1 files changed, 1222 insertions, 0 deletions
diff --git a/toolkit/components/reader/AboutReader.jsm b/toolkit/components/reader/AboutReader.jsm
new file mode 100644
index 0000000000..a1d6cd61a3
--- /dev/null
+++ b/toolkit/components/reader/AboutReader.jsm
@@ -0,0 +1,1222 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["AboutReader"];
+
+const { ReaderMode } = ChromeUtils.import(
+  "resource://gre/modules/ReaderMode.jsm"
+);
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+const { AppConstants } = ChromeUtils.import(
+  "resource://gre/modules/AppConstants.jsm"
+);
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "AsyncPrefs",
+  "resource://gre/modules/AsyncPrefs.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "NarrateControls",
+  "resource://gre/modules/narrate/NarrateControls.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "UITelemetry",
+  "resource://gre/modules/UITelemetry.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "PluralForm",
+  "resource://gre/modules/PluralForm.jsm"
+);
+
+var gStrings = Services.strings.createBundle(
+  "chrome://global/locale/aboutReader.properties"
+);
+
+const zoomOnCtrl =
+  Services.prefs.getIntPref("mousewheel.with_control.action", 3) == 3;
+const zoomOnMeta =
+  Services.prefs.getIntPref("mousewheel.with_meta.action", 1) == 3;
+const isAppLocaleRTL = Services.locale.isAppLocaleRTL;
+
+var AboutReader = function(actor, articlePromise) {
+  let win = actor.contentWindow;
+  let url = this._getOriginalUrl(win);
+  if (
+    !(
+      url.startsWith("http://") ||
+      url.startsWith("https://") ||
+      url.startsWith("file://")
+    )
+  ) {
+    let errorMsg =
+      "Only http://, https:// and file:// URLs can be loaded in about:reader.";
+    if (Services.prefs.getBoolPref("reader.errors.includeURLs")) {
+      errorMsg += " Tried to load: " + url + ".";
+    }
+    Cu.reportError(errorMsg);
+    win.location.href = "about:blank";
+    return;
+  }
+
+  let doc = win.document;
+  if (isAppLocaleRTL) {
+    doc.dir = "rtl";
+  }
+  doc.documentElement.setAttribute("platform", AppConstants.platform);
+
+  this._actor = actor;
+
+  this._docRef = Cu.getWeakReference(doc);
+  this._winRef = Cu.getWeakReference(win);
+  this._innerWindowId = win.windowGlobalChild.innerWindowId;
+
+  this._article = null;
+  this._languagePromise = new Promise(resolve => {
+    this._foundLanguage = resolve;
+  });
+
+  if (articlePromise) {
+    this._articlePromise = articlePromise;
+  }
+
+  this._headerElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-header")
+  );
+  this._domainElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-domain")
+  );
+  this._titleElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-title")
+  );
+  this._readTimeElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-estimated-time")
+  );
+  this._creditsElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-credits")
+  );
+  this._contentElementRef = Cu.getWeakReference(
+    doc.querySelector(".moz-reader-content")
+  );
+  this._toolbarContainerElementRef = Cu.getWeakReference(
+    doc.querySelector(".toolbar-container")
+  );
+  this._toolbarElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-controls")
+  );
+  this._messageElementRef = Cu.getWeakReference(
+    doc.querySelector(".reader-message")
+  );
+  this._containerElementRef = Cu.getWeakReference(
+    doc.querySelector(".container")
+  );
+
+  doc.addEventListener("mousedown", this);
+  doc.addEventListener("click", this);
+  doc.addEventListener("touchstart", this);
+
+  win.addEventListener("pagehide", this);
+  win.addEventListener("resize", this);
+  win.addEventListener("wheel", this, { passive: false });
+
+  this._topScrollChange = this._topScrollChange.bind(this);
+  this._intersectionObs = new win.IntersectionObserver(this._topScrollChange, {
+    root: null,
+    threshold: [0, 1],
+  });
+  this._intersectionObs.observe(doc.querySelector(".top-anchor"));
+
+  Services.obs.addObserver(this, "inner-window-destroyed");
+
+  this._setupButton(
+    "close-button",
+    this._onReaderClose.bind(this),
+    "aboutReader.toolbar.close"
+  );
+
+  // we're ready for any external setup, send a signal for that.
