From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 21:33:14 +0200
Subject: Adding upstream version 115.7.0esr.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 toolkit/actors/SelectParent.sys.mjs | 798 ++++++++++++++++++++++++++++++++++++
 1 file changed, 798 insertions(+)
 create mode 100644 toolkit/actors/SelectParent.sys.mjs

(limited to 'toolkit/actors/SelectParent.sys.mjs')

diff --git a/toolkit/actors/SelectParent.sys.mjs b/toolkit/actors/SelectParent.sys.mjs
new file mode 100644
index 0000000000..6c41903994
--- /dev/null
+++ b/toolkit/actors/SelectParent.sys.mjs
@@ -0,0 +1,798 @@
+/* vim: set ts=2 sw=2 sts=2 et tw=80: */
+/* 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/. */
+
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "DOM_FORMS_SELECTSEARCH",
+  "dom.forms.selectSearch",
+  false
+);
+
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "CUSTOM_STYLING_ENABLED",
+  "dom.forms.select.customstyling",
+  false
+);
+
+// Maximum number of rows to display in the select dropdown.
+const MAX_ROWS = 20;
+
+// Minimum elements required to show select search
+const SEARCH_MINIMUM_ELEMENTS = 40;
+
+// The properties that we should respect only when the item is not active.
+const PROPERTIES_RESET_WHEN_ACTIVE = [
+  "color",
+  "background-color",
+  "text-shadow",
+];
+
+// Duplicated in SelectChild.jsm
+// Please keep these lists in sync.
+const SUPPORTED_OPTION_OPTGROUP_PROPERTIES = [
+  "direction",
+  "color",
+  "background-color",
+  "text-shadow",
+  "text-transform",
+  "font-family",
+  "font-weight",
+  "font-size",
+  "font-style",
+];
+
+const SUPPORTED_SELECT_PROPERTIES = [
+  ...SUPPORTED_OPTION_OPTGROUP_PROPERTIES,
+  "scrollbar-width",
+  "scrollbar-color",
+];
+
+export var SelectParentHelper = {
+  /**
+   * `populate` takes the `menulist` element and a list of `items` and generates
+   * a popup list of options.
+   *
+   * If `CUSTOM_STYLING_ENABLED` is set to `true`, the function will also
+   * style the select and its popup trying to prevent the text
+   * and background to end up in the same color.
+   *
+   * All `ua*` variables represent the color values for the default colors
+   * for their respective form elements used by the user agent.
+   * The `select*` variables represent the color values defined for the
+   * particular <select> element.
+   *
+   * The `customoptionstyling` attribute controls the application of
+   * `-moz-appearance` on the elements and is disabled if the element is
+   * defining its own background-color.
+   *
+   * @param {Element}        menulist
+   * @param {Array<Element>} items
+   * @param {Array<Object>}  uniqueItemStyles
+   * @param {Number}         selectedIndex
+   * @param {Number}         zoom
+   * @param {Boolean}        custom
+   * @param {Boolean}        isDarkBackground
+   * @param {Object}         uaStyle
+   * @param {Object}         selectStyle
+   */
+  populate(
+    menulist,
+    items,
+    uniqueItemStyles,
+    selectedIndex,
+    zoom,
+    custom,
+    isDarkBackground,
+    uaStyle,
+    selectStyle
+  ) {
+    let doc = menulist.ownerDocument;
+
+    // Clear the current contents of the popup
+    let menupopup = menulist.menupopup;
+    menupopup.textContent = "";
+
+    let stylesheet = menulist.querySelector("#ContentSelectDropdownStylesheet");
+    if (stylesheet) {
+      stylesheet.remove();
+    }
+
+    menupopup.setAttribute("style", "");
+    menupopup.style.colorScheme = isDarkBackground ? "dark" : "light";
+    menupopup.style.direction = selectStyle.direction;
+
+    stylesheet = doc.createElementNS("http://www.w3.org/1999/xhtml", "style");
+    stylesheet.setAttribute("id", "ContentSelectDropdownStylesheet");
+    stylesheet.hidden = true;
+    stylesheet = menulist.appendChild(stylesheet);
+
+    let sheet = stylesheet.sheet;
+
+    if (!custom) {
+      selectStyle = uaStyle;
+    }
+
+    if (selectStyle["background-color"] == "rgba(0, 0, 0, 0)") {
+      selectStyle["background-color"] = uaStyle["background-color"];
+    }
+
+    if (selectStyle.color == selectStyle["background-color"]) {
+      selectStyle.color = uaStyle.color;
+    }
+
+    // We ensure that we set the content background if the color changes as
+    // well, to prevent contrast issues.
