Commenting on image diffs

21 files changed, 690 insertions, 51 deletions

diff --git a/app/assets/javascripts/commit.js b/app/assets/javascripts/commit.js
deleted file mode 100644
index 5f637524e30..00000000000
--- a/app/assets/javascripts/commit.js
+++ /dev/null
@@ -1,12 +0,0 @@
-/* eslint-disable func-names, space-before-function-paren, wrap-iife */
-/* global CommitFile */
-
-window.Commit = (function() {
-  function Commit() {
-    $('.files .diff-file').each(function() {
-      return new CommitFile(this);
-    });
-  }
-
-  return Commit;
-})();
diff --git a/app/assets/javascripts/commit/file.js b/app/assets/javascripts/commit/file.js
deleted file mode 100644
index ee087c978dd..00000000000
--- a/app/assets/javascripts/commit/file.js
+++ /dev/null
@@ -1,14 +0,0 @@
-/* eslint-disable func-names, space-before-function-paren, wrap-iife, no-new */
-/* global ImageFile */
-
-(function() {
-  this.CommitFile = (function() {
-    function CommitFile(file) {
-      if ($('.image', file).length) {
-        new gl.ImageFile(file);
-      }
-    }
-
-    return CommitFile;
-  })();
-}).call(window);
diff --git a/app/assets/javascripts/commit/image_file.js b/app/assets/javascripts/commit/image_file.js
index 4763985c802..e7adf8814b8 100644
--- a/app/assets/javascripts/commit/image_file.js
+++ b/app/assets/javascripts/commit/image_file.js
@@ -1,4 +1,6 @@
 /* eslint-disable func-names, space-before-function-paren, wrap-iife, no-var, no-use-before-define, prefer-arrow-callback, no-else-return, consistent-return, prefer-template, quotes, one-var, one-var-declaration-per-line, no-unused-vars, no-return-assign, comma-dangle, quote-props, no-unused-expressions, no-sequences, object-shorthand, max-len */
+import 'vendor/jquery.waitforimages';
+
 (function() {
   gl.ImageFile = (function() {
     var prepareFrames;
@@ -17,15 +19,10 @@
 
             // Load two-up view after images are loaded
             // so that we can display the correct width and height information
-            const images = $('.two-up.view img', _this.file);
-            let loadedCount = 0;
-
-            images.on('load', () => {
-              loadedCount += 1;
+            const $images = $('.two-up.view img', _this.file);
 
-              if (loadedCount === images.length) {
-                _this.initView('two-up');
-              }
+            $images.waitForImages(function() {
+              _this.initView('two-up');
             });
           });
         };
diff --git a/app/assets/javascripts/diff.js b/app/assets/javascripts/diff.js
index 9ddfdb6ae21..6c78662baa7 100644
--- a/app/assets/javascripts/diff.js
+++ b/app/assets/javascripts/diff.js
@@ -3,6 +3,7 @@
 import './lib/utils/url_utility';
 import FilesCommentButton from './files_comment_button';
 import SingleFileDiff from './single_file_diff';
+import imageDiffHelper from './image_diff/helpers/index';
 
 const UNFOLD_COUNT = 20;
 let isBound = false;
@@ -20,7 +21,9 @@ class Diff {
     const tab = document.getElementById('diffs');
     if (!tab || (tab && tab.dataset && tab.dataset.isLocked !== '')) FilesCommentButton.init($diffFile);
 
-    $diffFile.each((index, file) => new gl.ImageFile(file));
+    const firstFile = $('.files').first().get(0);
+    const canCreateNote = firstFile && firstFile.hasAttribute('data-can-create-note');
+    $diffFile.each((index, file) => imageDiffHelper.initImageDiff(file, canCreateNote));
 
     if (!isBound) {
       $(document)
diff --git a/app/assets/javascripts/diff_notes/components/jump_to_discussion.js b/app/assets/javascripts/diff_notes/components/jump_to_discussion.js
index 497c23f014f..e77910a83d4 100644
--- a/app/assets/javascripts/diff_notes/components/jump_to_discussion.js
+++ b/app/assets/javascripts/diff_notes/components/jump_to_discussion.js
@@ -171,7 +171,14 @@ const JumpToDiscussion = Vue.extend({
         // When jumping between unresolved discussions on the diffs tab, we show them.
         $target.closest(".content").show();
 
-        $target = $target.closest("tr.notes_holder");
+        const $notesHolder = $target.closest("tr.notes_holder");
+
+        // Image diff discussions does not use notes_holder
+        // so we should keep original $target value in those cases
+        if ($notesHolder.length > 0) {
+          $target = $notesHolder;
+        }
+
         $target.show();
 
