1 files changed, 275 insertions, 0 deletions
diff --git a/dom/base/ResizeObserver.h b/dom/base/ResizeObserver.h
new file mode 100644
index 0000000000..83843b8cf4
--- /dev/null
+++ b/dom/base/ResizeObserver.h
@@ -0,0 +1,275 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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_ResizeObserver_h
+#define mozilla_dom_ResizeObserver_h
+
+#include "js/TypeDecls.h"
+#include "mozilla/AppUnits.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/WritingModes.h"
+#include "mozilla/dom/DOMRect.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/ResizeObserverBinding.h"
+#include "nsCoord.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsRefPtrHashtable.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+
+// XXX Avoid including this here by moving function bodies to the cpp file
+#include "nsPIDOMWindow.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class Element;
+
+}  // namespace dom
+}  // namespace mozilla
+
+namespace mozilla {
+namespace dom {
+
+// For the internal implementation in ResizeObserver. Normally, this is owned by
+// ResizeObserver.
+class ResizeObservation final : public LinkedListElement<ResizeObservation> {
+ public:
+  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(ResizeObservation)
+  NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(ResizeObservation)
+
+  ResizeObservation(Element& aTarget, ResizeObserverBoxOptions aBox,
+                    const WritingMode aWM)
+      : mTarget(&aTarget),
+        mObservedBox(aBox),
+        // This starts us with a 0,0 last-reported-size:
+        mLastReportedSize(aWM),
+        mLastReportedWM(aWM) {
+    MOZ_ASSERT(mTarget, "Need a non-null target element");
+  }
+
+  Element* Target() const { return mTarget; }
+
+  ResizeObserverBoxOptions BoxOptions() const { return mObservedBox; }
+
+  /**
+   * Returns whether the observed target element size differs from the saved
+   * mLastReportedSize.
+   */
+  bool IsActive() const;
+
+  /**
+   * Update current mLastReportedSize with size from aSize.
+   */
+  void UpdateLastReportedSize(const nsSize& aSize);
+
+ protected:
+  ~ResizeObservation() = default;
+
+  nsCOMPtr<Element> mTarget;
+
+  const ResizeObserverBoxOptions mObservedBox;
+
+  // The latest recorded size of observed target.
+  // Per the spec, observation.lastReportedSize should be entry.borderBoxSize
+  // or entry.contentBoxSize (i.e. logical size), instead of entry.contentRect
+  // (i.e. physical rect), so we store this as LogicalSize.
+  LogicalSize mLastReportedSize;
+  WritingMode mLastReportedWM;
+};
+
+/**
+ * ResizeObserver interfaces and algorithms are based on
+ * https://drafts.csswg.org/resize-observer/#api
+ */
+class ResizeObserver final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(ResizeObserver)
+
+  ResizeObserver(nsCOMPtr<nsPIDOMWindowInner>&& aOwner, Document* aDocument,
+                 ResizeObserverCallback& aCb)
+      : mOwner(std::move(aOwner)), mDocument(aDocument), mCallback(&aCb) {
+    MOZ_ASSERT(mOwner, "Need a non-null owner window");
+    MOZ_ASSERT(mDocument, "Need a non-null doc");
+    MOZ_ASSERT(mDocument == mOwner->GetExtantDoc());
+  }
+
+  nsISupports* GetParentObject() const { return mOwner; }
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override {
+    return ResizeObserver_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  static already_AddRefed<ResizeObserver> Constructor(
+      const GlobalObject& aGlobal, ResizeObserverCallback& aCb,
+      ErrorResult& aRv);
+
+  void Observe(Element& aTarget, const ResizeObserverOptions& aOptions,
+               ErrorResult& aRv);
+
+  void Unobserve(Element& target, ErrorResult& aRv);
+
+  void Disconnect();
+
+  /**
+   * Gather all observations which have an observed target with size changed
+   * since last BroadcastActiveObservations() in this ResizeObserver.
+   * An observation will be skipped if the depth of its observed target is less
+   * or equal than aDepth. All gathered observations will be added to
+   * mActiveTargets.
+   */
+  void GatherActiveObservations(uint32_t aDepth);
+
+  /**
+   * Returns whether this ResizeObserver has any active observations
+   * since last GatherActiveObservations().
+   */
+  bool HasActiveObservations() const { return !mActiveTargets.IsEmpty(); }
+
+  /**
+   * Returns whether this ResizeObserver has any skipped observations
+   * since last GatherActiveObservations().
+   */
+  bool HasSkippedObservations() const { return mHasSkippedTargets; }
+
+  /**
+   * Invoke the callback function in JavaScript for all active observations
+   * and pass the sequence of ResizeObserverEntry so JavaScript can access them.