+  this._actor.sendAsyncMessage("Reader:OnSetup");
+
+  let colorSchemeValues = JSON.parse(
+    Services.prefs.getCharPref("reader.color_scheme.values")
+  );
+  let colorSchemeOptions = colorSchemeValues.map(value => {
+    return {
+      name: gStrings.GetStringFromName("aboutReader.colorScheme." + value),
+      groupName: "color-scheme",
+      value,
+      itemClass: value + "-button",
+    };
+  });
+
+  let colorScheme = Services.prefs.getCharPref("reader.color_scheme");
+  this._setupSegmentedButton(
+    "color-scheme-buttons",
+    colorSchemeOptions,
+    colorScheme,
+    this._setColorSchemePref.bind(this)
+  );
+  this._setColorSchemePref(colorScheme);
+
+  let styleButton = this._doc.querySelector(".style-button");
+  this._setButtonTip(styleButton, "aboutReader.toolbar.typeControls");
+
+  // See bug 1637089.
+  // let fontTypeSample = gStrings.GetStringFromName("aboutReader.fontTypeSample");
+
+  let fontTypeOptions = [
+    {
+      name: gStrings.GetStringFromName("aboutReader.fontType.sans-serif"),
+      groupName: "font-type",
+      value: "sans-serif",
+      itemClass: "sans-serif-button",
+    },
+    {
+      name: gStrings.GetStringFromName("aboutReader.fontType.serif"),
+      groupName: "font-type",
+      value: "serif",
+      itemClass: "serif-button",
+    },
+  ];
+
+  let fontType = Services.prefs.getCharPref("reader.font_type");
+  this._setupSegmentedButton(
+    "font-type-buttons",
+    fontTypeOptions,
+    fontType,
+    this._setFontType.bind(this)
+  );
+  this._setFontType(fontType);
+
+  this._setupFontSizeButtons();
+
+  this._setupContentWidthButtons();
+
+  this._setupLineHeightButtons();
+
+  if (win.speechSynthesis && Services.prefs.getBoolPref("narrate.enabled")) {
+    new NarrateControls(win, this._languagePromise);
+  }
+
+  this._loadArticle();
+
+  let dropdown = this._toolbarElement;
+
+  let elemL10nMap = {
+    ".minus-button": "minus",
+    ".plus-button": "plus",
+    ".content-width-minus-button": "contentwidthminus",
+    ".content-width-plus-button": "contentwidthplus",
+    ".line-height-minus-button": "lineheightminus",
+    ".line-height-plus-button": "lineheightplus",
+    ".light-button": "colorschemelight",
+    ".dark-button": "colorschemedark",
+    ".sepia-button": "colorschemesepia",
+  };
+
+  for (let [selector, stringID] of Object.entries(elemL10nMap)) {
+    dropdown
+      .querySelector(selector)
+      .setAttribute(
+        "title",
+        gStrings.GetStringFromName("aboutReader.toolbar." + stringID)
+      );
+  }
+};
+
+AboutReader.prototype = {
+  _BLOCK_IMAGES_SELECTOR:
+    ".content p > img:only-child, " +
+    ".content p > a:only-child > img:only-child, " +
+    ".content .wp-caption img, " +
+    ".content figure img",
+
+  FONT_SIZE_MIN: 1,
+
+  FONT_SIZE_LEGACY_MAX: 9,
+
+  FONT_SIZE_MAX: 15,
+
+  FONT_SIZE_EXTENDED_VALUES: [32, 40, 56, 72, 96, 128],
+
+  get _doc() {
+    return this._docRef.get();
+  },
+
+  get _win() {
+    return this._winRef.get();
+  },
+
+  get _headerElement() {
+    return this._headerElementRef.get();
+  },
+
+  get _domainElement() {
+    return this._domainElementRef.get();
+  },
+
+  get _titleElement() {
+    return this._titleElementRef.get();
+  },
+
+  get _readTimeElement() {
+    return this._readTimeElementRef.get();
+  },
+
+  get _creditsElement() {
+    return this._creditsElementRef.get();
+  },
+
+  get _contentElement() {
+    return this._contentElementRef.get();
+  },
+
+  get _toolbarElement() {
+    return this._toolbarElementRef.get();
+  },
+
+  get _toolbarContainerElement() {
+    return this._toolbarContainerElementRef.get();
+  },
+
+  get _messageElement() {
+    return this._messageElementRef.get();
+  },
+
+  get _containerElement() {
+    return this._containerElementRef.get();
+  },
+
+  get _isToolbarVertical() {
+    if (this._toolbarVertical !== undefined) {
+      return this._toolbarVertical;
+    }
+    return (this._toolbarVertical = Services.prefs.getBoolPref(
+      "reader.toolbar.vertical"
+    ));
+  },
+
+  receiveMessage(message) {
+    switch (message.name) {
+      case "Reader:AddButton": {
+        if (
+          message.data.id &&
+          message.data.image &&
+          !this._doc.getElementsByClassName(message.data.id)[0]
+        ) {
+          let btn = this._doc.createElement("button");
+          btn.dataset.buttonid = message.data.id;
+          btn.className = "button " + message.data.id;
+          let tip = this._doc.createElement("span");
+          tip.className = "hover-label";
