summaryrefslogtreecommitdiffstats
path: root/dom/base/ResizeObserver.cpp
blob: cc9865ee2ef7d7ede6ba4bb315a9b8caa5debad8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
/* -*- 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/. */

#include "mozilla/dom/ResizeObserver.h"

#include "mozilla/dom/DOMRect.h"
#include "mozilla/dom/Document.h"
#include "mozilla/SVGUtils.h"
#include "nsIContent.h"
#include "nsIContentInlines.h"
#include "nsIScrollableFrame.h"
#include "nsLayoutUtils.h"
#include <limits>

namespace mozilla::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.
 *
 * However, these is a spec issue about how to handle shadow DOM case. We
 * may need to update this function later:
 *   https://github.com/w3c/csswg-drafts/issues/3840
 *
 * 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;
}

static nsSize GetContentRectSize(const nsIFrame& aFrame) {
  if (const nsIScrollableFrame* f = do_QueryFrame(&aFrame)) {
    // We return the scrollport rect for compat with other UAs, see bug 1733042.
    // But the scrollPort includes padding (but not border!), so remove it.
    nsRect scrollPort = f->GetScrollPortRect();
    nsMargin padding =
        aFrame.GetUsedPadding().ApplySkipSides(aFrame.GetSkipSides());
    scrollPort.Deflate(padding);
    // This can break in some edge cases like when layout overflows sizes or
    // what not.
    NS_ASSERTION(
        !aFrame.PresContext()->UseOverlayScrollbars() ||
            scrollPort.Size() == aFrame.GetContentRectRelativeToSelf().Size(),
        "Wrong scrollport?");
    return scrollPort.Size();
  }
  return aFrame.GetContentRectRelativeToSelf().Size();
}

/**
 * Returns |aTarget|'s size in the form of gfx::Size (in pixels).
 * If the target is an SVG that does not participate in CSS layout,
 * its width and height are determined from bounding box.
 *
 * https://www.w3.org/TR/resize-observer-1/#calculate-box-size
 */
static AutoTArray<LogicalPixelSize, 1> CalculateBoxSize(
    Element* aTarget, ResizeObserverBoxOptions aBox,
    const ResizeObserver& aObserver) {
  nsIFrame* frame = aTarget->GetPrimaryFrame();

  if (!frame) {
    // TODO: Should this return an empty array instead?
    // https://github.com/w3c/csswg-drafts/issues/7734
    return {LogicalPixelSize()};
  }

  if (frame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT)) {
    // Per the spec, this target's SVG size is always its bounding box size no
    // matter what box option you choose, because SVG elements do not use
    // standard CSS box model.
    // TODO: what if the SVG is fragmented?
    // https://github.com/w3c/csswg-drafts/issues/7736
    const gfxRect bbox = SVGUtils::GetBBox(frame);
    gfx::Size size(static_cast<float>(bbox.width),
                   static_cast<float>(bbox.height));
    const WritingMode wm = frame->GetWritingMode();
    if (aBox == ResizeObserverBoxOptions::Device_pixel_content_box) {
      // Per spec, we calculate the inline/block sizes to target’s bounding box
      // {inline|block} length, in integral device pixels, so we round the final
      // result.
      // https://drafts.csswg.org/resize-observer/#dom-resizeobserverboxoptions-device-pixel-content-box
      const LayoutDeviceIntSize snappedSize =
          RoundedToInt(CSSSize::FromUnknownSize(size) *
                       frame->PresContext()->CSSToDevPixelScale());
      return {LogicalPixelSize(wm, gfx::Size(snappedSize.ToUnknownSize()))};
    }
    return {LogicalPixelSize(wm, size)};
  }

  // Per the spec, non-replaced inline Elements will always have an empty
  // content rect. Therefore, we always use the same trivially-empty size
  // for non-replaced inline elements here, and their IsActive() will
  // always return false. (So its observation won't be fired.)
  // TODO: Should we use an empty array instead?
  // https://github.com/w3c/csswg-drafts/issues/7734
  if (!frame->IsFrameOfType(nsIFrame::eReplaced) &&
      frame->IsFrameOfType(nsIFrame::eLineParticipant)) {
    return {LogicalPixelSize()};
  }

