NEWS.md
In litedown: A Lightweight Version of R Markdown

CHANGES IN litedown VERSION 0.3

Added a new engine md to output Markdown text both verbatim and as-is, which can be useful for showing Markdown examples, e.g.,

`md{md} You can see both the source and output of this md chunk. ```

You can also use {md} the engine **inline**. ````

Added a new engine mermaid to generate Mermaid diagrams, e.g.,

md ```{mermaid, fig.cap='A nice flowchart.'} graph TD; A-->B; A-->C; B-->D; C-->D; ```

Added helper functions pkg_desc(), pkg_news(), pkg_citation(), pkg_code(), and pkg_manual() to get various package information for building the full package documentation as a single-file book (thanks, @jangorecki @llrs #24, @TimTaylor #22).
LaTeX math environments such as equations can be numbered and cross-referenced now (thanks, @hturner, #32).
Section headings containing the class name "unlisted" will be excluded in the table of contents.
Provided a way to write <span> with attributes based on empty links, i.e., [text](){.class #id ...}. The empty URL here tells mark() to treat the link as a <span> instead of <a>.
Added back/forward/refresh/print buttons to the toolbar in the litedown::roam() preview interface.
Changed the behavior of .Rmd and .R file links in the litedown::roam() interface: previously, clicking on an .Rmd or .R filename will execute them; now it will only show their content, because fully executing the code may be expensive or even dangerous (especially when the files were not authored by you). A new "Run" button has been provided in the interface, on which you can click on to run a file in memory and preview it (i.e., the old behavior of clicking on filenames). You should use this button only if you trust the file.
Added the JS asset @mathjax-config to enable equation numbering by default when the JS math library is set to MathJax (thanks, @hturner, #32).
Set options(bitmapType = 'cairo') in fuse() if capabilities('cairo') is TRUE, which will generate smaller bitmap plot files (e.g., .png) than using quartz or Xlib, and is also a safer option for fuse() to be executed in parallel (rstudio/rmarkdown#2561).
Added a new vignette engine litedown::book to make it possible to build multiple vignettes into a book. To use this engine, declare \VignetteEngine{litedown::book} only in the book index file (e.g., index.Rmd) but not in other book chapter files.
Added support for an array of multiple authors in the YAML metadata (thanks, @AlbertLei, #28). If the author field in YAML is an array of length > 1, each author will be written to a separate <h2> in HTML output, or concatenated by \and in LaTeX output. Note that you can also write multiple authors in a single string (e.g., author: "Jane X and John Y") instead of using an array (author: ["Jane X", "John Y"]), in which case the string will be treated as a single author (they will be put inside a single <h2> in HTML output).
Fixed the bug that the leading -, +, or * in a LaTeX math expression was recognized as the bullet list marker, which would invalidate the math expression (thanks, @hturner, #33).
Changed the first - to : in automatically generated element IDs, including section, figure, and table IDs, e.g., the ID sec-intro-methods is changed to sec:intro-methods, and fig-nice-plot is changed to fig:nice-plot. You can still use - when manually assigning IDs to elements, e.g., # Intro Methods {#sec-intro-methods}. For backward compatibility, cross-references using - will be resolved if the : version of the ID can be found, e.g., @sec-intro-methods will be resolved to @sec:intro-methods if the former cannot be found but the latter can.
Fixed a bug that when LaTeX math environments are written in raw LaTeX blocks (i.e., ```{=latex}), mark() will not load the math JS library such as MathJax or KaTeX unless $ $ or $$ $$ expressions are present in the document.
As-is output accepts attributes via the chunk option attr.asis now. If provided, as-is output will be wrapped in a fenced Div with these attributes.
Numeric output from inline code will no longer be formatted if the value is wrapped in I().
The prefix for the automatic IDs of h1 headings has been changed from sec: to chp:. For other levels of headings, the prefix is still sec:.
Provided a new option embed_cleanup to clean up plot files that have been embedded in HTML output (thanks, @TimTaylor, #16).
fuse() supports the output format litedown::markdown_format now, which generates the intermediate Markdown from R Markdown without further rendering Markdown to other formats. Using this output format is equivalent to fuse(..., output = '.md') or fuse(..., output = 'markdown') (thanks, @mikmart, #35).

CHANGES IN litedown VERSION 0.2

A data frame (or matrix/tibble) wrapped in I() is fully printed to a table now by default. Without I(), data objects are truncated to 10 rows by default when printing to tables.
When options(litedown.fig.alt = TRUE) and the chunk option fig.alt is unset, fuse() will emit reminders about the missing alt text for code chunks containing plots (thanks, @TimTaylor, #23). Providing alt text can improve the accessibility of images in HTML output. To avoid omitting the alt text inadvertently, you can set the option litedown.fig.alt in your .Rprofile.
Added the meta variable plain-title for HTML output, which is the plain version of the document title (i.e., without HTML tags), and used in the <title> tag.
Check boxes from - [ ] ... are no longer disabled in HTML output.
The implicit latest version of jsdelivr resources will be resolved to an explicit version, e.g., https://cdn.jsdelivr.net/npm/@xiee/utils/css/default.css will be resolved to https://cdn.jsdelivr.net/npm/@xiee/utils@X.Y.Z/css/default.css, where X.Y.Z is the current latest version. This will make sure the HTML output containing jsdelivr resources is stable.