Added support for code-block delimiter and code fragment highlights.

This commit add support for a new code-block delimiter that provides a simple way to inject any source code file found within the repo as a Markdown code-block on a presentation slide. The delimiter syntax looks as follows:

—?code=path/to/source/code.file

This commit also introduces support for code fragment highlighting. The CF-marker syntax, one or more of which must follow a code-block in your markdown, looks as follows:

@[fragment-range](optional-note)

Where fragment-range identifies a single line number, @[1], or a range of numbers, @[5-10]. The optional note is plain text that is displayed on the slide below the code-block when the fragment is in focus.

app/Module.java

@@ -51,6 +51,7 @@ public class Module extends AbstractModule {
         bind(ImageService.class).asEagerSingleton();
         bind(VideoService.class).asEagerSingleton();
         bind(GISTService.class).asEagerSingleton();
+        bind(CodeService.class).asEagerSingleton();
         bind(ShortcutsService.class).asEagerSingleton();
         bind(WebService.class).asEagerSingleton();
         bind(ComposableService.class).asEagerSingleton();

app/com/gitpitch/models/MarkdownModel.java

@@ -28,6 +28,7 @@ import com.gitpitch.utils.*;
 import com.gitpitch.services.ImageService;
 import com.gitpitch.services.VideoService;
 import com.gitpitch.services.GISTService;
+import com.gitpitch.services.CodeService;
 import com.gitpitch.services.ShortcutsService;
 import org.apache.commons.io.FilenameUtils;
 import com.google.inject.assistedinject.Assisted;
@@ -53,6 +54,7 @@ public class MarkdownModel implements Markdown {
     private final ImageService imageService;
     private final VideoService videoService;
     private final GISTService  gistService;
+    private final CodeService  codeService;
     private final ShortcutsService shortcutsService;
     private final MarkdownRenderer mrndr;
     private final String markdown;
@@ -63,12 +65,14 @@ public class MarkdownModel implements Markdown {
     public MarkdownModel(ImageService imageService,
                          VideoService videoService,
                          GISTService  gistService,
+                         CodeService  codeService,
                          ShortcutsService  shortcutsService,
                          @Nullable @Assisted MarkdownRenderer mrndr) {
 
         this.imageService = imageService;
         this.videoService = videoService;
         this.gistService  = gistService;
+        this.codeService  = codeService;
         this.shortcutsService = shortcutsService;
         this.mrndr = mrndr;
 
@@ -122,7 +126,7 @@ public class MarkdownModel implements Markdown {
     }
 
     /*
-     * Process text, image, video and gist content
+     * Process text, image, video, gist, and code content
      * in PITCHME.md for online viewing.
      */
     private String process(String md,
@@ -175,11 +179,9 @@ public class MarkdownModel implements Markdown {
                         .toString();
 
             } else if (gistDelimFound(md)) {
-
+                return gistService.build(md, pp, yOpts, this);
-                String gist = new StringBuffer(gistService.build(md,
+            } else if(codeDelimFound(md)) {
-                                                pp, yOpts, this)).toString();
+                return codeService.build(md, pp, yOpts, gitRawBase, this);
-                return gist;
-
             }
 
             if (yOpts != null && yOpts.hasImageBg()) {
@@ -253,8 +255,10 @@ public class MarkdownModel implements Markdown {
                 String absTagLink = gitRawBase + tagLink;
                 return md.replace(tagLink, absTagLink);
             }
-        } else if(shortcutsService.fragmentFound(md)) {
+        } else if(shortcutsService.listFragmentFound(md)) {
-            return shortcutsService.expandFragment(md);
+            return shortcutsService.expandListFragment(md);
+        } else if(shortcutsService.codeFragmentFound(md)) {
+            return shortcutsService.expandCodeFragment(md);
         } else {
 
             /*
@@ -269,7 +273,7 @@ public class MarkdownModel implements Markdown {
     }
 
     /*
-     * Process text, image, video and gist content
+     * Process text, image, video, gist, and code content
      * in PITCHME.md for offline viewing.
      */
     public String offline(String md) {
@@ -402,6 +406,10 @@ public class MarkdownModel implements Markdown {
         return md.startsWith(horizGISTDelim()) || md.startsWith(vertGISTDelim());
     }
 
