Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2976 insertions, 0 deletions

diff --git a/browser/components/customizableui/CustomizeMode.sys.mjs b/browser/components/customizableui/CustomizeMode.sys.mjs
new file mode 100644
index 0000000000..86c5e1b786
--- /dev/null
+++ b/browser/components/customizableui/CustomizeMode.sys.mjs
@@ -0,0 +1,2976 @@
+/* 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/. */
+
+const kPrefCustomizationDebug = "browser.uiCustomization.debug";
+const kPaletteId = "customization-palette";
+const kDragDataTypePrefix = "text/toolbarwrapper-id/";
+const kSkipSourceNodePref = "browser.uiCustomization.skipSourceNodeCheck";
+const kDrawInTitlebarPref = "browser.tabs.inTitlebar";
+const kCompactModeShowPref = "browser.compactmode.show";
+const kBookmarksToolbarPref = "browser.toolbars.bookmarks.visibility";
+const kKeepBroadcastAttributes = "keepbroadcastattributeswhencustomizing";
+
+const kPanelItemContextMenu = "customizationPanelItemContextMenu";
+const kPaletteItemContextMenu = "customizationPaletteItemContextMenu";
+
+const kDownloadAutohideCheckboxId = "downloads-button-autohide-checkbox";
+const kDownloadAutohidePanelId = "downloads-button-autohide-panel";
+const kDownloadAutoHidePref = "browser.download.autohideButton";
+
+import { CustomizableUI } from "resource:///modules/CustomizableUI.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+  DragPositionManager: "resource:///modules/DragPositionManager.sys.mjs",
+  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
+  URILoadingHelper: "resource:///modules/URILoadingHelper.sys.mjs",
+});
+ChromeUtils.defineModuleGetter(
+  lazy,
+  "BrowserUsageTelemetry",
+  "resource:///modules/BrowserUsageTelemetry.jsm"
+);
+XPCOMUtils.defineLazyGetter(lazy, "gWidgetsBundle", function () {
+  const kUrl =
+    "chrome://browser/locale/customizableui/customizableWidgets.properties";
+  return Services.strings.createBundle(kUrl);
+});
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "gTouchBarUpdater",
+  "@mozilla.org/widget/touchbarupdater;1",
+  "nsITouchBarUpdater"
+);
+
+let gDebug;
+XPCOMUtils.defineLazyGetter(lazy, "log", () => {
+  let { ConsoleAPI } = ChromeUtils.importESModule(
+    "resource://gre/modules/Console.sys.mjs"
+  );
+  gDebug = Services.prefs.getBoolPref(kPrefCustomizationDebug, false);
+  let consoleOptions = {
+    maxLogLevel: gDebug ? "all" : "log",
+    prefix: "CustomizeMode",
+  };
+  return new ConsoleAPI(consoleOptions);
+});
+
+var gDraggingInToolbars;
+
+var gTab;
+
+function closeGlobalTab() {
+  let win = gTab.ownerGlobal;
+  if (win.gBrowser.browsers.length == 1) {
+    win.BrowserOpenTab();
+  }
+  win.gBrowser.removeTab(gTab, { animate: true });
+  gTab = null;
+}
+
+var gTabsProgressListener = {
+  onLocationChange(aBrowser, aWebProgress, aRequest, aLocation, aFlags) {
+    // Tear down customize mode when the customize mode tab loads some other page.
+    // Customize mode will be re-entered if "about:blank" is loaded again, so
+    // don't tear down in this case.
+    if (
+      !gTab ||
+      gTab.linkedBrowser != aBrowser ||
+      aLocation.spec == "about:blank"
+    ) {
+      return;
+    }
+
+    unregisterGlobalTab();
+  },
+};
+
+function unregisterGlobalTab() {
+  gTab.removeEventListener("TabClose", unregisterGlobalTab);
+  let win = gTab.ownerGlobal;
+  win.removeEventListener("unload", unregisterGlobalTab);
+  win.gBrowser.removeTabsProgressListener(gTabsProgressListener);
+
+  gTab.removeAttribute("customizemode");
+
+  gTab = null;
+}
+
+export function CustomizeMode(aWindow) {
+  this.window = aWindow;
+  this.document = aWindow.document;
+  this.browser = aWindow.gBrowser;
+  this.areas = new Set();
+
+  this._translationObserver = new aWindow.MutationObserver(mutations =>
+    this._onTranslations(mutations)
+  );
+  this._ensureCustomizationPanels();
+
+  let content = this.$("customization-content-container");
+  if (!content) {
+    this.window.MozXULElement.insertFTLIfNeeded("browser/customizeMode.ftl");
+    let container = this.$("customization-container");
+    container.replaceChild(
+      this.window.MozXULElement.parseXULToFragment(container.firstChild.data),
+      container.lastChild
+    );
+  }
+  // There are two palettes - there's the palette that can be overlayed with
+  // toolbar items in browser.xhtml. This is invisible, and never seen by the
+  // user. Then there's the visible palette, which gets populated and displayed
+  // to the user when in customizing mode.
+  this.visiblePalette = this.$(kPaletteId);
+  this.pongArena = this.$("customization-pong-arena");
+
+  if (this._canDrawInTitlebar()) {
+    this._updateTitlebarCheckbox();
+    Services.prefs.addObserver(kDrawInTitlebarPref, this);
+  } else {
+    this.$("customization-titlebar-visibility-checkbox").hidden = true;
+  }
+
+  // Observe pref changes to the bookmarks toolbar visibility,
+  // since we won't get a toolbarvisibilitychange event if the
+  // toolbar is changing from 'newtab' to 'always' in Customize mode
+  // since the toolbar is shown with the 'newtab' setting.
+  Services.prefs.addObserver(kBookmarksToolbarPref, this);
+
+  this.window.addEventListener("unload", this);
+}
+
+CustomizeMode.prototype = {
+  _changed: false,
+  _transitioning: false,
+  window: null,
+  document: null,
+  // areas is used to cache the customizable areas when in customization mode.
+  areas: null,
+  // When in customizing mode, we swap out the reference to the invisible
+  // palette in gNavToolbox.palette for our visiblePalette. This way, for the
+  // customizing browser window, when widgets are removed from customizable
+  // areas and added to the palette, they're added to the visible palette.
+  // _stowedPalette is a reference to the old invisible palette so we can
+  // restore gNavToolbox.palette to its original state after exiting
+  // customization mode.
+  _stowedPalette: null,
+  _dragOverItem: null,
+  _customizing: false,
+  _skipSourceNodeCheck: null,
+  _mainViewContext: null,
+
+  // These are the commands we continue to leave enabled while in customize mode.
+  // All other commands are disabled, and we remove the disabled attribute when
+  // leaving customize mode.
+  _enabledCommands: new Set([
+    "cmd_newNavigator",
+    "cmd_newNavigatorTab",
+    "cmd_newNavigatorTabNoEvent",
+    "cmd_close",
+    "cmd_closeWindow",
+    "cmd_quitApplication",
+    "View:FullScreen",
+    "Browser:NextTab",
+    "Browser:PrevTab",
+    "Browser:NewUserContextTab",
+    "Tools:PrivateBrowsing",
+    "minimizeWindow",
+    "zoomWindow",
+  ]),
+
+  get _handler() {
+    return this.window.CustomizationHandler;
+  },
+
+  uninit() {
+    if (this._canDrawInTitlebar()) {
+      Services.prefs.removeObserver(kDrawInTitlebarPref, this);
+    }
+    Services.prefs.removeObserver(kBookmarksToolbarPref, this);
+  },
+
+  $(id) {
+    return this.document.getElementById(id);
+  },
+
+  toggle() {
+    if (
+      this._handler.isEnteringCustomizeMode ||
+      this._handler.isExitingCustomizeMode
+    ) {
+      this._wantToBeInCustomizeMode = !this._wantToBeInCustomizeMode;
+      return;
+    }
+    if (this._customizing) {
+      this.exit();
+    } else {
+      this.enter();
+    }
+  },
+
+  setTab(aTab) {
+    if (gTab == aTab) {
+      return;
+    }
+
+    if (gTab) {
+      closeGlobalTab();
+    }
+
+    gTab = aTab;
+
+    gTab.setAttribute("customizemode", "true");
+    lazy.SessionStore.persistTabAttribute("customizemode");
+
+    if (gTab.linkedPanel) {
+      gTab.linkedBrowser.stop();
+    }
+
+    let win = gTab.ownerGlobal;
+
+    win.gBrowser.setTabTitle(gTab);
+    win.gBrowser.setIcon(gTab, "chrome://browser/skin/customize.svg");
+
+    gTab.addEventListener("TabClose", unregisterGlobalTab);
+
+    win.gBrowser.addTabsProgressListener(gTabsProgressListener);
+
+    win.addEventListener("unload", unregisterGlobalTab);
+
+    if (gTab.selected) {
+      win.gCustomizeMode.enter();
+    }
+  },
+
+  enter() {
+    if (!this.window.toolbar.visible) {
+      let w = lazy.URILoadingHelper.getTargetWindow(this.window, {
+        skipPopups: true,
+      });
+      if (w) {
+        w.gCustomizeMode.enter();
+        return;
+      }
+      let obs = () => {
+        Services.obs.removeObserver(obs, "browser-delayed-startup-finished");
+        w = lazy.URILoadingHelper.getTargetWindow(this.window, {
+          skipPopups: true,
+        });
+        w.gCustomizeMode.enter();
+      };
+      Services.obs.addObserver(obs, "browser-delayed-startup-finished");
+      this.window.openTrustedLinkIn("about:newtab", "window");
+      return;
+    }
+    this._wantToBeInCustomizeMode = true;
+
+    if (this._customizing || this._handler.isEnteringCustomizeMode) {
+      return;
+    }
+
+    // Exiting; want to re-enter once we've done that.
+    if (this._handler.isExitingCustomizeMode) {
+      lazy.log.debug(
+        "Attempted to enter while we're in the middle of exiting. " +
+          "We'll exit after we've entered"
+      );
+      return;
+    }
+
+    if (!gTab) {
+      this.setTab(
+        this.browser.addTab("about:blank", {
+          inBackground: false,
+          forceNotRemote: true,
+          skipAnimation: true,
+          triggeringPrincipal:
+            Services.scriptSecurityManager.getSystemPrincipal(),
+        })
+      );
+      return;
+    }
+    if (!gTab.selected) {
+      // This will force another .enter() to be called via the
+      // onlocationchange handler of the tabbrowser, so we return early.
+      gTab.ownerGlobal.gBrowser.selectedTab = gTab;
+      return;
+    }
+    gTab.ownerGlobal.focus();
+    if (gTab.ownerDocument != this.document) {
+      return;
+    }
+
+    let window = this.window;
+    let document = this.document;
+
+    this._handler.isEnteringCustomizeMode = true;
+
+    // Always disable the reset button at the start of customize mode, it'll be re-enabled
+    // if necessary when we finish entering:
+    let resetButton = this.$("customization-reset-button");
+    resetButton.setAttribute("disabled", "true");
+
+    (async () => {
+      // We shouldn't start customize mode until after browser-delayed-startup has finished:
+      if (!this.window.gBrowserInit.delayedStartupFinished) {
+        await new Promise(resolve => {
+          let delayedStartupObserver = aSubject => {
+            if (aSubject == this.window) {
+              Services.obs.removeObserver(
+                delayedStartupObserver,
+                "browser-delayed-startup-finished"
+              );
+              resolve();
+            }
+          };
+
+          Services.obs.addObserver(
+            delayedStartupObserver,
+            "browser-delayed-startup-finished"
+          );
+        });
+      }
+
+      CustomizableUI.dispatchToolboxEvent("beforecustomization", {}, window);
+      CustomizableUI.notifyStartCustomizing(this.window);
+
+      // Add a keypress listener to the document so that we can quickly exit
+      // customization mode when pressing ESC.
+      document.addEventListener("keypress", this);
+
+      // Same goes for the menu button - if we're customizing, a click on the
+      // menu button means a quick exit from customization mode.
+      window.PanelUI.hide();
+
+      let panelHolder = document.getElementById("customization-panelHolder");
+      let panelContextMenu = document.getElementById(kPanelItemContextMenu);
+      this._previousPanelContextMenuParent = panelContextMenu.parentNode;
+      document.getElementById("mainPopupSet").appendChild(panelContextMenu);
+      panelHolder.appendChild(window.PanelUI.overflowFixedList);
+
+      window.PanelUI.overflowFixedList.setAttribute("customizing", true);
+      window.PanelUI.menuButton.disabled = true;
+      document.getElementById("nav-bar-overflow-button").disabled = true;
+
+      this._transitioning = true;
+
+      let customizer = document.getElementById("customization-container");
+      let browser = document.getElementById("browser");
+      browser.collapsed = true;
+      customizer.hidden = false;
+
+      this._wrapToolbarItemSync(CustomizableUI.AREA_TABSTRIP);
+
+      this.document.documentElement.setAttribute("customizing", true);
+
+      let customizableToolbars = document.querySelectorAll(
+        "toolbar[customizable=true]:not([autohide=true], [collapsed=true])"
+      );
+      for (let toolbar of customizableToolbars) {
+        toolbar.setAttribute("customizing", true);
+      }
+
+      this._updateOverflowPanelArrowOffset();
+
+      // Let everybody in this window know that we're about to customize.