+    let selectBackgroundSet =
+      selectStyle["background-color"] != uaStyle["background-color"] ||
+      selectStyle.color != uaStyle.color;
+
+    if (custom) {
+      if (selectStyle["text-shadow"] != "none") {
+        sheet.insertRule(
+          `#ContentSelectDropdown > menupopup > :is(menuitem, menucaption)[_moz-menuactive="true"] {
+          text-shadow: none;
+        }`,
+          0
+        );
+      }
+
+      for (let property of SUPPORTED_SELECT_PROPERTIES) {
+        let shouldSkip = (function () {
+          if (property == "direction") {
+            // Handled elsewhere.
+            return true;
+          }
+          if (!selectStyle[property]) {
+            return true;
+          }
+          if (property == "background-color") {
+            // This also depends on whether "color" is set.
+            return !selectBackgroundSet;
+          }
+          return selectStyle[property] == uaStyle[property];
+        })();
+
+        if (shouldSkip) {
+          continue;
+        }
+        let value = selectStyle[property];
+        if (property == "scrollbar-width") {
+          // This needs to actually apply to the relevant scrollbox, because
+          // scrollbar-width doesn't inherit.
+          property = "--content-select-scrollbar-width";
+        }
+        if (property == "color") {
+          property = "--panel-color";
+        }
+        menupopup.style.setProperty(property, value);
+      }
+      // Some webpages set the <select> backgroundColor to transparent,
+      // but they don't intend to change the popup to transparent.
+      // So we remove the backgroundColor and turn it into an image instead.
+      if (selectBackgroundSet) {
+        // We intentionally use the parsed color to prevent color
+        // values like `url(..)` being injected into the
+        // `background-image` property.
+        let parsedColor = menupopup.style.backgroundColor;
+        menupopup.style.setProperty(
+          "--content-select-background-image",
+          `linear-gradient(${parsedColor}, ${parsedColor})`
+        );
+        // Always drop the background color to avoid messing with the custom
+        // shadow on Windows 10 styling.
+        menupopup.style.backgroundColor = "";
+        // If the background is set, we also make sure we set the color, to
+        // prevent contrast issues.
+        menupopup.style.setProperty("--panel-color", selectStyle.color);
+
+        sheet.insertRule(
+          `#ContentSelectDropdown > menupopup > :is(menuitem, menucaption):not([_moz-menuactive="true"]) {
+            color: inherit;
+        }`,
+          0
+        );
+      }
+    }
+
+    for (let i = 0, len = uniqueItemStyles.length; i < len; ++i) {
+      sheet.insertRule(
+        `#ContentSelectDropdown .ContentSelectDropdown-item-${i} {}`,
+        0
+      );
+      let style = uniqueItemStyles[i];
+      let rule = sheet.cssRules[0].style;
+      rule.direction = style.direction;
+      rule.fontSize = zoom * parseFloat(style["font-size"], 10) + "px";
+
+      if (!custom) {
+        continue;
+      }
+      let optionBackgroundIsTransparent =
+        style["background-color"] == "rgba(0, 0, 0, 0)";
+      let optionBackgroundSet =
+        !optionBackgroundIsTransparent || style.color != selectStyle.color;
+
+      if (optionBackgroundIsTransparent && style.color != selectStyle.color) {
+        style["background-color"] = selectStyle["background-color"];
+      }
+
+      if (style.color == style["background-color"]) {
+        style.color = selectStyle.color;
+      }
+
+      let inactiveRule = null;
+      for (const property of SUPPORTED_OPTION_OPTGROUP_PROPERTIES) {
+        let shouldSkip = (function () {
+          if (property == "direction" || property == "font-size") {
+            // Handled elsewhere.
