Add a table of contents plugin

This allows for displaying a nifty auto-scrolling table of contents pane to the right of
the current page of documentation. This is especially useful when viewing long documents
such as the installation instructions.

5 files changed, 515 insertions, 1 deletions

diff --git a/book.toml b/book.toml
index aefcb6a5bd..7255bf8372 100644
--- a/book.toml
+++ b/book.toml
@@ -23,4 +23,10 @@ create-missing = false
 git-repository-url = "https://github.com/matrix-org/synapse"
 
 # The path that the docs are hosted on
-site-url = "/synapse/"
\ No newline at end of file
+site-url = "/synapse/"
+
+# Additional HTML, JS, CSS that's injected into each page of the book.
+# More information is available in docs/website_files/README.md
+additional-css = ["docs/website_files/table-of-contents.css"]
+additional-js = ["docs/website_files/table-of-contents.js"]
+theme = "docs/website_files/theme"
\ No newline at end of file
diff --git a/docs/website_files/README.md b/docs/website_files/README.md
new file mode 100644
index 0000000000..acf73350d6
--- /dev/null
+++ b/docs/website_files/README.md
@@ -0,0 +1,20 @@
+# Documentation Website Files and Assets
+
+This directory contains extra files for modifying the look and functionality of 
+[mdbook](https://github.com/rust-lang/mdBook), the documentation software that's
+used to generate Synapse's documentation website.
+
+The configuration options in the `output.html` section of [book.toml](../../book.toml)
+point to additional JS/CSS in this directory that are added on each page load. In
+addition, the `theme` directory contains files that overwrite their counterparts in
+each of the default themes included with mdbook.
+
+Currently we use these files to generate a floating Table of Contents page.
+The code for which was partially taken from
+[JorelAli/mdBook-pagetoc](https://github.com/JorelAli/mdBook-pagetoc/)
+before being modified such that it scrolls with the content of the page.
+
+More information can be found in mdbook's official documentation for
+[injecting page JS/CSS](https://rust-lang.github.io/mdBook/format/config.html)
+and
+[customising the default themes](https://rust-lang.github.io/mdBook/format/theme/index.html).
\ No newline at end of file
diff --git a/docs/website_files/table-of-contents.css b/docs/website_files/table-of-contents.css
new file mode 100644
index 0000000000..d16bb3b988
--- /dev/null
+++ b/docs/website_files/table-of-contents.css
@@ -0,0 +1,42 @@
+@media only screen and (max-width:1439px) {
+    .sidetoc {
+        display: none;
+    }
+}
+
+@media only screen and (min-width:1440px) {
+    main {
+        position: relative;
+        margin-left: 100px !important;
+    }
+    .sidetoc {
+        margin-left: auto;
+        margin-right: auto;
+        left: calc(100% + (var(--content-max-width))/4 - 140px);
+        position: absolute;
+        text-align: right;
+    }
+    .pagetoc {
+        position: fixed;
+        width: 250px;
+        overflow: auto;
+        right: 20px;
+        height: calc(100% - var(--menu-bar-height));
+    }
+    .pagetoc a {
+        color: var(--fg) !important;
+        display: block;
+        padding: 5px 15px 5px 10px;
+        text-align: left;
+        text-decoration: none;
+    }
+    .pagetoc a:hover,
+    .pagetoc a.active {
+        background: var(--sidebar-bg) !important;
+        color: var(--sidebar-fg) !important;
+    }
+    .pagetoc .active {
+        background: var(--sidebar-bg);
+        color: var(--sidebar-fg);
+    }
+}
diff --git a/docs/website_files/table-of-contents.js b/docs/website_files/table-of-contents.js
new file mode 100644
index 0000000000..0de5960b22
--- /dev/null
+++ b/docs/website_files/table-of-contents.js
@@ -0,0 +1,134 @@
+const getPageToc = () => document.getElementsByClassName('pagetoc')[0];
+
+const pageToc = getPageToc();
+const pageTocChildren = [...pageToc.children];
+const headers = [...document.getElementsByClassName('header')];
+
+
+// Select highlighted item in ToC when clicking an item
+pageTocChildren.forEach(child => {
+    child.addEventHandler('click', () => {
+        pageTocChildren.forEach(child => {
+            child.classList.remove('active');
+        });
+        child.classList.add('active');
+    });
+});
+
+
+/**
+ * Test whether a node is in the viewport
+ */
+function isInViewport(node) {
+    const rect = node.getBoundingClientRect();
+    return rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && rect.right <= (window.innerWidth || document.documentElement.clientWidth);
+}
+
+
+/**
+ * Set a new ToC entry.