+      CustomizableUI.dispatchToolboxEvent("customizationstarting", {}, window);
+
+      await this._wrapToolbarItems();
+      this.populatePalette();
+
+      this._setupPaletteDragging();
+
+      window.gNavToolbox.addEventListener("toolbarvisibilitychange", this);
+
+      this._updateResetButton();
+      this._updateUndoResetButton();
+      this._updateTouchBarButton();
+      this._updateDensityMenu();
+
+      this._skipSourceNodeCheck =
+        Services.prefs.getPrefType(kSkipSourceNodePref) ==
+          Ci.nsIPrefBranch.PREF_BOOL &&
+        Services.prefs.getBoolPref(kSkipSourceNodePref);
+
+      CustomizableUI.addListener(this);
+      this._customizing = true;
+      this._transitioning = false;
+
+      // Show the palette now that the transition has finished.
+      this.visiblePalette.hidden = false;
+      window.setTimeout(() => {
+        // Force layout reflow to ensure the animation runs,
+        // and make it async so it doesn't affect the timing.
+        this.visiblePalette.clientTop;
+        this.visiblePalette.setAttribute("showing", "true");
+      }, 0);
+      this._updateEmptyPaletteNotice();
+
+      lazy.AddonManager.addAddonListener(this);
+
+      this._setupDownloadAutoHideToggle();
+
+      this._handler.isEnteringCustomizeMode = false;
+
+      CustomizableUI.dispatchToolboxEvent("customizationready", {}, window);
+
+      if (!this._wantToBeInCustomizeMode) {
+        this.exit();
+      }
+    })().catch(e => {
+      lazy.log.error("Error entering customize mode", e);
+      this._handler.isEnteringCustomizeMode = false;
+      // Exit customize mode to ensure proper clean-up when entering failed.
+      this.exit();
+    });
+  },
+
+  exit() {
+    this._wantToBeInCustomizeMode = false;
+
+    if (!this._customizing || this._handler.isExitingCustomizeMode) {
+      return;
+    }
+
+    // Entering; want to exit once we've done that.
+    if (this._handler.isEnteringCustomizeMode) {
+      lazy.log.debug(
+        "Attempted to exit while we're in the middle of entering. " +
+          "We'll exit after we've entered"
+      );
+      return;
+    }
+
+    if (this.resetting) {
+      lazy.log.debug(
+        "Attempted to exit while we're resetting. " +
+          "We'll exit after resetting has finished."
+      );
+      return;
+    }
+
+    this._handler.isExitingCustomizeMode = true;
+
+    this._translationObserver.disconnect();
+
+    this._teardownDownloadAutoHideToggle();
+
+    lazy.AddonManager.removeAddonListener(this);
+    CustomizableUI.removeListener(this);
+
+    let window = this.window;
+    let document = this.document;
+
+    document.removeEventListener("keypress", this);
+
+    this.togglePong(false);
+
+    // Disable the reset and undo reset buttons while transitioning:
+    let resetButton = this.$("customization-reset-button");
+    let undoResetButton = this.$("customization-undo-reset-button");
+    undoResetButton.hidden = resetButton.disabled = true;
+
+    this._transitioning = true;
+
+    this._depopulatePalette();
+
+    // We need to set this._customizing to false and remove the `customizing`
+    // attribute before removing the tab or else
+    // XULBrowserWindow.onLocationChange might think that we're still in
+    // customization mode and need to exit it for a second time.
+    this._customizing = false;
+    document.documentElement.removeAttribute("customizing");
+
+    if (this.browser.selectedTab == gTab) {
+      closeGlobalTab();
+    }
+
+    let customizer = document.getElementById("customization-container");
+    let browser = document.getElementById("browser");
+    customizer.hidden = true;
+    browser.collapsed = false;
+
+    window.gNavToolbox.removeEventListener("toolbarvisibilitychange", this);
+
+    this._teardownPaletteDragging();
+
+    (async () => {
+      await this._unwrapToolbarItems();
+
+      // And drop all area references.
+      this.areas.clear();
+
+      // Let everybody in this window know that we're starting to
+      // exit customization mode.
+      CustomizableUI.dispatchToolboxEvent("customizationending", {}, window);
+
+      window.PanelUI.menuButton.disabled = false;
+      let overflowContainer = document.getElementById(
+        "widget-overflow-mainView"
+      ).firstElementChild;
+      overflowContainer.appendChild(window.PanelUI.overflowFixedList);
+      document.getElementById("nav-bar-overflow-button").disabled = false;
+      let panelContextMenu = document.getElementById(kPanelItemContextMenu);
+      this._previousPanelContextMenuParent.appendChild(panelContextMenu);
+
+      let customizableToolbars = document.querySelectorAll(
+        "toolbar[customizable=true]:not([autohide=true])"
+      );
+      for (let toolbar of customizableToolbars) {
+        toolbar.removeAttribute("customizing");
+      }
+
+      this._maybeMoveDownloadsButtonToNavBar();
+
+      delete this._lastLightweightTheme;
+      this._changed = false;
+      this._transitioning = false;
+      this._handler.isExitingCustomizeMode = false;
+      CustomizableUI.dispatchToolboxEvent("aftercustomization", {}, window);
+      CustomizableUI.notifyEndCustomizing(window);
+
+      if (this._wantToBeInCustomizeMode) {
+        this.enter();
+      }
+    })().catch(e => {
+      lazy.log.error("Error exiting customize mode", e);
+      this._handler.isExitingCustomizeMode = false;
+    });
+  },
+
+  /**
+   * The overflow panel in customize mode should have its arrow pointing
+   * at the overflow button. In order to do this correctly, we pass the
+   * distance between the inside of window and the middle of the button
+   * to the customize mode markup in which the arrow and panel are placed.
+   */
+  async _updateOverflowPanelArrowOffset() {
+    let currentDensity =
+      this.document.documentElement.getAttribute("uidensity");
+    let offset = await this.window.promiseDocumentFlushed(() => {
+      let overflowButton = this.$("nav-bar-overflow-button");
+      let buttonRect = overflowButton.getBoundingClientRect();
+      let endDistance;
+      if (this.window.RTL_UI) {
+        endDistance = buttonRect.left;
+      } else {
+        endDistance = this.window.innerWidth - buttonRect.right;
+      }
+      return endDistance + buttonRect.width / 2;
+    });
+    if (
+      !this.document ||
+      currentDensity != this.document.documentElement.getAttribute("uidensity")
+    ) {
+      return;
+    }
+    this.$("customization-panelWrapper").style.setProperty(
+      "--panel-arrow-offset",
+      offset + "px"
+    );
+  },
+
+  _getCustomizableChildForNode(aNode) {
+    // NB: adjusted from _getCustomizableParent to keep that method fast
+    // (it's used during drags), and avoid multiple DOM loops
+    let areas = CustomizableUI.areas;
+    // Caching this length is important because otherwise we'll also iterate
+    // over items we add to the end from within the loop.
+    let numberOfAreas = areas.length;
+    for (let i = 0; i < numberOfAreas; i++) {
+      let area = areas[i];
+      let areaNode = aNode.ownerDocument.getElementById(area);
+      let customizationTarget = CustomizableUI.getCustomizationTarget(areaNode);
+      if (customizationTarget && customizationTarget != areaNode) {
+        areas.push(customizationTarget.id);
+      }
+      let overflowTarget =
+        areaNode && areaNode.getAttribute("default-overflowtarget");
+      if (overflowTarget) {
+        areas.push(overflowTarget);
+      }
+    }
+    areas.push(kPaletteId);
+
+    while (aNode && aNode.parentNode) {
+      let parent = aNode.parentNode;
+      if (areas.includes(parent.id)) {
+        return aNode;
+      }
+      aNode = parent;
+    }
+    return null;
+  },
+
+  _promiseWidgetAnimationOut(aNode) {
+    if (
+      this.window.gReduceMotion ||
+      aNode.getAttribute("cui-anchorid") == "nav-bar-overflow-button" ||
+      (aNode.tagName != "toolbaritem" && aNode.tagName != "toolbarbutton") ||
+      (aNode.id == "downloads-button" && aNode.hidden)
+    ) {
+      return null;
+    }
+
+    let animationNode;
+    if (aNode.parentNode && aNode.parentNode.id.startsWith("wrapper-")) {
+      animationNode = aNode.parentNode;
+    } else {
+      animationNode = aNode;
+    }
+    return new Promise(resolve => {
+      function cleanupCustomizationExit() {
+        resolveAnimationPromise();
+      }
+
+      function cleanupWidgetAnimationEnd(e) {
+        if (
+          e.animationName == "widget-animate-out" &&
+          e.target.id == animationNode.id
+        ) {
+          resolveAnimationPromise();
+        }
+      }
+
+      function resolveAnimationPromise() {
+        animationNode.removeEventListener(
+          "animationend",
+          cleanupWidgetAnimationEnd
+        );
+        animationNode.removeEventListener(
+          "customizationending",
+          cleanupCustomizationExit
+        );
+        resolve(animationNode);
+      }
+
+      // Wait until the next frame before setting the class to ensure
+      // we do start the animation.
+      this.window.requestAnimationFrame(() => {
+        this.window.requestAnimationFrame(() => {
+          animationNode.classList.add("animate-out");
+          animationNode.ownerGlobal.gNavToolbox.addEventListener(
+            "customizationending",
+            cleanupCustomizationExit
+          );
+          animationNode.addEventListener(
+            "animationend",
+            cleanupWidgetAnimationEnd
+          );
+        });
+      });
+    });
+  },
+
+  async addToToolbar(aNode, aReason) {
+    aNode = this._getCustomizableChildForNode(aNode);
+    if (aNode.localName == "toolbarpaletteitem" && aNode.firstElementChild) {
+      aNode = aNode.firstElementChild;
+    }
+    let widgetAnimationPromise = this._promiseWidgetAnimationOut(aNode);
+    let animationNode;
+    if (widgetAnimationPromise) {
+      animationNode = await widgetAnimationPromise;
+    }
+
+    let widgetToAdd = aNode.id;
+    if (
+      CustomizableUI.isSpecialWidget(widgetToAdd) &&
+      aNode.closest("#customization-palette")
+    ) {
+      widgetToAdd = widgetToAdd.match(
+        /^customizableui-special-(spring|spacer|separator)/
+      )[1];
+    }
+
+    CustomizableUI.addWidgetToArea(widgetToAdd, CustomizableUI.AREA_NAVBAR);
+    lazy.BrowserUsageTelemetry.recordWidgetChange(
+      widgetToAdd,
+      CustomizableUI.AREA_NAVBAR
+    );
+    if (!this._customizing) {
+      CustomizableUI.dispatchToolboxEvent("customizationchange");
+    }
+
+    // If the user explicitly moves this item, turn off autohide.
+    if (aNode.id == "downloads-button") {
+      Services.prefs.setBoolPref(kDownloadAutoHidePref, false);
+      if (this._customizing) {
+        this._showDownloadsAutoHidePanel();
+      }
+    }
+
+    if (animationNode) {
+      animationNode.classList.remove("animate-out");
+    }
+  },
+
+  async addToPanel(aNode, aReason) {
+    aNode = this._getCustomizableChildForNode(aNode);
+    if (aNode.localName == "toolbarpaletteitem" && aNode.firstElementChild) {
+      aNode = aNode.firstElementChild;
+    }
+    let widgetAnimationPromise = this._promiseWidgetAnimationOut(aNode);
+    let animationNode;
+    if (widgetAnimationPromise) {
+      animationNode = await widgetAnimationPromise;
+    }
+
+    let panel = CustomizableUI.AREA_FIXED_OVERFLOW_PANEL;
+    CustomizableUI.addWidgetToArea(aNode.id, panel);
+    lazy.BrowserUsageTelemetry.recordWidgetChange(aNode.id, panel, aReason);
+    if (!this._customizing) {
+      CustomizableUI.dispatchToolboxEvent("customizationchange");
+    }
+
+    // If the user explicitly moves this item, turn off autohide.
+    if (aNode.id == "downloads-button") {
+      Services.prefs.setBoolPref(kDownloadAutoHidePref, false);
+      if (this._customizing) {
+        this._showDownloadsAutoHidePanel();
+      }
+    }
+
+    if (animationNode) {
+      animationNode.classList.remove("animate-out");
+    }
+    if (!this.window.gReduceMotion) {
+      let overflowButton = this.$("nav-bar-overflow-button");
+      overflowButton.setAttribute("animate", "true");
+      overflowButton.addEventListener(
+        "animationend",
+        function onAnimationEnd(event) {
+          if (event.animationName.startsWith("overflow-animation")) {
+            this.removeEventListener("animationend", onAnimationEnd);
+            this.removeAttribute("animate");
+          }
+        }
+      );
+    }
+  },
+
+  async removeFromArea(aNode, aReason) {
+    aNode = this._getCustomizableChildForNode(aNode);
+    if (aNode.localName == "toolbarpaletteitem" && aNode.firstElementChild) {
+      aNode = aNode.firstElementChild;
+    }
+    let widgetAnimationPromise = this._promiseWidgetAnimationOut(aNode);
+    let animationNode;
+    if (widgetAnimationPromise) {
+      animationNode = await widgetAnimationPromise;
+    }
+
+    CustomizableUI.removeWidgetFromArea(aNode.id);
+    lazy.BrowserUsageTelemetry.recordWidgetChange(aNode.id, null, aReason);
+    if (!this._customizing) {
+      CustomizableUI.dispatchToolboxEvent("customizationchange");
+    }
+
+    // If the user explicitly removes this item, turn off autohide.