         // If we are on the diffs tab, we don't scroll to the discussion itself, but to
diff --git a/app/assets/javascripts/dispatcher.js b/app/assets/javascripts/dispatcher.js
index e4e7cae540e..33271c25146 100644
--- a/app/assets/javascripts/dispatcher.js
+++ b/app/assets/javascripts/dispatcher.js
@@ -7,7 +7,6 @@
 /* global IssuableForm */
 /* global LabelsSelect */
 /* global MilestoneSelect */
-/* global Commit */
 /* global CommitsList */
 /* global NewBranchForm */
 /* global NotificationsForm */
@@ -316,7 +315,6 @@ import { ajaxGet, convertPermissionToBoolean } from './lib/utils/common_utils';
           new gl.Activities();
           break;
         case 'projects:commit:show':
-          new Commit();
           new gl.Diff();
           new ZenMode();
           shortcut_handler = new ShortcutsNavigation();
diff --git a/app/assets/javascripts/image_diff/helpers/badge_helper.js b/app/assets/javascripts/image_diff/helpers/badge_helper.js
new file mode 100644
index 00000000000..6a6a668308d
--- /dev/null
+++ b/app/assets/javascripts/image_diff/helpers/badge_helper.js
@@ -0,0 +1,38 @@
+export function createImageBadge(noteId, { x, y }, classNames = []) {
+  const buttonEl = document.createElement('button');
+  const classList = classNames.concat(['js-image-badge']);
+  classList.forEach(className => buttonEl.classList.add(className));
+  buttonEl.setAttribute('type', 'button');
+  buttonEl.setAttribute('disabled', true);
+  buttonEl.dataset.noteId = noteId;
+  buttonEl.style.left = `${x}px`;
+  buttonEl.style.top = `${y}px`;
+
+  return buttonEl;
+}
+
+export function addImageBadge(containerEl, { coordinate, badgeText, noteId }) {
+  const buttonEl = createImageBadge(noteId, coordinate, ['badge']);
+  buttonEl.innerText = badgeText;
+
+  containerEl.appendChild(buttonEl);
+}
+
+export function addImageCommentBadge(containerEl, { coordinate, noteId }) {
+  const buttonEl = createImageBadge(noteId, coordinate, ['image-comment-badge', 'inverted']);
+  const iconEl = document.createElement('i');
+  iconEl.className = 'fa fa-comment-o';
+  iconEl.setAttribute('aria-label', 'comment');
+
+  buttonEl.appendChild(iconEl);
+  containerEl.appendChild(buttonEl);
+}
+
+export function addAvatarBadge(el, event) {
+  const { noteId, badgeNumber } = event.detail;
+
+  // Add badge to new comment
+  const avatarBadgeEl = el.querySelector(`#${noteId} .badge`);
+  avatarBadgeEl.innerText = badgeNumber;
+  avatarBadgeEl.classList.remove('hidden');
+}
diff --git a/app/assets/javascripts/image_diff/helpers/comment_indicator_helper.js b/app/assets/javascripts/image_diff/helpers/comment_indicator_helper.js
new file mode 100644
index 00000000000..05000c73052
--- /dev/null
+++ b/app/assets/javascripts/image_diff/helpers/comment_indicator_helper.js
@@ -0,0 +1,58 @@
+export function addCommentIndicator(containerEl, { x, y }) {
+  const buttonEl = document.createElement('button');
+  buttonEl.classList.add('btn-transparent');
+  buttonEl.classList.add('comment-indicator');
+  buttonEl.setAttribute('type', 'button');
+  buttonEl.style.left = `${x}px`;
+  buttonEl.style.top = `${y}px`;
+
+  buttonEl.innerHTML = gl.utils.spriteIcon('image-comment-dark');
+
+  containerEl.appendChild(buttonEl);
+}
+
+export function removeCommentIndicator(imageFrameEl) {
+  const commentIndicatorEl = imageFrameEl.querySelector('.comment-indicator');
+  const imageEl = imageFrameEl.querySelector('img');
+  const willRemove = !!commentIndicatorEl;
+  let meta = {};
+
+  if (willRemove) {
+    meta = {
+      x: parseInt(commentIndicatorEl.style.left, 10),
+      y: parseInt(commentIndicatorEl.style.top, 10),
+      image: {
+        width: imageEl.width,
+        height: imageEl.height,
+      },
+    };
+
+    commentIndicatorEl.remove();
+  }
+
+  return Object.assign({}, meta, {
+    removed: willRemove,
+  });
+}
+
+export function showCommentIndicator(imageFrameEl, coordinate) {
+  const { x, y } = coordinate;
+  const commentIndicatorEl = imageFrameEl.querySelector('.comment-indicator');
+
+  if (commentIndicatorEl) {
+    commentIndicatorEl.style.left = `${x}px`;
+    commentIndicatorEl.style.top = `${y}px`;
+  } else {
+    addCommentIndicator(imageFrameEl, coordinate);
+  }
+}
+
+export function commentIndicatorOnClick(event) {
+  // Prevent from triggering onAddImageDiffNote in notes.js
+  event.stopPropagation();
+
+  const buttonEl = event.currentTarget;
+  const diffViewerEl = buttonEl.closest('.diff-viewer');
+  const textareaEl = diffViewerEl.querySelector('.note-container .note-textarea');
+  textareaEl.focus();
+}
diff --git a/app/assets/javascripts/image_diff/helpers/dom_helper.js b/app/assets/javascripts/image_diff/helpers/dom_helper.js
new file mode 100644
index 00000000000..12d56714b34
--- /dev/null
+++ b/app/assets/javascripts/image_diff/helpers/dom_helper.js
@@ -0,0 +1,44 @@
+export function setPositionDataAttribute(el, options) {
+  // Update position data attribute so that the
+  // new comment form can use this data for ajax request
+  const { x, y, width, height } = options;
+  const position = el.dataset.position;
+  const positionObject = Object.assign({}, JSON.parse(position), {
+    x,
+    y,
+    width,
+    height,
+  });
+
+  el.setAttribute('data-position', JSON.stringify(positionObject));
+}
+
+export function updateDiscussionAvatarBadgeNumber(discussionEl, newBadgeNumber) {
+  const avatarBadgeEl = discussionEl.querySelector('.image-diff-avatar-link .badge');
+  avatarBadgeEl.innerText = newBadgeNumber;
+}
+
+export function updateDiscussionBadgeNumber(discussionEl, newBadgeNumber) {
+  const discussionBadgeEl = discussionEl.querySelector('.badge');
+  discussionBadgeEl.innerText = newBadgeNumber;
+}
+
+export function toggleCollapsed(event) {
+  const toggleButtonEl = event.currentTarget;
+  const discussionNotesEl = toggleButtonEl.closest('.discussion-notes');
+  const formEl = discussionNotesEl.querySelector('.discussion-form');
+  const isCollapsed = discussionNotesEl.classList.contains('collapsed');
+
+  if (isCollapsed) {
+    discussionNotesEl.classList.remove('collapsed');
+  } else {
+    discussionNotesEl.classList.add('collapsed');
+  }
+
+  // Override the inline display style set in notes.js
+  if (formEl && !isCollapsed) {
+    formEl.style.display = 'none';
+  } else if (formEl && isCollapsed) {
+    formEl.style.display = 'block';
+  }
+}
diff --git a/app/assets/javascripts/image_diff/helpers/index.js b/app/assets/javascripts/image_diff/helpers/index.js
new file mode 100644
index 00000000000..4a100631003
--- /dev/null
+++ b/app/assets/javascripts/image_diff/helpers/index.js
@@ -0,0 +1,25 @@
+import * as badgeHelper from './badge_helper';
+import * as commentIndicatorHelper from './comment_indicator_helper';
+import * as domHelper from './dom_helper';
+import * as utilsHelper from './utils_helper';
+
+export default {
+  addCommentIndicator: commentIndicatorHelper.addCommentIndicator,
+  removeCommentIndicator: commentIndicatorHelper.removeCommentIndicator,
+  showCommentIndicator: commentIndicatorHelper.showCommentIndicator,
+  commentIndicatorOnClick: commentIndicatorHelper.commentIndicatorOnClick,
+
+  addImageBadge: badgeHelper.addImageBadge,
+  addImageCommentBadge: badgeHelper.addImageCommentBadge,
+  addAvatarBadge: badgeHelper.addAvatarBadge,
+
+  setPositionDataAttribute: domHelper.setPositionDataAttribute,
+  updateDiscussionAvatarBadgeNumber: domHelper.updateDiscussionAvatarBadgeNumber,