  auto GetFrameSize = [aBox](nsIFrame* aFrame) {
    switch (aBox) {
      case ResizeObserverBoxOptions::Border_box:
        return CSSPixel::FromAppUnits(aFrame->GetSize()).ToUnknownSize();
      case ResizeObserverBoxOptions::Device_pixel_content_box: {
        // Simply converting from app units to device units is insufficient - we
        // need to take subpixel snapping into account. Subpixel snapping
        // happens with respect to the reference frame, so do the dev pixel
        // conversion with our rectangle positioned relative to the reference
        // frame, then get the size from there.
        const auto* referenceFrame = nsLayoutUtils::GetReferenceFrame(aFrame);
        // GetOffsetToCrossDoc version handles <iframe>s in addition to normal
        // cases. We don't expect this to tight loop for additional checks to
        // matter.
        const auto offset = aFrame->GetOffsetToCrossDoc(referenceFrame);
        const auto contentSize = GetContentRectSize(*aFrame);
        // Casting to double here is deliberate to minimize rounding error in
        // upcoming operations.
        const auto appUnitsPerDevPixel =
            static_cast<double>(aFrame->PresContext()->AppUnitsPerDevPixel());
        // Calculation here is a greatly simplified version of
        // `NSRectToSnappedRect` as 1) we're not actually drawing (i.e. no draw
        // target), and 2) transform does not need to be taken into account.
        gfx::Rect rect{gfx::Float(offset.X() / appUnitsPerDevPixel),
                       gfx::Float(offset.Y() / appUnitsPerDevPixel),
                       gfx::Float(contentSize.Width() / appUnitsPerDevPixel),
                       gfx::Float(contentSize.Height() / appUnitsPerDevPixel)};
        gfx::Point tl = rect.TopLeft().Round();
        gfx::Point br = rect.BottomRight().Round();

        rect.SizeTo(gfx::Size(br.x - tl.x, br.y - tl.y));
        rect.NudgeToIntegers();
        return rect.Size().ToUnknownSize();
      }
      case ResizeObserverBoxOptions::Content_box:
      default:
        break;
    }
    return CSSPixel::FromAppUnits(GetContentRectSize(*aFrame)).ToUnknownSize();
  };
  if (!StaticPrefs::dom_resize_observer_support_fragments() &&
      !aObserver.HasNativeCallback()) {
    return {LogicalPixelSize(frame->GetWritingMode(), GetFrameSize(frame))};
  }
  AutoTArray<LogicalPixelSize, 1> size;
  for (nsIFrame* cur = frame; cur; cur = cur->GetNextContinuation()) {
    const WritingMode wm = cur->GetWritingMode();
    size.AppendElement(LogicalPixelSize(wm, GetFrameSize(cur)));
  }
  return size;
}

NS_IMPL_CYCLE_COLLECTION_CLASS(ResizeObservation)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(ResizeObservation)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mTarget);
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ResizeObservation)
  tmp->Unlink(RemoveFromObserver::Yes);
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

ResizeObservation::ResizeObservation(Element& aTarget,
                                     ResizeObserver& aObserver,
                                     ResizeObserverBoxOptions aBox)
    : mTarget(&aTarget),
      mObserver(&aObserver),
      mObservedBox(aBox),
      mLastReportedSize(
          {StaticPrefs::dom_resize_observer_last_reported_size_invalid()
               ? LogicalPixelSize(WritingMode(), gfx::Size(-1, -1))
               : LogicalPixelSize()}) {
  aTarget.BindObject(mObserver);
}

void ResizeObservation::Unlink(RemoveFromObserver aRemoveFromObserver) {
  ResizeObserver* observer = std::exchange(mObserver, nullptr);
  nsCOMPtr<Element> target = std::move(mTarget);
  if (observer && target) {
    if (aRemoveFromObserver == RemoveFromObserver::Yes) {
      observer->Unobserve(*target);
    }
    target->UnbindObject(observer);
  }
}

bool ResizeObservation::IsActive() const {
  // As detailed in the css-contain specification, if the target is hidden by
  // `content-visibility` it should not call its ResizeObservation callbacks.
  nsIFrame* frame = mTarget->GetPrimaryFrame();
  if (frame && frame->IsHiddenByContentVisibilityOnAnyAncestor()) {
    return false;
  }

  return mLastReportedSize !=
         CalculateBoxSize(mTarget, mObservedBox, *mObserver);
}

void ResizeObservation::UpdateLastReportedSize(
    const nsTArray<LogicalPixelSize>& aSize) {
  mLastReportedSize.Assign(aSize);
}