+    if (aNode.id == "downloads-button") {
+      Services.prefs.setBoolPref(kDownloadAutoHidePref, false);
+      if (this._customizing) {
+        this._showDownloadsAutoHidePanel();
+      }
+    }
+    if (animationNode) {
+      animationNode.classList.remove("animate-out");
+    }
+  },
+
+  populatePalette() {
+    let fragment = this.document.createDocumentFragment();
+    let toolboxPalette = this.window.gNavToolbox.palette;
+
+    try {
+      let unusedWidgets = CustomizableUI.getUnusedWidgets(toolboxPalette);
+      for (let widget of unusedWidgets) {
+        let paletteItem = this.makePaletteItem(widget, "palette");
+        if (!paletteItem) {
+          continue;
+        }
+        fragment.appendChild(paletteItem);
+      }
+
+      let flexSpace = CustomizableUI.createSpecialWidget(
+        "spring",
+        this.document
+      );
+      fragment.appendChild(this.wrapToolbarItem(flexSpace, "palette"));
+
+      this.visiblePalette.appendChild(fragment);
+      this._stowedPalette = this.window.gNavToolbox.palette;
+      this.window.gNavToolbox.palette = this.visiblePalette;
+
+      // Now that the palette items are all here, disable all commands.
+      // We do this here rather than directly in `enter` because we
+      // need to do/undo this when we're called from reset(), too.
+      this._updateCommandsDisabledState(true);
+    } catch (ex) {
+      lazy.log.error(ex);
+    }
+  },
+
+  // XXXunf Maybe this should use -moz-element instead of wrapping the node?
+  //       Would ensure no weird interactions/event handling from original node,
+  //       and makes it possible to put this in a lazy-loaded iframe/real tab
+  //       while still getting rid of the need for overlays.
+  makePaletteItem(aWidget, aPlace) {
+    let widgetNode = aWidget.forWindow(this.window).node;
+    if (!widgetNode) {
+      lazy.log.error(
+        "Widget with id " + aWidget.id + " does not return a valid node"
+      );
+      return null;
+    }
+    // Do not build a palette item for hidden widgets; there's not much to show.
+    if (widgetNode.hidden) {
+      return null;
+    }
+
+    let wrapper = this.createOrUpdateWrapper(widgetNode, aPlace);
+    wrapper.appendChild(widgetNode);
+    return wrapper;
+  },
+
+  _depopulatePalette() {
+    // Quick, undo the command disabling before we depopulate completely:
+    this._updateCommandsDisabledState(false);
+
+    this.visiblePalette.hidden = true;
+    let paletteChild = this.visiblePalette.firstElementChild;
+    let nextChild;
+    while (paletteChild) {
+      nextChild = paletteChild.nextElementSibling;
+      let itemId = paletteChild.firstElementChild.id;
+      if (CustomizableUI.isSpecialWidget(itemId)) {
+        this.visiblePalette.removeChild(paletteChild);
+      } else {
+        // XXXunf Currently this doesn't destroy the (now unused) node in the
+        //       API provider case. It would be good to do so, but we need to
+        //       keep strong refs to it in CustomizableUI (can't iterate of
+        //       WeakMaps), and there's the question of what behavior
+        //       wrappers should have if consumers keep hold of them.
+        let unwrappedPaletteItem = this.unwrapToolbarItem(paletteChild);
+        this._stowedPalette.appendChild(unwrappedPaletteItem);
+      }
+
+      paletteChild = nextChild;
+    }
+    this.visiblePalette.hidden = false;
+    this.window.gNavToolbox.palette = this._stowedPalette;
+  },
+
+  _updateCommandsDisabledState(shouldBeDisabled) {
+    for (let command of this.document.querySelectorAll("command")) {
+      if (!command.id || !this._enabledCommands.has(command.id)) {
+        if (shouldBeDisabled) {
+          if (command.getAttribute("disabled") != "true") {
+            command.setAttribute("disabled", true);
+          } else {
+            command.setAttribute("wasdisabled", true);
+          }
+        } else if (command.getAttribute("wasdisabled") != "true") {
+          command.removeAttribute("disabled");
+        } else {
+          command.removeAttribute("wasdisabled");
+        }
+      }
+    }
+  },
+
+  isCustomizableItem(aNode) {
+    return (
+      aNode.localName == "toolbarbutton" ||
+      aNode.localName == "toolbaritem" ||
+      aNode.localName == "toolbarseparator" ||
+      aNode.localName == "toolbarspring" ||
+      aNode.localName == "toolbarspacer"
+    );
+  },
+
+  isWrappedToolbarItem(aNode) {
+    return aNode.localName == "toolbarpaletteitem";
+  },
+
+  deferredWrapToolbarItem(aNode, aPlace) {
+    return new Promise(resolve => {
+      dispatchFunction(() => {
+        let wrapper = this.wrapToolbarItem(aNode, aPlace);
+        resolve(wrapper);
+      });
+    });
+  },
+
+  wrapToolbarItem(aNode, aPlace) {
+    if (!this.isCustomizableItem(aNode)) {
+      return aNode;
+    }
+    let wrapper = this.createOrUpdateWrapper(aNode, aPlace);
+
+    // It's possible that this toolbar node is "mid-flight" and doesn't have
+    // a parent, in which case we skip replacing it. This can happen if a
+    // toolbar item has been dragged into the palette. In that case, we tell
+    // CustomizableUI to remove the widget from its area before putting the
+    // widget in the palette - so the node will have no parent.
+    if (aNode.parentNode) {
+      aNode = aNode.parentNode.replaceChild(wrapper, aNode);
+    }
+    wrapper.appendChild(aNode);
+    return wrapper;
+  },
+
+  /**
+   * Helper to set the label, either directly or to set up the translation
+   * observer so we can set the label once it's available.
+   */
+  _updateWrapperLabel(aNode, aIsUpdate, aWrapper = aNode.parentElement) {
+    if (aNode.hasAttribute("label")) {
+      aWrapper.setAttribute("title", aNode.getAttribute("label"));
+      aWrapper.setAttribute("tooltiptext", aNode.getAttribute("label"));
+    } else if (aNode.hasAttribute("title")) {
+      aWrapper.setAttribute("title", aNode.getAttribute("title"));
+      aWrapper.setAttribute("tooltiptext", aNode.getAttribute("title"));
+    } else if (aNode.hasAttribute("data-l10n-id") && !aIsUpdate) {
+      this._translationObserver.observe(aNode, {
+        attributes: true,
+        attributeFilter: ["label", "title"],
+      });
+    }
+  },
+
+  /**
+   * Called when a node without a label or title is updated.
+   */
+  _onTranslations(aMutations) {
+    for (let mut of aMutations) {
+      let { target } = mut;
+      if (
+        target.parentElement?.localName == "toolbarpaletteitem" &&
+        (target.hasAttribute("label") || mut.target.hasAttribute("title"))
+      ) {
+        this._updateWrapperLabel(target, true);
+      }
+    }
+  },
+
+  createOrUpdateWrapper(aNode, aPlace, aIsUpdate) {
+    let wrapper;
+    if (
+      aIsUpdate &&
+      aNode.parentNode &&
+      aNode.parentNode.localName == "toolbarpaletteitem"
+    ) {
+      wrapper = aNode.parentNode;
+      aPlace = wrapper.getAttribute("place");
+    } else {
+      wrapper = this.document.createXULElement("toolbarpaletteitem");
+      // "place" is used to show the label when it's sitting in the palette.
+      wrapper.setAttribute("place", aPlace);
+    }
+
+    // Ensure the wrapped item doesn't look like it's in any special state, and
+    // can't be interactved with when in the customization palette.
+    // Note that some buttons opt out of this with the
+    // keepbroadcastattributeswhencustomizing attribute.
+    if (
+      aNode.hasAttribute("command") &&
+      aNode.getAttribute(kKeepBroadcastAttributes) != "true"
+    ) {
+      wrapper.setAttribute("itemcommand", aNode.getAttribute("command"));
+      aNode.removeAttribute("command");
+    }
+
+    if (
+      aNode.hasAttribute("observes") &&
+      aNode.getAttribute(kKeepBroadcastAttributes) != "true"
+    ) {
+      wrapper.setAttribute("itemobserves", aNode.getAttribute("observes"));
+      aNode.removeAttribute("observes");
+    }
+
+    if (aNode.getAttribute("checked") == "true") {
+      wrapper.setAttribute("itemchecked", "true");
+      aNode.removeAttribute("checked");
+    }
+
+    if (aNode.hasAttribute("id")) {
+      wrapper.setAttribute("id", "wrapper-" + aNode.getAttribute("id"));
+    }
+
+    this._updateWrapperLabel(aNode, aIsUpdate, wrapper);
+
+    if (aNode.hasAttribute("flex")) {
+      wrapper.setAttribute("flex", aNode.getAttribute("flex"));
+    }
+
+    let removable =
+      aPlace == "palette" || CustomizableUI.isWidgetRemovable(aNode);
+    wrapper.setAttribute("removable", removable);
+
+    // Allow touch events to initiate dragging in customize mode.
+    // This is only supported on Windows for now.
+    wrapper.setAttribute("touchdownstartsdrag", "true");
+
+    let contextMenuAttrName = "";
+    if (aNode.getAttribute("context")) {
+      contextMenuAttrName = "context";
+    } else if (aNode.getAttribute("contextmenu")) {
+      contextMenuAttrName = "contextmenu";
+    }
+    let currentContextMenu = aNode.getAttribute(contextMenuAttrName);
+    let contextMenuForPlace =
+      aPlace == "panel" ? kPanelItemContextMenu : kPaletteItemContextMenu;
+    if (aPlace != "toolbar") {
+      wrapper.setAttribute("context", contextMenuForPlace);
+    }
+    // Only keep track of the menu if it is non-default.
+    if (currentContextMenu && currentContextMenu != contextMenuForPlace) {
+      aNode.setAttribute("wrapped-context", currentContextMenu);
+      aNode.setAttribute("wrapped-contextAttrName", contextMenuAttrName);
+      aNode.removeAttribute(contextMenuAttrName);
+    } else if (currentContextMenu == contextMenuForPlace) {
+      aNode.removeAttribute(contextMenuAttrName);
+    }
+
+    // Only add listeners for newly created wrappers:
+    if (!aIsUpdate) {
+      wrapper.addEventListener("mousedown", this);
+      wrapper.addEventListener("mouseup", this);
+    }
+
+    if (CustomizableUI.isSpecialWidget(aNode.id)) {
+      wrapper.setAttribute(
+        "title",
+        lazy.gWidgetsBundle.GetStringFromName(aNode.nodeName + ".label")
+      );
+    }
+
+    return wrapper;
+  },
+
+  deferredUnwrapToolbarItem(aWrapper) {
+    return new Promise(resolve => {
+      dispatchFunction(() => {
+        let item = null;
+        try {
+          item = this.unwrapToolbarItem(aWrapper);
+        } catch (ex) {
+          console.error(ex);
+        }
+        resolve(item);
+      });
+    });
+  },
+
+  unwrapToolbarItem(aWrapper) {
+    if (aWrapper.nodeName != "toolbarpaletteitem") {
+      return aWrapper;
+    }
+    aWrapper.removeEventListener("mousedown", this);
+    aWrapper.removeEventListener("mouseup", this);
+
+    let place = aWrapper.getAttribute("place");
+
+    let toolbarItem = aWrapper.firstElementChild;
+    if (!toolbarItem) {
+      lazy.log.error(
+        "no toolbarItem child for " + aWrapper.tagName + "#" + aWrapper.id
+      );
+      aWrapper.remove();
+      return null;
+    }
+
+    if (aWrapper.hasAttribute("itemobserves")) {
+      toolbarItem.setAttribute(
+        "observes",
+        aWrapper.getAttribute("itemobserves")
+      );
+    }
+
+    if (aWrapper.hasAttribute("itemchecked")) {
+      toolbarItem.checked = true;
+    }
+
+    if (aWrapper.hasAttribute("itemcommand")) {
+      let commandID = aWrapper.getAttribute("itemcommand");
+      toolbarItem.setAttribute("command", commandID);
+
+      // XXX Bug 309953 - toolbarbuttons aren't in sync with their commands after customizing
+      let command = this.$(commandID);
+      if (command && command.hasAttribute("disabled")) {
+        toolbarItem.setAttribute("disabled", command.getAttribute("disabled"));
+      }
+    }
+
+    let wrappedContext = toolbarItem.getAttribute("wrapped-context");
+    if (wrappedContext) {
+      let contextAttrName = toolbarItem.getAttribute("wrapped-contextAttrName");
+      toolbarItem.setAttribute(contextAttrName, wrappedContext);
+      toolbarItem.removeAttribute("wrapped-contextAttrName");
+      toolbarItem.removeAttribute("wrapped-context");
+    } else if (place == "panel") {
+      toolbarItem.setAttribute("context", kPanelItemContextMenu);
+    }
+
+    if (aWrapper.parentNode) {
+      aWrapper.parentNode.replaceChild(toolbarItem, aWrapper);
+    }
+    return toolbarItem;
+  },
+
+  async _wrapToolbarItem(aArea) {
+    let target = CustomizableUI.getCustomizeTargetForArea(aArea, this.window);
+    if (!target || this.areas.has(target)) {
+      return null;
+    }
+
+    this._addDragHandlers(target);
+    for (let child of target.children) {
+      if (this.isCustomizableItem(child) && !this.isWrappedToolbarItem(child)) {
+        await this.deferredWrapToolbarItem(
+          child,
+          CustomizableUI.getPlaceForItem(child)
+        ).catch(lazy.log.error);
+      }
+    }
+    this.areas.add(target);
+    return target;
+  },
+
+  _wrapToolbarItemSync(aArea) {
+    let target = CustomizableUI.getCustomizeTargetForArea(aArea, this.window);
+    if (!target || this.areas.has(target)) {
+      return null;
+    }
+
+    this._addDragHandlers(target);
+    try {
+      for (let child of target.children) {
+        if (
+          this.isCustomizableItem(child) &&
+          !this.isWrappedToolbarItem(child)
+        ) {
+          this.wrapToolbarItem(child, CustomizableUI.getPlaceForItem(child));
+        }
+      }
+    } catch (ex) {
+      lazy.log.error(ex, ex.stack);
+    }
+
+    this.areas.add(target);
+    return target;
+  },
+
+  async _wrapToolbarItems() {
+    for (let area of CustomizableUI.areas) {
+      await this._wrapToolbarItem(area);
+    }
+  },
+
+  _addDragHandlers(aTarget) {
+    // Allow dropping on the padding of the arrow panel.