+   * The active observations' mLastReportedSize fields will be updated, and
+   * mActiveTargets will be cleared. It also returns the shallowest depth of
+   * elements from active observations or numeric_limits<uint32_t>::max() if
+   * there are not any active observations.
+   */
+  MOZ_CAN_RUN_SCRIPT uint32_t BroadcastActiveObservations();
+
+ protected:
+  ~ResizeObserver() { mObservationList.clear(); }
+
+  nsCOMPtr<nsPIDOMWindowInner> mOwner;
+  // The window's document at the time of ResizeObserver creation.
+  RefPtr<Document> mDocument;
+  RefPtr<ResizeObserverCallback> mCallback;
+  nsTArray<RefPtr<ResizeObservation>> mActiveTargets;
+  // The spec uses a list to store the skipped targets. However, it seems what
+  // we want is to check if there are any skipped targets (i.e. existence).
+  // Therefore, we use a boolean value to represent the existence of skipped
+  // targets.
+  bool mHasSkippedTargets;
+
+  // Combination of HashTable and LinkedList so we can iterate through
+  // the elements of HashTable in order of insertion time, so we can deliver
+  // observations in the correct order
+  // FIXME: it will be nice if we have our own data structure for this in the
+  // future, and mObservationMap should be considered the "owning" storage for
+  // the observations, so it'd be better to drop mObservationList later.
+  nsRefPtrHashtable<nsPtrHashKey<Element>, ResizeObservation> mObservationMap;
+  LinkedList<ResizeObservation> mObservationList;
+};
+
+/**
+ * ResizeObserverEntry is the entry that contains the information for observed
+ * elements. This object is the one that's visible to JavaScript in callback
+ * function that is fired by ResizeObserver.
+ */
+class ResizeObserverEntry final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(ResizeObserverEntry)
+
+  ResizeObserverEntry(nsISupports* aOwner, Element& aTarget,
+                      const nsSize& aBorderBoxSize,
+                      const nsSize& aContentBoxSize)
+      : mOwner(aOwner), mTarget(&aTarget) {
+    MOZ_ASSERT(mOwner, "Need a non-null owner");
+    MOZ_ASSERT(mTarget, "Need a non-null target element");
+
+    SetBorderBoxSize(aBorderBoxSize);
+    SetContentRectAndSize(aContentBoxSize);
+  }
+
+  nsISupports* GetParentObject() const { return mOwner; }
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override {
+    return ResizeObserverEntry_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  Element* Target() const { return mTarget; }
+
+  /**
+   * Returns the DOMRectReadOnly of target's content rect so it can be
+   * accessed from JavaScript in callback function of ResizeObserver.
+   */
+  DOMRectReadOnly* ContentRect() const { return mContentRect; }
+
+  /**
+   * Returns target's logical border-box size and content-box size as
+   * ResizeObserverSize.
+   */
+  ResizeObserverSize* BorderBoxSize() const { return mBorderBoxSize; }
+  ResizeObserverSize* ContentBoxSize() const { return mContentBoxSize; }
+
+ private:
+  ~ResizeObserverEntry() = default;
+
+  // Set borderBoxSize.
+  void SetBorderBoxSize(const nsSize& aSize);
+  // Set contentRect and contentBoxSize.
+  void SetContentRectAndSize(const nsSize& aSize);
+
+  nsCOMPtr<nsISupports> mOwner;
+  nsCOMPtr<Element> mTarget;
+
+  RefPtr<DOMRectReadOnly> mContentRect;
+  RefPtr<ResizeObserverSize> mBorderBoxSize;
+  RefPtr<ResizeObserverSize> mContentBoxSize;
+};
+
+class ResizeObserverSize final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(ResizeObserverSize)
+
+  // Note: the unit of |aSize| is app unit, and we convert it into css pixel in
+  // the public JS APIs.
+  ResizeObserverSize(nsISupports* aOwner, const nsSize& aSize,
+                     const WritingMode aWM)
+      : mOwner(aOwner), mSize(aWM, aSize), mWM(aWM) {
+    MOZ_ASSERT(mOwner, "Need a non-null owner");
+  }
+
+  nsISupports* GetParentObject() const { return mOwner; }
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override {
+    return ResizeObserverSize_Binding::Wrap(aCx, this, aGivenProto);
+  }
+
+  double InlineSize() const {
+    return NSAppUnitsToDoublePixels(mSize.ISize(mWM), AppUnitsPerCSSPixel());
+  }
+
+  double BlockSize() const {
+    return NSAppUnitsToDoublePixels(mSize.BSize(mWM), AppUnitsPerCSSPixel());
+  }
+
+ protected:
+  ~ResizeObserverSize() = default;
+
+  nsCOMPtr<nsISupports> mOwner;
+  const LogicalSize mSize;
+  const WritingMode mWM;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_ResizeObserver_h