refactor(theme/book): Split into modules (#556)

Advantages:
 - Easier to reason about
 - Can easily disable some modules when debugging
 - Shared dependencies are explicit (playpen_text)
 - Enables some fancier things later one (e.g. run `codeSnippets` slightly later, to avoid blocking the page)

I'm aware that `codeSnippets` should be split into the highlighter and the editor, but I'm not sure I understand exactly how they interact so I've left it as it is for now.

src/theme/book.js

@@ -1,18 +1,115 @@
-var html, sidebar, sidebarLinks, sidebarToggleButton, themeToggleButton, themePopup;
+// Fix back button cache problem
+window.onunload = function () { };
 
-document.addEventListener('DOMContentLoaded', function() {
+// Global variable, shared between modules
+function playpen_text(playpen) {
+    let code_block = playpen.querySelector("code");
 
-    // url
+    if (window.ace && code_block.classList.contains("editable")) {
-    var url = window.location.pathname;
+        let editor = window.ace.edit(code_block);
+        return editor.getValue();
+    } else {
+        return code_block.textContent;
+    }
+}
 
-    // Fix back button cache problem
+(function codeSnippets() {
-    window.onunload = function(){};
+    // Hide Rust code lines prepended with a specific character
+    var hiding_character = "#";
+    var request = fetch("https://play.rust-lang.org/meta/crates", {
+        headers: {
+            'Content-Type': "application/json",
+        },
+        method: 'POST',
+        mode: 'cors',
+    });
 
-    // Set theme
+    function handle_crate_list_update(playpen_block, playground_crates) {
-    var theme = store.get('mdbook-theme');
+        // update the play buttons after receiving the response
-    if (theme === null || theme === undefined) { theme = 'light'; }
+        update_play_button(playpen_block, playground_crates);
 
-    set_theme(theme);
+        // and install on change listener to dynamically update ACE editors
+        if (window.ace) {
+            let code_block = playpen_block.querySelector("code");
+            if (code_block.classList.contains("editable")) {
+                let editor = window.ace.edit(code_block);
+                editor.addEventListener("change", function (e) {
+                    update_play_button(playpen_block, playground_crates);
+                });
+            }
+        }
+    }
+
+    // updates the visibility of play button based on `no_run` class and
+    // used crates vs ones available on http://play.rust-lang.org
+    function update_play_button(pre_block, playground_crates) {
+        var play_button = pre_block.querySelector(".play-button");
+
+        // skip if code is `no_run`
+        if (pre_block.querySelector('code').classList.contains("no_run")) {
+            play_button.classList.add("hidden");
+            return;
+        }
+
+        // get list of `extern crate`'s from snippet
+        var txt = playpen_text(pre_block);
+        var re = /extern\s+crate\s+([a-zA-Z_0-9]+)\s*;/g;
+        var snippet_crates = [];
+        while (item = re.exec(txt)) {
+            snippet_crates.push(item[1]);
+        }
+
+        // check if all used crates are available on play.rust-lang.org
+        var all_available = snippet_crates.every(function (elem) {
+            return playground_crates.indexOf(elem) > -1;
+        });
+
+        if (all_available) {
+            play_button.classList.remove("hidden");
+        } else {
+            play_button.classList.add("hidden");
+        }
+    }
+
+    function run_rust_code(code_block) {
+        var result_block = code_block.querySelector(".result");
+        if (!result_block) {
+            result_block = document.createElement('code');
+            result_block.className = 'result hljs language-bash';
+
+            code_block.append(result_block);
+        }
+
+        let text = playpen_text(code_block);
+
+        var params = {
+            channel: "stable",
+            mode: "debug",
+            crateType: "bin",
+            tests: false,
+            code: text,
+        }
+
+        if (text.indexOf("#![feature") !== -1) {
+            params.channel = "nightly";
+        }
+
+        result_block.innerText = "Running...";
+
+        var request = fetch("https://play.rust-lang.org/execute", {
+            headers: {
+                'Content-Type': "application/json",
+            },
+            method: 'POST',
+            mode: 'cors',
+            body: JSON.stringify(params)
+        });
+
+        request
+            .then(function (response) { return response.json(); })
+            .then(function (response) { result_block.innerText = response.success ? response.stdout : response.stderr; })
+            .catch(function (error) { result_block.innerText = "Playground communication" + error.message; });
+    }
 