+    if (aTarget.id == CustomizableUI.AREA_FIXED_OVERFLOW_PANEL) {
+      aTarget = this.$("customization-panelHolder");
+    }
+    aTarget.addEventListener("dragstart", this, true);
+    aTarget.addEventListener("dragover", this, true);
+    aTarget.addEventListener("dragleave", this, true);
+    aTarget.addEventListener("drop", this, true);
+    aTarget.addEventListener("dragend", this, true);
+  },
+
+  _wrapItemsInArea(target) {
+    for (let child of target.children) {
+      if (this.isCustomizableItem(child)) {
+        this.wrapToolbarItem(child, CustomizableUI.getPlaceForItem(child));
+      }
+    }
+  },
+
+  _removeDragHandlers(aTarget) {
+    // Remove handler from different target if it was added to
+    // allow dropping on the padding of the arrow panel.
+    if (aTarget.id == CustomizableUI.AREA_FIXED_OVERFLOW_PANEL) {
+      aTarget = this.$("customization-panelHolder");
+    }
+    aTarget.removeEventListener("dragstart", this, true);
+    aTarget.removeEventListener("dragover", this, true);
+    aTarget.removeEventListener("dragleave", this, true);
+    aTarget.removeEventListener("drop", this, true);
+    aTarget.removeEventListener("dragend", this, true);
+  },
+
+  _unwrapItemsInArea(target) {
+    for (let toolbarItem of target.children) {
+      if (this.isWrappedToolbarItem(toolbarItem)) {
+        this.unwrapToolbarItem(toolbarItem);
+      }
+    }
+  },
+
+  _unwrapToolbarItems() {
+    return (async () => {
+      for (let target of this.areas) {
+        for (let toolbarItem of target.children) {
+          if (this.isWrappedToolbarItem(toolbarItem)) {
+            await this.deferredUnwrapToolbarItem(toolbarItem);
+          }
+        }
+        this._removeDragHandlers(target);
+      }
+      this.areas.clear();
+    })().catch(lazy.log.error);
+  },
+
+  reset() {
+    this.resetting = true;
+    // Disable the reset button temporarily while resetting:
+    let btn = this.$("customization-reset-button");
+    btn.disabled = true;
+    return (async () => {
+      this._depopulatePalette();
+      await this._unwrapToolbarItems();
+
+      CustomizableUI.reset();
+
+      await this._wrapToolbarItems();
+      this.populatePalette();
+
+      this._updateResetButton();
+      this._updateUndoResetButton();
+      this._updateEmptyPaletteNotice();
+      this._moveDownloadsButtonToNavBar = false;
+      this.resetting = false;
+      if (!this._wantToBeInCustomizeMode) {
+        this.exit();
+      }
+    })().catch(lazy.log.error);
+  },
+
+  undoReset() {
+    this.resetting = true;
+
+    return (async () => {
+      this._depopulatePalette();
+      await this._unwrapToolbarItems();
+
+      CustomizableUI.undoReset();
+
+      await this._wrapToolbarItems();
+      this.populatePalette();
+
+      this._updateResetButton();
+      this._updateUndoResetButton();
+      this._updateEmptyPaletteNotice();
+      this._moveDownloadsButtonToNavBar = false;
+      this.resetting = false;
+    })().catch(lazy.log.error);
+  },
+
+  _onToolbarVisibilityChange(aEvent) {
+    let toolbar = aEvent.target;
+    if (
+      aEvent.detail.visible &&
+      toolbar.getAttribute("customizable") == "true"
+    ) {
+      toolbar.setAttribute("customizing", "true");
+    } else {
+      toolbar.removeAttribute("customizing");
+    }
+    this._onUIChange();
+  },
+
+  onWidgetMoved(aWidgetId, aArea, aOldPosition, aNewPosition) {
+    this._onUIChange();
+  },
+
+  onWidgetAdded(aWidgetId, aArea, aPosition) {
+    this._onUIChange();
+  },
+
+  onWidgetRemoved(aWidgetId, aArea) {
+    this._onUIChange();
+  },
+
+  onWidgetBeforeDOMChange(aNodeToChange, aSecondaryNode, aContainer) {
+    if (aContainer.ownerGlobal != this.window || this.resetting) {
+      return;
+    }
+    // If we get called for widgets that aren't in the window yet, they might not have
+    // a parentNode at all.
+    if (aNodeToChange.parentNode) {
+      this.unwrapToolbarItem(aNodeToChange.parentNode);
+    }
+    if (aSecondaryNode) {
+      this.unwrapToolbarItem(aSecondaryNode.parentNode);
+    }
+  },
+
+  onWidgetAfterDOMChange(aNodeToChange, aSecondaryNode, aContainer) {
+    if (aContainer.ownerGlobal != this.window || this.resetting) {
+      return;
+    }
+    // If the node is still attached to the container, wrap it again:
+    if (aNodeToChange.parentNode) {
+      let place = CustomizableUI.getPlaceForItem(aNodeToChange);
+      this.wrapToolbarItem(aNodeToChange, place);
+      if (aSecondaryNode) {
+        this.wrapToolbarItem(aSecondaryNode, place);
+      }
+    } else {
+      // If not, it got removed.
+
+      // If an API-based widget is removed while customizing, append it to the palette.
+      // The _applyDrop code itself will take care of positioning it correctly, if
+      // applicable. We need the code to be here so removing widgets using CustomizableUI's
+      // API also does the right thing (and adds it to the palette)
+      let widgetId = aNodeToChange.id;
+      let widget = CustomizableUI.getWidget(widgetId);
+      if (widget.provider == CustomizableUI.PROVIDER_API) {
+        let paletteItem = this.makePaletteItem(widget, "palette");
+        this.visiblePalette.appendChild(paletteItem);
+      }
+    }
+  },
+
+  onWidgetDestroyed(aWidgetId) {
+    let wrapper = this.$("wrapper-" + aWidgetId);
+    if (wrapper) {
+      wrapper.remove();
+    }
+  },
+
+  onWidgetAfterCreation(aWidgetId, aArea) {
+    // If the node was added to an area, we would have gotten an onWidgetAdded notification,
+    // plus associated DOM change notifications, so only do stuff for the palette:
+    if (!aArea) {
+      let widgetNode = this.$(aWidgetId);
+      if (widgetNode) {
+        this.wrapToolbarItem(widgetNode, "palette");
+      } else {
+        let widget = CustomizableUI.getWidget(aWidgetId);
+        this.visiblePalette.appendChild(
+          this.makePaletteItem(widget, "palette")
+        );
+      }
+    }
+  },
+
+  onAreaNodeRegistered(aArea, aContainer) {
+    if (aContainer.ownerDocument == this.document) {
+      this._wrapItemsInArea(aContainer);
+      this._addDragHandlers(aContainer);
+      this.areas.add(aContainer);
+    }
+  },
+
+  onAreaNodeUnregistered(aArea, aContainer, aReason) {
+    if (
+      aContainer.ownerDocument == this.document &&
+      aReason == CustomizableUI.REASON_AREA_UNREGISTERED
+    ) {
+      this._unwrapItemsInArea(aContainer);
+      this._removeDragHandlers(aContainer);
+      this.areas.delete(aContainer);
+    }
+  },
+
+  openAddonsManagerThemes() {
+    this.window.BrowserOpenAddonsMgr("addons://list/theme");
+  },
+
+  getMoreThemes(aEvent) {
+    aEvent.target.parentNode.parentNode.hidePopup();
+    let getMoreURL = Services.urlFormatter.formatURLPref(
+      "lightweightThemes.getMoreURL"
+    );
+    this.window.openTrustedLinkIn(getMoreURL, "tab");
+  },
+
+  updateUIDensity(mode) {
+    this.window.gUIDensity.update(mode);
+    this._updateOverflowPanelArrowOffset();
+  },
+
+  setUIDensity(mode) {
+    let win = this.window;
+    let gUIDensity = win.gUIDensity;
+    let currentDensity = gUIDensity.getCurrentDensity();
+    let panel = win.document.getElementById("customization-uidensity-menu");
+
+    Services.prefs.setIntPref(gUIDensity.uiDensityPref, mode);
+
+    // If the user is choosing a different UI density mode while
+    // the mode is overriden to Touch, remove the override.
+    if (currentDensity.overridden) {
+      Services.prefs.setBoolPref(gUIDensity.autoTouchModePref, false);
+    }
+
+    this._onUIChange();
+    panel.hidePopup();
+    this._updateOverflowPanelArrowOffset();
+  },
+
+  resetUIDensity() {
+    this.window.gUIDensity.update();
+    this._updateOverflowPanelArrowOffset();
+  },
+
+  onUIDensityMenuShowing() {
+    let win = this.window;
+    let doc = win.document;
+    let gUIDensity = win.gUIDensity;
+    let currentDensity = gUIDensity.getCurrentDensity();
+
+    let normalItem = doc.getElementById(
+      "customization-uidensity-menuitem-normal"
+    );
+    normalItem.mode = gUIDensity.MODE_NORMAL;
+
+    let items = [normalItem];
+
+    let compactItem = doc.getElementById(
+      "customization-uidensity-menuitem-compact"
+    );
+    compactItem.mode = gUIDensity.MODE_COMPACT;
+
+    if (Services.prefs.getBoolPref(kCompactModeShowPref)) {
+      compactItem.hidden = false;
+      items.push(compactItem);
+    } else {
+      compactItem.hidden = true;
+    }
+
+    let touchItem = doc.getElementById(
+      "customization-uidensity-menuitem-touch"
+    );
+    // Touch mode can not be enabled in OSX right now.
+    if (touchItem) {
+      touchItem.mode = gUIDensity.MODE_TOUCH;
+      items.push(touchItem);
+    }
+
+    // Mark the active mode menuitem.
+    for (let item of items) {
+      if (item.mode == currentDensity.mode) {
+        item.setAttribute("aria-checked", "true");
+        item.setAttribute("active", "true");
+      } else {
+        item.removeAttribute("aria-checked");
+        item.removeAttribute("active");
+      }
+    }
+
+    // Add menu items for automatically switching to Touch mode in Windows Tablet Mode,
+    // which is only available in Windows 10.
+    if (AppConstants.isPlatformAndVersionAtLeast("win", "10")) {
+      let spacer = doc.getElementById("customization-uidensity-touch-spacer");
+      let checkbox = doc.getElementById(
+        "customization-uidensity-autotouchmode-checkbox"
+      );
+      spacer.removeAttribute("hidden");
+      checkbox.removeAttribute("hidden");
+
+      // Show a hint that the UI density was overridden automatically.
+      if (currentDensity.overridden) {
+        let sb = Services.strings.createBundle(
+          "chrome://browser/locale/uiDensity.properties"
+        );
+        touchItem.setAttribute(
+          "acceltext",
+          sb.GetStringFromName("uiDensity.menuitem-touch.acceltext")
+        );
+      } else {
+        touchItem.removeAttribute("acceltext");
+      }
+
+      let autoTouchMode = Services.prefs.getBoolPref(
+        win.gUIDensity.autoTouchModePref
+      );
+      if (autoTouchMode) {
+        checkbox.setAttribute("checked", "true");
+      } else {
+        checkbox.removeAttribute("checked");
+      }
+    }
+  },
+
+  updateAutoTouchMode(checked) {
+    Services.prefs.setBoolPref("browser.touchmode.auto", checked);
+    // Re-render the menu items since the active mode might have
+    // change because of this.