+            return true;
+          }
+          if (!style[property]) {
+            return true;
+          }
+          if (property == "background-color" || property == "color") {
+            // This also depends on whether "color" is set.
+            return !optionBackgroundSet;
+          }
+          return style[property] == selectStyle[property];
+        })();
+        if (shouldSkip) {
+          continue;
+        }
+        if (PROPERTIES_RESET_WHEN_ACTIVE.includes(property)) {
+          if (!inactiveRule) {
+            sheet.insertRule(
+              `#ContentSelectDropdown .ContentSelectDropdown-item-${i}:not([_moz-menuactive="true"]) {}`,
+              0
+            );
+            inactiveRule = sheet.cssRules[0].style;
+          }
+          inactiveRule[property] = style[property];
+        } else {
+          rule[property] = style[property];
+        }
+      }
+      style.customStyling = selectBackgroundSet || optionBackgroundSet;
+    }
+
+    // We only set the `customoptionstyling` if the background has been
+    // manually set. This prevents the overlap between moz-appearance and
+    // background-color. `color` and `text-shadow` do not interfere with it.
+    if (custom && selectBackgroundSet) {
+      menulist.menupopup.setAttribute("customoptionstyling", "true");
+    } else {
+      menulist.menupopup.removeAttribute("customoptionstyling");
+    }
+
+    this._currentZoom = zoom;
+    this._currentMenulist = menulist;
+    this.populateChildren(menulist, items, uniqueItemStyles, selectedIndex);
+  },
+
+  open(browser, menulist, rect, isOpenedViaTouch, selectParentActor) {
+    this._actor = selectParentActor;
+    menulist.hidden = false;
+    this._currentBrowser = browser;
+    this._closedWithEnter = false;
+    this._selectRect = rect;
+    this._registerListeners(menulist.menupopup);
+
+    // Set the maximum height to show exactly MAX_ROWS items.
+    let menupopup = menulist.menupopup;
+    let firstItem = menupopup.firstElementChild;
+    while (firstItem && firstItem.hidden) {
+      firstItem = firstItem.nextElementSibling;
+    }
+
+    let win = menulist.ownerGlobal;
+    if (firstItem) {
+      let itemHeight = firstItem.getBoundingClientRect().height;
+
+      // Include the padding and border on the popup.