+    private boolean codeDelimFound(String md) {
+        return md.startsWith(horizCodeDelim()) || md.startsWith(vertCodeDelim());
+    }
+
     private String delimiter(String md) {
         return (md.startsWith(hSlideDelim)) ? horizDelim() : vertDelim();
     }
@@ -579,6 +587,10 @@ public class MarkdownModel implements Markdown {
         return isHorizontal(md) ? horizGISTDelim() : vertGISTDelim();
     }
 
+    public String extractCodeDelim(String md) {
+        return isHorizontal(md) ? horizCodeDelim() : vertCodeDelim();
+    }
+
     /*
      * Generate a key for querying the cache for matching MarkdownModel.
      */
@@ -629,6 +641,14 @@ public class MarkdownModel implements Markdown {
         return vertDelim() + MD_VSLIDE_GIST;
     }
 
+    public String horizCodeDelim() {
+        return horizDelim() + MD_HSLIDE_CODE;
+    }
+
+    public String vertCodeDelim() {
+        return vertDelim() + MD_VSLIDE_CODE;
+    }
+
     /*
      * The initial releases of GitPitch used #HSLIDE and #VSLIDE
      * as default delimiters. To provide backwards compatability
@@ -677,8 +697,14 @@ public class MarkdownModel implements Markdown {
     public static final String MD_CLOSER = "\" -->";
     public static final String MD_SPACER = "\n";
     public static final String DATA_IMAGE_ATTR = "data-background-image=";
-    public static final String MD_FRAG_OPEN = "- ";
+    public static final String MD_LIST_FRAG_OPEN = "- ";
-    public static final String MD_FRAG_CLOSE = "|";
+    public static final String MD_LIST_FRAG_CLOSE = "|";
+    public static final String MD_CODE_FRAG_OPEN = "@[";
+    public static final String MD_CODE_FRAG_CLOSE = "]";
+    public static final String MD_CODE_FRAG_NOTE_OPEN = "(";
+    public static final String MD_CODE_FRAG_NOTE_CLOSE = ")";
+    public static final String MD_CODE_BLOCK_OPEN = "```";
+    public static final String MD_CODE_BLOCK_CLOSE = "```";
 
     private static final String MD_HSLIDE_IMAGE = "?image=";
     private static final String MD_VSLIDE_IMAGE = "?image=";
@@ -686,6 +712,8 @@ public class MarkdownModel implements Markdown {
     private static final String MD_VSLIDE_VIDEO = "?video=";
     private static final String MD_HSLIDE_GIST = "?gist=";
     private static final String MD_VSLIDE_GIST = "?gist=";
+    private static final String MD_HSLIDE_CODE = "?code=";
+    private static final String MD_VSLIDE_CODE = "?code=";
 
     private static final String SLASH = "/";
     private static final String PARAM_BRANCH = "?b=";

app/com/gitpitch/policies/Dependencies.java

@@ -40,6 +40,7 @@ public final class Dependencies {
     private final String fontawesomeVersion;
     private final String octiconsVersion;
     private final String highlightjsVersion;
+    private final Boolean highlightPluginEnabled;
 
     @Inject
     public Dependencies(Configuration cfg) {
@@ -51,6 +52,8 @@ public final class Dependencies {
         this.fontawesomeVersion = cfg.getString("gitpitch.dependency.fontawesome");
         this.octiconsVersion = cfg.getString("gitpitch.dependency.octicons");
         this.highlightjsVersion = cfg.getString("gitpitch.dependency.highlightjs");
+        this.highlightPluginEnabled =
+            cfg.getBoolean("gitpitch.dependency.highlight.plugin", false);
     }
 
     public String revealjs(boolean offline, String versionOverride) {
@@ -86,6 +89,10 @@ public final class Dependencies {
         return build(offline, GIPITCHIMG);
     }
 