+    this.onUIDensityMenuShowing();
+    this._onUIChange();
+  },
+
+  _onUIChange() {
+    this._changed = true;
+    if (!this.resetting) {
+      this._updateResetButton();
+      this._updateUndoResetButton();
+      this._updateEmptyPaletteNotice();
+    }
+    CustomizableUI.dispatchToolboxEvent("customizationchange");
+  },
+
+  _updateEmptyPaletteNotice() {
+    let paletteItems =
+      this.visiblePalette.getElementsByTagName("toolbarpaletteitem");
+    let whimsyButton = this.$("whimsy-button");
+
+    if (
+      paletteItems.length == 1 &&
+      paletteItems[0].id.includes("wrapper-customizableui-special-spring")
+    ) {
+      whimsyButton.hidden = false;
+    } else {
+      this.togglePong(false);
+      whimsyButton.hidden = true;
+    }
+  },
+
+  _updateResetButton() {
+    let btn = this.$("customization-reset-button");
+    btn.disabled = CustomizableUI.inDefaultState;
+  },
+
+  _updateUndoResetButton() {
+    let undoResetButton = this.$("customization-undo-reset-button");
+    undoResetButton.hidden = !CustomizableUI.canUndoReset;
+  },
+
+  _updateTouchBarButton() {
+    if (AppConstants.platform != "macosx") {
+      return;
+    }
+    let touchBarButton = this.$("customization-touchbar-button");
+    let touchBarSpacer = this.$("customization-touchbar-spacer");
+
+    let isTouchBarInitialized = lazy.gTouchBarUpdater.isTouchBarInitialized();
+    touchBarButton.hidden = !isTouchBarInitialized;
+    touchBarSpacer.hidden = !isTouchBarInitialized;
+  },
+
+  _updateDensityMenu() {
+    // If we're entering Customize Mode, and we're using compact mode,
+    // then show the button after that.
+    let gUIDensity = this.window.gUIDensity;
+    if (gUIDensity.getCurrentDensity().mode == gUIDensity.MODE_COMPACT) {
+      Services.prefs.setBoolPref(kCompactModeShowPref, true);
+    }
+
+    let button = this.document.getElementById("customization-uidensity-button");
+    button.hidden =
+      !Services.prefs.getBoolPref(kCompactModeShowPref) &&
+      !button.querySelector("#customization-uidensity-menuitem-touch");
+  },
+
+  handleEvent(aEvent) {
+    switch (aEvent.type) {
+      case "toolbarvisibilitychange":
+        this._onToolbarVisibilityChange(aEvent);
+        break;
+      case "dragstart":
+        this._onDragStart(aEvent);
+        break;
+      case "dragover":
+        this._onDragOver(aEvent);
+        break;
+      case "drop":
+        this._onDragDrop(aEvent);
+        break;
+      case "dragleave":
+        this._onDragLeave(aEvent);
+        break;
+      case "dragend":
+        this._onDragEnd(aEvent);
+        break;
+      case "mousedown":
+        this._onMouseDown(aEvent);
+        break;
+      case "mouseup":
+        this._onMouseUp(aEvent);
+        break;
+      case "keypress":
+        if (aEvent.keyCode == aEvent.DOM_VK_ESCAPE) {
+          this.exit();
+        }
+        break;
+      case "unload":
+        this.uninit();
+        break;
+    }
+  },
+
+  /**
+   * We handle dragover/drop on the outer palette separately
+   * to avoid overlap with other drag/drop handlers.
+   */
+  _setupPaletteDragging() {
+    this._addDragHandlers(this.visiblePalette);
+
+    this.paletteDragHandler = aEvent => {
+      let originalTarget = aEvent.originalTarget;
+      if (
+        this._isUnwantedDragDrop(aEvent) ||
+        this.visiblePalette.contains(originalTarget) ||
+        this.$("customization-panelHolder").contains(originalTarget)
+      ) {
+        return;
+      }
+      // We have a dragover/drop on the palette.
+      if (aEvent.type == "dragover") {
+        this._onDragOver(aEvent, this.visiblePalette);
+      } else {
+        this._onDragDrop(aEvent, this.visiblePalette);
+      }
+    };
+    let contentContainer = this.$("customization-content-container");
+    contentContainer.addEventListener(
+      "dragover",
+      this.paletteDragHandler,
+      true
+    );
+    contentContainer.addEventListener("drop", this.paletteDragHandler, true);
+  },
+
+  _teardownPaletteDragging() {
+    lazy.DragPositionManager.stop();
+    this._removeDragHandlers(this.visiblePalette);
+
+    let contentContainer = this.$("customization-content-container");
+    contentContainer.removeEventListener(
+      "dragover",
+      this.paletteDragHandler,
+      true
+    );
+    contentContainer.removeEventListener("drop", this.paletteDragHandler, true);
+    delete this.paletteDragHandler;
+  },
+
+  observe(aSubject, aTopic, aData) {
+    switch (aTopic) {
+      case "nsPref:changed":
+        this._updateResetButton();
+        this._updateUndoResetButton();
+        if (this._canDrawInTitlebar()) {
+          this._updateTitlebarCheckbox();
+        }
+        break;
+    }
+  },
+
+  async onInstalled(addon) {
+    await this.onEnabled(addon);
+  },
+
+  async onEnabled(addon) {
+    if (addon.type != "theme") {
+      return;
+    }
+
+    if (this._nextThemeChangeUserTriggered) {
+      this._onUIChange();
+    }
+    this._nextThemeChangeUserTriggered = false;
+  },
+
+  _canDrawInTitlebar() {
+    return this.window.TabsInTitlebar.systemSupported;
+  },
+
+  _ensureCustomizationPanels() {
+    let template = this.$("customizationPanel");
+    template.replaceWith(template.content);
+
+    let wrapper = this.$("customModeWrapper");
+    wrapper.replaceWith(wrapper.content);
+  },
+
+  _updateTitlebarCheckbox() {
+    let drawInTitlebar = Services.appinfo.drawInTitlebar;
+    let checkbox = this.$("customization-titlebar-visibility-checkbox");
+    // Drawing in the titlebar means 'hiding' the titlebar.
+    // We use the attribute rather than a property because if we're not in
+    // customize mode the button is hidden and properties don't work.
+    if (drawInTitlebar) {
+      checkbox.removeAttribute("checked");
+    } else {
+      checkbox.setAttribute("checked", "true");
+    }
+  },
+
+  toggleTitlebar(aShouldShowTitlebar) {
+    // Drawing in the titlebar means not showing the titlebar, hence the negation:
+    Services.prefs.setIntPref(kDrawInTitlebarPref, !aShouldShowTitlebar);
+  },
+
+  _getBoundsWithoutFlushing(element) {
+    return this.window.windowUtils.getBoundsWithoutFlushing(element);
+  },
+
+  _onDragStart(aEvent) {
+    __dumpDragData(aEvent);
+    let item = aEvent.target;
+    while (item && item.localName != "toolbarpaletteitem") {
+      if (
+        item.localName == "toolbar" ||
+        item.id == kPaletteId ||
+        item.id == "customization-panelHolder"
+      ) {
+        return;
+      }
+      item = item.parentNode;
+    }
+
+    let draggedItem = item.firstElementChild;
+    let placeForItem = CustomizableUI.getPlaceForItem(item);
+
+    let dt = aEvent.dataTransfer;
+    let documentId = aEvent.target.ownerDocument.documentElement.id;
+
+    dt.mozSetDataAt(kDragDataTypePrefix + documentId, draggedItem.id, 0);
+    dt.effectAllowed = "move";
+
+    let itemRect = this._getBoundsWithoutFlushing(draggedItem);
+    let itemCenter = {
+      x: itemRect.left + itemRect.width / 2,
+      y: itemRect.top + itemRect.height / 2,
+    };
+    this._dragOffset = {
+      x: aEvent.clientX - itemCenter.x,
+      y: aEvent.clientY - itemCenter.y,
+    };
+
+    let toolbarParent = draggedItem.closest("toolbar");
+    if (toolbarParent) {
+      let toolbarRect = this._getBoundsWithoutFlushing(toolbarParent);
+      toolbarParent.style.minHeight = toolbarRect.height + "px";
+    }
+
+    gDraggingInToolbars = new Set();
+
+    // Hack needed so that the dragimage will still show the
+    // item as it appeared before it was hidden.
+    this._initializeDragAfterMove = () => {
+      // For automated tests, we sometimes start exiting customization mode
+      // before this fires, which leaves us with placeholders inserted after
+      // we've exited. So we need to check that we are indeed customizing.
+      if (this._customizing && !this._transitioning) {
+        item.hidden = true;
+        lazy.DragPositionManager.start(this.window);
+        let canUsePrevSibling =
+          placeForItem == "toolbar" || placeForItem == "panel";
+        if (item.nextElementSibling) {
+          this._setDragActive(
+            item.nextElementSibling,
+            "before",
+            draggedItem.id,
+            placeForItem
+          );
+          this._dragOverItem = item.nextElementSibling;
+        } else if (canUsePrevSibling && item.previousElementSibling) {
+          this._setDragActive(
+            item.previousElementSibling,
+            "after",
+            draggedItem.id,
+            placeForItem
+          );
+          this._dragOverItem = item.previousElementSibling;
+        }
+        let currentArea = this._getCustomizableParent(item);
+        currentArea.setAttribute("draggingover", "true");
+      }
+      this._initializeDragAfterMove = null;
+      this.window.clearTimeout(this._dragInitializeTimeout);
+    };
+    this._dragInitializeTimeout = this.window.setTimeout(
+      this._initializeDragAfterMove,
+      0
+    );
+  },
+
+  _onDragOver(aEvent, aOverrideTarget) {
+    if (this._isUnwantedDragDrop(aEvent)) {
+      return;
+    }
+    if (this._initializeDragAfterMove) {
+      this._initializeDragAfterMove();
+    }
+
+    __dumpDragData(aEvent);
+
+    let document = aEvent.target.ownerDocument;
+    let documentId = document.documentElement.id;
+    if (!aEvent.dataTransfer.mozTypesAt(0).length) {
+      return;
+    }
+
+    let draggedItemId = aEvent.dataTransfer.mozGetDataAt(
+      kDragDataTypePrefix + documentId,
+      0
+    );
+    let draggedWrapper = document.getElementById("wrapper-" + draggedItemId);
+    let targetArea = this._getCustomizableParent(
+      aOverrideTarget || aEvent.currentTarget
+    );
+    let originArea = this._getCustomizableParent(draggedWrapper);
+
+    // Do nothing if the target or origin are not customizable.
+    if (!targetArea || !originArea) {
+      return;
+    }
+
+    // Do nothing if the widget is not allowed to be removed.
+    if (
+      targetArea.id == kPaletteId &&
+      !CustomizableUI.isWidgetRemovable(draggedItemId)
+    ) {
+      return;
+    }
+
+    // Do nothing if the widget is not allowed to move to the target area.
+    if (!CustomizableUI.canWidgetMoveToArea(draggedItemId, targetArea.id)) {
+      return;
+    }
+
+    let targetAreaType = CustomizableUI.getPlaceForItem(targetArea);
+    let targetNode = this._getDragOverNode(
+      aEvent,
+      targetArea,
+      targetAreaType,
+      draggedItemId
+    );
+
+    // We need to determine the place that the widget is being dropped in
+    // the target.
+    let dragOverItem, dragValue;
+    if (targetNode == CustomizableUI.getCustomizationTarget(targetArea)) {
+      // We'll assume if the user is dragging directly over the target, that
+      // they're attempting to append a child to that target.
