Vignette engines for Quarto (#57)

DESCRIPTION

@@ -22,6 +22,7 @@ Imports:
     rmarkdown,
     rstudioapi,
     utils,
+    tools,
     yaml
 Suggests: 
     curl,
@@ -31,7 +32,7 @@ Suggests:
     withr,
     xfun
 VignetteBuilder: 
-    knitr
+    knitr, quarto
 Config/testthat/edition: 3
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)

NAMESPACE

@@ -26,5 +26,6 @@ importFrom(rlang,is_interactive)
 importFrom(rmarkdown,relative_to)
 importFrom(rstudioapi,isAvailable)
 importFrom(rstudioapi,viewer)
+importFrom(tools,vignetteEngine)
 importFrom(utils,browseURL)
 importFrom(yaml,write_yaml)

R/zzz.R

@@ -0,0 +1,24 @@
+
+#' Register engines to support Quarto vignettes
+#' @importFrom tools vignetteEngine
+#' @noRd
+.onLoad <- function(libname, pkgname) { # args ignored
+  vignetteEngine(name = "pdf",
+                 package = "quarto",
+                 pattern = "[.]qmd$",
+                 weave = function(file, ..., encoding = "UTF-8") {
+                   quarto_render(file, ..., output_format = "pdf")
+                 },
+                 tangle = vignetteEngine("knitr::rmarkdown")$tangle,
+                 aspell = vignetteEngine("knitr::rmarkdown")$aspell
+                 )
+  vignetteEngine(name = "html",
+                 package = "quarto",
+                 pattern = "[.]qmd$",
+                 weave = function(file, ..., encoding = "UTF-8") {
+                   quarto_render(file, ..., output_format = "html")
+                 },
+                 tangle = vignetteEngine("knitr::rmarkdown")$tangle,
+                 aspell = vignetteEngine("knitr::rmarkdown")$aspell
+                 )
+}

vignettes/hello.qmd

@@ -0,0 +1,36 @@
+---
+title: "Quarto Vignettes"
+format:
+  pdf:
+    toc: false
+  html:
+    toc: true
+vignette: >
+  %\VignetteIndexEntry{Vignettes}
+  %\VignetteEngine{quarto::pdf}
+  %\VignetteEncoding{UTF-8}
+---
+
+## Hello Vignette World!
+
+This is an example Quarto vignette, demonstrating how the **quarto** package can let you write package vignettes in Quarto.
+
+## Two Vignette Engines
+
+The **quarto** package registers 2 vignette engines, `quarto::pdf` and `quarto::html`. Either of these may be selected in a Quarto vignette's YAML header. For example, this vignette's header reads:
+```yaml
+---
+title: "Quarto Vignettes"
+format:
+  pdf:
+    toc: false
+  html:
+    toc: true
+vignette: >
+  %\VignetteIndexEntry{Vignettes}
+  %\VignetteEngine{quarto::pdf}
+  %\VignetteEncoding{UTF-8}
+---
+```
+
+Consequently, a PDF version of this vignette is built.