+    public Boolean highlightPluginEnabled() {
+        return highlightPluginEnabled;
+    }
+
     private String build(boolean offline, String libName) {
 
         if(offline) {

app/com/gitpitch/services/CodeService.java

@@ -0,0 +1,153 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2016 David Russell
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.gitpitch.services;
+
+import com.gitpitch.models.MarkdownModel;
+import com.gitpitch.git.GRS;
+import com.gitpitch.git.GRSService;
+import com.gitpitch.git.GRSManager;
+import com.gitpitch.services.DiskService;
+import com.gitpitch.utils.PitchParams;
+import com.gitpitch.utils.YAMLOptions;
+import java.util.*;
+import java.nio.file.*;
+import javax.inject.*;
+import play.Logger;
+import play.Logger.ALogger;
+
+/*
+ * PITCHME.md code support service.
+ */
+@Singleton
+public class CodeService {
+
+    private final Logger.ALogger log = Logger.of(this.getClass());
+
+    private final GRSManager grsManager;
+    private final DiskService diskService;
+
+    @Inject
+    public CodeService(GRSManager grsManager,
+                       DiskService diskService) {
+
+        this.grsManager = grsManager;
+        this.diskService = diskService;
+    }
+
+    public String build(String md,
+                        PitchParams pp,
+                        YAMLOptions yOpts,
+                        String gitRawBase,
+                        MarkdownModel mdm) {
+
+        String codeBlock = mdm.extractCodeDelim(md);
+
+        try {
+
+            String codePath = extractCodePath(md, gitRawBase, mdm);
+
+            GRS grs = grsManager.get(pp);
+            GRSService grsService = grsManager.getService(grs);
+
+            int downStatus =
+                grsService.download(pp, SOURCE_CODE, codePath);
+
+            if(downStatus == 0) {
+                String code = diskService.asText(pp, SOURCE_CODE);
+                return buildCodeBlock(mdm.extractCodeDelim(md), code);
+            } else {
+                return buildCodeBlockError(mdm.extractCodeDelim(md),
+                                            extractPath(md, mdm));
+            }
+
+        } catch (Exception gex) {}
+        return codeBlock;
+    }
+
+    public String extractCodePath(String md,
+                                  String gitRawBase,
+                                  MarkdownModel mdm) {
+
+        String codePath = null;
+
+        try {
+
+            String delim = mdm.extractCodeDelim(md);
+            codePath = md.substring(delim.length());
+
+            if (!mdm.linkAbsolute(codePath)) {
+                codePath =
+                    new StringBuffer(gitRawBase).append(codePath)
+                                                .toString();
+            }
+
+        } catch (Exception pex) {
+            log.warn("extractCodePath: ex={}", pex);
+        }
+        return codePath;
+    }
+
+    private String extractPath(String md, MarkdownModel mdm) {
+        String path = null;
+
+        try {
+            String delim = mdm.extractCodeDelim(md);
+            path = md.substring(delim.length());
+        } catch (Exception pex) {
+            log.warn("extractPath: ex={}", pex);
+        }
+        return path;
+    }
+
+    private String buildCodeBlock(String delim, String code) {
+        return new StringBuffer(delim)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(MarkdownModel.MD_CODE_BLOCK_OPEN)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(code)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(MarkdownModel.MD_CODE_BLOCK_CLOSE)
+                                .append(MarkdownModel.MD_SPACER)
+                                .toString();
+   }
+
+   private String buildCodeBlockError(String delim, String codePath) {
+        return new StringBuffer(delim)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(SOURCE_CODE_DELIMITER)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(codePath)
+                                .append(MarkdownModel.MD_SPACER)
+                                .append(SOURCE_CODE_NOT_FOUND)
+                                .append(MarkdownModel.MD_SPACER)
+                                .toString();
+   }
+
+    private static final String SOURCE_CODE = "PITCHME.code";
+    private static final String SOURCE_CODE_DELIMITER =
+        "### Code Block Delimiter";
+    private static final String SOURCE_CODE_NOT_FOUND =
+        "### Source File Not Found";
+
+}

app/com/gitpitch/services/DiskService.java

@@ -91,6 +91,19 @@ public class DiskService {
         return asPath(pp, filename).toFile();
     }
 