+      dragOverItem =
+        (targetAreaType == "toolbar"
+          ? this._findVisiblePreviousSiblingNode(targetNode.lastElementChild)
+          : targetNode.lastElementChild) || targetNode;
+      dragValue = "after";
+    } else {
+      let targetParent = targetNode.parentNode;
+      let position = Array.prototype.indexOf.call(
+        targetParent.children,
+        targetNode
+      );
+      if (position == -1) {
+        dragOverItem =
+          targetAreaType == "toolbar"
+            ? this._findVisiblePreviousSiblingNode(targetNode.lastElementChild)
+            : targetNode.lastElementChild;
+        dragValue = "after";
+      } else {
+        dragOverItem = targetParent.children[position];
+        if (targetAreaType == "toolbar") {
+          // Check if the aDraggedItem is hovered past the first half of dragOverItem
+          let itemRect = this._getBoundsWithoutFlushing(dragOverItem);
+          let dropTargetCenter = itemRect.left + itemRect.width / 2;
+          let existingDir = dragOverItem.getAttribute("dragover");
+          let dirFactor = this.window.RTL_UI ? -1 : 1;
+          if (existingDir == "before") {
+            dropTargetCenter +=
+              ((parseInt(dragOverItem.style.borderInlineStartWidth) || 0) / 2) *
+              dirFactor;
+          } else {
+            dropTargetCenter -=
+              ((parseInt(dragOverItem.style.borderInlineEndWidth) || 0) / 2) *
+              dirFactor;
+          }
+          let before = this.window.RTL_UI
+            ? aEvent.clientX > dropTargetCenter
+            : aEvent.clientX < dropTargetCenter;
+          dragValue = before ? "before" : "after";
+        } else if (targetAreaType == "panel") {
+          let itemRect = this._getBoundsWithoutFlushing(dragOverItem);
+          let dropTargetCenter = itemRect.top + itemRect.height / 2;
+          let existingDir = dragOverItem.getAttribute("dragover");
+          if (existingDir == "before") {
+            dropTargetCenter +=
+              (parseInt(dragOverItem.style.borderBlockStartWidth) || 0) / 2;
+          } else {
+            dropTargetCenter -=
+              (parseInt(dragOverItem.style.borderBlockEndWidth) || 0) / 2;
+          }
+          dragValue = aEvent.clientY < dropTargetCenter ? "before" : "after";
+        } else {
+          dragValue = "before";
+        }
+      }
+    }
+
+    if (this._dragOverItem && dragOverItem != this._dragOverItem) {
+      this._cancelDragActive(this._dragOverItem, dragOverItem);
+    }
+
+    if (
+      dragOverItem != this._dragOverItem ||
+      dragValue != dragOverItem.getAttribute("dragover")
+    ) {
+      if (dragOverItem != CustomizableUI.getCustomizationTarget(targetArea)) {
+        this._setDragActive(
+          dragOverItem,
+          dragValue,
+          draggedItemId,
+          targetAreaType
+        );
+      }
+      this._dragOverItem = dragOverItem;
+      targetArea.setAttribute("draggingover", "true");
+    }
+
+    aEvent.preventDefault();
+    aEvent.stopPropagation();
+  },
+
+  _onDragDrop(aEvent, aOverrideTarget) {
+    if (this._isUnwantedDragDrop(aEvent)) {
+      return;
+    }
+
+    __dumpDragData(aEvent);
+    this._initializeDragAfterMove = null;
+    this.window.clearTimeout(this._dragInitializeTimeout);
+
+    let targetArea = this._getCustomizableParent(
+      aOverrideTarget || aEvent.currentTarget
+    );
+    let document = aEvent.target.ownerDocument;
+    let documentId = document.documentElement.id;
+    let draggedItemId = aEvent.dataTransfer.mozGetDataAt(
+      kDragDataTypePrefix + documentId,
+      0
+    );
+    let draggedWrapper = document.getElementById("wrapper-" + draggedItemId);
+    let originArea = this._getCustomizableParent(draggedWrapper);
+    if (this._dragSizeMap) {
+      this._dragSizeMap = new WeakMap();
+    }
+    // Do nothing if the target area or origin area are not customizable.
+    if (!targetArea || !originArea) {
+      return;
+    }
+    let targetNode = this._dragOverItem;
+    let dropDir = targetNode.getAttribute("dragover");
+    // Need to insert *after* this node if we promised the user that:
+    if (targetNode != targetArea && dropDir == "after") {
+      if (targetNode.nextElementSibling) {
+        targetNode = targetNode.nextElementSibling;
+      } else {
+        targetNode = targetArea;
+      }
+    }
+    if (targetNode.tagName == "toolbarpaletteitem") {
+      targetNode = targetNode.firstElementChild;
+    }
+
+    this._cancelDragActive(this._dragOverItem, null, true);
+
+    try {
+      this._applyDrop(
+        aEvent,
+        targetArea,
+        originArea,
+        draggedItemId,
+        targetNode
+      );
+    } catch (ex) {
+      lazy.log.error(ex, ex.stack);
+    }
+
+    // If the user explicitly moves this item, turn off autohide.
+    if (draggedItemId == "downloads-button") {
+      Services.prefs.setBoolPref(kDownloadAutoHidePref, false);
+      this._showDownloadsAutoHidePanel();
+    }
+  },
+
+  _applyDrop(aEvent, aTargetArea, aOriginArea, aDraggedItemId, aTargetNode) {
+    let document = aEvent.target.ownerDocument;
+    let draggedItem = document.getElementById(aDraggedItemId);
+    draggedItem.hidden = false;
+    draggedItem.removeAttribute("mousedown");
+
+    let toolbarParent = draggedItem.closest("toolbar");
+    if (toolbarParent) {
+      toolbarParent.style.removeProperty("min-height");
+    }
+
+    // Do nothing if the target was dropped onto itself (ie, no change in area
+    // or position).
+    if (draggedItem == aTargetNode) {
+      return;
+    }
+
+    if (!CustomizableUI.canWidgetMoveToArea(aDraggedItemId, aTargetArea.id)) {
+      return;
+    }
+
+    // Is the target area the customization palette?
+    if (aTargetArea.id == kPaletteId) {
+      // Did we drag from outside the palette?
+      if (aOriginArea.id !== kPaletteId) {
+        if (!CustomizableUI.isWidgetRemovable(aDraggedItemId)) {
+          return;
+        }
+
+        CustomizableUI.removeWidgetFromArea(aDraggedItemId, "drag");
+        lazy.BrowserUsageTelemetry.recordWidgetChange(
+          aDraggedItemId,
+          null,
+          "drag"
+        );
+        // Special widgets are removed outright, we can return here:
+        if (CustomizableUI.isSpecialWidget(aDraggedItemId)) {
+          return;
+        }
+      }
+      draggedItem = draggedItem.parentNode;
+
+      // If the target node is the palette itself, just append
+      if (aTargetNode == this.visiblePalette) {
+        this.visiblePalette.appendChild(draggedItem);
+      } else {
+        // The items in the palette are wrapped, so we need the target node's parent here:
+        this.visiblePalette.insertBefore(draggedItem, aTargetNode.parentNode);
+      }
+      this._onDragEnd(aEvent);
+      return;
+    }
+
+    // Skipintoolbarset items won't really be moved:
+    let areaCustomizationTarget =
+      CustomizableUI.getCustomizationTarget(aTargetArea);
+    if (draggedItem.getAttribute("skipintoolbarset") == "true") {
+      // These items should never leave their area:
+      if (aTargetArea != aOriginArea) {
+        return;
+      }
+      let place = draggedItem.parentNode.getAttribute("place");
+      this.unwrapToolbarItem(draggedItem.parentNode);
+      if (aTargetNode == areaCustomizationTarget) {
+        areaCustomizationTarget.appendChild(draggedItem);
+      } else {
+        this.unwrapToolbarItem(aTargetNode.parentNode);
+        areaCustomizationTarget.insertBefore(draggedItem, aTargetNode);
+        this.wrapToolbarItem(aTargetNode, place);
+      }
+      this.wrapToolbarItem(draggedItem, place);
+      return;
+    }
+
+    // Force creating a new spacer/spring/separator if dragging from the palette
+    if (
+      CustomizableUI.isSpecialWidget(aDraggedItemId) &&
+      aOriginArea.id == kPaletteId
+    ) {
+      aDraggedItemId = aDraggedItemId.match(
+        /^customizableui-special-(spring|spacer|separator)/
+      )[1];
+    }
+
+    // Is the target the customization area itself? If so, we just add the
+    // widget to the end of the area.
+    if (aTargetNode == areaCustomizationTarget) {
+      CustomizableUI.addWidgetToArea(aDraggedItemId, aTargetArea.id);
+      lazy.BrowserUsageTelemetry.recordWidgetChange(
+        aDraggedItemId,
+        aTargetArea.id,
+        "drag"
+      );
+      this._onDragEnd(aEvent);
+      return;
+    }
+
+    // We need to determine the place that the widget is being dropped in
+    // the target.
+    let placement;
+    let itemForPlacement = aTargetNode;
+    // Skip the skipintoolbarset items when determining the place of the item:
+    while (
+      itemForPlacement &&
+      itemForPlacement.getAttribute("skipintoolbarset") == "true" &&
+      itemForPlacement.parentNode &&
+      itemForPlacement.parentNode.nodeName == "toolbarpaletteitem"
+    ) {
+      itemForPlacement = itemForPlacement.parentNode.nextElementSibling;
+      if (
+        itemForPlacement &&
+        itemForPlacement.nodeName == "toolbarpaletteitem"
+      ) {
+        itemForPlacement = itemForPlacement.firstElementChild;
+      }
+    }
+    if (itemForPlacement) {
+      let targetNodeId =
+        itemForPlacement.nodeName == "toolbarpaletteitem"
+          ? itemForPlacement.firstElementChild &&
+            itemForPlacement.firstElementChild.id
+          : itemForPlacement.id;
+      placement = CustomizableUI.getPlacementOfWidget(targetNodeId);
+    }
+    if (!placement) {
+      lazy.log.debug(
+        "Could not get a position for " +
+          aTargetNode.nodeName +
+          "#" +
+          aTargetNode.id +
+          "." +
+          aTargetNode.className
+      );
+    }
+    let position = placement ? placement.position : null;
+
+    // Is the target area the same as the origin? Since we've already handled
+    // the possibility that the target is the customization palette, we know
+    // that the widget is moving within a customizable area.
+    if (aTargetArea == aOriginArea) {
+      CustomizableUI.moveWidgetWithinArea(aDraggedItemId, position);
+      lazy.BrowserUsageTelemetry.recordWidgetChange(
+        aDraggedItemId,
+        aTargetArea.id,
+        "drag"
+      );
+    } else {
+      CustomizableUI.addWidgetToArea(aDraggedItemId, aTargetArea.id, position);
+      lazy.BrowserUsageTelemetry.recordWidgetChange(
+        aDraggedItemId,
+        aTargetArea.id,
+        "drag"
+      );
+    }
+
+    this._onDragEnd(aEvent);
+
+    // If we dropped onto a skipintoolbarset item, manually correct the drop location:
+    if (aTargetNode != itemForPlacement) {
+      let draggedWrapper = draggedItem.parentNode;
+      let container = draggedWrapper.parentNode;
+      container.insertBefore(draggedWrapper, aTargetNode.parentNode);
+    }
+  },
+
+  _onDragLeave(aEvent) {
+    if (this._isUnwantedDragDrop(aEvent)) {
+      return;
+    }
+
+    __dumpDragData(aEvent);
+
+    // When leaving customization areas, cancel the drag on the last dragover item
+    // We've attached the listener to areas, so aEvent.currentTarget will be the area.
+    // We don't care about dragleave events fired on descendants of the area,
+    // so we check that the event's target is the same as the area to which the listener
+    // was attached.
+    if (this._dragOverItem && aEvent.target == aEvent.currentTarget) {
+      this._cancelDragActive(this._dragOverItem);
+      this._dragOverItem = null;
+    }
+  },
+
+  /**
+   * To workaround bug 460801 we manually forward the drop event here when dragend wouldn't be fired.
+   *
+   * Note that that means that this function may be called multiple times by a single drag operation.
+   */
+  _onDragEnd(aEvent) {
+    if (this._isUnwantedDragDrop(aEvent)) {
+      return;
+    }
+    this._initializeDragAfterMove = null;
+    this.window.clearTimeout(this._dragInitializeTimeout);
+    __dumpDragData(aEvent, "_onDragEnd");
+
+    let document = aEvent.target.ownerDocument;
+    document.documentElement.removeAttribute("customizing-movingItem");
+
+    let documentId = document.documentElement.id;
+    if (!aEvent.dataTransfer.mozTypesAt(0)) {
+      return;
+    }
+
+    let draggedItemId = aEvent.dataTransfer.mozGetDataAt(
+      kDragDataTypePrefix + documentId,
+      0
+    );
+
+    let draggedWrapper = document.getElementById("wrapper-" + draggedItemId);
+
+    // DraggedWrapper might no longer available if a widget node is
+    // destroyed after starting (but before stopping) a drag.
+    if (draggedWrapper) {
+      draggedWrapper.hidden = false;
+      draggedWrapper.removeAttribute("mousedown");
+
+      let toolbarParent = draggedWrapper.closest("toolbar");
+      if (toolbarParent) {
+        toolbarParent.style.removeProperty("min-height");
+      }
+    }
+
+    if (this._dragOverItem) {
+      this._cancelDragActive(this._dragOverItem);
+      this._dragOverItem = null;
+    }
+    lazy.DragPositionManager.stop();
+  },
+
+  _isUnwantedDragDrop(aEvent) {
+    // The synthesized events for tests generated by synthesizePlainDragAndDrop
+    // and synthesizeDrop in mochitests are used only for testing whether the
+    // right data is being put into the dataTransfer. Neither cause a real drop
+    // to occur, so they don't set the source node. There isn't a means of
+    // testing real drag and drops, so this pref skips the check but it should
+    // only be set by test code.
+    if (this._skipSourceNodeCheck) {
+      return false;
+    }
+
+    /* Discard drag events that originated from a separate window to
+       prevent content->chrome privilege escalations. */
+    let mozSourceNode = aEvent.dataTransfer.mozSourceNode;
+    // mozSourceNode is null in the dragStart event handler or if
+    // the drag event originated in an external application.
