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/* -*- 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 */
#ifndef mozilla_dom_ResizeObserver_h
#define mozilla_dom_ResizeObserver_h
#include "gfxPoint.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;
// The logical size in pixels.
// Note: if LogicalPixelSize have usages other than ResizeObserver in the
// future, it might be better to change LogicalSize into a template class, and
// use it to implement LogicalPixelSize.
class LogicalPixelSize {
LogicalPixelSize() = default;
LogicalPixelSize(WritingMode aWM, const gfx::Size& aSize) {
mSize = aSize;
if (aWM.IsVertical()) {
std::swap(mSize.width, mSize.height);
gfx::Size PhysicalSize(WritingMode aWM) const {
if (!aWM.IsVertical()) {
return mSize;
gfx::Size result(mSize);
std::swap(result.width, result.height);
return result;
bool operator==(const LogicalPixelSize& aOther) const {
return mSize == aOther.mSize;
bool operator!=(const LogicalPixelSize& aOther) const {
return !(*this == aOther);
float ISize() const { return mSize.width; }
float BSize() const { return mSize.height; }
float& ISize() { return mSize.width; }
float& BSize() { return mSize.height; }
// |mSize.width| represents inline-size and |mSize.height| represents
// block-size.
gfx::Size mSize;
// For the internal implementation in ResizeObserver. Normally, this is owned by
// ResizeObserver.
class ResizeObservation final : public LinkedListElement<ResizeObservation> {
ResizeObservation(Element&, ResizeObserver&, ResizeObserverBoxOptions);
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 to aSize.
void UpdateLastReportedSize(const nsTArray<LogicalPixelSize>& aSize);
enum class RemoveFromObserver : bool { No, Yes };
void Unlink(RemoveFromObserver);
~ResizeObservation() { Unlink(RemoveFromObserver::No); };
nsCOMPtr<Element> mTarget;
// Weak, observer always outlives us.
ResizeObserver* mObserver;
const ResizeObserverBoxOptions mObservedBox;
// The latest recorded of observed target.
// This will be CSS pixels for border-box/content-box, or device pixels for
// device-pixel-content-box.
AutoTArray<LogicalPixelSize, 1> mLastReportedSize;
* ResizeObserver interfaces and algorithms are based on
class ResizeObserver final : public nsISupports, public nsWrapperCache {
using NativeCallback = void (*)(
const Sequence<OwningNonNull<ResizeObserverEntry>>&, ResizeObserver&);
ResizeObserver(Document& aDocument, NativeCallback aCallback);
ResizeObserver(nsCOMPtr<nsPIDOMWindowInner>&& aOwner, Document* aDocument,
ResizeObserverCallback& aCb)
: mOwner(std::move(aOwner)),
mCallback(RefPtr<ResizeObserverCallback>(&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&, const ResizeObserverOptions&);
void Unobserve(Element&);
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; }
* Returns whether this is an internal ResizeObserver with a native callback.
bool HasNativeCallback() const { return<NativeCallback>(); }
* 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();
static already_AddRefed<ResizeObserver> CreateLastRememberedSizeObserver(
~ResizeObserver() { Disconnect(); }
nsCOMPtr<nsPIDOMWindowInner> mOwner;
// The window's document at the time of ResizeObserver creation.
RefPtr<Document> mDocument;
Variant<RefPtr<ResizeObserverCallback>, NativeCallback> 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 = false;
// 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 {
nsISupports* aOwner, Element& aTarget,
const nsTArray<LogicalPixelSize>& aBorderBoxSize,
const nsTArray<LogicalPixelSize>& aContentBoxSize,
const nsTArray<LogicalPixelSize>& aDevicePixelContentBoxSize)
: mOwner(aOwner), mTarget(&aTarget) {
MOZ_ASSERT(mOwner, "Need a non-null owner");
MOZ_ASSERT(mTarget, "Need a non-null target element");
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, content-box size, and
* device-pixel-content-box as an array of ResizeObserverSize.
void GetBorderBoxSize(nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const;
void GetContentBoxSize(nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const;
void GetDevicePixelContentBoxSize(
nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const;
~ResizeObserverEntry() = default;
// Set borderBoxSize.
void SetBorderBoxSize(const nsTArray<LogicalPixelSize>& aSize);
// Set contentRect and contentBoxSize.
void SetContentRectAndSize(const nsTArray<LogicalPixelSize>& aSize);
// Set devicePixelContentBoxSize.
void SetDevicePixelContentSize(const nsTArray<LogicalPixelSize>& aSize);
nsCOMPtr<nsISupports> mOwner;
nsCOMPtr<Element> mTarget;
RefPtr<DOMRectReadOnly> mContentRect;
AutoTArray<RefPtr<ResizeObserverSize>, 1> mBorderBoxSize;
AutoTArray<RefPtr<ResizeObserverSize>, 1> mContentBoxSize;
AutoTArray<RefPtr<ResizeObserverSize>, 1> mDevicePixelContentBoxSize;
class ResizeObserverSize final : public nsISupports, public nsWrapperCache {
ResizeObserverSize(nsISupports* aOwner, const LogicalPixelSize& aSize)
: mOwner(aOwner), mSize(aSize) {
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);
float InlineSize() const { return mSize.ISize(); }
float BlockSize() const { return mSize.BSize(); }
~ResizeObserverSize() = default;
nsCOMPtr<nsISupports> mOwner;
// The logical size value:
// 1. content-box/border-box: in CSS pixels.
// 2. device-pixel-content-box: in device pixels.
const LogicalPixelSize mSize;
} // namespace dom
} // namespace mozilla
#endif // mozilla_dom_ResizeObserver_h