+    /*
+     * Return text contents for file within PitchParams branch working directory.
+     */
+    public String asText(PitchParams pp,
+                         String filename) {
+        String text = "";
+        try {
+            Path filePath = asPath(pp, filename);
+            text = new String(Files.readAllBytes(filePath));
+        } catch(Exception tex) {}
+        return text;
+    }
+
     /*
      * Ensure PitchParams branch working directory exists.
      */

app/com/gitpitch/services/ShortcutsService.java

@@ -40,12 +40,23 @@ public class ShortcutsService {
 
     private final Logger.ALogger log = Logger.of(this.getClass());
 
-    public boolean fragmentFound(String md) {
+    public boolean listFragmentFound(String md) {
         boolean found = false;
         if(md != null) {
             String trimmed = md.trim();
-            if(trimmed.startsWith(MarkdownModel.MD_FRAG_OPEN) &&
+            if(trimmed.startsWith(MarkdownModel.MD_LIST_FRAG_OPEN) &&
-                trimmed.endsWith(MarkdownModel.MD_FRAG_CLOSE)) {
+                trimmed.endsWith(MarkdownModel.MD_LIST_FRAG_CLOSE)) {
+                found = true;
+            }
+        }
+        return found;
+    }
+
+    public boolean codeFragmentFound(String md) {
+        boolean found = false;
+        if(md != null) {
+            String trimmed = md.trim();
+            if(trimmed.startsWith(MarkdownModel.MD_CODE_FRAG_OPEN)) {
                 found = true;
             }
         }
@@ -53,14 +64,69 @@ public class ShortcutsService {
     }
 
     /*
-     * Expand shortcut syntax for fragment with fully expanded
+     * Expand shortcut syntax for list fragment with fully expanded
      * HTML comment syntax.
      */
-    public String expandFragment(String md) {
+    public String expandListFragment(String md) {
-        int fragCloseIdx = md.lastIndexOf(MarkdownModel.MD_FRAG_CLOSE);
+        int fragCloseIdx = md.lastIndexOf(MarkdownModel.MD_LIST_FRAG_CLOSE);
         return md.substring(0, fragCloseIdx) + FRAGMENT;
     }
 
+    /*
+     * Expand shortcut syntax for code fragment with fully expanded
+     * HTML span syntax with data-code-focus class.
+     */
+    public String expandCodeFragment(String md) {
+
+        try {
+            String codeFragRange = null;
+            String codeFragNote = null;
+
+            int codeFragStart =
+                md.indexOf(MarkdownModel.MD_CODE_FRAG_OPEN);
+            int codeFragEnd =
+                md.indexOf(MarkdownModel.MD_CODE_FRAG_CLOSE);
+
+            if(codeFragEnd > codeFragStart) {
+                codeFragRange =
+                    md.substring(codeFragStart+2, codeFragEnd);
+            }
+
+            int codeFragNoteStart =
+                md.indexOf(MarkdownModel.MD_CODE_FRAG_NOTE_OPEN);
+            int codeFragNoteEnd =
+                md.indexOf(MarkdownModel.MD_CODE_FRAG_NOTE_CLOSE);
+
+            if(codeFragNoteEnd > codeFragNoteStart) {
+                codeFragNote =
+                    md.substring(codeFragNoteStart+1, codeFragNoteEnd);
+            }
+
+            if(codeFragRange != null) {
+                md = buildCodeFragment(codeFragRange, codeFragNote);
+            }
+
+        } catch(Exception cfex) {
+        } finally {
+            return md;
+        }
+    }
+
+    /*
+     * Construct a HTML fragment for a code fragment based on the
+     * reveal-code-focus plugin syntax:
+     * <span class="fragment current-only" data-code-focus="1-9">Note</span>
+     */
+    private String buildCodeFragment(String range, String note) {
+        if(note == null) note = "";
+        return new StringBuffer(HTML_CODE_FRAG_OPEN)
+                .append(range)
+                .append(HTML_CODE_FRAG_CLOSE)
+                .append(note)
+                .append(HTML_CODE_FRAG_NOTE_CLOSE)
+                .toString();
+    }
+
     /*
      * Note, the space before opening bracket is intentional
      * so tag injection can happen directly alongside other
@@ -68,4 +134,8 @@ public class ShortcutsService {
      */
     private static final String FRAGMENT =
         " <!-- .element: class=\"fragment\" -->";
+    private static final String HTML_CODE_FRAG_OPEN =
+        "<span class=\"fragment current-only\" data-code-focus=\"";
+    private static final String HTML_CODE_FRAG_CLOSE = "\">";
+    private static final String HTML_CODE_FRAG_NOTE_CLOSE = "</span>";
 }

