSE)
```

This Rmd file compiles just fine and gives me what I expect. So it seems to be an interaction between the default font, the svg device, expression(), and unicode.

[cderv]

Let's not the getting out of Rmarkdown and knitr framework still get us the error

Using R svg device in R script

svg("test.svg")
plot(1, axes=FALSE, type ='n')
## Line A: 
mtext(side = 2, text = expression(paste("A")))
## Line B:
mtext(side = 3, text = expression(paste("“B")))
## Line C: 
mtext(side = 4, text = expression(paste("C")))
axis(1, at = par()$usr[1:2], labels = c("More", "Less"), tick = FALSE)
dev.off()

I get the error when executing Line C part

> mtext(side = 4, text = expression(paste("C")))
Error in mtext(side = 4, text = expression(paste("C"))) : 
  metric information not available for this device

When specifying a device for knitr, it will use the corresponding R code for the device. If there is an issue with the device and the code for the plot already, it will also error in knitr.

I think this needs to be investigate at the R code level outside of knitr or rmarkdown for a better understanding.

Removing the special “ character in line B make the error disappear. I am not sure that such a character can be used in expression or maybe it is an encoding issue as you said this is OS related 🤷

Hope it helps understand better this

[richarddmorey]

Yes, confirmed that happens with just the svg device outside of knitr. Thanks. I'm going to close this up and report it elsewhere.

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