+ * Clear any previously highlighted ToC items, set the new one,
+ * and adjust the ToC scroll position.
+ */
+function setTocEntry() {
+    let activeEntry;
+    const pageTocChildren = [...getPageToc().children];
+
+    // Calculate which header is the current one at the top of screen
+    headers.forEach(header => {
+        if (window.pageYOffset >= header.offsetTop) {
+            activeEntry = header;
+        }
+    });
+
+    // Update selected item in ToC when scrolling
+    pageTocChildren.forEach(child => {
+        if (activeEntry.href.localeCompare(child.href) === 0) {
+            child.classList.add('active');
+        } else {
+            child.classList.remove('active');
+        }
+    });
+
+    let tocEntryForLocation = document.querySelector(`nav a[href="${activeEntry.href}"]`);
+    if (tocEntryForLocation) {
+        const headingForLocation = document.querySelector(activeEntry.hash);
+        if (headingForLocation && isInViewport(headingForLocation)) {
+            // Update ToC scroll
+            const nav = getPageToc();
+            const content = document.querySelector('html');
+            if (content.scrollTop !== 0) {
+                nav.scrollTo({
+                    top: tocEntryForLocation.offsetTop - 100,
+                    left: 0,
+                    behavior: 'smooth',
+                });
+            } else {
+                nav.scrollTop = 0;
+            }
+        }
+    }
+}
+
+
+/**
+ * Populate sidebar on load
+ */
+window.addEventListener('load', () => {
+    // Only create table of contents if there is more than one header on the page
+    if (headers.length <= 1) {
+        return;
+    }
+
+    // Create an entry in the page table of contents for each header in the document
+    headers.forEach((header, index) => {
+        const link = document.createElement('a');
+
+        // Indent shows hierarchy
+        let indent = '0px';
+        switch (header.parentElement.tagName) {
+            case 'H1':
+                indent = '5px';
+                break;
+            case 'H2':
+                indent = '20px';
+                break;
+            case 'H3':
+                indent = '30px';
+                break;
+            case 'H4':
+                indent = '40px';
+                break;
+            case 'H5':
+                indent = '50px';
+                break;
+            case 'H6':
+                indent = '60px';
+                break;
+            default:
+                break;
+        }
+
+        let tocEntry;
+        if (index == 0) {
+            // Create a bolded title for the first element
+            tocEntry = document.createElement("strong");
+            tocEntry.innerHTML = header.text;
+        } else {
+            // All other elements are non-bold
+            tocEntry = document.createTextNode(header.text);
+        }
+        link.appendChild(tocEntry);
+
+        link.style.paddingLeft = indent;
+        link.href = header.href;
+        pageToc.appendChild(link);
+    });
+    setTocEntry.call();
+});
+
+
+// Handle active headers on scroll, if there is more than one header on the page
+if (headers.length > 1) {
+    window.addEventListener('scroll', setTocEntry);
+}
diff --git a/docs/website_files/theme/index.hbs b/docs/website_files/theme/index.hbs
new file mode 100644
index 0000000000..3b7a5b6163
--- /dev/null
+++ b/docs/website_files/theme/index.hbs
@@ -0,0 +1,312 @@
+<!DOCTYPE HTML>
+<html lang="{{ language }}" class="sidebar-visible no-js {{ default_theme }}">
+    <head>
+        <!-- Book generated using mdBook -->
+        <meta charset="UTF-8">
+        <title>{{ title }}</title>
+        {{#if is_print }}
+        <meta name="robots" content="noindex" />
+        {{/if}}
+        {{#if base_url}}
+        <base href="{{ base_url }}">
+        {{/if}}
+
+
+        <!-- Custom HTML head -->
+        {{> head}}
+
+        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
+        <meta name="description" content="{{ description }}">
+        <meta name="viewport" content="width=device-width, initial-scale=1">
+        <meta name="theme-color" content="#ffffff" />
+
+        {{#if favicon_svg}}
+        <link rel="icon" href="{{ path_to_root }}favicon.svg">
+        {{/if}}
+        {{#if favicon_png}}
+        <link rel="shortcut icon" href="{{ path_to_root }}favicon.png">
+        {{/if}}
+        <link rel="stylesheet" href="{{ path_to_root }}css/variables.css">
+        <link rel="stylesheet" href="{{ path_to_root }}css/general.css">
+        <link rel="stylesheet" href="{{ path_to_root }}css/chrome.css">
+        {{#if print_enable}}
+        <link rel="stylesheet" href="{{ path_to_root }}css/print.css" media="print">
+        {{/if}}
+
+        <!-- Fonts -->
+        <link rel="stylesheet" href="{{ path_to_root }}FontAwesome/css/font-awesome.css">
+        {{#if copy_fonts}}
+        <link rel="stylesheet" href="{{ path_to_root }}fonts/fonts.css">
+        {{/if}}
+
+        <!-- Highlight.js Stylesheets -->
+        <link rel="stylesheet" href="{{ path_to_root }}highlight.css">
+        <link rel="stylesheet" href="{{ path_to_root }}tomorrow-night.css">
+        <link rel="stylesheet" href="{{ path_to_root }}ayu-highlight.css">
+
+        <!-- Custom theme stylesheets -->
+        {{#each additional_css}}
+        <link rel="stylesheet" href="{{ ../path_to_root }}{{ this }}">
+        {{/each}}
+
+        {{#if mathjax_support}}
+        <!-- MathJax -->
+        <script async type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
+        {{/if}}
+    </head>
