gecko-dev/layout/base/RestyleManager.cpp

/* -*- 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/RestyleManager.h"
#include "mozilla/RestyleManagerInlines.h"

#include "Layers.h"
#include "LayerAnimationInfo.h" // For LayerAnimationInfo::sRecords
#include "mozilla/StyleSetHandleInlines.h"
#include "nsIFrame.h"
#include "nsIPresShellInlines.h"


namespace mozilla {

RestyleManager::RestyleManager(StyleBackendType aType,
                               nsPresContext* aPresContext)
  : mPresContext(aPresContext)
  , mRestyleGeneration(1)
  , mUndisplayedRestyleGeneration(1)
  , mHoverGeneration(0)
  , mType(aType)
  , mInStyleRefresh(false)
  , mAnimationGeneration(0)
{
  MOZ_ASSERT(mPresContext);
}

void
RestyleManager::ContentInserted(nsINode* aContainer, nsIContent* aChild)
{
  RestyleForInsertOrChange(aContainer, aChild);
}

void
RestyleManager::ContentAppended(nsIContent* aContainer, nsIContent* aFirstNewContent)
{
  RestyleForAppend(aContainer, aFirstNewContent);
}

void
RestyleManager::RestyleForEmptyChange(Element* aContainer)
{
  // In some cases (:empty + E, :empty ~ E), a change in the content of
  // an element requires restyling its parent's siblings.
  nsRestyleHint hint = eRestyle_Subtree;
  nsIContent* grandparent = aContainer->GetParent();
  if (grandparent &&
      (grandparent->GetFlags() & NODE_HAS_SLOW_SELECTOR_LATER_SIBLINGS)) {
    hint = nsRestyleHint(hint | eRestyle_LaterSiblings);
  }
  PostRestyleEvent(aContainer, hint, nsChangeHint(0));
}

void
RestyleManager::RestyleForAppend(nsIContent* aContainer,
                                 nsIContent* aFirstNewContent)
{
  // The container cannot be a document, but might be a ShadowRoot.
  if (!aContainer->IsElement()) {
    return;
  }
  Element* container = aContainer->AsElement();

#ifdef DEBUG
  {
    for (nsIContent* cur = aFirstNewContent; cur; cur = cur->GetNextSibling()) {
      NS_ASSERTION(!cur->IsRootOfAnonymousSubtree(),
                   "anonymous nodes should not be in child lists");
    }
  }
#endif
  uint32_t selectorFlags =
    container->GetFlags() & (NODE_ALL_SELECTOR_FLAGS &
                             ~NODE_HAS_SLOW_SELECTOR_LATER_SIBLINGS);
  if (selectorFlags == 0)
    return;

  if (selectorFlags & NODE_HAS_EMPTY_SELECTOR) {
    // see whether we need to restyle the container
    bool wasEmpty = true; // :empty or :-moz-only-whitespace
    for (nsIContent* cur = container->GetFirstChild();
         cur != aFirstNewContent;
         cur = cur->GetNextSibling()) {
      // We don't know whether we're testing :empty or :-moz-only-whitespace,
      // so be conservative and assume :-moz-only-whitespace (i.e., make
      // IsSignificantChild less likely to be true, and thus make us more
      // likely to restyle).
      if (nsStyleUtil::IsSignificantChild(cur, true, false)) {
        wasEmpty = false;
        break;
      }
    }
    if (wasEmpty) {
      RestyleForEmptyChange(container);
      return;
    }
  }

  if (selectorFlags & NODE_HAS_SLOW_SELECTOR) {
    PostRestyleEvent(container, eRestyle_Subtree, nsChangeHint(0));
    // Restyling the container is the most we can do here, so we're done.
    return;
  }

  if (selectorFlags & NODE_HAS_EDGE_CHILD_SELECTOR) {
    // restyle the last element child before this node
    for (nsIContent* cur = aFirstNewContent->GetPreviousSibling();
         cur;
         cur = cur->GetPreviousSibling()) {
      if (cur->IsElement()) {
        PostRestyleEvent(cur->AsElement(), eRestyle_Subtree, nsChangeHint(0));
        break;
      }
    }
  }
}

// Needed since we can't use PostRestyleEvent on non-elements (with
// eRestyle_LaterSiblings or nsRestyleHint(eRestyle_Subtree |
// eRestyle_LaterSiblings) as appropriate).
static void
RestyleSiblingsStartingWith(RestyleManager* aRestyleManager,
                            nsIContent* aStartingSibling /* may be null */)
{
  for (nsIContent* sibling = aStartingSibling; sibling;
       sibling = sibling->GetNextSibling()) {
    if (sibling->IsElement()) {
      aRestyleManager->
        PostRestyleEvent(sibling->AsElement(),
                         nsRestyleHint(eRestyle_Subtree | eRestyle_LaterSiblings),
                         nsChangeHint(0));
      break;
    }
  }
}

// Restyling for a ContentInserted or CharacterDataChanged notification.
// This could be used for ContentRemoved as well if we got the
// notification before the removal happened (and sometimes
// CharacterDataChanged is more like a removal than an addition).
// The comments are written and variables are named in terms of it being
// a ContentInserted notification.
void
RestyleManager::RestyleForInsertOrChange(nsINode* aContainer,
                                         nsIContent* aChild)
{
  // The container might be a document or a ShadowRoot.
  if (!aContainer->IsElement()) {
    return;
  }
  Element* container = aContainer->AsElement();

  NS_ASSERTION(!aChild->IsRootOfAnonymousSubtree(),
               "anonymous nodes should not be in child lists");
  uint32_t selectorFlags = container->GetFlags() & NODE_ALL_SELECTOR_FLAGS;
  if (selectorFlags == 0)
    return;

  if (selectorFlags & NODE_HAS_EMPTY_SELECTOR) {
    // see whether we need to restyle the container
    bool wasEmpty = true; // :empty or :-moz-only-whitespace
    for (nsIContent* child = container->GetFirstChild();
         child;
         child = child->GetNextSibling()) {
      if (child == aChild)
        continue;
      // We don't know whether we're testing :empty or :-moz-only-whitespace,
      // so be conservative and assume :-moz-only-whitespace (i.e., make
      // IsSignificantChild less likely to be true, and thus make us more
      // likely to restyle).
      if (nsStyleUtil::IsSignificantChild(child, true, false)) {
        wasEmpty = false;
        break;
      }
    }
    if (wasEmpty) {
      RestyleForEmptyChange(container);
      return;
    }
  }

  if (selectorFlags & NODE_HAS_SLOW_SELECTOR) {
    PostRestyleEvent(container, eRestyle_Subtree, nsChangeHint(0));
    // Restyling the container is the most we can do here, so we're done.
    return;
  }

  if (selectorFlags & NODE_HAS_SLOW_SELECTOR_LATER_SIBLINGS) {
    // Restyle all later siblings.
    RestyleSiblingsStartingWith(this, aChild->GetNextSibling());
  }

  if (selectorFlags & NODE_HAS_EDGE_CHILD_SELECTOR) {
    // restyle the previously-first element child if it is after this node
    bool passedChild = false;
    for (nsIContent* content = container->GetFirstChild();
         content;
         content = content->GetNextSibling()) {
      if (content == aChild) {
        passedChild = true;
        continue;
      }
      if (content->IsElement()) {
        if (passedChild) {
          PostRestyleEvent(content->AsElement(), eRestyle_Subtree,
                           nsChangeHint(0));
        }
        break;
      }
    }
    // restyle the previously-last element child if it is before this node
    passedChild = false;
    for (nsIContent* content = container->GetLastChild();
         content;
         content = content->GetPreviousSibling()) {
      if (content == aChild) {
        passedChild = true;
        continue;
      }
      if (content->IsElement()) {
        if (passedChild) {
          PostRestyleEvent(content->AsElement(), eRestyle_Subtree,
                           nsChangeHint(0));
        }
        break;
      }
    }
  }
}

void
RestyleManager::ContentRemoved(nsINode* aContainer,
                               nsIContent* aOldChild,
                               nsIContent* aFollowingSibling)
{
  // The container might be a document or a ShadowRoot.
  if (!aContainer->IsElement()) {
    return;
  }
  Element* container = aContainer->AsElement();