+          tip.textContent = message.data.label;
+          btn.append(tip);
+          btn.setAttribute("aria-label", message.data.label);
+          btn.style.backgroundImage = "url('" + message.data.image + "')";
+          if (message.data.width && message.data.height) {
+            btn.style.backgroundSize = `${message.data.width}px ${message.data.height}px`;
+          }
+          let tb = this._toolbarElement;
+          tb.appendChild(btn);
+          this._setupButton(message.data.id, button => {
+            this._actor.sendAsyncMessage(
+              "Reader:Clicked-" + button.dataset.buttonid,
+              { article: this._article }
+            );
+          });
+        }
+        break;
+      }
+      case "Reader:RemoveButton": {
+        if (message.data.id) {
+          let btn = this._doc.getElementsByClassName(message.data.id)[0];
+          if (btn) {
+            btn.remove();
+          }
+        }
+        break;
+      }
+      case "Reader:ZoomIn": {
+        this._changeFontSize(+1);
+        break;
+      }
+      case "Reader:ZoomOut": {
+        this._changeFontSize(-1);
+        break;
+      }
+      case "Reader:ResetZoom": {
+        this._resetFontSize();
+        break;
+      }
+    }
+  },
+
+  handleEvent(aEvent) {
+    if (!aEvent.isTrusted) {
+      return;
+    }
+
+    let target = aEvent.target;
+    switch (aEvent.type) {
+      case "touchstart":
+      /* fall through */
+      case "mousedown":
+        if (
+          !target.closest(".dropdown-popup") &&
+          // Skip handling the toggle button here becase
+          // the dropdown will get toggled with the 'click' event.
+          !target.classList.contains("dropdown-toggle")
+        ) {
+          this._closeDropdowns();
+        }
+        break;
+      case "click":
+        if (target.classList.contains("dropdown-toggle")) {
+          this._toggleDropdownClicked(aEvent);
+        }
+        break;
+      case "scroll":
+        let lastHeight = this._lastHeight;
+        let { windowUtils } = this._win;
+        this._lastHeight = windowUtils.getBoundsWithoutFlushing(
+          this._doc.body
+        ).height;
+        // Only close dropdowns if the scroll events are not a result of line
+        // height / font-size changes that caused a page height change.
+        if (lastHeight == this._lastHeight) {
+          this._closeDropdowns(true);
+        }
+
+        break;
+      case "resize":
+        this._updateImageMargins();
+        this._scheduleToolbarOverlapHandler();
+        break;
+
+      case "wheel":
+        let doZoom =
+          (aEvent.ctrlKey && zoomOnCtrl) || (aEvent.metaKey && zoomOnMeta);
+        if (!doZoom) {
+          return;
+        }
+        aEvent.preventDefault();
+
+        // Throttle events to once per 150ms. This avoids excessively fast zooming.
+        if (aEvent.timeStamp <= this._zoomBackoffTime) {
+          return;
+        }
+        this._zoomBackoffTime = aEvent.timeStamp + 150;
+
+        // Determine the direction of the delta (we don't care about its size);
+        // This code is adapted from normalizeWheelEventDelta in
+        // toolkt/components/pdfjs/content/web/viewer.js
+        let delta = Math.abs(aEvent.deltaX) + Math.abs(aEvent.deltaY);
+        let angle = Math.atan2(aEvent.deltaY, aEvent.deltaX);
+        if (-0.25 * Math.PI < angle && angle < 0.75 * Math.PI) {
+          delta = -delta;
+        }
+
+        if (delta > 0) {
+          this._changeFontSize(+1);
+        } else if (delta < 0) {
+          this._changeFontSize(-1);
+        }
+        break;
+
+      case "pagehide":
+        this._closeDropdowns();
+
+        this._actor.readerModeHidden();
+        this.clearActor();
+        this._intersectionObs.unobserve(this._doc.querySelector(".top-anchor"));
+        delete this._intersectionObs;
+        break;
+    }
+  },
+
+  clearActor() {
+    this._actor = null;
+  },
+
+  _onReaderClose() {
+    ReaderMode.leaveReaderMode(this._actor.docShell, this._win);
+  },
+
+  async _resetFontSize() {
+    await AsyncPrefs.reset("reader.font_size");
+    let currentSize = Services.prefs.getIntPref("reader.font_size");
+    this._setFontSize(currentSize);
+  },
+
+  _setFontSize(newFontSize) {
+    this._fontSize = Math.min(
+      this.FONT_SIZE_MAX,
+      Math.max(this.FONT_SIZE_MIN, newFontSize)
+    );
+    let size;
+    if (this._fontSize > this.FONT_SIZE_LEGACY_MAX) {
+      // -1 because we're indexing into a 0-indexed array, so the first value
+      // over the legacy max should be 0, the next 1, etc.