     // Syntax highlighting Configuration
     hljs.configure({
@@ -25,161 +122,24 @@ document.addEventListener('DOMContentLoaded', function() {
         // blocks or highlightjs will capture events
         Array
             .from(document.querySelectorAll('code.editable'))
-            .forEach(function(block) { block.classList.remove('language-rust'); });
+            .forEach(function (block) { block.classList.remove('language-rust'); });
 
         Array
             .from(document.querySelectorAll('code:not(.editable)'))
-            .forEach(function(block) { hljs.highlightBlock(block); });
+            .forEach(function (block) { hljs.highlightBlock(block); });
     } else {
         Array
             .from(document.querySelectorAll('code'))
-            .forEach(function(block) { hljs.highlightBlock(block); });
+            .forEach(function (block) { hljs.highlightBlock(block); });
     }
 
     // Adding the hljs class gives code blocks the color css
     // even if highlighting doesn't apply
     Array
         .from(document.querySelectorAll('code'))
-        .forEach(function(block) { block.classList.add('hljs'); });
+        .forEach(function (block) { block.classList.add('hljs'); });
 
-    var KEY_CODES = {
+    Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
-        PREVIOUS_KEY: 37,
-        NEXT_KEY: 39,
-        ESCAPE_KEY: 27,
-    };
-
-    document.addEventListener('keydown', function (e) {
-        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
-        switch (e.keyCode) {
-            case KEY_CODES.NEXT_KEY:
-                e.preventDefault();
-                var nextButton = document.querySelector('.nav-chapters.next');
-                if(nextButton) {
-                    window.location.href = nextButton.href;
-                }
-                break;
-            case KEY_CODES.PREVIOUS_KEY:
-                e.preventDefault();
-                var previousButton = document.querySelector('.nav-chapters.previous');
-                if(previousButton) {
-                    window.location.href = previousButton.href;
-                }
-                break;
-            case KEY_CODES.ESCAPE_KEY:
-                e.preventDefault();
-                hideThemes();
-                break;
-        }
-    });
-
-    // Interesting DOM Elements
-    html = document.querySelector('html');
-    sidebar = document.getElementById("sidebar");
-    sidebarLinks = document.querySelectorAll('#sidebar a');
-    sidebarToggleButton = document.getElementById("sidebar-toggle");
-    themeToggleButton = document.getElementById('theme-toggle');
-    themePopup = document.getElementById('theme-list');
-
-    // Toggle sidebar
-    sidebarToggleButton.addEventListener('click', sidebarToggle);
-
-    // Scroll sidebar to current active section
-    var activeSection = sidebar.querySelector(".active");
-    if(activeSection) {
-        sidebar.scrollTop = activeSection.offsetTop;
-    }
-
-    var firstContact = null;
-
-    document.addEventListener('touchstart', function(e) {
-        firstContact = {
-            x: e.touches[0].clientX,
-            time: Date.now()
-        };
-    });
-    
-    document.addEventListener('touchmove', function(e) {
-        if (!firstContact) 
-            return;
-
-        var curX = e.touches[0].clientX;
-        var xDiff = curX - firstContact.x,
-            tDiff = Date.now() - firstContact.time;
-
-        if (tDiff < 250 && Math.abs(xDiff) >= 150) {
-            if (xDiff >= 0 && firstContact.x < Math.min(document.body.clientWidth * 0.25, 300))
-                showSidebar();
-            else if (xDiff < 0 && curX < 300)
-                hideSidebar();
-
-            firstContact = null;
-        }
-    });
-
-    // Theme button
-    themeToggleButton.addEventListener('click', function(){
-        if (themePopup.style.display === 'block') {
-            hideThemes();
-        } else {
-            showThemes();
-        }
-    });
-
-    themePopup.addEventListener('click', function(e){
-        var theme = e.target.id || e.target.parentElement.id;
-        set_theme(theme);
-    });
-
-    // Hide theme selector popup when clicking outside of it
-    document.addEventListener('click', function(event){
-        if(themePopup.style.display === 'block' && !themeToggleButton.contains(event.target) && !themePopup.contains(event.target)) {
-            hideThemes();
-        }
-    });
-
-    function set_theme(theme) {
-        let ace_theme;
-
-        if (theme == 'coal' || theme == 'navy') {
-            document.querySelector("[href='ayu-highlight.css']").disabled = true;
-            document.querySelector("[href='tomorrow-night.css']").disabled = false;
-            document.querySelector("[href='highlight.css']").disabled = true;
-
-            ace_theme = "ace/theme/tomorrow_night";
-        } else if (theme == 'ayu') {
-            document.querySelector("[href='ayu-highlight.css']").disabled = false;
-            document.querySelector("[href='tomorrow-night.css']").disabled = true;
-            document.querySelector("[href='highlight.css']").disabled = true;
-
-            ace_theme = "ace/theme/tomorrow_night";
-        } else {
-            document.querySelector("[href='ayu-highlight.css']").disabled = true;
-            document.querySelector("[href='tomorrow-night.css']").disabled = true;
-            document.querySelector("[href='highlight.css']").disabled = false;
-
-            ace_theme = "ace/theme/dawn";
-        }
-
-        setTimeout(function() {
-            document.querySelector('meta[name="theme-color"]').content = getComputedStyle(document.body).backgroundColor;
-        }, 1);
-
-        if (window.ace && window.editors) {
-            window.editors.forEach(function(editor) {
-                editor.setTheme(ace_theme);
-            });
-        }
-
-        store.set('mdbook-theme', theme);
-
-        document.body.className = theme;
-    }
-
-
-    // Hide Rust code lines prepended with a specific character
-    var hiding_character = "#";
-
-    Array.from(document.querySelectorAll("code.language-rust")).forEach(function(block){
 