  if (aOldChild->IsRootOfAnonymousSubtree()) {
    // This should be an assert, but this is called incorrectly in
    // HTMLEditor::DeleteRefToAnonymousNode and the assertions were clogging
    // up the logs.  Make it an assert again when that's fixed.
    MOZ_ASSERT(aOldChild->GetProperty(nsGkAtoms::restylableAnonymousNode),
               "anonymous nodes should not be in child lists (bug 439258)");
  }
  uint32_t selectorFlags = container->GetFlags() & NODE_ALL_SELECTOR_FLAGS;
  if (selectorFlags == 0)
    return;

  if (selectorFlags & NODE_HAS_EMPTY_SELECTOR) {
    // see whether we need to restyle the container
    bool isEmpty = true; // :empty or :-moz-only-whitespace
    for (nsIContent* child = container->GetFirstChild();
         child;
         child = child->GetNextSibling()) {
      // We don't know whether we're testing :empty or :-moz-only-whitespace,
      // so be conservative and assume :-moz-only-whitespace (i.e., make
      // IsSignificantChild less likely to be true, and thus make us more
      // likely to restyle).
      if (nsStyleUtil::IsSignificantChild(child, true, false)) {
        isEmpty = false;
        break;
      }
    }
    if (isEmpty) {
      RestyleForEmptyChange(container);
      return;
    }
  }

  if (selectorFlags & NODE_HAS_SLOW_SELECTOR) {
    PostRestyleEvent(container, eRestyle_Subtree, nsChangeHint(0));
    // Restyling the container is the most we can do here, so we're done.
    return;
  }

  if (selectorFlags & NODE_HAS_SLOW_SELECTOR_LATER_SIBLINGS) {
    // Restyle all later siblings.
    RestyleSiblingsStartingWith(this, aFollowingSibling);
  }

  if (selectorFlags & NODE_HAS_EDGE_CHILD_SELECTOR) {
    // restyle the now-first element child if it was after aOldChild
    bool reachedFollowingSibling = false;
    for (nsIContent* content = container->GetFirstChild();
         content;
         content = content->GetNextSibling()) {
      if (content == aFollowingSibling) {
        reachedFollowingSibling = true;
        // do NOT continue here; we might want to restyle this node
      }
      if (content->IsElement()) {
        if (reachedFollowingSibling) {
          PostRestyleEvent(content->AsElement(), eRestyle_Subtree,
                           nsChangeHint(0));
        }
        break;
      }
    }
    // restyle the now-last element child if it was before aOldChild
    reachedFollowingSibling = (aFollowingSibling == nullptr);
    for (nsIContent* content = container->GetLastChild();
         content;
         content = content->GetPreviousSibling()) {
      if (content->IsElement()) {
        if (reachedFollowingSibling) {
          PostRestyleEvent(content->AsElement(), eRestyle_Subtree, nsChangeHint(0));
        }
        break;
      }
      if (content == aFollowingSibling) {
        reachedFollowingSibling = true;
      }
    }
  }
}

/**
 * Calculates the change hint and the restyle hint for a given content state
 * change.
 *
 * This is called from both Restyle managers.
 */
void
RestyleManager::ContentStateChangedInternal(Element* aElement,
                                            EventStates aStateMask,
                                            nsChangeHint* aOutChangeHint)
{
  MOZ_ASSERT(!mInStyleRefresh);
  MOZ_ASSERT(aOutChangeHint);

  *aOutChangeHint = nsChangeHint(0);
  // Any change to a content state that affects which frames we construct
  // must lead to a frame reconstruct here if we already have a frame.
  // Note that we never decide through non-CSS means to not create frames
  // based on content states, so if we already don't have a frame we don't
  // need to force a reframe -- if it's needed, the HasStateDependentStyle
  // call will handle things.
  nsIFrame* primaryFrame = aElement->GetPrimaryFrame();
  if (primaryFrame) {
    // If it's generated content, ignore LOADING/etc state changes on it.
    if (!primaryFrame->IsGeneratedContentFrame() &&
        aStateMask.HasAtLeastOneOfStates(NS_EVENT_STATE_BROKEN |
                                         NS_EVENT_STATE_USERDISABLED |
                                         NS_EVENT_STATE_SUPPRESSED |
                                         NS_EVENT_STATE_LOADING)) {
      *aOutChangeHint = nsChangeHint_ReconstructFrame;
    } else {
      uint8_t app = primaryFrame->StyleDisplay()->mAppearance;
      if (app) {
        nsITheme* theme = PresContext()->GetTheme();
        if (theme &&
            theme->ThemeSupportsWidget(PresContext(), primaryFrame, app)) {
          bool repaint = false;
          theme->WidgetStateChanged(primaryFrame, app, nullptr, &repaint,
                                    nullptr);
          if (repaint) {
            *aOutChangeHint |= nsChangeHint_RepaintFrame;
          }
        }
      }
    }

    primaryFrame->ContentStatesChanged(aStateMask);
  }

  if (aStateMask.HasState(NS_EVENT_STATE_VISITED)) {
    // Exposing information to the page about whether the link is
    // visited or not isn't really something we can worry about here.
    // FIXME: We could probably do this a bit better.
    *aOutChangeHint |= nsChangeHint_RepaintFrame;
  }
}

/* static */ nsCString
RestyleManager::RestyleHintToString(nsRestyleHint aHint)
{
  nsCString result;
  bool any = false;
  const char* names[] = {
    "Self", "SomeDescendants", "Subtree", "LaterSiblings", "CSSTransitions",
    "CSSAnimations", "StyleAttribute", "StyleAttribute_Animations",
    "Force", "ForceDescendants"
  };
  uint32_t hint = aHint & ((1 << ArrayLength(names)) - 1);
  uint32_t rest = aHint & ~((1 << ArrayLength(names)) - 1);
  for (uint32_t i = 0; i < ArrayLength(names); i++) {
    if (hint & (1 << i)) {
      if (any) {
        result.AppendLiteral(" | ");
      }
      result.AppendPrintf("eRestyle_%s", names[i]);
      any = true;
    }
  }
  if (rest) {
    if (any) {
      result.AppendLiteral(" | ");
    }
    result.AppendPrintf("0x%0x", rest);
  } else {
    if (!any) {
      result.AppendLiteral("0");
    }
  }
  return result;
}

#ifdef DEBUG
/* static */ nsCString
RestyleManager::ChangeHintToString(nsChangeHint aHint)
{
  nsCString result;
  bool any = false;
  const char* names[] = {
    "RepaintFrame", "NeedReflow", "ClearAncestorIntrinsics",
    "ClearDescendantIntrinsics", "NeedDirtyReflow", "SyncFrameView",
    "UpdateCursor", "UpdateEffects", "UpdateOpacityLayer",
    "UpdateTransformLayer", "ReconstructFrame", "UpdateOverflow",
    "UpdateSubtreeOverflow", "UpdatePostTransformOverflow",
    "UpdateParentOverflow",
    "ChildrenOnlyTransform", "RecomputePosition", "UpdateContainingBlock",
    "BorderStyleNoneChange", "UpdateTextPath", "SchedulePaint",
    "NeutralChange", "InvalidateRenderingObservers",
    "ReflowChangesSizeOrPosition", "UpdateComputedBSize",
    "UpdateUsesOpacity", "UpdateBackgroundPosition",
    "AddOrRemoveTransform", "CSSOverflowChange",
    "UpdateWidgetProperties", "UpdateTableCellSpans"
  };
  static_assert(nsChangeHint_AllHints == (1u << ArrayLength(names)) - 1,
                "Name list doesn't match change hints.");
  uint32_t hint = aHint & ((1u << ArrayLength(names)) - 1);
  uint32_t rest = aHint & ~((1u << ArrayLength(names)) - 1);
  if ((hint & NS_STYLE_HINT_REFLOW) == NS_STYLE_HINT_REFLOW) {
    result.AppendLiteral("NS_STYLE_HINT_REFLOW");
    hint = hint & ~NS_STYLE_HINT_REFLOW;
    any = true;
  } else if ((hint & nsChangeHint_AllReflowHints) == nsChangeHint_AllReflowHints) {
    result.AppendLiteral("nsChangeHint_AllReflowHints");
    hint = hint & ~nsChangeHint_AllReflowHints;
    any = true;
  } else if ((hint & NS_STYLE_HINT_VISUAL) == NS_STYLE_HINT_VISUAL) {
    result.AppendLiteral("NS_STYLE_HINT_VISUAL");
    hint = hint & ~NS_STYLE_HINT_VISUAL;
    any = true;
  }
  for (uint32_t i = 0; i < ArrayLength(names); i++) {
    if (hint & (1 << i)) {
      if (any) {
        result.AppendLiteral(" | ");
      }
      result.AppendPrintf("nsChangeHint_%s", names[i]);
      any = true;
    }
  }
  if (rest) {
    if (any) {
      result.AppendLiteral(" | ");
    }
    result.AppendPrintf("0x%0x", rest);
  } else {
    if (!any) {
      result.AppendLiteral("nsChangeHint(0)");
    }
  }
  return result;
}
#endif