+    return !mozSourceNode || mozSourceNode.ownerGlobal != this.window;
+  },
+
+  _setDragActive(aItem, aValue, aDraggedItemId, aAreaType) {
+    if (!aItem) {
+      return;
+    }
+
+    if (aItem.getAttribute("dragover") != aValue) {
+      aItem.setAttribute("dragover", aValue);
+
+      let window = aItem.ownerGlobal;
+      let draggedItem = window.document.getElementById(aDraggedItemId);
+      if (aAreaType == "palette") {
+        this._setGridDragActive(aItem, draggedItem, aValue);
+      } else {
+        let targetArea = this._getCustomizableParent(aItem);
+        let makeSpaceImmediately = false;
+        if (!gDraggingInToolbars.has(targetArea.id)) {
+          gDraggingInToolbars.add(targetArea.id);
+          let draggedWrapper = this.$("wrapper-" + aDraggedItemId);
+          let originArea = this._getCustomizableParent(draggedWrapper);
+          makeSpaceImmediately = originArea == targetArea;
+        }
+        let propertyToMeasure = aAreaType == "toolbar" ? "width" : "height";
+        // Calculate width/height of the item when it'd be dropped in this position.
+        let borderWidth = this._getDragItemSize(aItem, draggedItem)[
+          propertyToMeasure
+        ];
+        let layoutSide = aAreaType == "toolbar" ? "Inline" : "Block";
+        let prop, otherProp;
+        if (aValue == "before") {
+          prop = "border" + layoutSide + "StartWidth";
+          otherProp = "border-" + layoutSide.toLowerCase() + "-end-width";
+        } else {
+          prop = "border" + layoutSide + "EndWidth";
+          otherProp = "border-" + layoutSide.toLowerCase() + "-start-width";
+        }
+        if (makeSpaceImmediately) {
+          aItem.setAttribute("notransition", "true");
+        }
+        aItem.style[prop] = borderWidth + "px";
+        aItem.style.removeProperty(otherProp);
+        if (makeSpaceImmediately) {
+          // Force a layout flush:
+          aItem.getBoundingClientRect();
+          aItem.removeAttribute("notransition");
+        }
+      }
+    }
+  },
+  _cancelDragActive(aItem, aNextItem, aNoTransition) {
+    let currentArea = this._getCustomizableParent(aItem);
+    if (!currentArea) {
+      return;
+    }
+    let nextArea = aNextItem ? this._getCustomizableParent(aNextItem) : null;
+    if (currentArea != nextArea) {
+      currentArea.removeAttribute("draggingover");
+    }
+    let areaType = CustomizableUI.getAreaType(currentArea.id);
+    if (areaType) {
+      if (aNoTransition) {
+        aItem.setAttribute("notransition", "true");
+      }
+      aItem.removeAttribute("dragover");
+      // Remove all property values in the case that the end padding
+      // had been set.
+      aItem.style.removeProperty("border-inline-start-width");
+      aItem.style.removeProperty("border-inline-end-width");
+      aItem.style.removeProperty("border-block-start-width");
+      aItem.style.removeProperty("border-block-end-width");
+      if (aNoTransition) {
+        // Force a layout flush:
+        aItem.getBoundingClientRect();
+        aItem.removeAttribute("notransition");
+      }
+    } else {
+      aItem.removeAttribute("dragover");
+      if (aNextItem) {
+        if (nextArea == currentArea) {
+          // No need to do anything if we're still dragging in this area:
+          return;
+        }
+      }
+      // Otherwise, clear everything out:
+      let positionManager =
+        lazy.DragPositionManager.getManagerForArea(currentArea);
+      positionManager.clearPlaceholders(currentArea, aNoTransition);
+    }
+  },
+
+  _setGridDragActive(aDragOverNode, aDraggedItem, aValue) {
+    let targetArea = this._getCustomizableParent(aDragOverNode);
+    let draggedWrapper = this.$("wrapper-" + aDraggedItem.id);
+    let originArea = this._getCustomizableParent(draggedWrapper);
+    let positionManager =
+      lazy.DragPositionManager.getManagerForArea(targetArea);
+    let draggedSize = this._getDragItemSize(aDragOverNode, aDraggedItem);
+    positionManager.insertPlaceholder(
+      targetArea,
+      aDragOverNode,
+      draggedSize,
+      originArea == targetArea
+    );
+  },
+
+  _getDragItemSize(aDragOverNode, aDraggedItem) {
+    // Cache it good, cache it real good.
+    if (!this._dragSizeMap) {
+      this._dragSizeMap = new WeakMap();
+    }
+    if (!this._dragSizeMap.has(aDraggedItem)) {
+      this._dragSizeMap.set(aDraggedItem, new WeakMap());
+    }
+    let itemMap = this._dragSizeMap.get(aDraggedItem);
+    let targetArea = this._getCustomizableParent(aDragOverNode);
+    let currentArea = this._getCustomizableParent(aDraggedItem);
+    // Return the size for this target from cache, if it exists.
+    let size = itemMap.get(targetArea);
+    if (size) {
+      return size;
+    }
+
+    // Calculate size of the item when it'd be dropped in this position.
+    let currentParent = aDraggedItem.parentNode;
+    let currentSibling = aDraggedItem.nextElementSibling;
+    const kAreaType = "cui-areatype";
+    let areaType, currentType;
+
+    if (targetArea != currentArea) {
+      // Move the widget temporarily next to the placeholder.
+      aDragOverNode.parentNode.insertBefore(aDraggedItem, aDragOverNode);
+      // Update the node's areaType.
+      areaType = CustomizableUI.getAreaType(targetArea.id);
+      currentType =
+        aDraggedItem.hasAttribute(kAreaType) &&
+        aDraggedItem.getAttribute(kAreaType);
+      if (areaType) {
+        aDraggedItem.setAttribute(kAreaType, areaType);
+      }
+      this.wrapToolbarItem(aDraggedItem, areaType || "palette");
+      CustomizableUI.onWidgetDrag(aDraggedItem.id, targetArea.id);
+    } else {
+      aDraggedItem.parentNode.hidden = false;
+    }
+
+    // Fetch the new size.
+    let rect = aDraggedItem.parentNode.getBoundingClientRect();
+    size = { width: rect.width, height: rect.height };
+    // Cache the found value of size for this target.
+    itemMap.set(targetArea, size);
+
+    if (targetArea != currentArea) {
+      this.unwrapToolbarItem(aDraggedItem.parentNode);
+      // Put the item back into its previous position.
+      currentParent.insertBefore(aDraggedItem, currentSibling);
+      // restore the areaType
+      if (areaType) {
+        if (currentType === false) {
+          aDraggedItem.removeAttribute(kAreaType);
+        } else {
+          aDraggedItem.setAttribute(kAreaType, currentType);
+        }
+      }
+      this.createOrUpdateWrapper(aDraggedItem, null, true);
+      CustomizableUI.onWidgetDrag(aDraggedItem.id);
+    } else {
+      aDraggedItem.parentNode.hidden = true;
+    }
+    return size;
+  },
+
+  _getCustomizableParent(aElement) {
+    if (aElement) {
+      // Deal with drag/drop on the padding of the panel.
+      let containingPanelHolder = aElement.closest(
+        "#customization-panelHolder"
+      );
+      if (containingPanelHolder) {
+        return containingPanelHolder.querySelector(
+          "#widget-overflow-fixed-list"
+        );
+      }
+    }
+
+    let areas = CustomizableUI.areas;
+    areas.push(kPaletteId);
+    return aElement.closest(areas.map(a => "#" + CSS.escape(a)).join(","));
+  },
+
+  _getDragOverNode(aEvent, aAreaElement, aAreaType, aDraggedItemId) {
+    let expectedParent =
+      CustomizableUI.getCustomizationTarget(aAreaElement) || aAreaElement;
+    if (!expectedParent.contains(aEvent.target)) {
+      return expectedParent;
+    }
+    // Offset the drag event's position with the offset to the center of
+    // the thing we're dragging
+    let dragX = aEvent.clientX - this._dragOffset.x;
+    let dragY = aEvent.clientY - this._dragOffset.y;
+
+    // Ensure this is within the container
+    let boundsContainer = expectedParent;
+    let bounds = this._getBoundsWithoutFlushing(boundsContainer);
+    dragX = Math.min(bounds.right, Math.max(dragX, bounds.left));
+    dragY = Math.min(bounds.bottom, Math.max(dragY, bounds.top));
+
+    let targetNode;
+    if (aAreaType == "toolbar" || aAreaType == "panel") {
+      targetNode = aAreaElement.ownerDocument.elementFromPoint(dragX, dragY);
+      while (targetNode && targetNode.parentNode != expectedParent) {
+        targetNode = targetNode.parentNode;
+      }
+    } else {
+      let positionManager =
+        lazy.DragPositionManager.getManagerForArea(aAreaElement);
+      // Make it relative to the container:
+      dragX -= bounds.left;
+      dragY -= bounds.top;
+      // Find the closest node:
+      targetNode = positionManager.find(aAreaElement, dragX, dragY);
+    }
+    return targetNode || aEvent.target;
+  },
+
+  _onMouseDown(aEvent) {
+    lazy.log.debug("_onMouseDown");
+    if (aEvent.button != 0) {
+      return;
+    }
+    let doc = aEvent.target.ownerDocument;
+    doc.documentElement.setAttribute("customizing-movingItem", true);
+    let item = this._getWrapper(aEvent.target);
+    if (item) {
+      item.setAttribute("mousedown", "true");
+    }
+  },
+
+  _onMouseUp(aEvent) {
+    lazy.log.debug("_onMouseUp");
+    if (aEvent.button != 0) {
+      return;
+    }
+    let doc = aEvent.target.ownerDocument;
+    doc.documentElement.removeAttribute("customizing-movingItem");
+    let item = this._getWrapper(aEvent.target);
+    if (item) {
+      item.removeAttribute("mousedown");
+    }
+  },
+
+  _getWrapper(aElement) {
+    while (aElement && aElement.localName != "toolbarpaletteitem") {
+      if (aElement.localName == "toolbar") {
+        return null;
+      }
+      aElement = aElement.parentNode;
+    }
+    return aElement;
+  },
+
+  _findVisiblePreviousSiblingNode(aReferenceNode) {
+    while (
+      aReferenceNode &&
+      aReferenceNode.localName == "toolbarpaletteitem" &&
+      aReferenceNode.firstElementChild.hidden
+    ) {
+      aReferenceNode = aReferenceNode.previousElementSibling;
+    }
+    return aReferenceNode;
+  },
+
+  onPaletteContextMenuShowing(event) {
+    let isFlexibleSpace = event.target.triggerNode.id.includes(
+      "wrapper-customizableui-special-spring"
+    );
+    event.target.querySelector(".customize-context-addToPanel").disabled =
+      isFlexibleSpace;
+  },
+
+  onPanelContextMenuShowing(event) {
+    let inPermanentArea = !!event.target.triggerNode.closest(
+      "#widget-overflow-fixed-list"
+    );
+    let doc = event.target.ownerDocument;
+    doc.getElementById("customizationPanelItemContextMenuUnpin").hidden =
+      !inPermanentArea;
+    doc.getElementById("customizationPanelItemContextMenuPin").hidden =
+      inPermanentArea;
+
+    doc.ownerGlobal.MozXULElement.insertFTLIfNeeded(
+      "browser/toolbarContextMenu.ftl"
+    );
+    event.target.querySelectorAll("[data-lazy-l10n-id]").forEach(el => {
+      el.setAttribute("data-l10n-id", el.getAttribute("data-lazy-l10n-id"));
+      el.removeAttribute("data-lazy-l10n-id");
+    });
+  },
+
+  _checkForDownloadsClick(event) {
+    if (
+      event.target.closest("#wrapper-downloads-button") &&
+      event.button == 0
+    ) {
+      event.view.gCustomizeMode._showDownloadsAutoHidePanel();
+    }
+  },
+
+  _setupDownloadAutoHideToggle() {
+    this.window.addEventListener("click", this._checkForDownloadsClick, true);
+  },
+
+  _teardownDownloadAutoHideToggle() {
+    this.window.removeEventListener(
+      "click",
+      this._checkForDownloadsClick,
+      true
+    );
+    this.$(kDownloadAutohidePanelId).hidePopup();
+  },
+
+  _maybeMoveDownloadsButtonToNavBar() {
+    // If the user toggled the autohide checkbox while the item was in the
+    // palette, and hasn't moved it since, move the item to the default
+    // location in the navbar for them.
+    if (
+      !CustomizableUI.getPlacementOfWidget("downloads-button") &&
+      this._moveDownloadsButtonToNavBar &&
+      this.window.DownloadsButton.autoHideDownloadsButton
+    ) {
+      let navbarPlacements = CustomizableUI.getWidgetIdsInArea("nav-bar");
+      let insertionPoint = navbarPlacements.indexOf("urlbar-container");
+      while (++insertionPoint < navbarPlacements.length) {
+        let widget = navbarPlacements[insertionPoint];
+        // If we find a non-searchbar, non-spacer node, break out of the loop:
+        if (
+          widget != "search-container" &&
+          !(CustomizableUI.isSpecialWidget(widget) && widget.includes("spring"))
+        ) {
+          break;
+        }
+      }
+      CustomizableUI.addWidgetToArea(
+        "downloads-button",
+        "nav-bar",
+        insertionPoint
+      );
+      lazy.BrowserUsageTelemetry.recordWidgetChange(
+        "downloads-button",
+        "nav-bar",
+        "move-downloads"
+      );
+    }
+  },
+
+  async _showDownloadsAutoHidePanel() {
+    let doc = this.document;
+    let panel = doc.getElementById(kDownloadAutohidePanelId);
+    panel.hidePopup();
+    let button = doc.getElementById("downloads-button");
+    // We don't show the tooltip if the button is in the panel.