         var code_block = block;
         var pre_block = block.parentNode;
@@ -188,9 +148,9 @@ document.addEventListener('DOMContentLoaded', function() {
         var first_non_hidden_line = false;
         var lines_hidden = false;
 
-        for(var n = 0; n < lines.length; n++){
+        for (var n = 0; n < lines.length; n++) {
-            if(lines[n].trim()[0] == hiding_character){
+            if (lines[n].trim()[0] == hiding_character) {
-                if(first_non_hidden_line){
+                if (first_non_hidden_line) {
                     lines[n] = "<span class=\"hidden\">" + "\n" + lines[n].replace(/(\s*)# ?/, "$1") + "</span>";
                 }
                 else {
@@ -198,7 +158,7 @@ document.addEventListener('DOMContentLoaded', function() {
                 }
                 lines_hidden = true;
             }
-            else if(first_non_hidden_line) {
+            else if (first_non_hidden_line) {
                 lines[n] = "\n" + lines[n];
             }
             else {
@@ -208,7 +168,7 @@ document.addEventListener('DOMContentLoaded', function() {
         code_block.innerHTML = lines.join("");
 
         // If no lines were hidden, return
-        if(!lines_hidden) { return; }
+        if (!lines_hidden) { return; }
 
         var buttons = document.createElement('div');
         buttons.className = 'buttons';
@@ -217,7 +177,7 @@ document.addEventListener('DOMContentLoaded', function() {
         // add expand button
         pre_block.prepend(buttons);
 
-        pre_block.querySelector('.buttons').addEventListener('click', function(e) {
+        pre_block.querySelector('.buttons').addEventListener('click', function (e) {
             if (e.target.classList.contains('fa-expand')) {
                 var lines = pre_block.querySelectorAll('span.hidden');
 
@@ -225,7 +185,7 @@ document.addEventListener('DOMContentLoaded', function() {
                 e.target.classList.add('fa-compress');
                 e.target.title = 'Hide lines';
 