/**
 * Frame construction helpers follow.
 */
#ifdef DEBUG
static bool gInApplyRenderingChangeToTree = false;
#endif

#ifdef DEBUG
static void
DumpContext(nsIFrame* aFrame, nsStyleContext* aContext)
{
  if (aFrame) {
    fputs("frame: ", stdout);
    nsAutoString name;
    aFrame->GetFrameName(name);
    fputs(NS_LossyConvertUTF16toASCII(name).get(), stdout);
    fprintf(stdout, " (%p)", static_cast<void*>(aFrame));
  }
  if (aContext) {
    fprintf(stdout, " style: %p ", static_cast<void*>(aContext));

    nsAtom* pseudoTag = aContext->GetPseudo();
    if (pseudoTag) {
      nsAutoString buffer;
      pseudoTag->ToString(buffer);
      fputs(NS_LossyConvertUTF16toASCII(buffer).get(), stdout);
      fputs(" ", stdout);
    }
    fputs("{}\n", stdout);
  }
}

static void
VerifySameTree(GeckoStyleContext* aContext1, GeckoStyleContext* aContext2)
{
  GeckoStyleContext* top1 = aContext1;
  GeckoStyleContext* top2 = aContext2;
  GeckoStyleContext* parent;
  for (;;) {
    parent = top1->GetParent();
    if (!parent)
      break;
    top1 = parent;
  }
  for (;;) {
    parent = top2->GetParent();
    if (!parent)
      break;
    top2 = parent;
  }
  NS_ASSERTION(top1 == top2,
               "Style contexts are not in the same style context tree");
}

static void
VerifyContextParent(nsIFrame* aFrame, GeckoStyleContext* aContext,
                    GeckoStyleContext* aParentContext)
{
  // get the contexts not provided
  if (!aContext) {
    aContext = aFrame->StyleContext()->AsGecko();
  }

  if (!aParentContext) {
    nsIFrame* providerFrame;
    nsStyleContext* parent = aFrame->GetParentStyleContext(&providerFrame);
    aParentContext = parent ? parent->AsGecko() : nullptr;
    // aParentContext could still be null
  }

  NS_ASSERTION(aContext, "Failure to get required contexts");
  GeckoStyleContext* actualParentContext = aContext->GetParent();

  if (aParentContext) {
    if (aParentContext != actualParentContext) {
      DumpContext(aFrame, aContext);
      if (aContext == aParentContext) {
        NS_ERROR("Using parent's style context");
      } else {
        NS_ERROR("Wrong parent style context");
        fputs("Wrong parent style context: ", stdout);
        DumpContext(nullptr, actualParentContext);
        fputs("should be using: ", stdout);
        DumpContext(nullptr, aParentContext);
        VerifySameTree(actualParentContext, aParentContext);
        fputs("\n", stdout);
      }
    }

  } else {
    if (actualParentContext) {
      NS_ERROR("Have parent context and shouldn't");
      DumpContext(aFrame, aContext);
      fputs("Has parent context: ", stdout);
      DumpContext(nullptr, actualParentContext);
      fputs("Should be null\n\n", stdout);
    }
  }

  GeckoStyleContext* childStyleIfVisited = aContext->GetStyleIfVisited();
  // Either childStyleIfVisited has aContext->GetParent()->GetStyleIfVisited()
  // as the parent or it has a different rulenode from aContext _and_ has
  // aContext->GetParent() as the parent.
  if (childStyleIfVisited &&
      !((childStyleIfVisited->RuleNode() != aContext->RuleNode() &&
         childStyleIfVisited->GetParent() == aContext->GetParent()) ||
        childStyleIfVisited->GetParent() ==
          aContext->GetParent()->GetStyleIfVisited())) {
    NS_ERROR("Visited style has wrong parent");
    DumpContext(aFrame, aContext);
    fputs("\n", stdout);
  }
}

static void
VerifyStyleTree(nsIFrame* aFrame)
{
  GeckoStyleContext* context = aFrame->StyleContext()->AsGecko();
  VerifyContextParent(aFrame, context, nullptr);

  nsIFrame::ChildListIterator lists(aFrame);
  for (; !lists.IsDone(); lists.Next()) {
    for (nsIFrame* child : lists.CurrentList()) {
      if (!(child->GetStateBits() & NS_FRAME_OUT_OF_FLOW)) {
        // only do frames that are in flow
        if (child->IsPlaceholderFrame()) {
          // placeholder: first recurse and verify the out of flow frame,
          // then verify the placeholder's context
          nsIFrame* outOfFlowFrame =
            nsPlaceholderFrame::GetRealFrameForPlaceholder(child);

          // recurse to out of flow frame, letting the parent context get resolved
          do {
            VerifyStyleTree(outOfFlowFrame);
          } while ((outOfFlowFrame = outOfFlowFrame->GetNextContinuation()));

          // verify placeholder using the parent frame's context as
          // parent context
          VerifyContextParent(child, nullptr, nullptr);
        } else { // regular frame
          VerifyStyleTree(child);
        }
      }
    }
  }

  // do additional contexts
  int32_t contextIndex = 0;
  for (nsStyleContext* extraContext;
       (extraContext = aFrame->GetAdditionalStyleContext(contextIndex));
       ++contextIndex) {
    VerifyContextParent(aFrame, extraContext->AsGecko(), context);
  }
}

void
RestyleManager::DebugVerifyStyleTree(nsIFrame* aFrame)
{
  if (IsServo()) {
    // XXXheycam For now, we know that we don't use the same inheritance
    // hierarchy for certain cases, so just skip these assertions until
    // we work out what we want to assert (bug 1322570).
    return;
  }
  if (aFrame) {
    VerifyStyleTree(aFrame);
  }
}

#endif // DEBUG

/**
 * Sync views on aFrame and all of aFrame's descendants (following placeholders),
 * if aChange has nsChangeHint_SyncFrameView.
 * Calls DoApplyRenderingChangeToTree on all aFrame's out-of-flow descendants
 * (following placeholders), if aChange has nsChangeHint_RepaintFrame.
 * aFrame should be some combination of nsChangeHint_SyncFrameView,
 * nsChangeHint_RepaintFrame, nsChangeHint_UpdateOpacityLayer and
 * nsChangeHint_SchedulePaint, nothing else.
*/
static void SyncViewsAndInvalidateDescendants(nsIFrame* aFrame,
                                              nsChangeHint aChange);

static void StyleChangeReflow(nsIFrame* aFrame, nsChangeHint aHint);