+    if (button.closest("#widget-overflow-fixed-list")) {
+      return;
+    }
+
+    let offsetX = 0,
+      offsetY = 0;
+    let panelOnTheLeft = false;
+    let toolbarContainer = button.closest("toolbar");
+    if (toolbarContainer && toolbarContainer.id == "nav-bar") {
+      let navbarWidgets = CustomizableUI.getWidgetIdsInArea("nav-bar");
+      if (
+        navbarWidgets.indexOf("urlbar-container") <=
+        navbarWidgets.indexOf("downloads-button")
+      ) {
+        panelOnTheLeft = true;
+      }
+    } else {
+      await this.window.promiseDocumentFlushed(() => {});
+
+      if (!this._customizing || !this._wantToBeInCustomizeMode) {
+        return;
+      }
+      let buttonBounds = this._getBoundsWithoutFlushing(button);
+      let windowBounds = this._getBoundsWithoutFlushing(doc.documentElement);
+      panelOnTheLeft =
+        buttonBounds.left + buttonBounds.width / 2 > windowBounds.width / 2;
+    }
+    let position;
+    if (panelOnTheLeft) {
+      // Tested in RTL, these get inverted automatically, so this does the
+      // right thing without taking RTL into account explicitly.
+      position = "topleft topright";
+      if (toolbarContainer) {
+        offsetX = 8;
+      }
+    } else {
+      position = "topright topleft";
+      if (toolbarContainer) {
+        offsetX = -8;
+      }
+    }
+
+    let checkbox = doc.getElementById(kDownloadAutohideCheckboxId);
+    if (this.window.DownloadsButton.autoHideDownloadsButton) {
+      checkbox.setAttribute("checked", "true");
+    } else {
+      checkbox.removeAttribute("checked");
+    }
+
+    // We don't use the icon to anchor because it might be resizing because of
+    // the animations for drag/drop. Hence the use of offsets.
+    panel.openPopup(button, position, offsetX, offsetY);
+  },
+
+  onDownloadsAutoHideChange(event) {
+    let checkbox = event.target.ownerDocument.getElementById(
+      kDownloadAutohideCheckboxId
+    );
+    Services.prefs.setBoolPref(kDownloadAutoHidePref, checkbox.checked);
+    // Ensure we move the button (back) after the user leaves customize mode.
+    event.view.gCustomizeMode._moveDownloadsButtonToNavBar = checkbox.checked;
+  },
+
+  customizeTouchBar() {
+    let updater = Cc["@mozilla.org/widget/touchbarupdater;1"].getService(
+      Ci.nsITouchBarUpdater
+    );
+    updater.enterCustomizeMode();
+  },
+
+  togglePong(enabled) {
+    // It's possible we're toggling for a reason other than hitting
+    // the button (we might be exiting, for example), so make sure that
+    // the state and checkbox are in sync.
+    let whimsyButton = this.$("whimsy-button");
+    whimsyButton.checked = enabled;
+
+    if (enabled) {
+      this.visiblePalette.setAttribute("whimsypong", "true");
+      this.pongArena.hidden = false;
+      if (!this.uninitWhimsy) {
+        this.uninitWhimsy = this.whimsypong();
+      }
+    } else {
+      this.visiblePalette.removeAttribute("whimsypong");
+      if (this.uninitWhimsy) {
+        this.uninitWhimsy();
+        this.uninitWhimsy = null;
+      }
+      this.pongArena.hidden = true;
+    }
+  },
+
+  whimsypong() {
+    function update() {
+      updateBall();
+      updatePlayers();
+    }
+
+    function updateBall() {
+      if (ball[1] <= 0 || ball[1] >= gameSide) {
+        if (
+          (ball[1] <= 0 && (ball[0] < p1 || ball[0] > p1 + paddleWidth)) ||
+          (ball[1] >= gameSide && (ball[0] < p2 || ball[0] > p2 + paddleWidth))
+        ) {
+          updateScore(ball[1] <= 0 ? 0 : 1);
+        } else {
+          if (
+            (ball[1] <= 0 &&
+              (ball[0] - p1 < paddleEdge ||
+                p1 + paddleWidth - ball[0] < paddleEdge)) ||
+            (ball[1] >= gameSide &&
+              (ball[0] - p2 < paddleEdge ||
+                p2 + paddleWidth - ball[0] < paddleEdge))
+          ) {
+            ballDxDy[0] *= Math.random() + 1.3;
+            ballDxDy[0] = Math.max(Math.min(ballDxDy[0], 6), -6);
+            if (Math.abs(ballDxDy[0]) == 6) {
+              ballDxDy[0] += Math.sign(ballDxDy[0]) * Math.random();
+            }
+          } else {
+            ballDxDy[0] /= 1.1;
+          }
+          ballDxDy[1] *= -1;
+          ball[1] = ball[1] <= 0 ? 0 : gameSide;
+        }
+      }
+      ball = [
+        Math.max(Math.min(ball[0] + ballDxDy[0], gameSide), 0),
+        Math.max(Math.min(ball[1] + ballDxDy[1], gameSide), 0),
+      ];
+      if (ball[0] <= 0 || ball[0] >= gameSide) {
+        ballDxDy[0] *= -1;
+      }
+    }
+
+    function updatePlayers() {
+      if (keydown) {
+        let p1Adj = 1;
+        if (
+          (keydown == 37 && !window.RTL_UI) ||
+          (keydown == 39 && window.RTL_UI)
+        ) {
+          p1Adj = -1;
+        }
+        p1 += p1Adj * 10 * keydownAdj;
+      }
+
+      let sign = Math.sign(ballDxDy[0]);
+      if (
+        (sign > 0 && ball[0] > p2 + paddleWidth / 2) ||
+        (sign < 0 && ball[0] < p2 + paddleWidth / 2)
+      ) {
+        p2 += sign * 3;
+      } else if (
+        (sign > 0 && ball[0] > p2 + paddleWidth / 1.1) ||
+        (sign < 0 && ball[0] < p2 + paddleWidth / 1.1)
+      ) {
+        p2 += sign * 9;
+      }
+
+      if (score >= winScore) {
+        p1 = ball[0];
+        p2 = ball[0];
+      }
+      p1 = Math.max(Math.min(p1, gameSide - paddleWidth), 0);
+      p2 = Math.max(Math.min(p2, gameSide - paddleWidth), 0);
+    }
+
+    function updateScore(adj) {
+      if (adj) {
+        score += adj;
+      } else if (--lives == 0) {
+        quit = true;
+      }
+      ball = ballDef.slice();
+      ballDxDy = ballDxDyDef.slice();
+      ballDxDy[1] *= score / winScore + 1;
+    }
+
+    function draw() {
+      let xAdj = window.RTL_UI ? -1 : 1;
+      elements["wp-player1"].style.transform =
+        "translate(" + xAdj * p1 + "px, -37px)";
+      elements["wp-player2"].style.transform =
+        "translate(" + xAdj * p2 + "px, " + gameSide + "px)";
+      elements["wp-ball"].style.transform =
+        "translate(" + xAdj * ball[0] + "px, " + ball[1] + "px)";
+      elements["wp-score"].textContent = score;
+      elements["wp-lives"].setAttribute("lives", lives);
+      if (score >= winScore) {
+        let arena = elements.arena;
+        let image = "url(chrome://browser/skin/customizableui/whimsy.png)";
+        let position = `${
+          (window.RTL_UI ? gameSide : 0) + xAdj * ball[0] - 10
+        }px ${ball[1] - 10}px`;
+        let repeat = "no-repeat";
+        let size = "20px";
+        if (arena.style.backgroundImage) {
+          if (arena.style.backgroundImage.split(",").length >= 160) {
+            quit = true;
+          }
+
+          image += ", " + arena.style.backgroundImage;
+          position += ", " + arena.style.backgroundPosition;
+          repeat += ", " + arena.style.backgroundRepeat;
+          size += ", " + arena.style.backgroundSize;
+        }
+        arena.style.backgroundImage = image;
+        arena.style.backgroundPosition = position;
+        arena.style.backgroundRepeat = repeat;
+        arena.style.backgroundSize = size;
+      }
+    }
+
+    function onkeydown(event) {
+      keys.push(event.which);
+      if (keys.length > 10) {
+        keys.shift();
+        let codeEntered = true;
+        for (let i = 0; i < keys.length; i++) {
+          if (keys[i] != keysCode[i]) {
+            codeEntered = false;
+            break;
+          }
+        }
+        if (codeEntered) {
+          elements.arena.setAttribute("kcode", "true");
+          let spacer = document.querySelector(
+            "#customization-palette > toolbarpaletteitem"
+          );
+          spacer.setAttribute("kcode", "true");
+        }
+      }
+      if (event.which == 37 /* left */ || event.which == 39 /* right */) {
+        keydown = event.which;
+        keydownAdj *= 1.05;
+      }
+    }
+
+    function onkeyup(event) {
+      if (event.which == 37 || event.which == 39) {
+        keydownAdj = 1;
+        keydown = 0;
+      }
+    }
+
+    function uninit() {
+      document.removeEventListener("keydown", onkeydown);
+      document.removeEventListener("keyup", onkeyup);
+      if (rAFHandle) {
+        window.cancelAnimationFrame(rAFHandle);
+      }
+      let arena = elements.arena;
+      while (arena.firstChild) {
+        arena.firstChild.remove();
+      }
+      arena.removeAttribute("score");
+      arena.removeAttribute("lives");
+      arena.removeAttribute("kcode");
+      arena.style.removeProperty("background-image");
+      arena.style.removeProperty("background-position");
+      arena.style.removeProperty("background-repeat");
+      arena.style.removeProperty("background-size");
+      let spacer = document.querySelector(
+        "#customization-palette > toolbarpaletteitem"
+      );
+      spacer.removeAttribute("kcode");
+      elements = null;
+      document = null;
+      quit = true;
+    }
+
+    if (this.uninitWhimsy) {
+      return this.uninitWhimsy;
+    }
+
+    let ballDef = [10, 10];
+    let ball = [10, 10];
+    let ballDxDyDef = [2, 2];
+    let ballDxDy = [2, 2];
+    let score = 0;
+    let p1 = 0;
+    let p2 = 10;
+    let gameSide = 300;
+    let paddleEdge = 30;
+    let paddleWidth = 84;
+    let keydownAdj = 1;
+    let keydown = 0;
+    let keys = [];
+    let keysCode = [38, 38, 40, 40, 37, 39, 37, 39, 66, 65];
+    let lives = 5;
+    let winScore = 11;
+    let quit = false;
+    let document = this.document;
+    let rAFHandle = 0;
+    let elements = {
+      arena: document.getElementById("customization-pong-arena"),
+    };
+
+    document.addEventListener("keydown", onkeydown);
+    document.addEventListener("keyup", onkeyup);
+
+    for (let id of ["player1", "player2", "ball", "score", "lives"]) {
+      let el = document.createXULElement("box");
+      el.id = "wp-" + id;
+      elements[el.id] = elements.arena.appendChild(el);
+    }
+
+    let spacer = this.visiblePalette.querySelector("toolbarpaletteitem");
+    for (let player of ["#wp-player1", "#wp-player2"]) {
+      let val = "-moz-element(#" + spacer.id + ") no-repeat";
+      elements.arena.querySelector(player).style.background = val;
+    }
+
+    let window = this.window;
+    rAFHandle = window.requestAnimationFrame(function animate() {
+      update();
+      draw();
+      if (quit) {
+        elements["wp-score"].textContent = score;
+        elements["wp-lives"] &&
+          elements["wp-lives"].setAttribute("lives", lives);
+        elements.arena.setAttribute("score", score);
+        elements.arena.setAttribute("lives", lives);
+      } else {
+        rAFHandle = window.requestAnimationFrame(animate);
+      }
+    });
+
+    return uninit;
+  },
+};
+
+function __dumpDragData(aEvent, caller) {
+  if (!gDebug) {
+    return;
+  }
+  let str =
+    "Dumping drag data (" +
+    (caller ? caller + " in " : "") +
+    "CustomizeMode.sys.mjs) {\n";
+  str += "  type: " + aEvent.type + "\n";
+  for (let el of ["target", "currentTarget", "relatedTarget"]) {
+    if (aEvent[el]) {
+      str +=
+        "  " +
+        el +
+        ": " +
+        aEvent[el] +
+        "(localName=" +
+        aEvent[el].localName +
+        "; id=" +
+        aEvent[el].id +
+        ")\n";
+    }
+  }
+  for (let prop in aEvent.dataTransfer) {
+    if (typeof aEvent.dataTransfer[prop] != "function") {
+      str +=
+        "  dataTransfer[" + prop + "]: " + aEvent.dataTransfer[prop] + "\n";
+    }
+  }
+  str += "}";
+  lazy.log.debug(str);
+}
+
+function dispatchFunction(aFunc) {
+  Services.tm.dispatchToMainThread(aFunc);
+}