+    <body>
+        <!-- Provide site root to javascript -->
+        <script type="text/javascript">
+            var path_to_root = "{{ path_to_root }}";
+            var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "{{ preferred_dark_theme }}" : "{{ default_theme }}";
+        </script>
+
+        <!-- Work around some values being stored in localStorage wrapped in quotes -->
+        <script type="text/javascript">
+            try {
+                var theme = localStorage.getItem('mdbook-theme');
+                var sidebar = localStorage.getItem('mdbook-sidebar');
+                if (theme.startsWith('"') && theme.endsWith('"')) {
+                    localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
+                }
+                if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
+                    localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
+                }
+            } catch (e) { }
+        </script>
+
+        <!-- Set the theme before any content is loaded, prevents flash -->
+        <script type="text/javascript">
+            var theme;
+            try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
+            if (theme === null || theme === undefined) { theme = default_theme; }
+            var html = document.querySelector('html');
+            html.classList.remove('no-js')
+            html.classList.remove('{{ default_theme }}')
+            html.classList.add(theme);
+            html.classList.add('js');
+        </script>
+
+        <!-- Hide / unhide sidebar before it is displayed -->
+        <script type="text/javascript">
+            var html = document.querySelector('html');
+            var sidebar = 'hidden';
+            if (document.body.clientWidth >= 1080) {
+                try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
+                sidebar = sidebar || 'visible';
+            }
+            html.classList.remove('sidebar-visible');
+            html.classList.add("sidebar-" + sidebar);
+        </script>
+
+        <nav id="sidebar" class="sidebar" aria-label="Table of contents">
+            <div class="sidebar-scrollbox">
+                {{#toc}}{{/toc}}
+            </div>
+            <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
+        </nav>
+
+        <div id="page-wrapper" class="page-wrapper">
+
+            <div class="page">
+                {{> header}}
+                <div id="menu-bar-hover-placeholder"></div>
+                <div id="menu-bar" class="menu-bar sticky bordered">
+                    <div class="left-buttons">
+                        <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                            <i class="fa fa-bars"></i>
+                        </button>
+                        <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
+                            <i class="fa fa-paint-brush"></i>
+                        </button>
+                        <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
+                            <li role="none"><button role="menuitem" class="theme" id="light">{{ theme_option "Light" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="rust">{{ theme_option "Rust" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="coal">{{ theme_option "Coal" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="navy">{{ theme_option "Navy" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="ayu">{{ theme_option "Ayu" }}</button></li>
+                        </ul>
+                        {{#if search_enabled}}
+                        <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
+                            <i class="fa fa-search"></i>
+                        </button>
+                        {{/if}}
+                    </div>
+
+                    <h1 class="menu-title">{{ book_title }}</h1>
+
+                    <div class="right-buttons">
+                        {{#if print_enable}}
+                        <a href="{{ path_to_root }}print.html" title="Print this book" aria-label="Print this book">
+                            <i id="print-button" class="fa fa-print"></i>
+                        </a>
+                        {{/if}}
+                        {{#if git_repository_url}}
+                        <a href="{{git_repository_url}}" title="Git repository" aria-label="Git repository">
+                            <i id="git-repository-button" class="fa {{git_repository_icon}}"></i>
+                        </a>
+                        {{/if}}
+                        {{#if git_repository_edit_url}}
+                        <a href="{{git_repository_edit_url}}" title="Suggest an edit" aria-label="Suggest an edit">
+                            <i id="git-edit-button" class="fa fa-edit"></i>
+                        </a>
+                        {{/if}}
+
+                    </div>
+                </div>
+
+                {{#if search_enabled}}
+                <div id="search-wrapper" class="hidden">
+                    <form id="searchbar-outer" class="searchbar-outer">
+                        <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
+                    </form>
+                    <div id="searchresults-outer" class="searchresults-outer hidden">
+                        <div id="searchresults-header" class="searchresults-header"></div>
+                        <ul id="searchresults">
+                        </ul>
+                    </div>
+                </div>
+                {{/if}}
+
+                <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
