YAML font options ignored for revealjs presentations

[ryanraaum]

Bug description

mainfont, monofont, fontsize, linestretch, and monobackgroundcolor are listed as YAML header options for Revealjs presentations, but they are ignored when the presentation is rendered - only shows the defaults for these theme elements.

System is Mac OS X (Big Sur 11.6.8) with the latest RStudio Preview release (22.07.01 Build 554) and the latest Quarto release (1.0.38). The full test Quarto document is:

---
title: "Test"
format: 
  revealjs:
    mainfont: "Times New Roman"
    monofont: "Times New Roman"
    fontsize: "10px"
    linestretch: 5
    monobackgroundcolor: green
---

## Hello, World!

Hello, world!

```{r}
#| echo: true
print("Hello, world!")
```

The (no format change) result is the same for any option in isolation or in combination. But the YAML header options work fine if the format is switched to html.

I can make all these format changes just fine using a Sass theme - so the question is not how to make these changes, but rather whether or not they should work using the YAML header options.

quarto check Output

[✓] Checking Quarto installation......OK
      Version: 1.0.38
      Path: /Applications/quarto/bin

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.9.7
      Path: /Users/ryan/.pyenv/versions/3.9.7/bin/python3
      Jupyter: 4.11.1
      Kernels: julia-0.4, ir, julia 0.3, python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.2.1
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.2/Resources/library
      rmarkdown: 2.14

[✓] Checking Knitr engine render......OK

quarto tools check Output

[✓] Inspecting tools

Tool         Status                    Installed     Latest  
chromium     Not installed             ---           869685  
tinytex      External Installation     ---           v2022.08

Checklist

• formatted your issue so it is easier for us to read?
• included a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• documented the quarto version you're running, by pasting the output from running quarto check in the "Quarto Check Output" text area?
• documented the version of the quarto tools you're running, by providing the output from running quarto tools check in the "Quarto Tools Check Output" text area?
• documented the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• documented which operating system you're running? If on Linux, please provide the specific distribution as well.
• upgraded to the latest version, including your versions of R, the RStudio IDE, and relevant R packages?

[jjallaire]

@dragonstyle It does appear that these variables in fact do not work for Reveal. The cause is that we are calling pandocVariablesToThemeDefaults() for Reveal however this is setting bootstrap default values. For now I am going to update the docs to indicate this doesn't work, longer term we should try to get this working.