+      let index = this._fontSize - this.FONT_SIZE_LEGACY_MAX - 1;
+      size = this.FONT_SIZE_EXTENDED_VALUES[index];
+    } else {
+      size = 10 + 2 * this._fontSize;
+    }
+
+    let readerBody = this._doc.body;
+    readerBody.style.setProperty("--font-size", size + "px");
+    return AsyncPrefs.set("reader.font_size", this._fontSize);
+  },
+
+  _setupFontSizeButtons() {
+    let plusButton = this._doc.querySelector(".plus-button");
+    let minusButton = this._doc.querySelector(".minus-button");
+
+    let currentSize = Services.prefs.getIntPref("reader.font_size");
+    this._setFontSize(currentSize);
+    this._updateFontSizeButtonControls();
+
+    plusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+        this._changeFontSize(+1);
+      },
+      true
+    );
+
+    minusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+        this._changeFontSize(-1);
+      },
+      true
+    );
+  },
+
+  _updateFontSizeButtonControls() {
+    let plusButton = this._doc.querySelector(".plus-button");
+    let minusButton = this._doc.querySelector(".minus-button");
+
+    let currentSize = this._fontSize;
+    let fontValue = this._doc.querySelector(".font-size-value");
+    fontValue.textContent = currentSize;
+
+    if (currentSize === this.FONT_SIZE_MIN) {
+      minusButton.setAttribute("disabled", true);
+    } else {
+      minusButton.removeAttribute("disabled");
+    }
+    if (currentSize === this.FONT_SIZE_MAX) {
+      plusButton.setAttribute("disabled", true);
+    } else {
+      plusButton.removeAttribute("disabled");
+    }
+  },
+
+  _changeFontSize(changeAmount) {
+    let currentSize =
+      Services.prefs.getIntPref("reader.font_size") + changeAmount;
+    this._setFontSize(currentSize);
+    this._updateFontSizeButtonControls();
+    this._scheduleToolbarOverlapHandler();
+  },
+
+  _setContentWidth(newContentWidth) {
+    this._contentWidth = newContentWidth;
+    this._displayContentWidth(newContentWidth);
+    let width = 20 + 5 * (this._contentWidth - 1) + "em";
+    this._doc.body.style.setProperty("--content-width", width);
+    this._scheduleToolbarOverlapHandler();
+    return AsyncPrefs.set("reader.content_width", this._contentWidth);
+  },
+
+  _displayContentWidth(currentContentWidth) {
+    let contentWidthValue = this._doc.querySelector(".content-width-value");
+    contentWidthValue.textContent = currentContentWidth;
+  },
+
+  _setupContentWidthButtons() {
+    const CONTENT_WIDTH_MIN = 1;
+    const CONTENT_WIDTH_MAX = 9;
+
+    let currentContentWidth = Services.prefs.getIntPref("reader.content_width");
+    currentContentWidth = Math.max(
+      CONTENT_WIDTH_MIN,
+      Math.min(CONTENT_WIDTH_MAX, currentContentWidth)
+    );
+
+    this._displayContentWidth(currentContentWidth);
+
+    let plusButton = this._doc.querySelector(".content-width-plus-button");
+    let minusButton = this._doc.querySelector(".content-width-minus-button");
+
+    function updateControls() {
+      if (currentContentWidth === CONTENT_WIDTH_MIN) {
+        minusButton.setAttribute("disabled", true);
+      } else {
+        minusButton.removeAttribute("disabled");
+      }
+      if (currentContentWidth === CONTENT_WIDTH_MAX) {
+        plusButton.setAttribute("disabled", true);
+      } else {
+        plusButton.removeAttribute("disabled");
+      }
+    }
+
+    updateControls();
+    this._setContentWidth(currentContentWidth);
+
+    plusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+
+        if (currentContentWidth >= CONTENT_WIDTH_MAX) {
+          return;
+        }
+
+        currentContentWidth++;
+        updateControls();
+        this._setContentWidth(currentContentWidth);
+      },
+      true
+    );
+
+    minusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+
+        if (currentContentWidth <= CONTENT_WIDTH_MIN) {
+          return;
+        }
+
+        currentContentWidth--;
+        updateControls();