+  updateDiscussionBadgeNumber: domHelper.updateDiscussionBadgeNumber,
+  toggleCollapsed: domHelper.toggleCollapsed,
+
+  resizeCoordinatesToImageElement: utilsHelper.resizeCoordinatesToImageElement,
+  generateBadgeFromDiscussionDOM: utilsHelper.generateBadgeFromDiscussionDOM,
+  getTargetSelection: utilsHelper.getTargetSelection,
+  initImageDiff: utilsHelper.initImageDiff,
+};
diff --git a/app/assets/javascripts/image_diff/helpers/utils_helper.js b/app/assets/javascripts/image_diff/helpers/utils_helper.js
new file mode 100644
index 00000000000..96fc735e629
--- /dev/null
+++ b/app/assets/javascripts/image_diff/helpers/utils_helper.js
@@ -0,0 +1,95 @@
+import ImageBadge from '../image_badge';
+import ImageDiff from '../image_diff';
+import ReplacedImageDiff from '../replaced_image_diff';
+import '../../commit/image_file';
+
+export function resizeCoordinatesToImageElement(imageEl, meta) {
+  const { x, y, width, height } = meta;
+
+  const imageWidth = imageEl.width;
+  const imageHeight = imageEl.height;
+
+  const widthRatio = imageWidth / width;
+  const heightRatio = imageHeight / height;
+
+  return {
+    x: Math.round(x * widthRatio),
+    y: Math.round(y * heightRatio),
+    width: imageWidth,
+    height: imageHeight,
+  };
+}
+
+export function generateBadgeFromDiscussionDOM(imageFrameEl, discussionEl) {
+  const position = JSON.parse(discussionEl.dataset.position);
+  const firstNoteEl = discussionEl.querySelector('.note');
+  const badge = new ImageBadge({
+    actual: position,
+    imageEl: imageFrameEl.querySelector('img'),
+    noteId: firstNoteEl.id,
+    discussionId: discussionEl.dataset.discussionId,
+  });
+
+  return badge;
+}
+
+export function getTargetSelection(event) {
+  const containerEl = event.currentTarget;
+  const imageEl = containerEl.querySelector('img');
+
+  const x = event.offsetX;
+  const y = event.offsetY;
+
+  const width = imageEl.width;
+  const height = imageEl.height;
+
+  const actualWidth = imageEl.naturalWidth;
+  const actualHeight = imageEl.naturalHeight;
+
+  const widthRatio = actualWidth / width;
+  const heightRatio = actualHeight / height;
+
+  // Browser will include the frame as a clickable target,
+  // which would result in potential 1px out of bounds value
+  // This bound the coordinates to inside the frame
+  const normalizedX = Math.max(0, x) && Math.min(x, width);
+  const normalizedY = Math.max(0, y) && Math.min(y, height);
+
+  return {
+    browser: {
+      x: normalizedX,
+      y: normalizedY,
+      width,
+      height,
+    },
+    actual: {
+      // Round x, y so that we don't need to deal with decimals
+      x: Math.round(normalizedX * widthRatio),
+      y: Math.round(normalizedY * heightRatio),
+      width: actualWidth,
+      height: actualHeight,
+    },
+  };
+}
+
+export function initImageDiff(fileEl, canCreateNote, renderCommentBadge) {
+  const options = {
+    canCreateNote,
+    renderCommentBadge,
+  };
+  let diff;
+
+  // ImageFile needs to be invoked before initImageDiff so that badges
+  // can mount to the correct location
+  new gl.ImageFile(fileEl); // eslint-disable-line no-new
+
+  if (fileEl.querySelector('.diff-file .js-single-image')) {
+    diff = new ImageDiff(fileEl, options);
+    diff.init();
+  } else if (fileEl.querySelector('.diff-file .js-replaced-image')) {
+    diff = new ReplacedImageDiff(fileEl, options);
+    diff.init();
+  }
+
+  return diff;
+}
diff --git a/app/assets/javascripts/image_diff/image_badge.js b/app/assets/javascripts/image_diff/image_badge.js
new file mode 100644
index 00000000000..51a8cda98d7
--- /dev/null
+++ b/app/assets/javascripts/image_diff/image_badge.js
@@ -0,0 +1,23 @@
+import imageDiffHelper from './helpers/index';
+
+const defaultMeta = {
+  x: 0,
+  y: 0,
+  width: 0,
+  height: 0,
+};
+
+export default class ImageBadge {
+  constructor(options) {
+    const { noteId, discussionId } = options;
+
+    this.actual = options.actual || defaultMeta;
+    this.browser = options.browser || defaultMeta;
+    this.noteId = noteId;
+    this.discussionId = discussionId;
+
+    if (options.imageEl && !options.browser) {
+      this.browser = imageDiffHelper.resizeCoordinatesToImageElement(options.imageEl, this.actual);
+    }
+  }
+}
diff --git a/app/assets/javascripts/image_diff/image_diff.js b/app/assets/javascripts/image_diff/image_diff.js
new file mode 100644
index 00000000000..f3af92cf2b0
--- /dev/null
+++ b/app/assets/javascripts/image_diff/image_diff.js
@@ -0,0 +1,143 @@
+import imageDiffHelper from './helpers/index';
+import ImageBadge from './image_badge';
+import { isImageLoaded } from '../lib/utils/image_utility';
+
+export default class ImageDiff {
+  constructor(el, options) {
+    this.el = el;
+    this.canCreateNote = !!(options && options.canCreateNote);
+    this.renderCommentBadge = !!(options && options.renderCommentBadge);
+    this.$noteContainer = $('.note-container', this.el);
+    this.imageBadges = [];
+  }
+
+  init() {
+    this.imageFrameEl = this.el.querySelector('.diff-file .js-image-frame');
+    this.imageEl = this.imageFrameEl.querySelector('img');
+
+    this.bindEvents();
+  }
+
+  bindEvents() {
+    this.imageClickedWrapper = this.imageClicked.bind(this);
+    this.imageBlurredWrapper = imageDiffHelper.removeCommentIndicator.bind(null, this.imageFrameEl);
+    this.addBadgeWrapper = this.addBadge.bind(this);
+    this.removeBadgeWrapper = this.removeBadge.bind(this);
+    this.renderBadgesWrapper = this.renderBadges.bind(this);
+
+    // Render badges
+    if (isImageLoaded(this.imageEl)) {
+      this.renderBadges();
+    } else {
+      this.imageEl.addEventListener('load', this.renderBadgesWrapper);
+    }
+
+    // jquery makes the event delegation here much simpler
+    this.$noteContainer.on('click', '.js-diff-notes-toggle', imageDiffHelper.toggleCollapsed);
+    $(this.el).on('click', '.comment-indicator', imageDiffHelper.commentIndicatorOnClick);
+
+    if (this.canCreateNote) {
+      this.el.addEventListener('click.imageDiff', this.imageClickedWrapper);
+      this.el.addEventListener('blur.imageDiff', this.imageBlurredWrapper);
+      this.el.addEventListener('addBadge.imageDiff', this.addBadgeWrapper);
+      this.el.addEventListener('removeBadge.imageDiff', this.removeBadgeWrapper);
+    }
+  }
+
+  imageClicked(event) {
+    const customEvent = event.detail;
+    const selection = imageDiffHelper.getTargetSelection(customEvent);
+    const el = customEvent.currentTarget;
+
+    imageDiffHelper.setPositionDataAttribute(el, selection.actual);
+    imageDiffHelper.showCommentIndicator(this.imageFrameEl, selection.browser);
+  }
+
+  renderBadges() {
+    const discussionsEls = this.el.querySelectorAll('.note-container .discussion-notes .notes');
+    [...discussionsEls].forEach(this.renderBadge.bind(this));
+  }
+
+  renderBadge(discussionEl, index) {
+    const imageBadge = imageDiffHelper
+      .generateBadgeFromDiscussionDOM(this.imageFrameEl, discussionEl);
+
+    this.imageBadges.push(imageBadge);
+
+    const options = {
+      coordinate: imageBadge.browser,
+      noteId: imageBadge.noteId,
+    };
+
+    if (this.renderCommentBadge) {
+      imageDiffHelper.addImageCommentBadge(this.imageFrameEl, options);
+    } else {
+      const numberBadgeOptions = Object.assign({}, options, {
+        badgeText: index + 1,
+      });
+
