path: root/dom/base/ResizeObserver.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/ResizeObserver.h"

#include "mozilla/dom/DOMRect.h"
#include "nsIContentInlines.h"
#include "nsIFrame.h"
#include "nsSVGUtils.h"

namespace mozilla {
namespace dom {

/**
 * Returns the length of the parent-traversal path (in terms of the number of
 * nodes) to an unparented/root node from aNode. An unparented/root node is
 * considered to have a depth of 1, its children have a depth of 2, etc.
 * aNode is expected to be non-null.
 * Note: The shadow root is not part of the calculation because the caller,
 * ResizeObserver, doesn't observe the shadow root, and only needs relative
 * depths among all the observed targets. In other words, we calculate the
 * depth of the flattened tree.
 *
 * Note: these is a spec issue about how to handle shadow DOM case. We
 * may need to update this function later.
 *
 *
 * https://drafts.csswg.org/resize-observer/#calculate-depth-for-node-h
 */
static uint32_t
GetNodeDepth(nsINode* aNode) {
  uint32_t depth = 1;

  MOZ_ASSERT(aNode, "Node shouldn't be null");

  // Use GetFlattenedTreeParentNode to bypass the shadow root and cross the
  // shadow boundary to calculate the node depth without the shadow root.
  while ((aNode = aNode->GetFlattenedTreeParentNode())) {
    ++depth;
  }

  return depth;
}

/**
 * Returns |aTarget|'s size in the form of an nsSize.
 * If the target is an SVG, width and height are determined from the bounding box.
 */
static nsSize
GetTargetSize(Element* aTarget, ResizeObserverBoxOptions aBox) {
  nsSize size;
  nsIFrame* frame = aTarget->GetPrimaryFrame();

  if (!frame) {
    return size;
  }

  if (aTarget->IsSVGElement()) {
    // Per the spec, an SVG size is always its bounding box size, no matter what
    // box option you choose, because SVG elements do not use the standard CSS box
    // model.
    gfxRect bbox = nsSVGUtils::GetBBox(frame);
    size.width = NSFloatPixelsToAppUnits(bbox.width, AppUnitsPerCSSPixel());
    size.height = NSFloatPixelsToAppUnits(bbox.height, AppUnitsPerCSSPixel());
  } else {
    // Per the spec, non-replaced inline Elements will always have an empty
    // content rect. We therefore always use the same empty size for
    // non-replaced inline elements here, and their IsActive() will
    // always return false. (So its observation won't be fired.)
    if (!frame->IsFrameOfType(nsIFrame::eReplaced) &&
        frame->IsFrameOfType(nsIFrame::eLineParticipant)) {
      return size;
    }

    switch (aBox) {
      case ResizeObserverBoxOptions::Border_box:
        // GetSize() includes the content area, borders, and padding.
        size = frame->GetSize();
        break;
      case ResizeObserverBoxOptions::Content_box:
      default:
        size = frame->GetContentRectRelativeToSelf().Size();
    }
  }

  return size;
}

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObserver)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObserver)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObserver)

NS_IMPL_CYCLE_COLLECTION_CLASS(ResizeObserver)

NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(ResizeObserver)
  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_TRACE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ResizeObserver)
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mCallback)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mObservationMap)
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(ResizeObserver)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCallback)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mObservationMap)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

already_AddRefed<ResizeObserver>
ResizeObserver::Constructor(const GlobalObject& aGlobal,
                            ResizeObserverCallback& aCb,
                            ErrorResult& aRv)
{
  nsCOMPtr<nsPIDOMWindowInner> window =
    do_QueryInterface(aGlobal.GetAsSupports());

  if (!window) {
    aRv.Throw(NS_ERROR_FAILURE);
    return nullptr;
  }

  nsCOMPtr<nsIDocument> document = window->GetExtantDoc();

  if (!document) {
    aRv.Throw(NS_ERROR_FAILURE);
    return nullptr;
  }

  RefPtr<ResizeObserver> observer = new ResizeObserver(window.forget(), aCb);
  document->AddResizeObserver(observer);

  return observer.forget();
}

void
ResizeObserver::Observe(Element* aTarget,
                        const ResizeObserverOptions& aOptions,
                        ErrorResult& aRv)
{
  if (!aTarget) {
    aRv.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
    return;
  }

  RefPtr<ResizeObservation> observation;

  if (!mObservationMap.Get(aTarget, getter_AddRefs(observation))) {
    nsIFrame* frame = aTarget->GetPrimaryFrame();
    WritingMode wm = frame ? frame->GetWritingMode() : WritingMode();
    observation = new ResizeObservation(aTarget->OwnerDoc(), aTarget, aOptions.mBox, wm);

    mObservationMap.Put(aTarget, observation);
    mObservationList.insertBack(observation);

    // Per the spec, we need to trigger notification in event loop that
    // contains ResizeObserver observe call even when resize/reflow does
    // not happen.
    aTarget->OwnerDoc()->ScheduleResizeObserversNotification();
  }
}

void
ResizeObserver::Unobserve(Element* aTarget,
                          ErrorResult& aRv)
{
  if (!aTarget) {
    aRv.Throw(NS_ERROR_DOM_NOT_FOUND_ERR);
    return;
  }

  RefPtr<ResizeObservation> observation;

  if (mObservationMap.Get(aTarget, getter_AddRefs(observation))) {
    mObservationMap.Remove(aTarget);