app/com/gitpitch/views/Slideshow.scala.html

@@ -22,6 +22,7 @@
     <link href="@deps.octicons(offline)/octicons.css" rel="stylesheet" type="text/css"/>
     <link href="@deps.fontawesome(offline)/css/font-awesome.min.css" rel="stylesheet" type="text/css"/>
     @SlideshowStyle()
+    @SlideshowCodeFragHighlightStyle()
     @if(ssm.hasThemeOverride()) {
     <style>
     @Html(ssm.fetchThemeOverride())

app/com/gitpitch/views/frags/SlideshowCodeFragHighlightStyle.scala.html

@@ -0,0 +1,23 @@
+    <style>
+      .reveal .slides section .fragment.current-only {
+        opacity: 1;
+        visibility: visible;
+        display: none;
+      }
+      .reveal .slides section .fragment.current-only.current-fragment {
+        display: block;
+      }
+      .line { display: block; }
+      .line.focus { background: #fdf6e3; color: #657b83; }
+      .line.focus .hljs-comment, .line.focus .hljs-quote { color: #93a1a1; }
+      .line.focus .hljs-keyword, .line.focus .hljs-selector-tag, .line.focus .hljs-addition { color: #859900; }
+      .line.focus .hljs-number, .line.focus .hljs-string, .line.focus .hljs-meta .hljs-meta-string, .line.focus .hljs-literal, .line.focus .hljs-doctag, .line.focus .hljs-regexp { color: #2aa198; }
+      .line.focus .hljs-title, .line.focus .hljs-section, .line.focus .hljs-name, .line.focus .hljs-selector-id, .line.focus .hljs-selector-class { color: #268bd2; }
+      .line.focus .hljs-attribute, .line.focus .hljs-attr, .line.focus .hljs-variable, .line.focus .hljs-template-variable, .line.focus .hljs-class .hljs-title, .line.focus .hljs-type { color: #b58900; }
+      .line.focus .hljs-symbol, .line.focus .hljs-bullet, .line.focus .hljs-subst, .line.focus .hljs-meta, .line.focus .hljs-meta .hljs-keyword, .line.focus .hljs-selector-attr, .line.focus .hljs-selector-pseudo, .line.focus .hljs-link { color: #cb4b16; }
+      .line.focus .hljs-built_in, .line.focus .hljs-deletion { color: #dc322f; }
+      .line.focus .hljs-formula { background: #eee8d5; }
+      .line.focus .hljs-emphasis { font-style: italic; }
+      .line.focus .hljs-strong { font-weight: bold; }
+      .yellow-slide .line.focus:nth-child(2) { background: yellow; }
+    </style>

app/com/gitpitch/views/frags/SlideshowReveal.scala.html

@@ -34,7 +34,16 @@
                 @if(offline) {
                 { src: "@deps.revealjs(offline, ssm.fetchRevealVersionOverride())/plugin/notes/notes.js", async: true },
                 }
+                @if(deps.highlightPluginEnabled()) {
                 { src: "@deps.revealjs(offline, ssm.fetchRevealVersionOverride())/plugin/highlight/highlight.js", async: true, callback: function() { hljs.initHighlightingOnLoad(); } },
+                } else {
+                { src: '@deps.highlightjs(offline)/highlight.js' },
+                { src: '@deps.highlightjs(offline)/reveal-code-focus.js',
+                  callback: function() {
+                    RevealCodeFocus();
+                  }
+                },
+                }
                 @if(ssm.mathEnabled()) {
                     { src: "@deps.revealjs(offline, ssm.fetchRevealVersionOverride())/plugin/math/math.js", async: true }
                 }