+      imageDiffHelper.addImageBadge(this.imageFrameEl, numberBadgeOptions);
+    }
+  }
+
+  addBadge(event) {
+    const { x, y, width, height, noteId, discussionId } = event.detail;
+    const badgeText = this.imageBadges.length + 1;
+    const imageBadge = new ImageBadge({
+      actual: {
+        x,
+        y,
+        width,
+        height,
+      },
+      imageEl: this.imageFrameEl.querySelector('img'),
+      noteId,
+      discussionId,
+    });
+
+    this.imageBadges.push(imageBadge);
+
+    imageDiffHelper.addImageBadge(this.imageFrameEl, {
+      coordinate: imageBadge.browser,
+      badgeText,
+      noteId,
+    });
+
+    imageDiffHelper.addAvatarBadge(this.el, {
+      detail: {
+        noteId,
+        badgeNumber: badgeText,
+      },
+    });
+
+    const discussionEl = this.el.querySelector(`#discussion_${discussionId}`);
+    imageDiffHelper.updateDiscussionBadgeNumber(discussionEl, badgeText);
+  }
+
+  removeBadge(event) {
+    const { badgeNumber } = event.detail;
+    const indexToRemove = badgeNumber - 1;
+    const imageBadgeEls = this.imageFrameEl.querySelectorAll('.badge');
+
+    if (this.imageBadges.length !== badgeNumber) {
+      // Cascade badges count numbers for (avatar badges + image badges)
+      this.imageBadges.forEach((badge, index) => {
+        if (index > indexToRemove) {
+          const { discussionId } = badge;
+          const updatedBadgeNumber = index;
+          const discussionEl = this.el.querySelector(`#discussion_${discussionId}`);
+
+          imageBadgeEls[index].innerText = updatedBadgeNumber;
+
+          imageDiffHelper.updateDiscussionBadgeNumber(discussionEl, updatedBadgeNumber);
+          imageDiffHelper.updateDiscussionAvatarBadgeNumber(discussionEl, updatedBadgeNumber);
+        }
+      });
+    }
+
+    this.imageBadges.splice(indexToRemove, 1);
+
+    const imageBadgeEl = imageBadgeEls[indexToRemove];
+    imageBadgeEl.remove();
+  }
+}
diff --git a/app/assets/javascripts/image_diff/init_discussion_tab.js b/app/assets/javascripts/image_diff/init_discussion_tab.js
new file mode 100644
index 00000000000..2f16c6ef115
--- /dev/null
+++ b/app/assets/javascripts/image_diff/init_discussion_tab.js
@@ -0,0 +1,12 @@
+import imageDiffHelper from './helpers/index';
+
+export default () => {
+  // Always pass can-create-note as false because a user
+  // cannot place new badge markers on discussion tab
+  const canCreateNote = false;
+  const renderCommentBadge = true;
+
+  const diffFileEls = document.querySelectorAll('.timeline-content .diff-file.js-image-file');
+  [...diffFileEls].forEach(diffFileEl =>
+    imageDiffHelper.initImageDiff(diffFileEl, canCreateNote, renderCommentBadge));
+};
diff --git a/app/assets/javascripts/image_diff/replaced_image_diff.js b/app/assets/javascripts/image_diff/replaced_image_diff.js
new file mode 100644
index 00000000000..4abd13fb472
--- /dev/null
+++ b/app/assets/javascripts/image_diff/replaced_image_diff.js
@@ -0,0 +1,92 @@
+import imageDiffHelper from './helpers/index';
+import { viewTypes, isValidViewType } from './view_types';
+import ImageDiff from './image_diff';
+
+export default class ReplacedImageDiff extends ImageDiff {
+  init(defaultViewType = viewTypes.TWO_UP) {
+    this.imageFrameEls = {
+      [viewTypes.TWO_UP]: this.el.querySelector('.two-up .js-image-frame'),
+      [viewTypes.SWIPE]: this.el.querySelector('.swipe .js-image-frame'),
+      [viewTypes.ONION_SKIN]: this.el.querySelector('.onion-skin .js-image-frame'),
+    };
+
+    const viewModesEl = this.el.querySelector('.view-modes-menu');
+    this.viewModesEls = {
+      [viewTypes.TWO_UP]: viewModesEl.querySelector('.two-up'),
+      [viewTypes.SWIPE]: viewModesEl.querySelector('.swipe'),
+      [viewTypes.ONION_SKIN]: viewModesEl.querySelector('.onion-skin'),
+    };
+
+    this.currentView = defaultViewType;
+    this.generateImageEls();
+    this.bindEvents();
+  }
+
+  generateImageEls() {
+    this.imageEls = {};
+
+    const viewTypeNames = Object.getOwnPropertyNames(viewTypes);
+    viewTypeNames.forEach((viewType) => {
+      this.imageEls[viewType] = this.imageFrameEls[viewType].querySelector('img');
+    });
+  }
+
+  bindEvents() {
+    super.bindEvents();
+
+    this.changeToViewTwoUp = this.changeView.bind(this, viewTypes.TWO_UP);
+    this.changeToViewSwipe = this.changeView.bind(this, viewTypes.SWIPE);
+    this.changeToViewOnionSkin = this.changeView.bind(this, viewTypes.ONION_SKIN);
+
+    this.viewModesEls[viewTypes.TWO_UP].addEventListener('click', this.changeToViewTwoUp);
+    this.viewModesEls[viewTypes.SWIPE].addEventListener('click', this.changeToViewSwipe);
+    this.viewModesEls[viewTypes.ONION_SKIN].addEventListener('click', this.changeToViewOnionSkin);
+  }
+
+  get imageEl() {
+    return this.imageEls[this.currentView];
+  }
+
+  get imageFrameEl() {
+    return this.imageFrameEls[this.currentView];
+  }
+
+  changeView(newView) {
+    if (!isValidViewType(newView)) {
+      return;
+    }
+
+    const indicator = imageDiffHelper.removeCommentIndicator(this.imageFrameEl);
+
+    this.currentView = newView;
+
+    // Clear existing badges on new view
+    const existingBadges = this.imageFrameEl.querySelectorAll('.badge');
+    [...existingBadges].map(badge => badge.remove());
+
+    // Remove existing references to old view image badges
+    this.imageBadges = [];
+
+    // Image_file.js has a fade animation of 200ms for loading the view
+    // Need to wait an additional 250ms for the images to be displayed
+    // on window in order to re-normalize their dimensions
+    setTimeout(this.renderNewView.bind(this, indicator), 250);
+  }
+
+  renderNewView(indicator) {
+    // Generate badge coordinates on new view
+    this.renderBadges();
+
+    // Re-render indicator in new view
+    if (indicator.removed) {
+      const normalizedIndicator = imageDiffHelper
+        .resizeCoordinatesToImageElement(this.imageEl, {
+          x: indicator.x,
+          y: indicator.y,
+          width: indicator.image.width,
+          height: indicator.image.height,
+        });
+      imageDiffHelper.showCommentIndicator(this.imageFrameEl, normalizedIndicator);
+    }
+  }
+}
diff --git a/app/assets/javascripts/image_diff/view_types.js b/app/assets/javascripts/image_diff/view_types.js
new file mode 100644
index 00000000000..ab0a595571f
--- /dev/null
+++ b/app/assets/javascripts/image_diff/view_types.js
@@ -0,0 +1,9 @@
+export const viewTypes = {
+  TWO_UP: 'TWO_UP',
+  SWIPE: 'SWIPE',
+  ONION_SKIN: 'ONION_SKIN',
+};
+
+export function isValidViewType(validate) {
+  return !!Object.getOwnPropertyNames(viewTypes).find(viewType => viewType === validate);
+}
diff --git a/app/assets/javascripts/lib/utils/image_utility.js b/app/assets/javascripts/lib/utils/image_utility.js
new file mode 100644
index 00000000000..2977ec821cb
--- /dev/null
+++ b/app/assets/javascripts/lib/utils/image_utility.js
@@ -0,0 +1,5 @@
+/* eslint-disable import/prefer-default-export */
+
+export function isImageLoaded(element) {
+  return element.complete && element.naturalHeight !== 0;
+}
diff --git a/app/assets/javascripts/main.js b/app/assets/javascripts/main.js
index 2c1dcc374ff..5858c2b6fd8 100644
--- a/app/assets/javascripts/main.js
+++ b/app/assets/javascripts/main.js
@@ -35,8 +35,6 @@ import './shortcuts_network';
 import './templates/issuable_template_selector';
 import './templates/issuable_template_selectors';
 