/**
 * To handle nsChangeHint_ChildrenOnlyTransform we must iterate over the child
 * frames of the SVG frame concerned. This helper function is used to find that
 * SVG frame when we encounter nsChangeHint_ChildrenOnlyTransform to ensure
 * that we iterate over the intended children, since sometimes we end up
 * handling that hint while processing hints for one of the SVG frame's
 * ancestor frames.
 *
 * The reason that we sometimes end up trying to process the hint for an
 * ancestor of the SVG frame that the hint is intended for is due to the way we
 * process restyle events. ApplyRenderingChangeToTree adjusts the frame from
 * the restyled element's principle frame to one of its ancestor frames based
 * on what nsCSSRendering::FindBackground returns, since the background style
 * may have been propagated up to an ancestor frame. Processing hints using an
 * ancestor frame is fine in general, but nsChangeHint_ChildrenOnlyTransform is
 * a special case since it is intended to update the children of a specific
 * frame.
 */
static nsIFrame*
GetFrameForChildrenOnlyTransformHint(nsIFrame* aFrame)
{
  if (aFrame->IsViewportFrame()) {
    // This happens if the root-<svg> is fixed positioned, in which case we
    // can't use aFrame->GetContent() to find the primary frame, since
    // GetContent() returns nullptr for ViewportFrame.
    aFrame = aFrame->PrincipalChildList().FirstChild();
  }
  // For an nsHTMLScrollFrame, this will get the SVG frame that has the
  // children-only transforms:
  aFrame = aFrame->GetContent()->GetPrimaryFrame();
  if (aFrame->IsSVGOuterSVGFrame()) {
    aFrame = aFrame->PrincipalChildList().FirstChild();
    MOZ_ASSERT(aFrame->IsSVGOuterSVGAnonChildFrame(),
               "Where is the nsSVGOuterSVGFrame's anon child??");
  }
  MOZ_ASSERT(aFrame->IsFrameOfType(nsIFrame::eSVG | nsIFrame::eSVGContainer),
             "Children-only transforms only expected on SVG frames");
  return aFrame;
}

// Returns true if this function managed to successfully move a frame, and
// false if it could not process the position change, and a reflow should
// be performed instead.
bool
RecomputePosition(nsIFrame* aFrame)
{
  // Don't process position changes on table frames, since we already handle
  // the dynamic position change on the table wrapper frame, and the
  // reflow-based fallback code path also ignores positions on inner table
  // frames.
  if (aFrame->IsTableFrame()) {
    return true;
  }

  const nsStyleDisplay* display = aFrame->StyleDisplay();
  // Changes to the offsets of a non-positioned element can safely be ignored.
  if (display->mPosition == NS_STYLE_POSITION_STATIC) {
    return true;
  }

  // Don't process position changes on frames which have views or the ones which
  // have a view somewhere in their descendants, because the corresponding view
  // needs to be repositioned properly as well.
  if (aFrame->HasView() ||
      (aFrame->GetStateBits() & NS_FRAME_HAS_CHILD_WITH_VIEW)) {
    StyleChangeReflow(aFrame, nsChangeHint_NeedReflow);
    return false;
  }

  // Flexbox and Grid layout supports CSS Align and the optimizations below
  // don't support that yet.
  if (aFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW)) {
    nsIFrame* ph = aFrame->GetPlaceholderFrame();
    if (ph && ph->HasAnyStateBits(PLACEHOLDER_STATICPOS_NEEDS_CSSALIGN)) {
      StyleChangeReflow(aFrame, nsChangeHint_NeedReflow);
      return false;
    }
  }

  aFrame->SchedulePaint();

  // For relative positioning, we can simply update the frame rect
  if (display->IsRelativelyPositionedStyle()) {
    // Move the frame
    if (display->mPosition == NS_STYLE_POSITION_STICKY) {
      // Update sticky positioning for an entire element at once, starting with
      // the first continuation or ib-split sibling.
      // It's rare that the frame we already have isn't already the first
      // continuation or ib-split sibling, but it can happen when styles differ
      // across continuations such as ::first-line or ::first-letter, and in
      // those cases we will generally (but maybe not always) do the work twice.
      nsIFrame* firstContinuation =
        nsLayoutUtils::FirstContinuationOrIBSplitSibling(aFrame);

      StickyScrollContainer::ComputeStickyOffsets(firstContinuation);
      StickyScrollContainer* ssc =
        StickyScrollContainer::GetStickyScrollContainerForFrame(
          firstContinuation);
      if (ssc) {
        ssc->PositionContinuations(firstContinuation);
      }
    } else {
      MOZ_ASSERT(NS_STYLE_POSITION_RELATIVE == display->mPosition,
                 "Unexpected type of positioning");
      for (nsIFrame* cont = aFrame; cont;
           cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
        nsIFrame* cb = cont->GetContainingBlock();
        nsMargin newOffsets;
        WritingMode wm = cb->GetWritingMode();
        const LogicalSize size(wm, cb->GetContentRectRelativeToSelf().Size());

        ReflowInput::ComputeRelativeOffsets(wm, cont, size, newOffsets);
        NS_ASSERTION(newOffsets.left == -newOffsets.right &&
                     newOffsets.top == -newOffsets.bottom,
                     "ComputeRelativeOffsets should return valid results");

        // ReflowInput::ApplyRelativePositioning would work here, but
        // since we've already checked mPosition and aren't changing the frame's
        // normal position, go ahead and add the offsets directly.
        // First, we need to ensure that the normal position is stored though.
        bool hasProperty;
        nsPoint normalPosition = cont->GetNormalPosition(&hasProperty);
        if (!hasProperty) {
          cont->AddProperty(nsIFrame::NormalPositionProperty(),
                            new nsPoint(normalPosition));
        }
        cont->SetPosition(normalPosition +
                          nsPoint(newOffsets.left, newOffsets.top));
      }
    }

    return true;
  }

  // For the absolute positioning case, set up a fake HTML reflow state for
  // the frame, and then get the offsets and size from it. If the frame's size
  // doesn't need to change, we can simply update the frame position. Otherwise
  // we fall back to a reflow.
  RefPtr<gfxContext> rc =
    aFrame->PresShell()->CreateReferenceRenderingContext();

  // Construct a bogus parent reflow state so that there's a usable
  // containing block reflow state.
  nsIFrame* parentFrame = aFrame->GetParent();
  WritingMode parentWM = parentFrame->GetWritingMode();
  WritingMode frameWM = aFrame->GetWritingMode();
  LogicalSize parentSize = parentFrame->GetLogicalSize();

  nsFrameState savedState = parentFrame->GetStateBits();
  ReflowInput parentReflowInput(aFrame->PresContext(), parentFrame, rc,
                                parentSize);
  parentFrame->RemoveStateBits(~nsFrameState(0));
  parentFrame->AddStateBits(savedState);

  // The bogus parent state here was created with no parent state of its own,
  // and therefore it won't have an mCBReflowInput set up.
  // But we may need one (for InitCBReflowInput in a child state), so let's
  // try to create one here for the cases where it will be needed.
  Maybe<ReflowInput> cbReflowInput;
  nsIFrame* cbFrame = parentFrame->GetContainingBlock();
  if (cbFrame && (aFrame->GetContainingBlock() != parentFrame ||
                  parentFrame->IsTableFrame())) {
    LogicalSize cbSize = cbFrame->GetLogicalSize();
    cbReflowInput.emplace(cbFrame->PresContext(), cbFrame, rc, cbSize);
    cbReflowInput->ComputedPhysicalMargin() = cbFrame->GetUsedMargin();
    cbReflowInput->ComputedPhysicalPadding() = cbFrame->GetUsedPadding();
    cbReflowInput->ComputedPhysicalBorderPadding() =
      cbFrame->GetUsedBorderAndPadding();
    parentReflowInput.mCBReflowInput = cbReflowInput.ptr();
  }

  NS_WARNING_ASSERTION(parentSize.ISize(parentWM) != NS_INTRINSICSIZE &&
                       parentSize.BSize(parentWM) != NS_INTRINSICSIZE,
                       "parentSize should be valid");
  parentReflowInput.SetComputedISize(std::max(parentSize.ISize(parentWM), 0));
  parentReflowInput.SetComputedBSize(std::max(parentSize.BSize(parentWM), 0));
  parentReflowInput.ComputedPhysicalMargin().SizeTo(0, 0, 0, 0);

  parentReflowInput.ComputedPhysicalPadding() = parentFrame->GetUsedPadding();
  parentReflowInput.ComputedPhysicalBorderPadding() =
    parentFrame->GetUsedBorderAndPadding();
  LogicalSize availSize = parentSize.ConvertTo(frameWM, parentWM);
  availSize.BSize(frameWM) = NS_INTRINSICSIZE;