+                <script type="text/javascript">
+                    document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
+                    document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
+                    Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
+                        link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
+                    });
+                </script>
+
+                <div id="content" class="content">
+                    <main>
+                        <!-- Page table of contents -->
+                        <div class="sidetoc">
+                            <nav class="pagetoc"></nav>
+                        </div>
+
+                        {{{ content }}}
+                    </main>
+
+                    <nav class="nav-wrapper" aria-label="Page navigation">
+                        <!-- Mobile navigation buttons -->
+                        {{#previous}}
+                            <a rel="prev" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
+                                <i class="fa fa-angle-left"></i>
+                            </a>
+                        {{/previous}}
+
+                        {{#next}}
+                            <a rel="next" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                                <i class="fa fa-angle-right"></i>
+                            </a>
+                        {{/next}}
+
+                        <div style="clear: both"></div>
+                    </nav>
+                </div>
+            </div>
+
+            <nav class="nav-wide-wrapper" aria-label="Page navigation">
+                {{#previous}}
+                    <a rel="prev" href="{{ path_to_root }}{{link}}" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
+                        <i class="fa fa-angle-left"></i>
+                    </a>
+                {{/previous}}
+
+                {{#next}}
+                    <a rel="next" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                        <i class="fa fa-angle-right"></i>
+                    </a>
+                {{/next}}
+            </nav>
+
+        </div>
+
+        {{#if livereload}}
+        <!-- Livereload script (if served using the cli tool) -->
+        <script type="text/javascript">
+            var socket = new WebSocket("{{{livereload}}}");
+            socket.onmessage = function (event) {
+                if (event.data === "reload") {
+                    socket.close();
+                    location.reload();
+                }
+            };
+            window.onbeforeunload = function() {
+                socket.close();
+            }
+        </script>
+        {{/if}}
+
+        {{#if google_analytics}}
+        <!-- Google Analytics Tag -->
+        <script type="text/javascript">
+            var localAddrs = ["localhost", "127.0.0.1", ""];
+            // make sure we don't activate google analytics if the developer is
+            // inspecting the book locally...
+            if (localAddrs.indexOf(document.location.hostname) === -1) {
+                (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+                (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+                m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+                })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
+                ga('create', '{{google_analytics}}', 'auto');
+                ga('send', 'pageview');
+            }
+        </script>
+        {{/if}}
+
+        {{#if playground_line_numbers}}
+        <script type="text/javascript">
+            window.playground_line_numbers = true;
+        </script>
+        {{/if}}
+
+        {{#if playground_copyable}}
+        <script type="text/javascript">
+            window.playground_copyable = true;
+        </script>
+        {{/if}}
+
+        {{#if playground_js}}
+        <script src="{{ path_to_root }}ace.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}editor.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}mode-rust.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}theme-dawn.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}theme-tomorrow_night.js" type="text/javascript" charset="utf-8"></script>
+        {{/if}}
+
+        {{#if search_js}}
+        <script src="{{ path_to_root }}elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}mark.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}searcher.js" type="text/javascript" charset="utf-8"></script>
+        {{/if}}
+
+        <script src="{{ path_to_root }}clipboard.min.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}highlight.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}book.js" type="text/javascript" charset="utf-8"></script>
+
+        <!-- Custom JS scripts -->
+        {{#each additional_js}}
+        <script type="text/javascript" src="{{ ../path_to_root }}{{this}}"></script>
+        {{/each}}
+
+        {{#if is_print}}
+        {{#if mathjax_support}}
+        <script type="text/javascript">
+        window.addEventListener('load', function() {
+            MathJax.Hub.Register.StartupHook('End', function() {
+                window.setTimeout(window.print, 100);
+            });
+        });
+        </script>
+        {{else}}
+        <script type="text/javascript">
+        window.addEventListener('load', function() {
+            window.setTimeout(window.print, 100);
+        });
+        </script>
+        {{/if}}
+        {{/if}}
+
+    </body>
+</html>
\ No newline at end of file