// Only needed for refcounted objects.
NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(ResizeObserver)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(ResizeObserver)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner, mDocument, mActiveTargets,
                                    mObservationMap);
  if (tmp->mCallback.is<RefPtr<ResizeObserverCallback>>()) {
    ImplCycleCollectionTraverse(
        cb, tmp->mCallback.as<RefPtr<ResizeObserverCallback>>(), "mCallback",
        0);
  }
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ResizeObserver)
  tmp->Disconnect();
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner, mDocument, mActiveTargets,
                                  mObservationMap);
  if (tmp->mCallback.is<RefPtr<ResizeObserverCallback>>()) {
    ImplCycleCollectionUnlink(
        tmp->mCallback.as<RefPtr<ResizeObserverCallback>>());
  }
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObserver)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObserver)
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObserver)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

ResizeObserver::ResizeObserver(Document& aDocument, NativeCallback aCallback)
    : mOwner(aDocument.GetInnerWindow()),
      mDocument(&aDocument),
      mCallback(aCallback) {
  MOZ_ASSERT(mOwner, "Need a non-null owner window");
  MOZ_ASSERT(mDocument == mOwner->GetExtantDoc());
}

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;
  }

  Document* doc = window->GetExtantDoc();
  if (!doc) {
    aRv.Throw(NS_ERROR_FAILURE);
    return nullptr;
  }

  return do_AddRef(new ResizeObserver(std::move(window), doc, aCb));
}

void ResizeObserver::Observe(Element& aTarget,
                             const ResizeObserverOptions& aOptions) {
  if (MOZ_UNLIKELY(!mDocument)) {
    MOZ_ASSERT_UNREACHABLE("How did we call observe() after unlink?");
    return;
  }

  // NOTE(emilio): Per spec, this is supposed to happen on construction, but the
  // spec isn't particularly sane here, see
  // https://github.com/w3c/csswg-drafts/issues/4518
  if (mObservationList.isEmpty()) {
    MOZ_ASSERT(mObservationMap.IsEmpty());
    mDocument->AddResizeObserver(*this);
  }

  auto& observation = mObservationMap.LookupOrInsert(&aTarget);
  if (observation) {
    if (observation->BoxOptions() == aOptions.mBox) {
      // Already observed this target and the observed box is the same, so
      // return.
      // Note: Based on the spec, we should unobserve it first. However,
      // calling Unobserve() when we observe the same box will remove original
      // ResizeObservation and then add a new one, this may cause an unexpected
      // result because ResizeObservation stores the mLastReportedSize which
      // should be kept to make sure IsActive() returns the correct result.
      return;
    }
    // Remove the pre-existing entry, but without unregistering ourselves from
    // the controller.
    observation->remove();
    observation = nullptr;
  }

  observation = new ResizeObservation(aTarget, *this, aOptions.mBox);
  if (!StaticPrefs::dom_resize_observer_last_reported_size_invalid() &&
      this == mDocument->GetLastRememberedSizeObserver()) {
    // Resize observations are initialized with a (0, 0) mLastReportedSize,
    // this means that the callback won't be called if the element is 0x0.
    // But we need it called for handling the last remembered size, so set
    // mLastReportedSize to an invalid size to ensure IsActive() is true
    // for the current element size.
    // See https://github.com/w3c/csswg-drafts/issues/3664 about doing this in
    // the general case, then we won't need this hack for the last remembered
    // size, and will have consistency with IntersectionObserver.
    observation->UpdateLastReportedSize(
        {LogicalPixelSize(WritingMode(), gfx::Size(-1, -1))});
    MOZ_ASSERT(observation->IsActive());
  }
  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.
  mDocument->ScheduleResizeObserversNotification();
}

void ResizeObserver::Unobserve(Element& aTarget) {
  RefPtr<ResizeObservation> observation;
  if (!mObservationMap.Remove(&aTarget, getter_AddRefs(observation))) {
    return;
  }