+      let cs = win.getComputedStyle(menupopup);
+      let bpHeight =
+        parseFloat(cs.borderTopWidth) +
+        parseFloat(cs.borderBottomWidth) +
+        parseFloat(cs.paddingTop) +
+        parseFloat(cs.paddingBottom);
+      menupopup.style.maxHeight = itemHeight * MAX_ROWS + bpHeight + "px";
+    }
+
+    menupopup.classList.toggle("isOpenedViaTouch", isOpenedViaTouch);
+
+    if (browser) {
+      browser.constrainPopup(menupopup);
+    } else {
+      menupopup.setConstraintRect(new win.DOMRect(0, 0, 0, 0));
+    }
+    menupopup.openPopupAtScreenRect(
+      AppConstants.platform == "macosx" ? "selection" : "after_start",
+      rect.left,
+      rect.top,
+      rect.width,
+      rect.height,
+      false,
+      false
+    );
+  },
+
+  hide(menulist, browser) {
+    if (this._currentBrowser == browser) {
+      menulist.menupopup.hidePopup();
+    }
+  },
+
+  handleEvent(event) {
+    switch (event.type) {
+      case "mouseup":
+        function inRect(rect, x, y) {
+          return (
+            x >= rect.left &&
+            x <= rect.left + rect.width &&
+            y >= rect.top &&
+            y <= rect.top + rect.height
+          );
+        }
+
+        let x = event.screenX,
+          y = event.screenY;
+        let onAnchor =
+          !inRect(this._currentMenulist.menupopup.getOuterScreenRect(), x, y) &&
+          inRect(this._selectRect, x, y) &&
+          this._currentMenulist.menupopup.state == "open";
+        this._actor.sendAsyncMessage("Forms:MouseUp", { onAnchor });
+        break;
+
+      case "mouseover":
+        if (
+          !event.relatedTarget ||
+          !this._currentMenulist.contains(event.relatedTarget)
+        ) {
+          this._actor.sendAsyncMessage("Forms:MouseOver", {});
+        }
+        break;
+
+      case "mouseout":
+        if (
+          !event.relatedTarget ||
+          !this._currentMenulist.contains(event.relatedTarget)
+        ) {
+          this._actor.sendAsyncMessage("Forms:MouseOut", {});
+        }
+        break;
+
+      case "keydown":
+        if (event.keyCode == event.DOM_VK_RETURN) {
+          this._closedWithEnter = true;
+        }
+        break;
+
+      case "command":
+        if (event.target.hasAttribute("value")) {
+          this._actor.sendAsyncMessage("Forms:SelectDropDownItem", {
+            value: event.target.value,
+            closedWithEnter: this._closedWithEnter,
+          });
+        }
+        break;
+
+      case "fullscreen":
+        if (this._currentMenulist) {
+          this._currentMenulist.menupopup.hidePopup();
+        }
+        break;
+
+      case "popuphidden":
+        this._actor.sendAsyncMessage("Forms:DismissedDropDown", {});
+        let popup = event.target;
+        this._unregisterListeners(popup);
+        popup.parentNode.hidden = true;
+        this._currentBrowser = null;
+        this._currentMenulist = null;
+        this._selectRect = null;
+        this._currentZoom = 1;
+        this._actor = null;
+        break;
+    }
+  },
+
+  receiveMessage(browser, msg) {
+    // Sanity check - we'd better know what the currently opened menulist is,
+    // and what browser it belongs to...
+    if (!this._currentMenulist || this._currentBrowser != browser) {
+      return;
+    }
+
+    if (msg.name == "Forms:UpdateDropDown") {
+      let scrollBox = this._currentMenulist.menupopup.scrollBox.scrollbox;
+      let scrollTop = scrollBox.scrollTop;
+
+      let options = msg.data.options;
+      let selectedIndex = msg.data.selectedIndex;
+      this.populate(
+        this._currentMenulist,
+        options.options,
+        options.uniqueStyles,
+        selectedIndex,
+        this._currentZoom,
+        msg.data.custom && lazy.CUSTOM_STYLING_ENABLED,
+        msg.data.isDarkBackground,
+        msg.data.defaultStyle,
+        msg.data.style
+      );
+
+      // Restore scroll position to what it was prior to the update.
+      scrollBox.scrollTop = scrollTop;
+    } else if (msg.name == "Forms:BlurDropDown-Ping") {
+      this._actor.sendAsyncMessage("Forms:BlurDropDown-Pong", {});
+    }
+  },
+
+  _registerListeners(popup) {
+    popup.addEventListener("command", this);
+    popup.addEventListener("popuphidden", this);
+    popup.addEventListener("mouseover", this);
+    popup.addEventListener("mouseout", this);
+    popup.ownerGlobal.addEventListener("mouseup", this, true);
+    popup.ownerGlobal.addEventListener("keydown", this, true);
+    popup.ownerGlobal.addEventListener("fullscreen", this, true);
+  },
+
+  _unregisterListeners(popup) {
+    popup.removeEventListener("command", this);
+    popup.removeEventListener("popuphidden", this);
+    popup.removeEventListener("mouseover", this);
+    popup.removeEventListener("mouseout", this);
+    popup.ownerGlobal.removeEventListener("mouseup", this, true);
+    popup.ownerGlobal.removeEventListener("keydown", this, true);
+    popup.ownerGlobal.removeEventListener("fullscreen", this, true);
+  },
+
+  /**
+   * `populateChildren` creates all <menuitem> elements for the popup menu
+   * based on the list of <option> elements from the <select> element.