    MOZ_ASSERT(!mObservationList.isEmpty(),
               "If ResizeObservation found for an element, observation list "
               "must be not empty.");

    observation->remove();
  }
}

void
ResizeObserver::Disconnect()
{
  mObservationMap.Clear();
  mObservationList.clear();
  mActiveTargets.Clear();
}

void
ResizeObserver::GatherActiveObservations(uint32_t aDepth)
{
  mActiveTargets.Clear();
  mHasSkippedTargets = false;

  for (auto observation : mObservationList) {
    if (observation->IsActive()) {
      uint32_t targetDepth = GetNodeDepth(observation->Target());

      if (targetDepth > aDepth) {
        mActiveTargets.AppendElement(observation);
      } else {
        mHasSkippedTargets = true;
      }
    }
  }
}

bool
ResizeObserver::HasActiveObservations() const
{
  return !mActiveTargets.IsEmpty();
}

bool
ResizeObserver::HasSkippedObservations() const
{
  return mHasSkippedTargets;
}

uint32_t
ResizeObserver::BroadcastActiveObservations()
{
  uint32_t shallowestTargetDepth = UINT32_MAX;

  if (HasActiveObservations()) {
    Sequence<OwningNonNull<ResizeObserverEntry>> entries;

    for (auto observation : mActiveTargets) {
      Element* target = observation->Target();
      RefPtr<ResizeObserverEntry> entry = new ResizeObserverEntry(this, target);

      nsSize borderBoxSize = GetTargetSize(target, ResizeObserverBoxOptions::Border_box);
      entry->SetBorderBoxSize(borderBoxSize);

      nsSize contentBoxSize = GetTargetSize(target, ResizeObserverBoxOptions::Content_box);
      entry->SetContentRectAndSize(contentBoxSize);

      if (!entries.AppendElement(entry.forget(), fallible)) {
        // Out of memory.
        break;
      }

      // Sync the broadcast size of observation so the next size inspection
      // will be based on the updated size from last delivered observations.
      switch (observation->BoxOptions()) {
        case ResizeObserverBoxOptions::Border_box:
          observation->UpdateLastReportedSize(borderBoxSize);
          break;
        case ResizeObserverBoxOptions::Content_box:
        default:
          observation->UpdateLastReportedSize(contentBoxSize);
      }

      uint32_t targetDepth = GetNodeDepth(observation->Target());

      if (targetDepth < shallowestTargetDepth) {
        shallowestTargetDepth = targetDepth;
      }
    }

    mCallback->Call(this, entries, *this);
    mActiveTargets.Clear();
    mHasSkippedTargets = false;
  }

  return shallowestTargetDepth;
}

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObserverEntry)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObserverEntry)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObserverEntry)

NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(ResizeObserverEntry,
                                      mOwner,
                                      mTarget,
                                      mContentRect,
                                      mBorderBoxSize,
                                      mContentBoxSize)

already_AddRefed<ResizeObserverEntry>
ResizeObserverEntry::Constructor(const GlobalObject& aGlobal,
                                 Element* aTarget,
                                 ErrorResult& aRv)
{
  RefPtr<ResizeObserverEntry> observerEntry =
    new ResizeObserverEntry(aGlobal.GetAsSupports(), aTarget);
  return observerEntry.forget();
}

void
ResizeObserverEntry::SetBorderBoxSize(const nsSize& aSize) {
  nsIFrame* frame = mTarget->GetPrimaryFrame();
  WritingMode wm = frame ? frame->GetWritingMode() : WritingMode();
  mBorderBoxSize = new ResizeObserverSize(this, aSize, wm);
}

void
ResizeObserverEntry::SetContentRectAndSize(const nsSize& aSize) {
  nsIFrame* frame = mTarget->GetPrimaryFrame();

  // Update mContentRect.
  nsMargin padding = frame ? frame->GetUsedPadding(): nsMargin();
  // Per the spec, we need to use the top-left padding offset as the origin of
  // our contentRect.
  nsRect rect(nsPoint(padding.left, padding.top), aSize);
  RefPtr<DOMRect> contentRect = new DOMRect(mTarget);
  contentRect->SetLayoutRect(rect);
  mContentRect = contentRect.forget();

  // Update mContentBoxSize.
  WritingMode wm = frame ? frame->GetWritingMode() : WritingMode();
  mContentBoxSize = new ResizeObserverSize(this, aSize, wm);
}

ResizeObserverEntry::~ResizeObserverEntry()
{
}

NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(ResizeObserverSize, mOwner)
NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObserverSize)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObserverSize)
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObserverSize)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObservation)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObservation)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObservation)

NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(ResizeObservation,
                                      mTarget, mOwner)

bool
ResizeObservation::IsActive() const
{
  nsIFrame* frame = mTarget->GetPrimaryFrame();
  WritingMode wm = frame ? frame->GetWritingMode() : WritingMode();
  LogicalSize size(wm, GetTargetSize(mTarget, mObservedBox));
  return mLastReportedSize.ISize(mLastReportedWM) != size.ISize(wm) ||
         mLastReportedSize.BSize(mLastReportedWM) != size.BSize(wm);
}

void
ResizeObservation::UpdateLastReportedSize(const nsSize& aSize) {
  nsIFrame* frame = mTarget->GetPrimaryFrame();
  mLastReportedWM = frame ? frame->GetWritingMode() : WritingMode();
  mLastReportedSize = LogicalSize(mLastReportedWM, aSize);
}

ResizeObservation::~ResizeObservation()
{
}

} // namespace dom
} // namespace mozilla