+        this._setContentWidth(currentContentWidth);
+      },
+      true
+    );
+  },
+
+  _setLineHeight(newLineHeight) {
+    this._displayLineHeight(newLineHeight);
+    let height = 1 + 0.2 * (newLineHeight - 1) + "em";
+    this._containerElement.style.setProperty("--line-height", height);
+    return AsyncPrefs.set("reader.line_height", newLineHeight);
+  },
+
+  _displayLineHeight(currentLineHeight) {
+    let lineHeightValue = this._doc.querySelector(".line-height-value");
+    lineHeightValue.textContent = currentLineHeight;
+  },
+
+  _setupLineHeightButtons() {
+    const LINE_HEIGHT_MIN = 1;
+    const LINE_HEIGHT_MAX = 9;
+
+    let currentLineHeight = Services.prefs.getIntPref("reader.line_height");
+    currentLineHeight = Math.max(
+      LINE_HEIGHT_MIN,
+      Math.min(LINE_HEIGHT_MAX, currentLineHeight)
+    );
+
+    this._displayLineHeight(currentLineHeight);
+
+    let plusButton = this._doc.querySelector(".line-height-plus-button");
+    let minusButton = this._doc.querySelector(".line-height-minus-button");
+
+    function updateControls() {
+      if (currentLineHeight === LINE_HEIGHT_MIN) {
+        minusButton.setAttribute("disabled", true);
+      } else {
+        minusButton.removeAttribute("disabled");
+      }
+      if (currentLineHeight === LINE_HEIGHT_MAX) {
+        plusButton.setAttribute("disabled", true);
+      } else {
+        plusButton.removeAttribute("disabled");
+      }
+    }
+
+    updateControls();
+    this._setLineHeight(currentLineHeight);
+
+    plusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+
+        if (currentLineHeight >= LINE_HEIGHT_MAX) {
+          return;
+        }
+
+        currentLineHeight++;
+        updateControls();
+        this._setLineHeight(currentLineHeight);
+      },
+      true
+    );
+
+    minusButton.addEventListener(
+      "click",
+      event => {
+        if (!event.isTrusted) {
+          return;
+        }
+        event.stopPropagation();
+
+        if (currentLineHeight <= LINE_HEIGHT_MIN) {
+          return;
+        }
+
+        currentLineHeight--;
+        updateControls();
+        this._setLineHeight(currentLineHeight);
+      },
+      true
+    );
+  },
+
+  _setColorScheme(newColorScheme) {
+    // "auto" is not a real color scheme
+    if (this._colorScheme === newColorScheme || newColorScheme === "auto") {
+      return;
+    }
+
+    let bodyClasses = this._doc.body.classList;
+
+    if (this._colorScheme) {
+      bodyClasses.remove(this._colorScheme);
+    }
+
+    this._colorScheme = newColorScheme;
+    bodyClasses.add(this._colorScheme);
+  },
+
+  // Pref values include "dark", "light", and "sepia"
+  _setColorSchemePref(colorSchemePref) {
+    this._setColorScheme(colorSchemePref);
+
+    AsyncPrefs.set("reader.color_scheme", colorSchemePref);
+  },
+
+  _setFontType(newFontType) {
+    if (this._fontType === newFontType) {
+      return;
+    }
+
+    let bodyClasses = this._doc.body.classList;
+
+    if (this._fontType) {
+      bodyClasses.remove(this._fontType);
+    }
+
+    this._fontType = newFontType;
+    bodyClasses.add(this._fontType);
+
+    AsyncPrefs.set("reader.font_type", this._fontType);
+  },
+
+  async _loadArticle() {
+    let url = this._getOriginalUrl();
+    this._showProgressDelayed();
+
+    let article;
+    if (this._articlePromise) {
+      article = await this._articlePromise;
+    }
+
+    if (!article) {
+      try {
+        article = await ReaderMode.downloadAndParseDocument(url);
+      } catch (e) {
+        if (e && e.newURL) {
+          let readerURL = "about:reader?url=" + encodeURIComponent(e.newURL);
+          this._win.location.replace(readerURL);
+          return;
+        }
+      }
+    }
+
+    if (!this._actor) {
+      return;
+    }
+
+    // Replace the loading message with an error message if there's a failure.
+    // Users are supposed to navigate away by themselves (because we cannot
+    // remove ourselves from session history.)