-                Array.from(lines).forEach(function(line) {
+                Array.from(lines).forEach(function (line) {
                     line.classList.remove('hidden');
                     line.classList.add('unhidden');
                 });
@@ -236,7 +196,7 @@ document.addEventListener('DOMContentLoaded', function() {
                 e.target.classList.add('fa-expand');
                 e.target.title = 'Show hidden lines';
 
-                Array.from(lines).forEach(function(line) {
+                Array.from(lines).forEach(function (line) {
                     line.classList.remove('unhidden');
                     line.classList.add('hidden');
                 });
@@ -244,11 +204,11 @@ document.addEventListener('DOMContentLoaded', function() {
         });
     });
 
-    Array.from(document.querySelectorAll('pre code')).forEach(function(block) {
+    Array.from(document.querySelectorAll('pre code')).forEach(function (block) {
         var pre_block = block.parentNode;
-        if( !pre_block.classList.contains('playpen') ) {
+        if (!pre_block.classList.contains('playpen')) {
             var buttons = pre_block.querySelector(".buttons");
-            if(!buttons) {
+            if (!buttons) {
                 buttons = document.createElement('div');
                 buttons.className = 'buttons';
                 pre_block.prepend(buttons);
@@ -260,17 +220,14 @@ document.addEventListener('DOMContentLoaded', function() {
             clipButton.innerHTML = '<i class=\"tooltiptext\"></i>';
 
             buttons.prepend(clipButton);
-            clipButton.addEventListener('mouseout', function(e){
-                hideTooltip(e.currentTarget);
-            });
         }
     });
 
     // Process playpen code blocks
-    Array.from(document.querySelectorAll(".playpen")).forEach(function(pre_block){
+    Array.from(document.querySelectorAll(".playpen")).forEach(function (pre_block) {
         // Add play button
         var buttons = pre_block.querySelector(".buttons");
-        if(!buttons) {
+        if (!buttons) {
             buttons = document.createElement('div');
             buttons.className = 'buttons';
             pre_block.prepend(buttons);
@@ -289,12 +246,9 @@ document.addEventListener('DOMContentLoaded', function() {
         buttons.prepend(runCodeButton);
         buttons.prepend(copyCodeClipboardButton);
 
-        runCodeButton.addEventListener('click', function(e){
+        runCodeButton.addEventListener('click', function (e) {
             run_rust_code(pre_block);
         });
-        copyCodeClipboardButton.addEventListener('mouseout', function(e){
-            hideTooltip(e.currentTarget);
-        });
 
         let code_block = pre_block.querySelector("code");
         if (window.ace && code_block.classList.contains("editable")) {
@@ -304,7 +258,7 @@ document.addEventListener('DOMContentLoaded', function() {
 
             buttons.prepend(undoChangesButton);
 
-            undoChangesButton.addEventListener('click', function() {
+            undoChangesButton.addEventListener('click', function () {
                 let editor = window.ace.edit(code_block);
                 editor.setValue(editor.originalCode);
                 editor.clearSelection();
@@ -312,195 +266,247 @@ document.addEventListener('DOMContentLoaded', function() {
         }
     });
 
-    var clipboardSnippets = new Clipboard('.clip-button', {
-        text: function(trigger) {
-            hideTooltip(trigger);
-            let playpen = trigger.closest("pre");
-            return playpen_text(playpen);
-        }
-    });
-    clipboardSnippets.on('success', function(e) {
-            e.clearSelection();
-            showTooltip(e.trigger, "Copied!");
-    });
-    clipboardSnippets.on('error', function(e) {
-            showTooltip(e.trigger, "Clipboard error!");
-    });
-
-    var request = fetch("https://play.rust-lang.org/meta/crates", {
-        headers: {
-            'Content-Type': "application/json",
-        },
-        method: 'POST',
-        mode: 'cors',
-    });
-
     request
-        .then(function(response) { return response.json(); })
+        .then(function (response) { return response.json(); })
-        .then(function(response) {
+        .then(function (response) {
             // get list of crates available in the rust playground
-            let playground_crates = response.crates.map(function(item) {return item["id"];} );
+            let playground_crates = response.crates.map(function (item) { return item["id"]; });
-            Array.from(document.querySelectorAll(".playpen")).forEach(function(block) {
+            Array.from(document.querySelectorAll(".playpen")).forEach(function (block) {
                 handle_crate_list_update(block, playground_crates);
             });
         });
 