  ViewportFrame* viewport = do_QueryFrame(parentFrame);
  nsSize cbSize = viewport ?
    viewport->AdjustReflowInputAsContainingBlock(&parentReflowInput).Size()
    : aFrame->GetContainingBlock()->GetSize();
  const nsMargin& parentBorder =
    parentReflowInput.mStyleBorder->GetComputedBorder();
  cbSize -= nsSize(parentBorder.LeftRight(), parentBorder.TopBottom());
  LogicalSize lcbSize(frameWM, cbSize);
  ReflowInput reflowInput(aFrame->PresContext(), parentReflowInput, aFrame,
                          availSize, &lcbSize);
  nsSize computedSize(reflowInput.ComputedWidth(),
                      reflowInput.ComputedHeight());
  computedSize.width += reflowInput.ComputedPhysicalBorderPadding().LeftRight();
  if (computedSize.height != NS_INTRINSICSIZE) {
    computedSize.height +=
      reflowInput.ComputedPhysicalBorderPadding().TopBottom();
  }
  nsSize size = aFrame->GetSize();
  // The RecomputePosition hint is not used if any offset changed between auto
  // and non-auto. If computedSize.height == NS_INTRINSICSIZE then the new
  // element height will be its intrinsic height, and since 'top' and 'bottom''s
  // auto-ness hasn't changed, the old height must also be its intrinsic
  // height, which we can assume hasn't changed (or reflow would have
  // been triggered).
  if (computedSize.width == size.width &&
      (computedSize.height == NS_INTRINSICSIZE || computedSize.height == size.height)) {
    // If we're solving for 'left' or 'top', then compute it here, in order to
    // match the reflow code path.
    if (NS_AUTOOFFSET == reflowInput.ComputedPhysicalOffsets().left) {
      reflowInput.ComputedPhysicalOffsets().left = cbSize.width -
                                          reflowInput.ComputedPhysicalOffsets().right -
                                          reflowInput.ComputedPhysicalMargin().right -
                                          size.width -
                                          reflowInput.ComputedPhysicalMargin().left;
    }

    if (NS_AUTOOFFSET == reflowInput.ComputedPhysicalOffsets().top) {
      reflowInput.ComputedPhysicalOffsets().top = cbSize.height -
                                         reflowInput.ComputedPhysicalOffsets().bottom -
                                         reflowInput.ComputedPhysicalMargin().bottom -
                                         size.height -
                                         reflowInput.ComputedPhysicalMargin().top;
    }

    // Move the frame
    nsPoint pos(parentBorder.left + reflowInput.ComputedPhysicalOffsets().left +
                reflowInput.ComputedPhysicalMargin().left,
                parentBorder.top + reflowInput.ComputedPhysicalOffsets().top +
                reflowInput.ComputedPhysicalMargin().top);
    aFrame->SetPosition(pos);

    return true;
  }

  // Fall back to a reflow
  StyleChangeReflow(aFrame, nsChangeHint_NeedReflow);
  return false;
}

static bool
HasBoxAncestor(nsIFrame* aFrame)
{
  for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
    if (f->IsXULBoxFrame()) {
      return true;
    }
  }
  return false;
}

/**
 * Return true if aFrame's subtree has placeholders for out-of-flow content
 * whose 'position' style's bit in aPositionMask is set.
 */
static bool
FrameHasPositionedPlaceholderDescendants(nsIFrame* aFrame,
                                         uint32_t aPositionMask)
{
  MOZ_ASSERT(aPositionMask & (1 << NS_STYLE_POSITION_FIXED));

  for (nsIFrame::ChildListIterator lists(aFrame); !lists.IsDone(); lists.Next()) {
    for (nsIFrame* f : lists.CurrentList()) {
      if (f->IsPlaceholderFrame()) {
        nsIFrame* outOfFlow =
          nsPlaceholderFrame::GetRealFrameForPlaceholder(f);
        // If SVG text frames could appear here, they could confuse us since
        // they ignore their position style ... but they can't.
        NS_ASSERTION(!nsSVGUtils::IsInSVGTextSubtree(outOfFlow),
                     "SVG text frames can't be out of flow");
        if (aPositionMask & (1 << outOfFlow->StyleDisplay()->mPosition)) {
          return true;
        }
      }
      uint32_t positionMask = aPositionMask;
      // NOTE:  It's tempting to check f->IsAbsPosContainingBlock() or
      // f->IsFixedPosContainingBlock() here.  However, that would only
      // be testing the *new* style of the frame, which might exclude
      // descendants that currently have this frame as an abs-pos
      // containing block.  Taking the codepath where we don't reframe
      // could lead to an unsafe call to
      // cont->MarkAsNotAbsoluteContainingBlock() before we've reframed
      // the descendant and taken it off the absolute list.
      if (FrameHasPositionedPlaceholderDescendants(f, positionMask)) {
        return true;
      }
    }
  }
  return false;
}

static bool
NeedToReframeForAddingOrRemovingTransform(nsIFrame* aFrame)
{
  static_assert(0 <= NS_STYLE_POSITION_ABSOLUTE &&
                NS_STYLE_POSITION_ABSOLUTE < 32, "Style constant out of range");
  static_assert(0 <= NS_STYLE_POSITION_FIXED &&
                NS_STYLE_POSITION_FIXED < 32, "Style constant out of range");

  uint32_t positionMask;
  // Don't call aFrame->IsPositioned here, since that returns true if
  // the frame already has a transform, and we want to ignore that here
  if (aFrame->IsAbsolutelyPositioned() || aFrame->IsRelativelyPositioned()) {
    // This frame is a container for abs-pos descendants whether or not it
    // has a transform.
    // So abs-pos descendants are no problem; we only need to reframe if
    // we have fixed-pos descendants.
    positionMask = 1 << NS_STYLE_POSITION_FIXED;
  } else {
    // This frame may not be a container for abs-pos descendants already.
    // So reframe if we have abs-pos or fixed-pos descendants.
    positionMask =
      (1 << NS_STYLE_POSITION_FIXED) | (1 << NS_STYLE_POSITION_ABSOLUTE);
  }
  for (nsIFrame* f = aFrame; f;
       f = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(f)) {
    if (FrameHasPositionedPlaceholderDescendants(f, positionMask)) {
      return true;
    }
  }
  return false;
}

static void
DoApplyRenderingChangeToTree(nsIFrame* aFrame,
                             nsChangeHint aChange)
{
  NS_PRECONDITION(gInApplyRenderingChangeToTree,
                  "should only be called within ApplyRenderingChangeToTree");

  for ( ; aFrame; aFrame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(aFrame)) {
    // Invalidate and sync views on all descendant frames, following placeholders.
    // We don't need to update transforms in SyncViewsAndInvalidateDescendants, because
    // there can't be any out-of-flows or popups that need to be transformed;
    // all out-of-flow descendants of the transformed element must also be
    // descendants of the transformed frame.
    SyncViewsAndInvalidateDescendants(aFrame,
      nsChangeHint(aChange & (nsChangeHint_RepaintFrame |
                              nsChangeHint_SyncFrameView |
                              nsChangeHint_UpdateOpacityLayer |
                              nsChangeHint_SchedulePaint)));
    // This must be set to true if the rendering change needs to
    // invalidate content.  If it's false, a composite-only paint
    // (empty transaction) will be scheduled.
    bool needInvalidatingPaint = false;

