1 files changed, 69 insertions, 0 deletions
diff --git a/toolkit/content/TopLevelVideoDocument.js b/toolkit/content/TopLevelVideoDocument.js
new file mode 100644
index 0000000000..4505a93d18
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+++ b/toolkit/content/TopLevelVideoDocument.js
@@ -0,0 +1,69 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// Hide our variables from the web content, even though the spec allows them
+// (and the DOM) to be accessible (see bug 1474832)
+{
+  // <video> is used for top-level audio documents as well
+  let videoElement = document.getElementsByTagName("video")[0];
+
+  let setFocusToVideoElement = function (e) {
+    // We don't want to retarget focus if it goes to the controls in
+    // the video element. Because they're anonymous content, the target
+    // will be the video element in that case. Avoid calling .focus()
+    // for those events:
+    if (e && e.target == videoElement) {
+      return;
+    }
+    videoElement.focus();
+  };
+
+  // Redirect focus to the video element whenever the document receives
+  // focus.
+  document.addEventListener("focus", setFocusToVideoElement, true);
+
+  // Focus on the video in the newly created document.
+  setFocusToVideoElement();
+
+  // Opt out of moving focus away if the DOM tree changes (from add-on or web content)
+  let observer = new MutationObserver(() => {
+    observer.disconnect();
+    document.removeEventListener("focus", setFocusToVideoElement, true);
+  });
+  observer.observe(document.documentElement, {
+    childList: true,
+    subtree: true,
+  });
+
+  // Handle fullscreen mode
+  document.addEventListener("keypress", ev => {
+    // Maximize the standalone video when pressing F11,
+    // but ignore audio elements
+    if (
+      ev.key == "F11" &&
+      videoElement.videoWidth != 0 &&
+      videoElement.videoHeight != 0
+    ) {
+      // If we're in browser fullscreen mode, it means the user pressed F11
+      // while browser chrome or another tab had focus.
+      // Don't break leaving that mode, so do nothing here.
+      if (window.fullScreen) {
+        return;
+      }
+
+      // If we're not in browser fullscreen mode, prevent entering into that,
+      // so we don't end up there after pressing Esc.
+      ev.preventDefault();
+      ev.stopPropagation();
+
+      if (!document.fullscreenElement) {
+        videoElement.requestFullscreen();
+      } else {
+        document.exitFullscreen();
+      }
+    }
+  });
+}