Media: lock orientation when <video> goes fullscreen.

third_party/WebKit/Source/core/html/shadow/MediaControlsOrientationLockDelegate.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MediaControlsOrientationLockDelegate_h
+#define MediaControlsOrientationLockDelegate_h
+
+#include "core/CoreExport.h"
+#include "core/events/EventListener.h"
+#include "public/platform/modules/screen_orientation/WebScreenOrientationLockType.h"
+
+namespace blink {
+
+class Document;
+class HTMLVideoElement;
+
+// MediaControlsOrientationLockDelegate is implementing the orientation lock
+// feature when a <video> is fullscreen. It is meant to be created by
+// `MediaControls` when the feature apply. Once created, it will use events to
+// change state.
+//
+// The different states of the class are:
+// - PendingFullscreen: the object is created and is waiting for the associated
+//   <video> to go fullscreen in order to apply an orientation lock;
+// - PendingMetadata: the <video> is fullscreen but the metadata have not been
+//   downloaded yet. It can happen because of network latency or because the
+//   <video> went fullscreen before playback and download started;
+// - MaybeLockedFullscreen: the <video> is fullscreen and a screen orientation
+//   lock was applied.
+//
+// The possible state transitions are:
+// - PendingFullscreen => PendingMetadata: on fullscreenchange event (entering
+//   fullscreen) when metadata are not available;
+// - PendingFullscreen => MaybeLockedFullscreen: on fullscreenchange event
+//   (entering fullscreen) when metadata are available;
+// - PendingMetadata => MaybeLockedFullscreen: on loadedmetadata;
+// - PendingMetadata => PendingFullscreen: on fullscreenchange event (leaving
+//   fullscreen);
+// - MaybeLockedFullscreen => PendingFullscreen: on fullscreenchange event
+//   (leaving fullscreen).
+class CORE_EXPORT MediaControlsOrientationLockDelegate final
+    : public EventListener {
+ public:
+  explicit MediaControlsOrientationLockDelegate(HTMLVideoElement&);
+
+  // EventListener implementation.
+  bool operator==(const EventListener&) const override;
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  friend class MediaControlsOrientationLockDelegateTest;
+
+  enum class State {
+    PendingFullscreen,
+    PendingMetadata,
+    MaybeLockedFullscreen,
+  };
+
+  // EventListener implementation.
+  void handleEvent(ExecutionContext*, Event*) override;
+
+  HTMLVideoElement& videoElement() const;
+  Document& document() const;
+
+  // Returns the orientation in which the video should be locked based on its
+  // size.
+  WebScreenOrientationLockType computeOrientationLock() const;
+
+  // Locks the screen orientation if the video has metadata information
+  // available. Delays locking orientation until metadata are available
+  // otherwise.
+  void maybeLockOrientation();
+
+  // Unlocks the screen orientation if the screen orientation was previously
+  // locked.
+  void maybeUnlockOrientation();
+
+  // Current state of the object. See comment at the top of the file for a
+  // detailed description.
+  State m_state = State::PendingFullscreen;
+
+  // Whether the controls should unlock the screen orientation when possible.
+  // In other words, whether the orientation was locked.
+  bool m_shouldUnlockOrientation = false;
+
+  // `m_videoElement` owns MediaControls that owns |this|.
+  Member<HTMLVideoElement> m_videoElement;
+};
+
+}  // namespace blink
+
+#endif  // MediaControlsOrientationLockDelegate_h