    // if frame has view, will already be invalidated
    if (aChange & nsChangeHint_RepaintFrame) {
      // Note that this whole block will be skipped when painting is suppressed
      // (due to our caller ApplyRendingChangeToTree() discarding the
      // nsChangeHint_RepaintFrame hint).  If you add handling for any other
      // hints within this block, be sure that they too should be ignored when
      // painting is suppressed.
      needInvalidatingPaint = true;
      aFrame->InvalidateFrameSubtree();
      if ((aChange & nsChangeHint_UpdateEffects) &&
          aFrame->IsFrameOfType(nsIFrame::eSVG) &&
          !(aFrame->GetStateBits() & NS_STATE_IS_OUTER_SVG)) {
        // Need to update our overflow rects:
        nsSVGUtils::ScheduleReflowSVG(aFrame);
      }
    }
    if (aChange & nsChangeHint_UpdateTextPath) {
      if (nsSVGUtils::IsInSVGTextSubtree(aFrame)) {
        // Invalidate and reflow the entire SVGTextFrame:
        NS_ASSERTION(aFrame->GetContent()->IsSVGElement(nsGkAtoms::textPath),
                     "expected frame for a <textPath> element");
        nsIFrame* text = nsLayoutUtils::GetClosestFrameOfType(
          aFrame, LayoutFrameType::SVGText);
        NS_ASSERTION(text, "expected to find an ancestor SVGTextFrame");
        static_cast<SVGTextFrame*>(text)->NotifyGlyphMetricsChange();
      } else {
        MOZ_ASSERT(false, "unexpected frame got nsChangeHint_UpdateTextPath");
      }
    }
    if (aChange & nsChangeHint_UpdateOpacityLayer) {
      // FIXME/bug 796697: we can get away with empty transactions for
      // opacity updates in many cases.
      needInvalidatingPaint = true;

      ActiveLayerTracker::NotifyRestyle(aFrame, eCSSProperty_opacity);
      if (nsSVGIntegrationUtils::UsingEffectsForFrame(aFrame)) {
        // SVG effects paints the opacity without using
        // nsDisplayOpacity. We need to invalidate manually.
        aFrame->InvalidateFrameSubtree();
      }
    }
    if ((aChange & nsChangeHint_UpdateTransformLayer) &&
        aFrame->IsTransformed()) {
      ActiveLayerTracker::NotifyRestyle(aFrame, eCSSProperty_transform);
      // If we're not already going to do an invalidating paint, see
      // if we can get away with only updating the transform on a
      // layer for this frame, and not scheduling an invalidating
      // paint.
      if (!needInvalidatingPaint) {
        Layer* layer;
        needInvalidatingPaint |= !aFrame->TryUpdateTransformOnly(&layer);

        if (!needInvalidatingPaint) {
          // Since we're not going to paint, we need to resend animation
          // data to the layer.
          MOZ_ASSERT(layer, "this can't happen if there's no layer");
          nsDisplayListBuilder::AddAnimationsAndTransitionsToLayer(
            layer, nullptr, nullptr, aFrame, eCSSProperty_transform);
        }
      }
    }
    if (aChange & nsChangeHint_ChildrenOnlyTransform) {
      needInvalidatingPaint = true;
      nsIFrame* childFrame =
        GetFrameForChildrenOnlyTransformHint(aFrame)->PrincipalChildList().FirstChild();
      for ( ; childFrame; childFrame = childFrame->GetNextSibling()) {
        ActiveLayerTracker::NotifyRestyle(childFrame, eCSSProperty_transform);
      }
    }
    if (aChange & nsChangeHint_SchedulePaint) {
      needInvalidatingPaint = true;
    }
    aFrame->SchedulePaint(needInvalidatingPaint
                            ? nsIFrame::PAINT_DEFAULT
                            : nsIFrame::PAINT_COMPOSITE_ONLY);
  }
}

static void
SyncViewsAndInvalidateDescendants(nsIFrame* aFrame, nsChangeHint aChange)
{
  NS_PRECONDITION(gInApplyRenderingChangeToTree,
                  "should only be called within ApplyRenderingChangeToTree");
  NS_ASSERTION(nsChangeHint_size_t(aChange) ==
                          (aChange & (nsChangeHint_RepaintFrame |
                                      nsChangeHint_SyncFrameView |
                                      nsChangeHint_UpdateOpacityLayer |
                                      nsChangeHint_SchedulePaint)),
               "Invalid change flag");

  if (aChange & nsChangeHint_SyncFrameView) {
    aFrame->SyncFrameViewProperties();
  }

  nsIFrame::ChildListIterator lists(aFrame);
  for (; !lists.IsDone(); lists.Next()) {
    for (nsIFrame* child : lists.CurrentList()) {
      if (!(child->GetStateBits() & NS_FRAME_OUT_OF_FLOW)) {
        // only do frames that don't have placeholders
        if (child->IsPlaceholderFrame()) {
          // do the out-of-flow frame and its continuations
          nsIFrame* outOfFlowFrame =
            nsPlaceholderFrame::GetRealFrameForPlaceholder(child);
          DoApplyRenderingChangeToTree(outOfFlowFrame, aChange);
        } else if (lists.CurrentID() == nsIFrame::kPopupList) {
          DoApplyRenderingChangeToTree(child, aChange);
        } else { // regular frame
          SyncViewsAndInvalidateDescendants(child, aChange);
        }
      }
    }
  }
}

static void
ApplyRenderingChangeToTree(nsIPresShell* aPresShell,
                           nsIFrame* aFrame,
                           nsChangeHint aChange)
{
  // We check StyleDisplay()->HasTransformStyle() in addition to checking
  // IsTransformed() since we can get here for some frames that don't support
  // CSS transforms.
  NS_ASSERTION(!(aChange & nsChangeHint_UpdateTransformLayer) ||
               aFrame->IsTransformed() ||
               aFrame->StyleDisplay()->HasTransformStyle(),
               "Unexpected UpdateTransformLayer hint");

  if (aPresShell->IsPaintingSuppressed()) {
    // Don't allow synchronous rendering changes when painting is turned off.
    aChange &= ~nsChangeHint_RepaintFrame;
    if (!aChange) {
      return;
    }
  }

// Trigger rendering updates by damaging this frame and any
// continuations of this frame.
#ifdef DEBUG
  gInApplyRenderingChangeToTree = true;
#endif
  if (aChange & nsChangeHint_RepaintFrame) {
    // If the frame's background is propagated to an ancestor, walk up to
    // that ancestor and apply the RepaintFrame change hint to it.
    nsStyleContext* bgSC;
    nsIFrame* propagatedFrame = aFrame;
    while (!nsCSSRendering::FindBackground(propagatedFrame, &bgSC)) {
      propagatedFrame = propagatedFrame->GetParent();
      NS_ASSERTION(aFrame, "root frame must paint");
    }

    if (propagatedFrame != aFrame) {
      DoApplyRenderingChangeToTree(propagatedFrame, nsChangeHint_RepaintFrame);
      aChange &= ~nsChangeHint_RepaintFrame;
      if (!aChange) {
        return;
      }
    }
  }
  DoApplyRenderingChangeToTree(aFrame, aChange);
#ifdef DEBUG
  gInApplyRenderingChangeToTree = false;
#endif
}

static void
AddSubtreeToOverflowTracker(nsIFrame* aFrame,
                            OverflowChangedTracker& aOverflowChangedTracker)
{
  if (aFrame->FrameMaintainsOverflow()) {
    aOverflowChangedTracker.AddFrame(aFrame,
                                     OverflowChangedTracker::CHILDREN_CHANGED);
  }
  nsIFrame::ChildListIterator lists(aFrame);
  for (; !lists.IsDone(); lists.Next()) {
    for (nsIFrame* child : lists.CurrentList()) {
      AddSubtreeToOverflowTracker(child, aOverflowChangedTracker);
    }
  }
}

static void
StyleChangeReflow(nsIFrame* aFrame, nsChangeHint aHint)
{
  nsIPresShell::IntrinsicDirty dirtyType;
  if (aHint & nsChangeHint_ClearDescendantIntrinsics) {
    NS_ASSERTION(aHint & nsChangeHint_ClearAncestorIntrinsics,
                 "Please read the comments in nsChangeHint.h");
    NS_ASSERTION(aHint & nsChangeHint_NeedDirtyReflow,
                 "ClearDescendantIntrinsics requires NeedDirtyReflow");
    dirtyType = nsIPresShell::eStyleChange;
  } else if ((aHint & nsChangeHint_UpdateComputedBSize) &&
             aFrame->HasAnyStateBits(
               NS_FRAME_DESCENDANT_INTRINSIC_ISIZE_DEPENDS_ON_BSIZE)) {
    dirtyType = nsIPresShell::eStyleChange;
  } else if (aHint & nsChangeHint_ClearAncestorIntrinsics) {
    dirtyType = nsIPresShell::eTreeChange;
  } else if ((aHint & nsChangeHint_UpdateComputedBSize) &&
             HasBoxAncestor(aFrame)) {
    // The frame's computed BSize is changing, and we have a box ancestor
    // whose cached intrinsic height may need to be updated.
    dirtyType = nsIPresShell::eTreeChange;
  } else {
    dirtyType = nsIPresShell::eResize;
  }

  nsFrameState dirtyBits;
  if (aFrame->GetStateBits() & NS_FRAME_FIRST_REFLOW) {
    dirtyBits = nsFrameState(0);
  } else if ((aHint & nsChangeHint_NeedDirtyReflow) ||
             dirtyType == nsIPresShell::eStyleChange) {
    dirtyBits = NS_FRAME_IS_DIRTY;
  } else {
    dirtyBits = NS_FRAME_HAS_DIRTY_CHILDREN;
  }