conf/application.conf

@@ -409,6 +409,9 @@ gitpitch {
     fontawesome = "4.6.3"
     octicons    = "3.5.0"
     highlightjs = "9.6.0"
+    highlight {
+        plugin = false
+    }
   }
 
   github {

public/libs/highlight.js/9.6.0/reveal-code-focus.js

@@ -0,0 +1,229 @@
+/*!
+ * reveal-code-focus 1.0.0
+ * Copyright 2015-2017 Benjamin Tan <https://demoneaux.github.io/>
+ * Available under MIT license <https://github.com/demoneaux/reveal-code-focus/blob/master/LICENSE>
+ */
+;(function(window, Reveal, hljs) {
+  if (typeof window.RevealCodeFocus == 'function') {
+    return;
+  }
+
+  var currentSlide, currentFragments, scrollToFocused = true, prevSlideData = null;
+
+  // Iterates through `array`, running `callback` for each `array` element.
+  function forEach(array, callback) {
+    var i = -1, length = array ? array.length : 0;
+    while (++i < length) {
+      callback(array[i]);
+    }
+  }
+
+  function indexOf(array, elem) {
+    var i = -1, length = array ? array.length : 0;
+    while (++i < length) {
+      if (array[i] === elem) {
+        return i;
+      }
+    }
+  }
+
+  function initialize(e) {
+    // Initialize code only once.
+    // TODO: figure out why `initialize` is being called twice.
+    if (initialize.ran) {
+      return;
+    }
+    initialize.ran = true;
+
+    // TODO: mark as parsed.
+    forEach(document.querySelectorAll('pre code'), function(element) {
+      // Trim whitespace if the `data-trim` attribute is present.
+      if (element.hasAttribute('data-trim') && typeof element.innerHTML.trim == 'function') {
+        element.innerHTML = element.innerHTML.trim();
+      }
+
+      // Highlight code using highlight.js.
+      hljs.highlightBlock(element);
+
+      // Split highlighted code into lines.
+      var openTags = [], reHtmlTag = /<(\/?)span(?:\s+(?:class=(['"])hljs-.*?\2)?\s*|\s*)>/g;
+      element.innerHTML = element.innerHTML.replace(/(.*?)\r?\n/g, function(_, string) {
+        if (!string) {
+          return '<span class=line>&nbsp;</span>';
+        }
+        var openTag, stringPrepend;
+        // Re-open all tags that were previously closed.
+        if (openTags.length) {
+          stringPrepend = openTags.join('');
+        }
+        // Match all HTML `<span>` tags.
+        reHtmlTag.lastIndex = 0;
+        while (openTag = reHtmlTag.exec(string)) {
+          // If it is a closing tag, remove the opening tag from the list.
+          if (openTag[1]) {
+            openTags.pop();
+          }
+          // Otherwise if it is an opening tag, push it to the list.
+          else {
+            openTags.push(openTag[0]);
+          }
+        }
+        // Close all opened tags, so that strings can be wrapped with `span.line`.
+        if (openTags.length) {
+          string += Array(openTags.length + 1).join('</span>');
+        }
+        if (stringPrepend) {
+          string = stringPrepend + string;
+        }
+        return '<span class=line>' + string + '</span>';
+      });
+    });
+
+    Reveal.addEventListener('slidechanged', updateCurrentSlide);
+
+    Reveal.addEventListener('fragmentshown', function(e) {
+      focusFragment(e.fragment);
+    });
+
+    // TODO: make this configurable.
+    // When a fragment is hidden, clear the current focused fragment,
+    // and focus on the previous fragment.
+    Reveal.addEventListener('fragmenthidden', function(e) {
+      var index = indexOf(currentFragments, e.fragment);
+      focusFragment(currentFragments[index - 1]);
+    });
+
+    updateCurrentSlide(e);
+  }