+    if (!article) {
+      this._showError();
+      return;
+    }
+
+    this._showContent(article);
+  },
+
+  async _requestFavicon() {
+    let iconDetails = await this._actor.sendQuery("Reader:FaviconRequest", {
+      url: this._article.url,
+      preferredWidth: 16 * this._win.devicePixelRatio,
+    });
+
+    if (iconDetails) {
+      this._loadFavicon(iconDetails.url, iconDetails.faviconUrl);
+    }
+  },
+
+  _loadFavicon(url, faviconUrl) {
+    if (this._article.url !== url) {
+      return;
+    }
+
+    let doc = this._doc;
+
+    let link = doc.createElement("link");
+    link.rel = "shortcut icon";
+    link.href = faviconUrl;
+
+    doc.getElementsByTagName("head")[0].appendChild(link);
+  },
+
+  _updateImageMargins() {
+    let windowWidth = this._win.innerWidth;
+    let bodyWidth = this._doc.body.clientWidth;
+
+    let setImageMargins = function(img) {
+      // If the image is at least as wide as the window, make it fill edge-to-edge on mobile.
+      if (img.naturalWidth >= windowWidth) {
+        img.setAttribute("moz-reader-full-width", true);
+      } else {
+        img.removeAttribute("moz-reader-full-width");
+      }
+
+      // If the image is at least half as wide as the body, center it on desktop.
+      if (img.naturalWidth >= bodyWidth / 2) {
+        img.setAttribute("moz-reader-center", true);
+      } else {
+        img.removeAttribute("moz-reader-center");
+      }
+    };
+
+    let imgs = this._doc.querySelectorAll(this._BLOCK_IMAGES_SELECTOR);
+    for (let i = imgs.length; --i >= 0; ) {
+      let img = imgs[i];
+
+      if (img.naturalWidth > 0) {
+        setImageMargins(img);
+      } else {
+        img.onload = function() {
+          setImageMargins(img);
+        };
+      }
+    }
+  },
+
+  _maybeSetTextDirection: function Read_maybeSetTextDirection(article) {
+    // Set the article's "dir" on the contents.
+    // If no direction is specified, the contents should automatically be LTR
+    // regardless of the UI direction to avoid inheriting the parent's direction
+    // if the UI is RTL.
+    this._containerElement.dir = article.dir || "ltr";
+
+    // The native locale could be set differently than the article's text direction.
+    this._readTimeElement.dir = isAppLocaleRTL ? "rtl" : "ltr";
+
+    // This is used to mirror the line height buttons in the toolbar, when relevant.
+    this._toolbarElement.setAttribute("articledir", article.dir || "ltr");
+  },
+
+  _formatReadTime(slowEstimate, fastEstimate) {
+    let displayStringKey = "aboutReader.estimatedReadTimeRange1";
+
+    // only show one reading estimate when they are the same value
+    if (slowEstimate == fastEstimate) {
+      displayStringKey = "aboutReader.estimatedReadTimeValue1";
+    }
+
+    return PluralForm.get(
+      slowEstimate,
+      gStrings.GetStringFromName(displayStringKey)
+    )
+      .replace("#1", fastEstimate)
+      .replace("#2", slowEstimate);
+  },
+
+  _showError() {
+    this._headerElement.classList.remove("reader-show-element");
+    this._contentElement.classList.remove("reader-show-element");
+
+    let errorMessage = gStrings.GetStringFromName("aboutReader.loadError");
+    this._messageElement.textContent = errorMessage;
+    this._messageElement.style.display = "block";
+
+    this._doc.title = errorMessage;
+
+    this._doc.documentElement.dataset.isError = true;
+
+    this._error = true;
+
+    this._doc.dispatchEvent(
+      new this._win.CustomEvent("AboutReaderContentError", {
+        bubbles: true,
+        cancelable: false,
+      })
+    );
+  },
+
+  // This function is the JS version of Java's StringUtils.stripCommonSubdomains.