-// commit
-import './commit/file';
 import './commit/image_file';
 
 // lib/utils
@@ -70,7 +68,6 @@ import './build';
 import './build_artifacts';
 import './build_variables';
 import './ci_lint_editor';
-import './commit';
 import './commits';
 import './compare';
 import './compare_autocomplete';
diff --git a/app/assets/javascripts/merge_request_tabs.js b/app/assets/javascripts/merge_request_tabs.js
index d3299c15720..c042b22d1fd 100644
--- a/app/assets/javascripts/merge_request_tabs.js
+++ b/app/assets/javascripts/merge_request_tabs.js
@@ -13,6 +13,8 @@ import {
   isMetaClick,
 } from './lib/utils/common_utils';
 
+import initDiscussionTab from './image_diff/init_discussion_tab';
+
 /* eslint-disable max-len */
 // MergeRequestTabs
 //
@@ -154,6 +156,8 @@ import {
         }
         this.resetViewContainer();
         this.destroyPipelinesView();
+
+        initDiscussionTab();
       }
       if (this.setUrl) {
         this.setCurrentAction(action);
diff --git a/app/assets/javascripts/notes.js b/app/assets/javascripts/notes.js
index 93aa29454a0..24de21f2ce2 100644
--- a/app/assets/javascripts/notes.js
+++ b/app/assets/javascripts/notes.js
@@ -24,6 +24,7 @@ import './autosave';
 import './dropzone_input';
 import TaskList from './task_list';
 import { ajaxPost, isInViewport, getPagePath, scrollToElement, isMetaKey } from './lib/utils/common_utils';
+import imageDiffHelper from './image_diff/helpers/index';
 