  MOZ_ASSERT(!mObservationList.isEmpty(),
             "If ResizeObservation found for an element, observation list "
             "must be not empty.");
  observation->remove();
  if (mObservationList.isEmpty()) {
    if (MOZ_LIKELY(mDocument)) {
      mDocument->RemoveResizeObserver(*this);
    }
  }
}

void ResizeObserver::Disconnect() {
  const bool registered = !mObservationList.isEmpty();
  while (auto* observation = mObservationList.popFirst()) {
    observation->Unlink(ResizeObservation::RemoveFromObserver::No);
  }
  MOZ_ASSERT(mObservationList.isEmpty());
  mObservationMap.Clear();
  mActiveTargets.Clear();
  if (registered && MOZ_LIKELY(mDocument)) {
    mDocument->RemoveResizeObserver(*this);
  }
}

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

  for (auto* observation : mObservationList) {
    if (!observation->IsActive()) {
      continue;
    }

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

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

uint32_t ResizeObserver::BroadcastActiveObservations() {
  uint32_t shallowestTargetDepth = std::numeric_limits<uint32_t>::max();

  if (!HasActiveObservations()) {
    return shallowestTargetDepth;
  }

  Sequence<OwningNonNull<ResizeObserverEntry>> entries;

  for (auto& observation : mActiveTargets) {
    Element* target = observation->Target();

    auto borderBoxSize =
        CalculateBoxSize(target, ResizeObserverBoxOptions::Border_box, *this);
    auto contentBoxSize =
        CalculateBoxSize(target, ResizeObserverBoxOptions::Content_box, *this);
    auto devicePixelContentBoxSize = CalculateBoxSize(
        target, ResizeObserverBoxOptions::Device_pixel_content_box, *this);
    RefPtr<ResizeObserverEntry> entry =
        new ResizeObserverEntry(mOwner, *target, borderBoxSize, contentBoxSize,
                                devicePixelContentBoxSize);

    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::Device_pixel_content_box:
        observation->UpdateLastReportedSize(devicePixelContentBoxSize);
        break;
      case ResizeObserverBoxOptions::Content_box:
      default:
        observation->UpdateLastReportedSize(contentBoxSize);
    }

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

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

  if (mCallback.is<RefPtr<ResizeObserverCallback>>()) {
    RefPtr<ResizeObserverCallback> callback(
        mCallback.as<RefPtr<ResizeObserverCallback>>());
    callback->Call(this, entries, *this);
  } else {
    mCallback.as<NativeCallback>()(entries, *this);
  }

  mActiveTargets.Clear();
  mHasSkippedTargets = false;

  return shallowestTargetDepth;
}

NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(ResizeObserverEntry, mOwner, mTarget,
                                      mContentRect, mBorderBoxSize,
                                      mContentBoxSize,
                                      mDevicePixelContentBoxSize)
NS_IMPL_CYCLE_COLLECTING_ADDREF(ResizeObserverEntry)
NS_IMPL_CYCLE_COLLECTING_RELEASE(ResizeObserverEntry)
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ResizeObserverEntry)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

void ResizeObserverEntry::GetBorderBoxSize(
    nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const {
  // In the resize-observer-1 spec, there will only be a single
  // ResizeObserverSize returned in the FrozenArray for now.
  //
  // Note: the usage of FrozenArray is to support elements that have multiple
  // fragments, which occur in multi-column scenarios.
  // https://drafts.csswg.org/resize-observer/#resize-observer-entry-interface
  aRetVal.Assign(mBorderBoxSize);
}

void ResizeObserverEntry::GetContentBoxSize(
    nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const {
  // In the resize-observer-1 spec, there will only be a single
  // ResizeObserverSize returned in the FrozenArray for now.
  //
  // Note: the usage of FrozenArray is to support elements that have multiple
  // fragments, which occur in multi-column scenarios.
  // https://drafts.csswg.org/resize-observer/#resize-observer-entry-interface
  aRetVal.Assign(mContentBoxSize);
}

void ResizeObserverEntry::GetDevicePixelContentBoxSize(
    nsTArray<RefPtr<ResizeObserverSize>>& aRetVal) const {
  // In the resize-observer-1 spec, there will only be a single
  // ResizeObserverSize returned in the FrozenArray for now.
  //
  // Note: the usage of FrozenArray is to support elements that have multiple
  // fragments, which occur in multi-column scenarios.
  // https://drafts.csswg.org/resize-observer/#resize-observer-entry-interface
  aRetVal.Assign(mDevicePixelContentBoxSize);
}

void ResizeObserverEntry::SetBorderBoxSize(
    const nsTArray<LogicalPixelSize>& aSize) {
  mBorderBoxSize.Clear();
  mBorderBoxSize.SetCapacity(aSize.Length());
  for (const LogicalPixelSize& size : aSize) {
    mBorderBoxSize.AppendElement(new ResizeObserverSize(mOwner, size));
  }
}

