1 files changed, 113 insertions, 0 deletions
diff --git a/layout/base/nsRefreshObservers.h b/layout/base/nsRefreshObservers.h
new file mode 100644
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+++ b/layout/base/nsRefreshObservers.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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/. */
+
+/*
+ * Code to notify things that animate before a refresh, at an appropriate
+ * refresh rate.  (Perhaps temporary, until replaced by compositor.)
+ */
+
+#ifndef LAYOUT_BASE_NSREFRESHOBSERVERS_H_
+#define LAYOUT_BASE_NSREFRESHOBSERVERS_H_
+
+#include <functional>
+
+#include "mozilla/Attributes.h"
+#include "mozilla/TimeStamp.h"
+#include "nsISupports.h"
+
+class nsPresContext;
+
+namespace mozilla {
+class AnimationEventDispatcher;
+class PendingFullscreenEvent;
+class PresShell;
+class RefreshDriverTimer;
+}  // namespace mozilla
+
+/**
+ * An abstract base class to be implemented by callers wanting to be
+ * notified at refresh times.  When nothing needs to be painted, callers
+ * may not be notified.
+ */
+class nsARefreshObserver {
+ public:
+  // AddRef and Release signatures that match nsISupports.  Implementors
+  // must implement reference counting, and those that do implement
+  // nsISupports will already have methods with the correct signature.
+  //
+  // The refresh driver does NOT hold references to refresh observers
+  // except while it is notifying them.
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  MOZ_CAN_RUN_SCRIPT virtual void WillRefresh(mozilla::TimeStamp aTime) = 0;
+
+#ifdef DEBUG
+  // Count of the active registrations we currently have with nsRefreshDrivers.
+  // This is incremented in nsRefreshDriver::AddRefreshObserver, decremented in
+  // nsRefreshDriver::RemoveRefreshObserver. No other code should modify this.
+  // We expect this to be 0 when we're destructed.
+  int32_t mRegistrationCount = 0;
+
+  // Virtual destructor to enforce the mRegistrationCount invariant.
+  virtual ~nsARefreshObserver() {
+    MOZ_ASSERT(mRegistrationCount == 0,
+               "Refresh observer AddRefreshObserver/RemoveRefreshObserver "
+               "calls should have balanced out to zero");
+  }
+#endif  // DEBUG
+};
+
+/**
+ * An abstract base class to be implemented by callers wanting to be notified
+ * when the observing refresh driver updated mMostRecentRefresh due to active
+ * timer changes. Callers must ensure an observer is removed before it is
+ * destroyed.
+ */
+class nsATimerAdjustmentObserver {
+ public:
+  virtual void NotifyTimerAdjusted(mozilla::TimeStamp aTime) = 0;
+};
+
+/**
+ * An abstract base class to be implemented by callers wanting to be notified
+ * that a refresh has occurred. Callers must ensure an observer is removed
+ * before it is destroyed.
+ */
+class nsAPostRefreshObserver {
+ public:
+  virtual void DidRefresh() = 0;
+};
+
+namespace mozilla {
+
+/**
+ * A wrapper for nsAPostRefreshObserver that's refcounted and might unregister
+ * itself after firing.
+ *
+ * Note, while the observer unregisters itself, the registering still needs to
+ * be done by the caller.
+ */
+class ManagedPostRefreshObserver : public nsAPostRefreshObserver {
+ public:
+  // Whether the post-refresh observer should be unregistered after it has
+  // fired.
+  enum class Unregister : bool { No, Yes };
+  using Action = std::function<Unregister(bool aWasCanceled)>;
+  NS_INLINE_DECL_REFCOUNTING(ManagedPostRefreshObserver)
+  ManagedPostRefreshObserver(nsPresContext*, Action&&);
+  explicit ManagedPostRefreshObserver(nsPresContext*);
+  void DidRefresh() override;
+  void Cancel();
+
+ protected:
+  virtual ~ManagedPostRefreshObserver();
+  RefPtr<nsPresContext> mPresContext;
+  Action mAction;
+};
+
+}  // namespace mozilla
+
+#endif