 window.autosize = autosize;
 window.Dropzone = Dropzone;
@@ -42,6 +43,7 @@ export default class Notes {
     this.visibilityChange = this.visibilityChange.bind(this);
     this.cancelDiscussionForm = this.cancelDiscussionForm.bind(this);
     this.onAddDiffNote = this.onAddDiffNote.bind(this);
+    this.onAddImageDiffNote = this.onAddImageDiffNote.bind(this);
     this.setupDiscussionNoteForm = this.setupDiscussionNoteForm.bind(this);
     this.onReplyToDiscussionNote = this.onReplyToDiscussionNote.bind(this);
     this.removeNote = this.removeNote.bind(this);
@@ -114,6 +116,8 @@ export default class Notes {
     $(document).on('click', '.js-discussion-reply-button', this.onReplyToDiscussionNote);
     // add diff note
     $(document).on('click', '.js-add-diff-note-button', this.onAddDiffNote);
+    // add diff note for images
+    $(document).on('click', '.js-add-image-diff-note-button', this.onAddImageDiffNote);
     // hide diff note form
     $(document).on('click', '.js-close-discussion-note-form', this.cancelDiscussionForm);
     // toggle commit list
@@ -140,6 +144,7 @@ export default class Notes {
     $(document).off('click', '.js-note-attachment-delete');
     $(document).off('click', '.js-discussion-reply-button');
     $(document).off('click', '.js-add-diff-note-button');
+    $(document).off('click', '.js-add-image-diff-note-button');
     $(document).off('visibilitychange');
     $(document).off('keyup input', '.js-note-text');
     $(document).off('click', '.js-note-target-reopen');
@@ -412,6 +417,11 @@ export default class Notes {
     this.note_ids.push(noteEntity.id);
     form = $form || $(`.js-discussion-note-form[data-discussion-id="${noteEntity.discussion_id}"]`);
     row = form.closest('tr');
+
+    if (noteEntity.on_image) {
+      row = form;
+    }
+
     lineType = this.isParallelView() ? form.find('#line_type').val() : 'old';
     diffAvatarContainer = row.prevAll('.line_holder').first().find('.js-avatar-container.' + lineType + '_line');
     // is this the first note of discussion?
@@ -423,7 +433,7 @@ export default class Notes {
       if (noteEntity.diff_discussion_html) {
         var $discussion = $(noteEntity.diff_discussion_html).renderGFM();
 