-});
+})();
 
-function playpen_text(playpen) {
+(function themes() {
-    let code_block = playpen.querySelector("code");
+    var themeToggleButton = document.getElementById('theme-toggle');
+    var themePopup = document.getElementById('theme-list');
+    var themeColorMetaTag = document.querySelector('meta[name="theme-color"]');
+    var stylesheets = {
+        ayuHighlight: document.querySelector("[href='ayu-highlight.css']"),
+        tomorrowNight: document.querySelector("[href='tomorrow-night.css']"),
+        highlight: document.querySelector("[href='highlight.css']"),
+    };
 
-    if (window.ace && code_block.classList.contains("editable")) {
+    function showThemes() {
-        let editor = window.ace.edit(code_block);
-        return editor.getValue();
-    } else {
-        return code_block.textContent;
-    }
-}
-
-function handle_crate_list_update(playpen_block, playground_crates) {
-    // update the play buttons after receiving the response
-    update_play_button(playpen_block, playground_crates);
-
-    // and install on change listener to dynamically update ACE editors
-    if (window.ace) {
-        let code_block = playpen_block.querySelector("code");
-        if (code_block.classList.contains("editable")) {
-            let editor = window.ace.edit(code_block);
-            editor.addEventListener("change", function(e){
-                update_play_button(playpen_block, playground_crates);
-            });
-        }
-    }
-}
-
-// updates the visibility of play button based on `no_run` class and
-// used crates vs ones available on http://play.rust-lang.org
-function update_play_button(pre_block, playground_crates) {
-    var play_button = pre_block.querySelector(".play-button");
-
-    // skip if code is `no_run`
-    if (pre_block.querySelector('code').classList.contains("no_run")) {
-        play_button.classList.add("hidden");
-        return;
-    }
-
-    // get list of `extern crate`'s from snippet
-    var txt = playpen_text(pre_block);
-    var re = /extern\s+crate\s+([a-zA-Z_0-9]+)\s*;/g;
-    var snippet_crates = [];
-    while (item = re.exec(txt)) {
-        snippet_crates.push(item[1]);
-    }
-
-    // check if all used crates are available on play.rust-lang.org
-    var all_available = snippet_crates.every(function(elem) {
-        return playground_crates.indexOf(elem) > -1;
-    });
-
-    if (all_available) {
-        play_button.classList.remove("hidden");
-    } else {
-        play_button.classList.add("hidden");
-    }
-}
-
-function hideTooltip(elem) {
-    elem.firstChild.innerText="";
-    elem.className = 'fa fa-copy clip-button';
-}
-
-function showTooltip(elem, msg) {
-    elem.firstChild.innerText=msg;
-    elem.className = 'fa fa-copy tooltipped';
-}
-
-function sidebarToggle() {
-    var html = document.querySelector("html");
-    if (html.classList.contains("sidebar-hidden")) {
-        showSidebar();
-    } else if (html.classList.contains("sidebar-visible")) {
-        hideSidebar();
-    } else {
-        if (getComputedStyle(sidebar)['transform'] === 'none'){
-            hideSidebar();
-        } else {
-            showSidebar();
-        }
-    }
-}
-
-function showThemes() {
         themePopup.style.display = 'block';
         themeToggleButton.setAttribute('aria-expanded', true);
-}
+    }
 
-function hideThemes() {
+    function hideThemes() {
         themePopup.style.display = 'none';
         themeToggleButton.setAttribute('aria-expanded', false);
-}
+    }
 
