Issue #1643 - Part 3: Implement ResizeObserverController

1 files changed, 129 insertions, 0 deletions

diff --git a/dom/base/ResizeObserverController.h b/dom/base/ResizeObserverController.h
new file mode 100644
index 0000000000..a775115874
--- /dev/null
+++ b/dom/base/ResizeObserverController.h
@@ -0,0 +1,129 @@
+/* -*- 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/. */
+
+#ifndef mozilla_dom_ResizeObserverController_h
+#define mozilla_dom_ResizeObserverController_h
+
+#include "mozilla/dom/ResizeObserver.h"
+#include "mozilla/TimeStamp.h"
+#include "nsRefreshDriver.h"
+
+namespace mozilla {
+namespace dom {
+
+class ResizeObserverController;
+
+/*
+ * ResizeObserverNotificationHelper will trigger ResizeObserver notifications
+ * by registering with the Refresh Driver.
+*/
+class ResizeObserverNotificationHelper final : public nsARefreshObserver
+{
+public:
+  NS_INLINE_DECL_REFCOUNTING(ResizeObserverNotificationHelper, override)
+
+  explicit ResizeObserverNotificationHelper(ResizeObserverController* aOwner)
+    : mOwner(aOwner)
+    , mRegistered(false)
+  {
+    MOZ_ASSERT(mOwner, "Need a non-null owner");
+  }
+
+  void WillRefresh(TimeStamp aTime) override;
+
+  nsRefreshDriver* GetRefreshDriver() const;
+
+  void Register();
+
+  void Unregister();
+
+  void Disconnect();
+
+protected:
+  virtual ~ResizeObserverNotificationHelper();
+
+  ResizeObserverController* mOwner;
+  bool mRegistered;
+};
+
+/*
+ * ResizeObserverController contains the list of ResizeObservers and controls
+ * the flow of notification.
+*/
+class ResizeObserverController final
+{
+public:
+  explicit ResizeObserverController(nsIDocument* aDocument)
+    : mDocument(aDocument)
+    , mIsNotificationActive(false)
+  {
+    MOZ_ASSERT(mDocument, "Need a non-null document");
+    mResizeObserverNotificationHelper =
+      new ResizeObserverNotificationHelper(this);
+  }
+
+  // Methods for supporting cycle-collection
+  void Traverse(nsCycleCollectionTraversalCallback& aCb);
+  void Unlink();
+
+  void AddResizeObserver(ResizeObserver* aObserver);
+
+  /*
+   * Schedule the notification via ResizeObserverNotificationHelper refresh
+   * observer.
+  */
+  void ScheduleNotification();
+
+  /*
+   * Notify all ResizeObservers by gathering and broadcasting all active
+   * observations.
+  */
+  void Notify();
+
+  nsIPresShell* GetShell() const;
+
+  ~ResizeObserverController();
+
+private:
+  /*
+   * Calls GatherActiveObservations(aDepth) for all ResizeObservers in this
+   * controller. All observations in each ResizeObserver with element's depth
+   * more than aDepth will be gathered.
+  */
+  void GatherAllActiveObservations(uint32_t aDepth);
+
+  /*
+   * Calls BroadcastActiveObservations() for all ResizeObservers in this
+   * controller. It also returns the shallowest depth of observed target
+   * elements from all ResizeObserver or UINT32_MAX if there is no any
+   * active obsevations at all.
+  */
+  uint32_t BroadcastAllActiveObservations();
+
+  /*
+   * Returns whether there is any ResizeObserver that has active observations.
+  */
+  bool HasAnyActiveObservations() const;
+
+  /*
+   * Returns whether there is any ResizeObserver that has skipped observations.
+  */
+  bool HasAnySkippedObservations() const;
+
+protected:
+  // Raw pointer is OK because mDocument strongly owns us & hence must outlive
+  // us.
+  nsIDocument* const mDocument;
+
+  RefPtr<ResizeObserverNotificationHelper> mResizeObserverNotificationHelper;
+  nsTArray<RefPtr<ResizeObserver>> mResizeObservers;
+  bool mIsNotificationActive;
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_ResizeObserverController_h