+  _stripHost(host) {
+    if (!host) {
+      return host;
+    }
+
+    let start = 0;
+
+    if (host.startsWith("www.")) {
+      start = 4;
+    } else if (host.startsWith("m.")) {
+      start = 2;
+    } else if (host.startsWith("mobile.")) {
+      start = 7;
+    }
+
+    return host.substring(start);
+  },
+
+  _showContent(article) {
+    this._messageElement.classList.remove("reader-show-element");
+
+    this._article = article;
+
+    this._domainElement.href = article.url;
+    let articleUri = Services.io.newURI(article.url);
+    this._domainElement.textContent = this._stripHost(articleUri.host);
+    this._creditsElement.textContent = article.byline;
+
+    this._titleElement.textContent = article.title;
+    this._readTimeElement.textContent = this._formatReadTime(
+      article.readingTimeMinsSlow,
+      article.readingTimeMinsFast
+    );
+    this._doc.title = article.title;
+
+    this._headerElement.classList.add("reader-show-element");
+
+    let parserUtils = Cc["@mozilla.org/parserutils;1"].getService(
+      Ci.nsIParserUtils
+    );
+    let contentFragment = parserUtils.parseFragment(
+      article.content,
+      Ci.nsIParserUtils.SanitizerDropForms |
+        Ci.nsIParserUtils.SanitizerAllowStyle,
+      false,
+      articleUri,
+      this._contentElement
+    );
+    this._contentElement.innerHTML = "";
+    this._contentElement.appendChild(contentFragment);
+    this._maybeSetTextDirection(article);
+    this._foundLanguage(article.language);
+
+    this._contentElement.classList.add("reader-show-element");
+    this._updateImageMargins();
+
+    this._requestFavicon();
+    this._doc.body.classList.add("loaded");
+
+    this._goToReference(articleUri.ref);
+
+    Services.obs.notifyObservers(this._win, "AboutReader:Ready");
+
+    this._doc.dispatchEvent(
+      new this._win.CustomEvent("AboutReaderContentReady", {
+        bubbles: true,
+        cancelable: false,
+      })
+    );
+  },
+
+  _hideContent() {
+    this._headerElement.classList.remove("reader-show-element");
+    this._contentElement.classList.remove("reader-show-element");
+  },
+
+  _showProgressDelayed() {
+    this._win.setTimeout(() => {
+      // No need to show progress if the article has been loaded,
+      // if the window has been unloaded, or if there was an error
+      // trying to load the article.
+      if (this._article || !this._actor || this._error) {
+        return;
+      }
+
+      this._headerElement.classList.remove("reader-show-element");
+      this._contentElement.classList.remove("reader-show-element");
+
+      this._messageElement.textContent = gStrings.GetStringFromName(
+        "aboutReader.loading2"
+      );
+      this._messageElement.classList.add("reader-show-element");
+    }, 300);
+  },
+
+  /**
+   * Returns the original article URL for this about:reader view.
+   */
+  _getOriginalUrl(win) {
+    let url = win ? win.location.href : this._win.location.href;
+    return ReaderMode.getOriginalUrl(url) || url;
+  },
+
+  _setupSegmentedButton(id, options, initialValue, callback) {
+    let doc = this._doc;
+    let segmentedButton = doc.getElementsByClassName(id)[0];
+
+    for (let option of options) {
+      let radioButton = doc.createElement("input");
+      radioButton.id = "radio-item" + option.itemClass;
+      radioButton.type = "radio";
+      radioButton.classList.add("radio-button");
+      radioButton.name = option.groupName;
+      segmentedButton.appendChild(radioButton);
+
+      let item = doc.createElement("label");
+      item.textContent = option.name;
+      item.htmlFor = radioButton.id;
+      item.classList.add(option.itemClass);
+
+      segmentedButton.appendChild(item);
+
+      radioButton.addEventListener(
+        "input",
+        function(aEvent) {
+          if (!aEvent.isTrusted) {
+            return;
+          }
+
+          // Just pass the ID of the button as an extra and hope the ID doesn't change
+          // unless the context changes
+          UITelemetry.addEvent("action.1", "button", null, id);
+
+          let labels = segmentedButton.children;
+          for (let label of labels) {
+            label.removeAttribute("checked");
+          }
+
+          aEvent.target.nextElementSibling.setAttribute("checked", "true");
+          callback(option.value);
+        },
+        true
+      );
+
+      if (option.value === initialValue) {
+        radioButton.checked = true;
+        item.setAttribute("checked", "true");
+      }
+    }
+  },
+
+  _setupButton(id, callback, titleEntity) {
+    let button = this._doc.querySelector("." + id);
+    if (titleEntity) {
+      this._setButtonTip(button, titleEntity);
+    }
+
+    button.removeAttribute("hidden");
+    button.addEventListener(
+      "click",
+      function(aEvent) {
+        if (!aEvent.isTrusted) {
+          return;
+        }
+
+        let btn = aEvent.target;
+        callback(btn);
+      },
+      true
+    );
+  },
+
+  /**
+   * Sets a tooltip-style label on a button.
+   * @param   Localizable string providing UI element usage tip.
+   */
+  _setButtonTip(button, titleEntity) {
+    let tip = this._doc.createElement("span");
+    let localizedString = gStrings.GetStringFromName(titleEntity);
+    tip.textContent = localizedString;
+    tip.className = "hover-label";
+    button.setAttribute("aria-label", localizedString);
+    button.append(tip);
+  },
+
+  _toggleDropdownClicked(event) {
+    let dropdown = event.target.closest(".dropdown");
+
+    if (!dropdown) {
+      return;
+    }
+
+    event.stopPropagation();
+
+    if (dropdown.classList.contains("open")) {
+      this._closeDropdowns();
+    } else {
+      this._openDropdown(dropdown);
+    }
+  },
+
+  /*
+   * If the ReaderView banner font-dropdown is closed, open it.