  // If we're not going to clear any intrinsic sizes on the frames, and
  // there are no dirty bits to set, then there's nothing to do.
  if (dirtyType == nsIPresShell::eResize && !dirtyBits)
    return;

  nsIPresShell::ReflowRootHandling rootHandling;
  if (aHint & nsChangeHint_ReflowChangesSizeOrPosition) {
    rootHandling = nsIPresShell::ePositionOrSizeChange;
  } else {
    rootHandling = nsIPresShell::eNoPositionOrSizeChange;
  }

  do {
    aFrame->PresShell()->FrameNeedsReflow(
      aFrame, dirtyType, dirtyBits, rootHandling);
    aFrame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(aFrame);
  } while (aFrame);
}

// Get the next sibling which might have a frame.  This only considers siblings
// that stylo post-traversal looks at, so only elements and text.  In
// particular, it ignores comments.
static nsIContent*
NextSiblingWhichMayHaveFrame(nsIContent* aContent)
{
  for (nsIContent* next = aContent->GetNextSibling();
       next;
       next = next->GetNextSibling()) {
    if (next->IsElement() || next->IsNodeOfType(nsINode::eTEXT)) {
      return next;
    }
  }

  return nullptr;
}

void
RestyleManager::ProcessRestyledFrames(nsStyleChangeList& aChangeList)
{
  NS_ASSERTION(!nsContentUtils::IsSafeToRunScript(),
               "Someone forgot a script blocker");

  // See bug 1378219 comment 9:
  // Recursive calls here are a bit worrying, but apparently do happen in the
  // wild (although not currently in any of our automated tests). Try to get a
  // stack from Nightly/Dev channel to figure out what's going on and whether
  // it's OK.
  MOZ_DIAGNOSTIC_ASSERT(!mDestroyedFrames, "ProcessRestyledFrames recursion");

  if (aChangeList.IsEmpty()) {
    return;
  }

  // If mDestroyedFrames is null, we want to create a new hashtable here
  // and destroy it on exit; but if it is already non-null (because we're in
  // a recursive call), we will continue to use the existing table to
  // accumulate destroyed frames, and NOT clear mDestroyedFrames on exit.
  // We use a MaybeClearDestroyedFrames helper to conditionally reset the
  // mDestroyedFrames pointer when this method returns.
  typedef decltype(mDestroyedFrames) DestroyedFramesT;
  class MOZ_RAII MaybeClearDestroyedFrames
  {
  private:
    DestroyedFramesT& mDestroyedFramesRef; // ref to caller's mDestroyedFrames
    const bool        mResetOnDestruction;
  public:
    explicit MaybeClearDestroyedFrames(DestroyedFramesT& aTarget)
      : mDestroyedFramesRef(aTarget)
      , mResetOnDestruction(!aTarget) // reset only if target starts out null
    {
    }
    ~MaybeClearDestroyedFrames()
    {
      if (mResetOnDestruction) {
        mDestroyedFramesRef.reset(nullptr);
      }
    }
  };

  MaybeClearDestroyedFrames maybeClear(mDestroyedFrames);
  if (!mDestroyedFrames) {
    mDestroyedFrames = MakeUnique<nsTHashtable<nsPtrHashKey<const nsIFrame>>>();
  }

  AUTO_PROFILER_LABEL("RestyleManager::ProcessRestyledFrames", CSS);

  nsPresContext* presContext = PresContext();
  nsCSSFrameConstructor* frameConstructor = presContext->FrameConstructor();

  // Handle nsChangeHint_CSSOverflowChange, by either updating the
  // scrollbars on the viewport, or upgrading the change hint to frame-reconstruct.
  for (nsStyleChangeData& data : aChangeList) {
    if (data.mHint & nsChangeHint_CSSOverflowChange) {
      data.mHint &= ~nsChangeHint_CSSOverflowChange;
      bool doReconstruct = true; // assume the worst

      // Only bother with this if we're html/body, since:
      //  (a) It'd be *expensive* to reframe these particular nodes.  They're
      //      at the root, so reframing would mean rebuilding the world.
      //  (b) It's often *unnecessary* to reframe for "overflow" changes on
      //      these particular nodes.  In general, the only reason we reframe
      //      for "overflow" changes is so we can construct (or destroy) a
      //      scrollframe & scrollbars -- and the html/body nodes often don't
      //      need their own scrollframe/scrollbars because they coopt the ones
      //      on the viewport (which always exist). So depending on whether
      //      that's happening, we can skip the reframe for these nodes.
      if (data.mContent->IsAnyOfHTMLElements(nsGkAtoms::body,
                                             nsGkAtoms::html)) {
        // If the restyled element provided/provides the scrollbar styles for
        // the viewport before and/or after this restyle, AND it's not coopting
        // that responsibility from some other element (which would need
        // reconstruction to make its own scrollframe now), THEN: we don't need
        // to reconstruct - we can just reflow, because no scrollframe is being
        // added/removed.
        nsIContent* prevOverrideNode =
          presContext->GetViewportScrollbarStylesOverrideElement();
        nsIContent* newOverrideNode =
          presContext->UpdateViewportScrollbarStylesOverride();

        if (data.mContent == prevOverrideNode ||
            data.mContent == newOverrideNode) {
          // If we get here, the restyled element provided the scrollbar styles
          // for viewport before this restyle, OR it will provide them after.
          if (!prevOverrideNode || !newOverrideNode ||
              prevOverrideNode == newOverrideNode) {
            // If we get here, the restyled element is NOT replacing (or being
            // replaced by) some other element as the viewport's
            // scrollbar-styles provider. (If it were, we'd potentially need to
            // reframe to create a dedicated scrollframe for whichever element
            // is being booted from providing viewport scrollbar styles.)
            //
            // Under these conditions, we're OK to assume that this "overflow"
            // change only impacts the root viewport's scrollframe, which
            // already exists, so we can simply reflow instead of reframing.
            // When requesting this reflow, we send the exact same change hints
            // that "width" and "height" would send (since conceptually,
            // adding/removing scrollbars is like changing the available
            // space).
            data.mHint |= (nsChangeHint_ReflowHintsForISizeChange |
                           nsChangeHint_ReflowHintsForBSizeChange);
            doReconstruct = false;
          }
        }
      }
      if (doReconstruct) {
        data.mHint |= nsChangeHint_ReconstructFrame;
      }
    }
  }