-        if (!this.isParallelView() || row.hasClass('js-temp-notes-holder')) {
+        if (!this.isParallelView() || row.hasClass('js-temp-notes-holder') || noteEntity.on_image) {
           // insert the note and the reply button after the temp row
           row.after($discussion);
         } else {
@@ -449,6 +459,7 @@ export default class Notes {
 
     if (typeof gl.diffNotesCompileComponents !== 'undefined' && noteEntity.discussion_resolvable) {
       gl.diffNotesCompileComponents();
+
       this.renderDiscussionAvatar(diffAvatarContainer, noteEntity);
     }
 
@@ -561,7 +572,7 @@ export default class Notes {
       form.find('#note_line_code').val(),
 
       // DiffNote
-      form.find('#note_position').val()
+      form.find('#note_position').val(),
     ];
     return new Autosave(textarea, key);
   }
@@ -783,9 +794,22 @@ export default class Notes {
           $(`.js-diff-avatars-${discussionId}`).trigger('remove.vue');
 
           // The notes tr can contain multiple lists of notes, like on the parallel diff
-          if (notesTr.find('.discussion-notes').length > 1) {
+          // notesTr does not exist for image diffs
+          if (notesTr.find('.discussion-notes').length > 1 || notesTr.length === 0) {
+            const $diffFile = $notes.closest('.diff-file');
+            if ($diffFile.length > 0) {
+              const removeBadgeEvent = new CustomEvent('removeBadge.imageDiff', {
+                detail: {
+                  // badgeNumber's start with 1 and index starts with 0
+                  badgeNumber: $notes.index() + 1,
+                },
+              });
+
+              $diffFile[0].dispatchEvent(removeBadgeEvent);
+            }
+
             $notes.remove();
-          } else {
+          } else if (notesTr.length > 0) {
             notesTr.remove();
           }
         }
@@ -841,7 +865,11 @@ export default class Notes {
    */
   setupDiscussionNoteForm(dataHolder, form) {
     // setup note target
-    const diffFileData = dataHolder.closest('.text-file');
+    let diffFileData = dataHolder.closest('.text-file');
+
+    if (diffFileData.length === 0) {
+      diffFileData = dataHolder.closest('.image');
+    }
 
     var discussionID = dataHolder.data('discussionId');
 
