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