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index.hbs

index.hbs is the handlebars template that is used to render the book. The markdown files are processed to html and then injected in that template.

If you want to change the layout or style of your book, chances are that you will have to modify this template a little bit. Here is what you need to know.

Data

A lot of data is exposed to the handlebars template with the “context”. In the handlebars template you can access this information by using

{{name_of_property}}

Here is a list of the properties that are exposed:

  • language Language of the book in the form en, as specified in book.toml (if not specified, defaults to en). To use in <html lang="{{ language }}"> for example.

  • title Title used for the current page. This is identical to {{ chapter_title }} - {{ book_title }} unless book_title is not set in which case it just defaults to the chapter_title.

  • book_title Title of the book, as specified in book.toml

  • chapter_title Title of the current chapter, as listed in SUMMARY.md

  • path Relative path to the original markdown file from the source directory

  • content This is the rendered markdown.

  • path_to_root This is a path containing exclusively ../’s that points to the root of the book from the current file. Since the original directory structure is maintained, it is useful to prepend relative links with this path_to_root.

  • previous and next These are objects used for linking to the previous and next chapter. They contain the properties title and link of the corresponding chapter.

  • chapters Is an array of dictionaries of the form

    {"section": "1.2.1", "name": "name of this chapter", "path": "dir/markdown.md"}

    containing all the chapters of the book. It is used for example to construct the table of contents (sidebar).

Handlebars helpers

In addition to the properties you can access, there are some handlebars helpers at your disposal.

toc

The toc helper is used like this

{{#toc}}{{/toc}}

and outputs something that looks like this, depending on the structure of your book

<ul class="chapter">
    <li><a href="link/to/file.html">Some chapter</a></li>
    <li>
        <ul class="section">
            <li><a href="link/to/other_file.html">Some other Chapter</a></li>
        </ul>
    </li>
</ul>

If you would like to make a toc with another structure, you have access to the chapters property containing all the data. The only limitation at the moment is that you would have to do it with JavaScript instead of with a handlebars helper.

<script>
var chapters = {{chapters}};
// Processing here
</script>

resource

The path to a static file. It implicitly includes path_to_root, and accounts for files that are renamed with a hash in their filename.

<link rel="stylesheet" href="{{ resource "css/chrome.css" }}">

fa

mdBook includes a copy of Font Awesome Free’s MIT-licensed SVG files. It accepts three positional arguments:

  1. Type: one of “solid”, “regular”, and “brands” (light and duotone are not currently supported)
  2. Icon: anything chosen from the free icon set
  3. ID (optional): if included, an HTML ID attribute will be added to the icon’s wrapping <span> tag

For example, this handlebars syntax will become this HTML:

{{fa "solid" "print" "print-button"}}

<span class=fa-svg id="print-button"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path d="M448 192V77.25c0-8.49-3.37-16.62-9.37-22.63L393.37 9.37c-6-6-14.14-9.37-22.63-9.37H96C78.33 0 64 14.33 64 32v160c-35.35 0-64 28.65-64 64v112c0 8.84 7.16 16 16 16h48v96c0 17.67 14.33 32 32 32h320c17.67 0 32-14.33 32-32v-96h48c8.84 0 16-7.16 16-16V256c0-35.35-28.65-64-64-64zm-64 256H128v-96h256v96zm0-224H128V64h192v48c0 8.84 7.16 16 16 16h48v96zm48 72c-13.25 0-24-10.75-24-24 0-13.26 10.75-24 24-24s24 10.74 24 24c0 13.25-10.75 24-24 24z"/></svg></span>