1 files changed, 119 insertions, 0 deletions
diff --git a/toolkit/modules/HiddenFrame.sys.mjs b/toolkit/modules/HiddenFrame.sys.mjs
new file mode 100644
index 0000000000..23ad57c0d3
--- /dev/null
+++ b/toolkit/modules/HiddenFrame.sys.mjs
@@ -0,0 +1,119 @@
+/* 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 XUL_PAGE = Services.io.newURI("chrome://global/content/win.xhtml");
+
+const gAllHiddenFrames = new Set();
+
+let cleanupRegistered = false;
+function ensureCleanupRegistered() {
+  if (!cleanupRegistered) {
+    cleanupRegistered = true;
+    Services.obs.addObserver(function () {
+      for (let hiddenFrame of gAllHiddenFrames) {
+        hiddenFrame.destroy();
+      }
+    }, "xpcom-shutdown");
+  }
+}
+
+/**
+ * An hidden frame object. It takes care of creating a windowless browser and
+ * passing the window containing a blank XUL <window> back.
+ */
+export function HiddenFrame() {}
+
+HiddenFrame.prototype = {
+  _frame: null,
+  _browser: null,
+  _listener: null,
+  _webProgress: null,
+  _deferred: null,
+
+  /**
+   * Gets the |contentWindow| of the hidden frame. Creates the frame if needed.
+   * @returns Promise Returns a promise which is resolved when the hidden frame has finished
+   *          loading.
+   */
+  get() {
+    if (!this._deferred) {
+      this._deferred = Promise.withResolvers();
+      this._create();
+    }
+
+    return this._deferred.promise;
+  },
+
+  /**
+   * Fetch a sync ref to the window inside the frame (needed for the add-on SDK).
+   */
+  getWindow() {
+    this.get();
+    return this._browser.document.ownerGlobal;
+  },
+
+  destroy() {
+    if (this._browser) {
+      if (this._listener) {
+        this._webProgress.removeProgressListener(this._listener);
+        this._listener = null;
+        this._webProgress = null;
+      }
+      this._frame = null;
+      this._deferred = null;
+
+      gAllHiddenFrames.delete(this);
+      this._browser.close();
+      this._browser = null;
+    }
+  },
+
+  _create() {
+    ensureCleanupRegistered();
+    let chromeFlags = Ci.nsIWebBrowserChrome.CHROME_REMOTE_WINDOW;
+    if (Services.appinfo.fissionAutostart) {
+      chromeFlags |= Ci.nsIWebBrowserChrome.CHROME_FISSION_WINDOW;
+    }
+    this._browser = Services.appShell.createWindowlessBrowser(
+      true,
+      chromeFlags
+    );
+    this._browser.QueryInterface(Ci.nsIInterfaceRequestor);
+    gAllHiddenFrames.add(this);
+    this._webProgress = this._browser.getInterface(Ci.nsIWebProgress);
+    this._listener = {
+      QueryInterface: ChromeUtils.generateQI([
+        "nsIWebProgressListener",
+        "nsIWebProgressListener2",
+        "nsISupportsWeakReference",
+      ]),
+    };
+    this._listener.onStateChange = (wbp, request, stateFlags, status) => {
+      if (!request) {
+        return;
+      }
+      if (stateFlags & Ci.nsIWebProgressListener.STATE_STOP) {
+        this._webProgress.removeProgressListener(this._listener);
+        this._listener = null;
+        this._webProgress = null;
+        // Get the window reference via the document.
+        this._frame = this._browser.document.ownerGlobal;
+        this._deferred.resolve(this._frame);
+      }
+    };
+    this._webProgress.addProgressListener(
+      this._listener,
+      Ci.nsIWebProgress.NOTIFY_STATE_DOCUMENT
+    );
+    let docShell = this._browser.docShell;
+    let systemPrincipal = Services.scriptSecurityManager.getSystemPrincipal();
+    docShell.createAboutBlankDocumentViewer(systemPrincipal, systemPrincipal);
+    let browsingContext = this._browser.browsingContext;
+    browsingContext.useGlobalHistory = false;
+    let loadURIOptions = {
+      triggeringPrincipal: systemPrincipal,
+    };
+    this._browser.loadURI(XUL_PAGE, loadURIOptions);
+  },
+};