+   *
+   * It attempts to intelligently add per-item CSS rules if the single
+   * item values differ from the parent menu values and attempting to avoid
+   * ending up with the same color of text and background.
+   *
+   * @param {Element}        menulist
+   * @param {Array<Element>} options
+   * @param {Array<Object>}  uniqueOptionStyles
+   * @param {Number}         selectedIndex
+   * @param {Element}        parentElement
+   * @param {Boolean}        isGroupDisabled
+   * @param {Boolean}        addSearch
+   * @param {Number}         nthChildIndex
+   * @returns {Number}
+   */
+  populateChildren(
+    menulist,
+    options,
+    uniqueOptionStyles,
+    selectedIndex,
+    parentElement = null,
+    isGroupDisabled = false,
+    addSearch = true,
+    nthChildIndex = 1
+  ) {
+    let element = menulist.menupopup;
+
+    let ariaOwns = "";
+    for (let option of options) {
+      let isOptGroup = option.isOptGroup;
+      let item = element.ownerDocument.createXULElement(
+        isOptGroup ? "menucaption" : "menuitem"
+      );
+      if (isOptGroup) {
+        item.setAttribute("role", "group");
+      }
+      item.setAttribute("label", option.textContent);
+      item.className = `ContentSelectDropdown-item-${option.styleIndex}`;
+      item.hidden =
+        option.display == "none" || (parentElement && parentElement.hidden);
+      // Keep track of which options are hidden by page content, so we can avoid
+      // showing them on search input.
+      item.hiddenByContent = item.hidden;
+      item.setAttribute("tooltiptext", option.tooltip);
+
+      if (uniqueOptionStyles[option.styleIndex].customStyling) {
+        item.setAttribute("customoptionstyling", "true");
+      } else {
+        item.removeAttribute("customoptionstyling");
+      }
+
+      if (parentElement) {
+        // In the menupopup, the optgroup is a sibling of its contained options.
+        // For accessibility, we want to preserve the hierarchy such that the
+        // options are inside the optgroup. We do this using aria-owns on the
+        // parent.
+        item.id = "ContentSelectDropdownOption" + nthChildIndex;
+        item.setAttribute("aria-level", "2");
+        ariaOwns += item.id + " ";
+      }
+
+      element.appendChild(item);
+      nthChildIndex++;
+
+      // A disabled optgroup disables all of its child options.
+      let isDisabled = isGroupDisabled || option.disabled;
+      if (isDisabled) {
+        item.setAttribute("disabled", "true");
+      }
+
+      if (isOptGroup) {
+        nthChildIndex = this.populateChildren(
+          menulist,
+          option.children,
+          uniqueOptionStyles,
+          selectedIndex,
+          item,
+          isDisabled,
+          false,
+          nthChildIndex
+        );
+      } else {
+        if (option.index == selectedIndex) {
+          // We expect the parent element of the popup to be a <xul:menulist> that
+          // has the popuponly attribute set to "true". This is necessary in order
+          // for a <xul:menupopup> to act like a proper <html:select> dropdown, as
+          // the <xul:menulist> does things like remember state and set the
+          // _moz-menuactive attribute on the selected <xul:menuitem>.