+  initialize.ran = false;
+
+  function updateCurrentSlide(e) {
+    currentSlide = e.currentSlide;
+    currentFragments = currentSlide.getElementsByClassName('fragment');
+    clearPreviousFocus();
+
+    // If moving back to a previous slide…
+    if (
+        currentFragments.length &&
+        prevSlideData &&
+        (
+          prevSlideData.indexh > e.indexh ||
+          (prevSlideData.indexh == e.indexh && prevSlideData.indexv > e.indexv)
+        )
+    ) {
+      // …return to the last fragment and highlight the code.
+      while (Reveal.nextFragment()) {}
+      var currentFragment = currentFragments[currentFragments.length - 1];
+      currentFragment.classList.add('current-fragment');
+      focusFragment(currentFragment);
+    }
+
+    // Update previous slide information.
+    prevSlideData = {
+      'indexh': e.indexh,
+      'indexv': e.indexv
+    };
+  }
+
+  // Removes any previously focused lines.
+  function clearPreviousFocus() {
+    forEach(currentSlide.querySelectorAll('pre code .line.focus'), function(line) {
+      line.classList.remove('focus');
+    });
+  }
+
+  function focusFragment(fragment) {
+    clearPreviousFocus();
+    if (!fragment) {
+      return;
+    }
+
+    var lines = fragment.getAttribute('data-code-focus');
+    if (!lines) {
+      return;
+    }
+
+    var codeBlock = parseInt(fragment.getAttribute('data-code-block'));
+    if (isNaN(codeBlock)) {
+      codeBlock = 1;
+    }
+
+    var preElems = currentSlide.querySelectorAll('pre');
+    if (!preElems.length) {
+      return;
+    }
+
+    var pre = preElems[codeBlock - 1];
+    var code = pre.querySelectorAll('code .line');
+    if (!code.length) {
+      return;
+    }
+
+    var topLineNumber, bottomLineNumber;
+
+    forEach(lines.split(','), function(line) {
+      lines = line.split('-');
+      if (lines.length == 1) {
+        focusLine(lines[0]);
+      } else {
+        var i = lines[0] - 1, j = lines[1];
+
+        while (++i <= j) {
+          focusLine(i);
+        }
+      }
+    });
+
+    function focusLine(lineNumber) {
+      // Convert from 1-based index to 0-based index.
+      lineNumber -= 1;
+
+      var line = code[lineNumber];
+      if (!line) {
+        return;
+      }
+
+      line.classList.add('focus');
+
+      if (scrollToFocused) {
+        if (topLineNumber == null) {
+          topLineNumber = bottomLineNumber = lineNumber;
+        } else {
+          if (lineNumber < topLineNumber) {
+            topLineNumber = lineNumber;
+          }
+          if (lineNumber > bottomLineNumber) {
+            bottomLineNumber = lineNumber;
+          }
+        }
+      }
+    }
+
+    if (scrollToFocused && topLineNumber != null) {
+      var topLine =  code[topLineNumber];
+      var bottomLine = code[bottomLineNumber];
+      var codeParent = topLine.parentNode;
+      var scrollTop = topLine.offsetTop;
+      var scrollBottom = bottomLine.offsetTop + bottomLine.clientHeight;
+      codeParent.scrollTop = scrollTop - (codeParent.clientHeight - (scrollBottom - scrollTop)) / 2;
+    }
+  }
+
+  function RevealCodeFocus(options) {
+    options || (options = {
+      'scrollToFocused': true
+    });
+
+    if (options.scrollToFocused != null) {
+      scrollToFocused = options.scrollToFocused;
+    }
+
+    if (Reveal.isReady()) {
+      initialize({ 'currentSlide': Reveal.getCurrentSlide() });
+    } else {
+      Reveal.addEventListener('ready', initialize);
+    }
+  }
+
+  window.RevealCodeFocus = RevealCodeFocus;
+}(this, this.Reveal, this.hljs));