@@ -907,6 +935,31 @@ export default class Notes {
     });
   }
 
+  onAddImageDiffNote(e) {
+    const $link = $(e.currentTarget || e.target);
+    const $diffFile = $link.closest('.diff-file');
+
+    const clickEvent = new CustomEvent('click.imageDiff', {
+      detail: e,
+    });
+
+    $diffFile[0].dispatchEvent(clickEvent);
+
+    // Setup comment form
+    let newForm;
+    const $noteContainer = $link.closest('.diff-viewer').find('.note-container');
+    const $form = $noteContainer.find('> .discussion-form');
+
+    if ($form.length === 0) {
+      newForm = this.cleanForm(this.formClone.clone());
+      newForm.appendTo($noteContainer);
+    } else {
+      newForm = $form;
+    }
+
+    this.setupDiscussionNoteForm($link, newForm);
+  }
+
   toggleDiffNote({
     target,
     lineType,
@@ -999,10 +1052,25 @@ export default class Notes {
   }
 
   cancelDiscussionForm(e) {
-    var form;
     e.preventDefault();
-    form = $(e.target).closest('.js-discussion-note-form');
-    return this.removeDiscussionNoteForm(form);
+    const $form = $(e.target).closest('.js-discussion-note-form');
+    const $discussionNote = $(e.target).closest('.discussion-notes');
+
+    if ($discussionNote.length === 0) {
+      // Only send blur event when the discussion form
+      // is not part of a discussion note
+      const $diffFile = $form.closest('.diff-file');
+
+      if ($diffFile.length > 0) {
+        const blurEvent = new CustomEvent('blur.imageDiff', {
+          detail: e,
+        });
+
+        $diffFile[0].dispatchEvent(blurEvent);
+      }
+    }
+
+    return this.removeDiscussionNoteForm($form);
   }
 
   /**
@@ -1414,6 +1482,15 @@ export default class Notes {
         // Submission successful! remove placeholder
         $notesContainer.find(`#${noteUniqueId}`).remove();
 
+        const $diffFile = $form.closest('.diff-file');
+        if ($diffFile.length > 0) {
+          const blurEvent = new CustomEvent('blur.imageDiff', {
+            detail: e,
+          });
+
+          $diffFile[0].dispatchEvent(blurEvent);
+        }
+
         // Reset cached commands list when command is applied
         if (hasQuickActions) {
           $form.find('textarea.js-note-text').trigger('clear-commands-cache.atwho');
@@ -1436,7 +1513,28 @@ export default class Notes {
           }
 
           // Show final note element on UI
-          this.addDiscussionNote($form, note, $notesContainer.length === 0);
+          const isNewDiffComment = $notesContainer.length === 0;
+          this.addDiscussionNote($form, note, isNewDiffComment);
+
+          if (isNewDiffComment) {
+            // Add image badge, avatar badge and toggle discussion badge for new image diffs
+            const notePosition = $form.find('#note_position').val();
+            if ($diffFile.length > 0 && notePosition.length > 0) {
+              const { x, y, width, height } = JSON.parse(notePosition);
+              const addBadgeEvent = new CustomEvent('addBadge.imageDiff', {
+                detail: {
+                  x,
+                  y,
+                  width,
+                  height,
+                  noteId: `note_${note.id}`,
+                  discussionId: note.discussion_id,
+                },
+              });
+
+              $diffFile[0].dispatchEvent(addBadgeEvent);
+            }
+          }
 
           // append flash-container to the Notes list
           if ($notesContainer.length) {
@@ -1457,6 +1555,16 @@ export default class Notes {
         // Submission failed, remove placeholder note and show Flash error message
         $notesContainer.find(`#${noteUniqueId}`).remove();
 
+        const blurEvent = new CustomEvent('blur.imageDiff', {
+          detail: e,
+        });
+
+        const closestDiffFile = $form.closest('.diff-file');
+
+        if (closestDiffFile.length) {
+          closestDiffFile[0].dispatchEvent(blurEvent);
+        }
+
         if (hasQuickActions) {
           $notesContainer.find(`#${systemNoteUniqueId}`).remove();
         }
@@ -1500,6 +1608,8 @@ export default class Notes {
     const $noteBody = $editingNote.find('.js-task-list-container');
     const $noteBodyText = $noteBody.find('.note-text');
     const { formData, formContent, formAction } = this.getFormData($form);
+    const $diffFile = $form.closest('.diff-file');
+    const $notesContainer = $form.closest('.notes');
 
     // Cache original comment content
     const cachedNoteBodyText = $noteBodyText.html();
diff --git a/app/assets/javascripts/single_file_diff.js b/app/assets/javascripts/single_file_diff.js
index 4505a79a2df..3f811c59cb9 100644
--- a/app/assets/javascripts/single_file_diff.js
+++ b/app/assets/javascripts/single_file_diff.js
@@ -1,6 +1,7 @@
 /* eslint-disable func-names, prefer-arrow-callback, space-before-function-paren, no-var, prefer-rest-params, wrap-iife, one-var, one-var-declaration-per-line, consistent-return, no-param-reassign, max-len */
 
 import FilesCommentButton from './files_comment_button';
+import imageDiffHelper from './image_diff/helpers/index';
 
 const WRAPPER = '<div class="diff-content"></div>';
 const LOADING_HTML = '<i class="fa fa-spinner fa-spin"></i>';
@@ -74,7 +75,11 @@ export default class SingleFileDiff {
           gl.diffNotesCompileComponents();
         }
 
-        FilesCommentButton.init($(_this.file));
+        const $file = $(_this.file);
+        FilesCommentButton.init($file);
+
+        const canCreateNote = $file.closest('.files').is('[data-can-create-note]');
+        imageDiffHelper.initImageDiff($file[0], canCreateNote);
 
         if (cb) cb();
       };