+          menulist.selectedItem = item;
+
+          // It's hack time. In the event that we've re-populated the menulist due
+          // to a mutation in the <select> in content, that means that the -moz_activemenu
+          // may have been removed from the selected item. Since that's normally only
+          // set for the initially selected on popupshowing for the menulist, and we
+          // don't want to close and re-open the popup, we manually set it here.
+          menulist.activeChild = item;
+        }
+
+        item.setAttribute("value", option.index);
+
+        if (parentElement) {
+          item.classList.add("contentSelectDropdown-ingroup");
+        }
+      }
+    }
+
+    if (parentElement && ariaOwns) {
+      parentElement.setAttribute("aria-owns", ariaOwns);
+    }
+
+    // Check if search pref is enabled, if this is the first time iterating through
+    // the dropdown, and if the list is long enough for a search element to be added.
+    if (
+      lazy.DOM_FORMS_SELECTSEARCH &&
+      addSearch &&
+      element.childElementCount > SEARCH_MINIMUM_ELEMENTS
+    ) {
+      // Add a search text field as the first element of the dropdown
+      let searchbox = element.ownerDocument.createXULElement("search-textbox");
+      searchbox.className = "contentSelectDropdown-searchbox";
+      searchbox.addEventListener("input", this.onSearchInput);
+      searchbox.addEventListener("focus", this.onSearchFocus.bind(this));
+      searchbox.addEventListener("blur", this.onSearchBlur);
+      searchbox.addEventListener("command", this.onSearchInput);
+
+      // Handle special keys for exiting search
+      searchbox.addEventListener(
+        "keydown",
+        event => {
+          this.onSearchKeydown(event, menulist);
+        },
+        true
+      );
+
+      element.insertBefore(searchbox, element.children[0]);
+    }
+
+    return nthChildIndex;
+  },
+
+  onSearchKeydown(event, menulist) {
+    if (event.defaultPrevented) {
+      return;
+    }
+
+    let searchbox = event.currentTarget;
+    switch (event.key) {
+      case "Escape":
+        searchbox.parentElement.hidePopup();
+        break;
+      case "ArrowDown":
+      case "Enter":
+      case "Tab":
+        searchbox.blur();
+        if (
+          searchbox.nextElementSibling.localName == "menuitem" &&
+          !searchbox.nextElementSibling.hidden
+        ) {
+          menulist.activeChild = searchbox.nextElementSibling;
+        } else {
+          let currentOption = searchbox.nextElementSibling;
+          while (
+            currentOption &&
+            (currentOption.localName != "menuitem" || currentOption.hidden)
+          ) {
+            currentOption = currentOption.nextElementSibling;
+          }
+          if (currentOption) {
+            menulist.activeChild = currentOption;
+          } else {
+            searchbox.focus();
+          }
+        }
+        break;
+      default:
+        return;
+    }
+    event.preventDefault();
+  },
+
+  onSearchInput(event) {
+    let searchObj = event.currentTarget;
+
+    // Get input from search field, set to all lower case for comparison
+    let input = searchObj.value.toLowerCase();
+    // Get all items in dropdown (could be options or optgroups)
+    let menupopup = searchObj.parentElement;
+    let menuItems = menupopup.querySelectorAll("menuitem, menucaption");
+
+    // Flag used to detect any group headers with no visible options.
+    // These group headers should be hidden.
+    let allHidden = true;
+    // Keep a reference to the previous group header (menucaption) to go back
+    // and set to hidden if all options within are hidden.
