Issue #1643 - Part 3: Implement ResizeObserverController

dom/base/ResizeObserverController.cpp

@@ -0,0 +1,234 @@
+/* -*- 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/. */
+
+#include "mozilla/dom/ResizeObserverController.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/ErrorEvent.h"
+#include "nsIPresShell.h"
+#include "nsPresContext.h"
+
+namespace mozilla {
+namespace dom {
+
+void
+ResizeObserverNotificationHelper::WillRefresh(TimeStamp aTime)
+{
+  MOZ_ASSERT(mOwner, "Why is mOwner already dead when this RefreshObserver is still registered?");
+  if (mOwner) {
+    mOwner->Notify();
+  }
+}
+
+nsRefreshDriver*
+ResizeObserverNotificationHelper::GetRefreshDriver() const
+{
+  nsIPresShell* presShell = mOwner->GetShell();
+  if (MOZ_UNLIKELY(!presShell)) {
+    return nullptr;
+  }
+
+  nsPresContext* presContext = presShell->GetPresContext();
+  if (MOZ_UNLIKELY(!presContext)) {
+    return nullptr;
+  }
+
+  return presContext->RefreshDriver();
+}
+
+void
+ResizeObserverNotificationHelper::Register()
+{
+  if (mRegistered) {
+    return;
+  }
+
+  nsRefreshDriver* refreshDriver = GetRefreshDriver();
+  if (!refreshDriver) {
+    // We maybe navigating away from this page or currently in an iframe with
+    // display: none. Just abort the Register(), no need to do notification.
+    return;
+  }
+
+  refreshDriver->AddRefreshObserver(this, Flush_Display);
+  mRegistered = true;
+}
+
+void
+ResizeObserverNotificationHelper::Unregister()
+{
+  if (!mRegistered) {
+    return;
+  }
+
+  nsRefreshDriver* refreshDriver = GetRefreshDriver();
+  if (!refreshDriver) {
+    // We can't access RefreshDriver now. Just abort the Unregister().
+    return;
+  }
+
+  refreshDriver->RemoveRefreshObserver(this, Flush_Display);
+  mRegistered = false;
+}
+
+void
+ResizeObserverNotificationHelper::Disconnect()
+{
+  Unregister();
+  // Our owner is dying. Clear our pointer to it, in case we outlive it.
+  mOwner = nullptr;
+}
+
+ResizeObserverNotificationHelper::~ResizeObserverNotificationHelper()
+{
+  Unregister();
+}
+
+void
+ResizeObserverController::Traverse(nsCycleCollectionTraversalCallback& aCb)
+{
+  ImplCycleCollectionTraverse(aCb, mResizeObservers, "mResizeObservers");
+}
+
+void
+ResizeObserverController::Unlink()
+{
+  mResizeObservers.Clear();
+}
+
+void
+ResizeObserverController::AddResizeObserver(ResizeObserver* aObserver)
+{
+  MOZ_ASSERT(aObserver, "AddResizeObserver() should never be called with "
+                        "a null parameter");
+  mResizeObservers.AppendElement(aObserver);
+}
+
+void
+ResizeObserverController::Notify()
+{
+  if (mResizeObservers.IsEmpty()) {
+    return;
+  }
+
+  uint32_t shallowestTargetDepth = 0;
+
+  GatherAllActiveObservations(shallowestTargetDepth);
+
+  while (HasAnyActiveObservations()) {
+    DebugOnly<uint32_t> oldShallowestTargetDepth = shallowestTargetDepth;
+    shallowestTargetDepth = BroadcastAllActiveObservations();
+    NS_ASSERTION(oldShallowestTargetDepth < shallowestTargetDepth,
+                 "shallowestTargetDepth should be getting strictly deeper");
+
+    // Flush layout, so that any callback functions' style changes / resizes
+    // get a chance to take effect.
+    mDocument->FlushPendingNotifications(Flush_Layout);
+
+    // To avoid infinite resize loop, we only gather all active observations
+    // that have the depth of observed target element more than current
+    // shallowestTargetDepth.
+    GatherAllActiveObservations(shallowestTargetDepth);
+  }
+
+  mResizeObserverNotificationHelper->Unregister();
+
+  // Per spec, we deliver an error if the document has any skipped observations.
+  if (HasAnySkippedObservations()) {
+    RootedDictionary<ErrorEventInit> init(RootingCx());
+
+    init.mMessage.AssignLiteral("ResizeObserver loop completed with undelivered"
+                                " notifications.");
+    init.mCancelable = true;
+    init.mBubbles = true;
+
+    nsEventStatus status = nsEventStatus_eIgnore;
+
+    nsCOMPtr<nsPIDOMWindowInner> window =
+      mDocument->GetWindow()->GetCurrentInnerWindow();
+
+    if (window) {
+      nsCOMPtr<nsIScriptGlobalObject> sgo = do_QueryInterface(window);
+      MOZ_ASSERT(sgo);
+
+      if (NS_WARN_IF(NS_FAILED(sgo->HandleScriptError(init, &status)))) {
+        status = nsEventStatus_eIgnore;
+      }
+    } else {
+      // We don't fire error events at any global for non-window JS on the main
+      // thread.
+    }
+
+    // We need to deliver pending notifications in next cycle.
+    ScheduleNotification();
+  }
+}
+
+void
+ResizeObserverController::GatherAllActiveObservations(uint32_t aDepth)
+{
+  for (auto observer : mResizeObservers) {
+    observer->GatherActiveObservations(aDepth);
+  }
+}
+
+uint32_t
+ResizeObserverController::BroadcastAllActiveObservations()
+{
+  uint32_t shallowestTargetDepth = UINT32_MAX;
+
+  for (auto observer : mResizeObservers) {
+
+    uint32_t targetDepth = observer->BroadcastActiveObservations();
+
+    if (targetDepth < shallowestTargetDepth) {
+      shallowestTargetDepth = targetDepth;
+    }
+  }
+
+  return shallowestTargetDepth;
+}
+
+bool
+ResizeObserverController::HasAnyActiveObservations() const
+{
+  for (auto observer : mResizeObservers) {
+    if (observer->HasActiveObservations()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool
+ResizeObserverController::HasAnySkippedObservations() const
+{
+  for (auto observer : mResizeObservers) {
+    if (observer->HasSkippedObservations()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void
+ResizeObserverController::ScheduleNotification()
+{
+  mResizeObserverNotificationHelper->Register();
+}
+
+nsIPresShell*
+ResizeObserverController::GetShell() const
+{
+  return mDocument->GetShell();
+}
+
+ResizeObserverController::~ResizeObserverController()
+{
+  mResizeObserverNotificationHelper->Disconnect();
+}
+
+} // namespace dom
+} // namespace mozilla

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

dom/base/moz.build

@@ -205,6 +205,7 @@ EXPORTS.mozilla.dom += [
     'Pose.h',
     'ProcessGlobal.h',
     'ResizeObserver.h',
+    'ResizeObserverController.h',
     'ResponsiveImageSelector.h',
     'SameProcessMessageQueue.h',
     'ScreenOrientation.h',
@@ -352,6 +353,7 @@ SOURCES += [
     'PostMessageEvent.cpp',
     'ProcessGlobal.cpp',
     'ResizeObserver.cpp',
+    'ResizeObserverController.cpp',
     'ResponsiveImageSelector.cpp',
     'SameProcessMessageQueue.cpp',
     'ScreenOrientation.cpp',