make citations work for single chapter preview

.gitignore

@@ -6,3 +6,4 @@
 /examples/figures/
 /site/doc/
 /site/_footer.md
+/docs/packages.bib

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: litedown
 Type: Package
 Title: A Lightweight Version of R Markdown
-Version: 0.5.15
+Version: 0.5.16
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666", URL = "https://yihui.org")),
     person("Tim", "Taylor", role = "ctb", comment = c(ORCID = "0000-0002-8587-7113")),

R/mark.R

@@ -324,6 +324,11 @@ mark = function(input, output = NULL, text = NULL, options = NULL, meta = list()
   pkg_cite = yaml_field(yaml, format, 'citation_package')
   if (length(pkg_cite) != 1) pkg_cite = 'natbib'
   bib = yaml[['bibliography']]
+  # temporarily save the bib values when previewing a book because bib may only
+  # be specified in index.Rmd but not other chapters
+  if (is.character(b <- .env$current_book)) {
+    if (length(bib)) .env$bib[[b]] = bib else bib = .env$bib[[b]]
+  }
   if (length(bib) == 1 && grepl(',', bib)) bib = strsplit(bib, ',\\s*')[[1]]
   # add [@citation] (.bib files are assumed to be under output dir)
   if (length(bib)) {

docs/02-fuse.Rmd

@@ -1347,7 +1347,7 @@ this `md` chunk.
 You can also use `{md} the engine **inline**`.
 ````
 
-### The CSS/JS engines {#engine-css}
+### The CSS/JS engines {#sec:engine-css}
 
 You can insert CSS/JS to the output via the `css`/`js` engines, e.g.,
 

docs/03-syntax.Rmd

@@ -671,8 +671,8 @@ the number and reference of the block above:
 
 ### Citations
 
-This feature requires the R package **rbibutils**. Please make sure it is
-installed before using citations.
+This feature requires the R package **rbibutils** [@R-rbibutils]. Please make
+sure it is installed before using citations.
 
 ``` r
 xfun::pkg_load2("rbibutils")

docs/04-mark.Rmd

@@ -119,6 +119,17 @@ included via the `<img>` tag, and their elements cannot be manipulated or
 styled.
 :::
 
+When embedding `https` resources, only these elements are considered:
+
+``` html
+<img src="..." />
+<link rel="stylesheet" href="...">
+<script src="..."></script>
+```
+
+If an external CSS file contains `url()` resources, these resources will also be
+downloaded and embedded.
+
 ### `js_highlight`
 
 Specify the JavaScript library to syntax highlight code blocks. Possible values

docs/05-assets.Rmd

@@ -552,6 +552,25 @@ _Anything_ on the right.
 :::
 ```
 
+In case you are interested in the technical detail, it's quite simple to move an
+element into the margin using CSS. For example, the `.side-right` class above is
+roughly defined as:
+
+``` css
+.side-right {
+  width: 200px;
+  float: right;
+  margin-right: -200px
+}
+```
+
+That basically means the width of the element is 200px and it floats to the
+right. Now its right side will touch the right margin of its parent element (the
+article body). What we need to do next is move it further to the right by 200px
+(i.e., its width), which is done by the `-200px` right margin. Remember, a
+positive right margin in CSS moves an element to the left, and a negative right
+margin moves it to the right.
+
 ### Body elements
 
 Inside the article body, you can write a few special elements.

docs/index.Rmd

@@ -2,14 +2,10 @@
 title: "litedown: R Markdown Reimagined"
 author: "Yihui Xie"
 date: "`{r} Sys.Date()`"
+bibliography: ["packages.bib"]
 ---
 
 ```{r, include = FALSE}
-if (packageVersion('xfun') < '0.49.7') stop(
-  'package versions too low; please install newer versions:\n',
-  "install.packages(c('litedown', 'xfun'), repos = 'https://yihui.r-universe.dev')"
-)
-
 options(width = 80)
 
 # return an example file in fenced Div
@@ -41,6 +37,8 @@ options(width = 80)
   x2 = .ex(n, ext[2], ...)
   xfun::fenced_div(c(x1, x2), '.flex-col')
 }
+
+xfun::pkg_bib(c('litedown', 'commonmark', 'xfun', 'rbibutils'), 'packages.bib')
 ```
 
 ```{js, echo = FALSE, type = 'module'}
@@ -152,16 +150,16 @@ just want to make the HTML world a little bit better.
 
 ## Overview
 
-The **litedown** package is an attempt to reimagine R Markdown with one primary
-goal—do HTML, and do it well, with the minimalism principle. Before LaTeX fans
-walk away in disappointment, let me quickly clarify that LaTeX output is also
-supported, but please do not expect anything fancy before you learn to customize
-LaTeX templates. Most other output formats are not supported. No Word, RTF,
-PowerPoint, or EPUB.
+The **litedown** package [@R-litedown] is an attempt to reimagine R Markdown
+with one primary goal—do HTML, and do it well, with the minimalism principle.
+Before LaTeX fans walk away in disappointment, let me quickly clarify that LaTeX
+output is also supported, but please do not expect anything fancy before you
+learn to customize LaTeX templates. Most other output formats are not supported.
+No Word, RTF, PowerPoint, or EPUB.
 
 R Markdown is rendered via `litedown::fuse()`, which is similar to
 `rmarkdown::render()` and `knitr::knit()`. Markdown is rendered via
-`litedown::mark()`, which uses **commonmark** instead of Pandoc.
+`litedown::mark()`, which uses **commonmark** [@R-commonmark] instead of Pandoc.
 
 The **commonmark** package follows the GFM (GitHub Flavored Markdown) spec,
 which can be seen as a subset of Pandoc's Markdown. Therefore the **litedown**
@@ -355,7 +353,8 @@ JavaScript, yet it is quite flexible (@chp:widgets).
 ### Small footprint
 
 Almost everything in **litedown** was written from scratch. The package is very
-lightweight, with only two R package dependencies: **commonmark** and **xfun**.
+lightweight, with only two R package dependencies: **commonmark** and **xfun**
+[@R-xfun].
 
 It is a deliberate design choice to keep this package lightweight, to make it
 relatively easy to use and simple to maintain. The functions `mark()` and