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

  // 1. 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.
  gfx::Size sizeForRect;
  MOZ_DIAGNOSTIC_ASSERT(!aSize.IsEmpty());
  if (!aSize.IsEmpty()) {
    const WritingMode wm = frame ? frame->GetWritingMode() : WritingMode();
    sizeForRect = aSize[0].PhysicalSize(wm);
  }
  nsRect rect(nsPoint(padding.left, padding.top),
              CSSPixel::ToAppUnits(CSSSize::FromUnknownSize(sizeForRect)));
  RefPtr<DOMRect> contentRect = new DOMRect(mOwner);
  contentRect->SetLayoutRect(rect);
  mContentRect = std::move(contentRect);

  // 2. Update mContentBoxSize.
  mContentBoxSize.Clear();
  mContentBoxSize.SetCapacity(aSize.Length());
  for (const LogicalPixelSize& size : aSize) {
    mContentBoxSize.AppendElement(new ResizeObserverSize(mOwner, size));
  }
}

void ResizeObserverEntry::SetDevicePixelContentSize(
    const nsTArray<LogicalPixelSize>& aSize) {
  mDevicePixelContentBoxSize.Clear();
  mDevicePixelContentBoxSize.SetCapacity(aSize.Length());
  for (const LogicalPixelSize& size : aSize) {
    mDevicePixelContentBoxSize.AppendElement(
        new ResizeObserverSize(mOwner, size));
  }
}

static void LastRememberedSizeCallback(
    const Sequence<OwningNonNull<ResizeObserverEntry>>& aEntries,
    ResizeObserver& aObserver) {
  for (const auto& entry : aEntries) {
    Element* target = entry->Target();
    if (!target->IsInComposedDoc()) {
      aObserver.Unobserve(*target);
      target->RemoveLastRememberedBSize();
      target->RemoveLastRememberedISize();
      continue;
    }
    nsIFrame* frame = target->GetPrimaryFrame();
    if (!frame) {
      aObserver.Unobserve(*target);
      continue;
    }
    MOZ_ASSERT(!frame->IsFrameOfType(nsIFrame::eLineParticipant) ||
                   frame->IsFrameOfType(nsIFrame::eReplaced),
               "Should have unobserved non-replaced inline.");
    MOZ_ASSERT(!frame->HidesContent(),
               "Should have unobserved element skipping its contents.");
    const nsStylePosition* stylePos = frame->StylePosition();
    const WritingMode wm = frame->GetWritingMode();
    bool canUpdateBSize = stylePos->ContainIntrinsicBSize(wm).IsAutoLength();
    bool canUpdateISize = stylePos->ContainIntrinsicISize(wm).IsAutoLength();
    MOZ_ASSERT(canUpdateBSize || !target->HasLastRememberedBSize(),
               "Should have removed the last remembered block size.");
    MOZ_ASSERT(canUpdateISize || !target->HasLastRememberedISize(),
               "Should have removed the last remembered inline size.");
    MOZ_ASSERT(canUpdateBSize || canUpdateISize,
               "Should have unobserved if we can't update any size.");
    AutoTArray<RefPtr<ResizeObserverSize>, 1> contentSizeList;
    entry->GetContentBoxSize(contentSizeList);
    MOZ_ASSERT(!contentSizeList.IsEmpty());
    if (canUpdateBSize) {
      float bSize = 0;
      for (const auto& current : contentSizeList) {
        bSize += current->BlockSize();
      }
      target->SetLastRememberedBSize(bSize);
    }
    if (canUpdateISize) {
      float iSize = 0;
      for (const auto& current : contentSizeList) {
        iSize = std::max(iSize, current->InlineSize());
      }
      target->SetLastRememberedISize(iSize);
    }
  }
}

/* static */ already_AddRefed<ResizeObserver>
ResizeObserver::CreateLastRememberedSizeObserver(Document& aDocument) {
  return do_AddRef(new ResizeObserver(aDocument, LastRememberedSizeCallback));
}

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

}  // namespace mozilla::dom