-function showSidebar() {
+    function set_theme(theme) {
+        let ace_theme;
+
+        if (theme == 'coal' || theme == 'navy') {
+            stylesheets.ayuHighlight.disabled = true;
+            stylesheets.tomorrowNight.disabled = false;
+            stylesheets.highlight.disabled = true;
+
+            ace_theme = "ace/theme/tomorrow_night";
+        } else if (theme == 'ayu') {
+            stylesheets.ayuHighlight.disabled = false;
+            stylesheets.tomorrowNight.disabled = true;
+            stylesheets.highlight.disabled = true;
+
+            ace_theme = "ace/theme/tomorrow_night";
+        } else {
+            stylesheets.ayuHighlight.disabled = true;
+            stylesheets.tomorrowNight.disabled = true;
+            stylesheets.highlight.disabled = false;
+
+            ace_theme = "ace/theme/dawn";
+        }
+
+        setTimeout(function () {
+            themeColorMetaTag.content = getComputedStyle(document.body).backgroundColor;
+        }, 1);
+
+        if (window.ace && window.editors) {
+            window.editors.forEach(function (editor) {
+                editor.setTheme(ace_theme);
+            });
+        }
+
+        store.set('mdbook-theme', theme);
+
+        document.body.className = theme;
+    }
+
+    // Set theme
+    var theme = store.get('mdbook-theme');
+    if (theme === null || theme === undefined) { theme = 'light'; }
+
+    set_theme(theme);
+
+    themeToggleButton.addEventListener('click', function () {
+        if (themePopup.style.display === 'block') {
+            hideThemes();
+        } else {
+            showThemes();
+        }
+    });
+
+    themePopup.addEventListener('click', function (e) {
+        var theme = e.target.id || e.target.parentElement.id;
+        set_theme(theme);
+    });
+
+    // Hide theme selector popup when clicking outside of it
+    document.addEventListener('click', function (event) {
+        if (themePopup.style.display === 'block' && !themeToggleButton.contains(event.target) && !themePopup.contains(event.target)) {
+            hideThemes();
+        }
+    });
+
+    document.addEventListener('keydown', function (e) {
+        switch (e.key) {
+            case 'Escape':
+                e.preventDefault();
+                hideThemes();
+                break;
+        }
+    });
+})();
+
+(function sidebar() {
+    var html = document.querySelector("html");
+    var sidebar = document.getElementById("sidebar");
+    var sidebarLinks = document.querySelectorAll('#sidebar a');
+    var sidebarToggleButton = document.getElementById("sidebar-toggle");
+    var firstContact = null;
+
+    function showSidebar() {
         html.classList.remove('sidebar-hidden')
         html.classList.add('sidebar-visible');
-    Array.from(sidebarLinks).forEach(function(link) {
+        Array.from(sidebarLinks).forEach(function (link) {
             link.setAttribute('tabIndex', 0);
         });
         sidebarToggleButton.setAttribute('aria-expanded', true);
         sidebar.setAttribute('aria-hidden', false);
         store.set('mdbook-sidebar', 'visible');
-}
+    }
 
-function hideSidebar() {
+    function hideSidebar() {
         html.classList.remove('sidebar-visible')
         html.classList.add('sidebar-hidden');
-    Array.from(sidebarLinks).forEach(function(link) {
+        Array.from(sidebarLinks).forEach(function (link) {
             link.setAttribute('tabIndex', -1);
         });
         sidebarToggleButton.setAttribute('aria-expanded', false);
         sidebar.setAttribute('aria-hidden', true);
         store.set('mdbook-sidebar', 'hidden');
-}
-
-function run_rust_code(code_block) {
-    var result_block = code_block.querySelector(".result");
-    if(!result_block) {
-        result_block = document.createElement('code');
-        result_block.className = 'result hljs language-bash';
-
-        code_block.append(result_block);
     }
 
-    let text = playpen_text(code_block);
+    // Toggle sidebar
-    
+    sidebarToggleButton.addEventListener('click', function sidebarToggle() {
-    var params = {
+        if (html.classList.contains("sidebar-hidden")) {
-	channel: "stable",
+            showSidebar();
-	mode: "debug",
+        } else if (html.classList.contains("sidebar-visible")) {
-	crateType: "bin",
+            hideSidebar();
-	tests: false,
+        } else {
-	code: text,
+            if (getComputedStyle(sidebar)['transform'] === 'none') {
+                hideSidebar();
+            } else {
+                showSidebar();
             }
-
-    if(text.indexOf("#![feature") !== -1) {
-        params.channel = "nightly";
         }
-
-    result_block.innerText = "Running...";
-
-    var request = fetch("https://play.rust-lang.org/execute", {
-        headers: {
-            'Content-Type': "application/json",
-        },
-        method: 'POST',
-        mode: 'cors',
-        body: JSON.stringify(params)
     });
 