+   */
+  _openDropdown(dropdown, window) {
+    if (dropdown.classList.contains("open")) {
+      return;
+    }
+
+    this._closeDropdowns();
+
+    // Get the height of the doc and start handling scrolling:
+    let { windowUtils } = this._win;
+    this._lastHeight = windowUtils.getBoundsWithoutFlushing(
+      this._doc.body
+    ).height;
+    this._doc.addEventListener("scroll", this);
+
+    dropdown.classList.add("open");
+    this._toolbarElement.classList.add("dropdown-open");
+
+    this._toolbarContainerElement.classList.add("dropdown-open");
+    this._toggleToolbarFixedPosition(true);
+  },
+
+  /*
+   * If the ReaderView has open dropdowns, close them. If we are closing the
+   * dropdowns because the page is scrolling, allow popups to stay open with
+   * the keep-open class.
+   */
+  _closeDropdowns(scrolling) {
+    let selector = ".dropdown.open";
+    if (scrolling) {
+      selector += ":not(.keep-open)";
+    }
+
+    let openDropdowns = this._doc.querySelectorAll(selector);
+    let haveOpenDropdowns = openDropdowns.length;
+    for (let dropdown of openDropdowns) {
+      dropdown.classList.remove("open");
+    }
+    this._toolbarElement.classList.remove("dropdown-open");
+
+    if (haveOpenDropdowns) {
+      this._toolbarContainerElement.classList.remove("dropdown-open");
+      this._toggleToolbarFixedPosition(false);
+    }
+
+    // Stop handling scrolling:
+    this._doc.removeEventListener("scroll", this);
+  },
+
+  _toggleToolbarFixedPosition(shouldBeFixed) {
+    let el = this._toolbarContainerElement;
+    let fontSize = this._doc.body.style.getPropertyValue("--font-size");
+    let contentWidth = this._doc.body.style.getPropertyValue("--content-width");
+    if (shouldBeFixed) {
+      el.style.setProperty("--font-size", fontSize);
+      el.style.setProperty("--content-width", contentWidth);
+      el.classList.add("transition-location");
+    } else {
+      let expectTransition =
+        el.style.getPropertyValue("--font-size") != fontSize ||
+        el.style.getPropertyValue("--content-width") != contentWidth;
+      if (expectTransition) {
+        el.addEventListener(
+          "transitionend",
+          () => el.classList.remove("transition-location"),
+          { once: true }
+        );
+      } else {
+        el.classList.remove("transition-location");
+      }
+      el.style.removeProperty("--font-size");
+      el.style.removeProperty("--content-width");
+      el.classList.remove("overlaps");
+    }
+  },
+
+  _scheduleToolbarOverlapHandler() {
+    if (this._enqueuedToolbarOverlapHandler) {
+      return;
+    }
+    this._enqueuedToolbarOverlapHandler = this._win.requestAnimationFrame(
+      () => {
+        this._win.setTimeout(() => this._toolbarOverlapHandler(), 0);
+      }
+    );
+  },
+
+  _toolbarOverlapHandler() {
+    delete this._enqueuedToolbarOverlapHandler;
+    // Ensure the dropdown is still open to avoid racing with that changing.
+    if (this._toolbarContainerElement.classList.contains("dropdown-open")) {
+      let { windowUtils } = this._win;
+      let toolbarBounds = windowUtils.getBoundsWithoutFlushing(
+        this._toolbarElement.parentNode
+      );
+      let textBounds = windowUtils.getBoundsWithoutFlushing(
+        this._containerElement
+      );
+      let overlaps = false;
+      if (isAppLocaleRTL) {
+        overlaps = textBounds.right > toolbarBounds.left;
+      } else {
+        overlaps = textBounds.left < toolbarBounds.right;
+      }
+      this._toolbarContainerElement.classList.toggle("overlaps", overlaps);
+    }
+  },
+
+  _topScrollChange(entries) {
+    if (!entries.length) {
+      return;
+    }
+    // If we don't intersect the item at the top of the document, we're
+    // scrolled down:
+    let scrolled = !entries[entries.length - 1].isIntersecting;
+    let tbc = this._toolbarContainerElement;
+    tbc.classList.toggle("scrolled", scrolled);
+  },
+
+  /*
+   * Scroll reader view to a reference
+   */
+  _goToReference(ref) {
+    if (ref) {
+      this._win.location.hash = ref;
+    }
+  },
+};