+    let prevCaption = null;
+
+    for (let currentItem of menuItems) {
+      // Make sure we don't show any options that were hidden by page content
+      if (!currentItem.hiddenByContent) {
+        // Get label and tooltip (title) from option and change to
+        // lower case for comparison
+        let itemLabel = currentItem.getAttribute("label").toLowerCase();
+        let itemTooltip = currentItem.getAttribute("title").toLowerCase();
+
+        // If search input is empty, all options should be shown
+        if (!input) {
+          currentItem.hidden = false;
+        } else if (currentItem.localName == "menucaption") {
+          if (prevCaption != null) {
+            prevCaption.hidden = allHidden;
+          }
+          prevCaption = currentItem;
+          allHidden = true;
+        } else {
+          if (
+            !currentItem.classList.contains("contentSelectDropdown-ingroup") &&
+            currentItem.previousElementSibling.classList.contains(
+              "contentSelectDropdown-ingroup"
+            )
+          ) {
+            if (prevCaption != null) {
+              prevCaption.hidden = allHidden;
+            }
+            prevCaption = null;
+            allHidden = true;
+          }
+          if (itemLabel.includes(input) || itemTooltip.includes(input)) {
+            currentItem.hidden = false;
+            allHidden = false;
+          } else {
+            currentItem.hidden = true;
+          }
+        }
+        if (prevCaption != null) {
+          prevCaption.hidden = allHidden;
+        }
+      }
+    }
+  },
+
+  onSearchFocus(event) {
+    let menupopup = event.target.closest("menupopup");
+    menupopup.parentElement.activeChild = null;
+    menupopup.setAttribute("ignorekeys", "true");
+    this._actor.sendAsyncMessage("Forms:SearchFocused", {});
+  },
+
+  onSearchBlur(event) {
+    let menupopup = event.target.closest("menupopup");
+    menupopup.setAttribute(
+      "ignorekeys",
+      AppConstants.platform == "win" ? "shortcuts" : "false"
+    );
+  },
+};
+
+export class SelectParent extends JSWindowActorParent {
+  get relevantBrowser() {
+    return this.browsingContext.top.embedderElement;
+  }
+
+  get _document() {
+    return this.browsingContext.topChromeWindow.document;
+  }
+
+  get _menulist() {
+    return this._document.getElementById("ContentSelectDropdown");
+  }
+
+  _createMenulist() {
+    let document = this._document;
+    let menulist = document.createXULElement("menulist");
+    menulist.setAttribute("id", "ContentSelectDropdown");
+    menulist.setAttribute("popuponly", "true");
+    menulist.setAttribute("hidden", "true");
+
+    let popup = menulist.appendChild(document.createXULElement("menupopup"));
+    popup.setAttribute("id", "ContentSelectDropdownPopup");
+    popup.setAttribute("activateontab", "true");
+    popup.setAttribute("position", "after_start");
+    popup.setAttribute("level", "parent");
+    if (AppConstants.platform == "win") {
+      popup.setAttribute("consumeoutsideclicks", "false");
+      popup.setAttribute("ignorekeys", "shortcuts");
+    }
+
+    let container =
+      document.getElementById("mainPopupSet") ||
+      document.querySelector("popupset") ||
+      document.documentElement.appendChild(
+        document.createXULElement("popupset")
+      );
+
+    container.appendChild(menulist);
+    return menulist;
+  }
+
+  receiveMessage(message) {
+    switch (message.name) {
+      case "Forms:ShowDropDown": {
+        let menulist = this._menulist || this._createMenulist();
+
+        let data = message.data;
+
+        SelectParentHelper.populate(
+          menulist,
+          data.options.options,
+          data.options.uniqueStyles,
+          data.selectedIndex,
+          // We only want to apply the full zoom. The text zoom is already
+          // applied in the font-size.
+          this.browsingContext.fullZoom,
+          data.custom && lazy.CUSTOM_STYLING_ENABLED,
+          data.isDarkBackground,
+          data.defaultStyle,
+          data.style
+        );
+        SelectParentHelper.open(
+          this.relevantBrowser,
+          menulist,
+          data.rect,
+          data.isOpenedViaTouch,
+          this
+        );
+        break;
+      }
+
+      case "Forms:HideDropDown": {
+        SelectParentHelper.hide(this._menulist, this.relevantBrowser);
+        break;
+      }
+
+      default:
+        SelectParentHelper.receiveMessage(this.relevantBrowser, message);
+    }
+  }
+}
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