-    request
+    document.addEventListener('touchstart', function (e) {
-        .then(function(response) { return response.json(); })
+        firstContact = {
-        .then(function(response) { result_block.innerText = response.success ? response.stdout : response.stderr; })
+            x: e.touches[0].clientX,
-        .catch(function(error) { result_block.innerText = "Playground communication" + error.message; });
+            time: Date.now()
-}
+        };
+    });
+
+    document.addEventListener('touchmove', function (e) {
+        if (!firstContact)
+            return;
+
+        var curX = e.touches[0].clientX;
+        var xDiff = curX - firstContact.x,
+            tDiff = Date.now() - firstContact.time;
+
+        if (tDiff < 250 && Math.abs(xDiff) >= 150) {
+            if (xDiff >= 0 && firstContact.x < Math.min(document.body.clientWidth * 0.25, 300))
+                showSidebar();
+            else if (xDiff < 0 && curX < 300)
+                hideSidebar();
+
+            firstContact = null;
+        }
+    });
+
+    // Scroll sidebar to current active section
+    var activeSection = sidebar.querySelector(".active");
+    if (activeSection) {
+        sidebar.scrollTop = activeSection.offsetTop;
+    }
+})();
+
+(function chapterNavigation() {
+    document.addEventListener('keydown', function (e) {
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
+
+        switch (e.key) {
+            case 'ArrowRight':
+                e.preventDefault();
+                var nextButton = document.querySelector('.nav-chapters.next');
+                if (nextButton) {
+                    window.location.href = nextButton.href;
+                }
+                break;
+            case 'ArrowLeft':
+                e.preventDefault();
+                var previousButton = document.querySelector('.nav-chapters.previous');
+                if (previousButton) {
+                    window.location.href = previousButton.href;
+                }
+                break;
+        }
+    });
+})();
+
+(function clipboard() {
+    var clipButtons = document.querySelectorAll('.clip-button');
+
+    function hideTooltip(elem) {
+        elem.firstChild.innerText = "";
+        elem.className = 'fa fa-copy clip-button';
+    }
+
+    function showTooltip(elem, msg) {
+        elem.firstChild.innerText = msg;
+        elem.className = 'fa fa-copy tooltipped';
+    }
+
+    var clipboardSnippets = new Clipboard('.clip-button', {
+        text: function (trigger) {
+            hideTooltip(trigger);
+            let playpen = trigger.closest("pre");
+            return playpen_text(playpen);
+        }
+    });
+
+    Array.from(clipButtons).forEach(function (clipButton) {
+        clipButton.addEventListener('mouseout', function (e) {
+            hideTooltip(e.currentTarget);
+        });
+    });
+
+    clipboardSnippets.on('success', function (e) {
+        e.clearSelection();
+        showTooltip(e.trigger, "Copied!");
+    });
+
+    clipboardSnippets.on('error', function (e) {
+        showTooltip(e.trigger, "Clipboard error!");
+    });
+})();
 
 (function autoHideMenu() {
     var scrollingContainer = document.querySelector('html');
@@ -508,7 +514,7 @@ function run_rust_code(code_block) {
 
     var previousScrollTop = scrollingContainer.scrollTop;
 
-    document.addEventListener('scroll', function() {
+    document.addEventListener('scroll', function () {
         if (menu.classList.contains('folded') && scrollingContainer.scrollTop < previousScrollTop) {
             menu.classList.remove('folded');
         } else if (!menu.classList.contains('folded') && scrollingContainer.scrollTop > previousScrollTop) {
@@ -524,6 +530,5 @@ function run_rust_code(code_block) {
         }
 
         previousScrollTop = scrollingContainer.scrollTop;
-        hideThemes();
     }, { passive: true });
 })();