  // Make sure to not rebuild quote or counter lists while we're
  // processing restyles
  frameConstructor->BeginUpdate();

  bool didUpdateCursor = false;

  for (size_t i = 0; i < aChangeList.Length(); ++i) {

    // Collect and coalesce adjacent siblings for lazy frame construction.
    // Eventually it would be even better to make RecreateFramesForContent
    // accept a range and coalesce all adjacent reconstructs (bug 1344139).
    size_t lazyRangeStart = i;
    while (i < aChangeList.Length() &&
           aChangeList[i].mContent &&
           aChangeList[i].mContent->HasFlag(NODE_NEEDS_FRAME) &&
           (i == lazyRangeStart ||
            NextSiblingWhichMayHaveFrame(aChangeList[i - 1].mContent) ==
              aChangeList[i].mContent))
    {
      MOZ_ASSERT(aChangeList[i].mHint & nsChangeHint_ReconstructFrame);
      MOZ_ASSERT(!aChangeList[i].mFrame);
      ++i;
    }
    if (i != lazyRangeStart) {
      nsIContent* start = aChangeList[lazyRangeStart].mContent;
      nsIContent* end = NextSiblingWhichMayHaveFrame(aChangeList[i-1].mContent);
      nsIContent* container = start->GetParent();
      MOZ_ASSERT(container);
      if (!end) {
        frameConstructor->ContentAppended(
            container,
            start,
            nsCSSFrameConstructor::InsertionKind::Sync);
      } else {
        frameConstructor->ContentRangeInserted(
            container,
            start,
            end,
            nullptr,
            nsCSSFrameConstructor::InsertionKind::Sync);
      }
    }
    for (size_t j = lazyRangeStart; j < i; ++j) {
      MOZ_ASSERT(!aChangeList[j].mContent->GetPrimaryFrame() ||
                 !aChangeList[j].mContent->HasFlag(NODE_NEEDS_FRAME));
    }
    if (i == aChangeList.Length()) {
      break;
    }

    const nsStyleChangeData& data = aChangeList[i];
    nsIFrame* frame = data.mFrame;
    nsIContent* content = data.mContent;
    nsChangeHint hint = data.mHint;
    bool didReflowThisFrame = false;

    NS_ASSERTION(!(hint & nsChangeHint_AllReflowHints) ||
                 (hint & nsChangeHint_NeedReflow),
                 "Reflow hint bits set without actually asking for a reflow");

    // skip any frame that has been destroyed due to a ripple effect
    if (frame && mDestroyedFrames->Contains(frame)) {
      continue;
    }

    if (frame && frame->GetContent() != content) {
      // XXXbz this is due to image maps messing with the primary frame of
      // <area>s.  See bug 135040.  Remove this block once that's fixed.
      frame = nullptr;
      if (!(hint & nsChangeHint_ReconstructFrame)) {
        continue;
      }
    }

    if ((hint & nsChangeHint_UpdateContainingBlock) && frame &&
        !(hint & nsChangeHint_ReconstructFrame)) {
      if (NeedToReframeForAddingOrRemovingTransform(frame) ||
          frame->IsFieldSetFrame() ||
          frame->GetContentInsertionFrame() != frame) {
        // The frame has positioned children that need to be reparented, or
        // it can't easily be converted to/from being an abs-pos container correctly.
        hint |= nsChangeHint_ReconstructFrame;
      } else {
        for (nsIFrame* cont = frame; cont;
             cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
          // Normally frame construction would set state bits as needed,
          // but we're not going to reconstruct the frame so we need to set them.
          // It's because we need to set this state on each affected frame
          // that we can't coalesce nsChangeHint_UpdateContainingBlock hints up
          // to ancestors (i.e. it can't be an change hint that is handled for
          // descendants).
          if (cont->IsAbsPosContainingBlock()) {
            if (!cont->IsAbsoluteContainer() &&
                (cont->GetStateBits() & NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN)) {
              cont->MarkAsAbsoluteContainingBlock();
            }
          } else {
            if (cont->IsAbsoluteContainer()) {
              if (cont->HasAbsolutelyPositionedChildren()) {
                // If |cont| still has absolutely positioned children,
                // we can't call MarkAsNotAbsoluteContainingBlock.  This
                // will remove a frame list that still has children in
                // it that we need to keep track of.
                // The optimization of removing it isn't particularly
                // important, although it does mean we skip some tests.
                NS_WARNING("skipping removal of absolute containing block");
              } else {
                cont->MarkAsNotAbsoluteContainingBlock();
              }
            }
          }
        }
      }
    }

    if ((hint & nsChangeHint_AddOrRemoveTransform) && frame &&
        !(hint & nsChangeHint_ReconstructFrame)) {
      for (nsIFrame* cont = frame; cont;
           cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
        if (cont->StyleDisplay()->HasTransform(cont)) {
          cont->AddStateBits(NS_FRAME_MAY_BE_TRANSFORMED);
        }
        // Don't remove NS_FRAME_MAY_BE_TRANSFORMED since it may still be
        // transformed by other means. It's OK to have the bit even if it's
        // not needed.
      }
    }

    if (hint & nsChangeHint_ReconstructFrame) {
      // If we ever start passing true here, be careful of restyles
      // that involve a reframe and animations.  In particular, if the
      // restyle we're processing here is an animation restyle, but
      // the style resolution we will do for the frame construction
      // happens async when we're not in an animation restyle already,
      // problems could arise.
      // We could also have problems with triggering of CSS transitions
      // on elements whose frames are reconstructed, since we depend on
      // the reconstruction happening synchronously.
      frameConstructor->RecreateFramesForContent(
        content, nsCSSFrameConstructor::InsertionKind::Sync);
    } else {
      NS_ASSERTION(frame, "This shouldn't happen");

      if (!frame->FrameMaintainsOverflow()) {
        // frame does not maintain overflow rects, so avoid calling
        // FinishAndStoreOverflow on it:
        hint &= ~(nsChangeHint_UpdateOverflow |
                  nsChangeHint_ChildrenOnlyTransform |
                  nsChangeHint_UpdatePostTransformOverflow |
                  nsChangeHint_UpdateParentOverflow);
      }

      if (!(frame->GetStateBits() & NS_FRAME_MAY_BE_TRANSFORMED)) {
        // Frame can not be transformed, and thus a change in transform will
        // have no effect and we should not use the
        // nsChangeHint_UpdatePostTransformOverflow hint.
        hint &= ~nsChangeHint_UpdatePostTransformOverflow;
      }

      if (hint & nsChangeHint_AddOrRemoveTransform) {
        // When dropping a running transform animation we will first add an
        // nsChangeHint_UpdateTransformLayer hint as part of the animation-only
        // restyle. During the subsequent regular restyle, if the animation was
        // the only reason the element had any transform applied, we will add
        // nsChangeHint_AddOrRemoveTransform as part of the regular restyle.
        //
        // With the Gecko backend, these two change hints are processed
        // after each restyle but when using the Servo backend they accumulate
        // and are processed together after we have already removed the
        // transform as part of the regular restyle. Since we don't actually
        // need the nsChangeHint_UpdateTransformLayer hint if we already have
        // a nsChangeHint_AddOrRemoveTransform hint, and since we
        // will fail an assertion in ApplyRenderingChangeToTree if we try
        // specify nsChangeHint_UpdateTransformLayer but don't have any
        // transform style, we just drop the unneeded hint here.
        hint &= ~nsChangeHint_UpdateTransformLayer;
      }

      if (hint & nsChangeHint_UpdateEffects) {
        for (nsIFrame* cont = frame; cont;
             cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
          SVGObserverUtils::UpdateEffects(cont);
        }
      }
      if ((hint & nsChangeHint_InvalidateRenderingObservers) ||
          ((hint & nsChangeHint_UpdateOpacityLayer) &&
           frame->IsFrameOfType(nsIFrame::eSVG) &&
           !(frame->GetStateBits() & NS_STATE_IS_OUTER_SVG))) {
        SVGObserverUtils::InvalidateRenderingObservers(frame);
        frame->SchedulePaint();
      }
      if (hint & nsChangeHint_NeedReflow) {
        StyleChangeReflow(frame, hint);
        didReflowThisFrame = true;
      }

      // Here we need to propagate repaint frame change hint instead of update
      // opacity layer change hint when we do opacity optimization for SVG.
      // We can't do it in nsStyleEffects::CalcDifference() just like we do
      // for the optimization for 0.99 over opacity values since we have no way
      // to call nsSVGUtils::CanOptimizeOpacity() there.
      if ((hint & nsChangeHint_UpdateOpacityLayer) &&
          nsSVGUtils::CanOptimizeOpacity(frame) &&
          frame->IsFrameOfType(nsIFrame::eSVGGeometry)) {
        hint &= ~nsChangeHint_UpdateOpacityLayer;
        hint |= nsChangeHint_RepaintFrame;
      }

      if ((hint & nsChangeHint_UpdateUsesOpacity) &&
          frame->IsFrameOfType(nsIFrame::eTablePart)) {
        NS_ASSERTION(hint & nsChangeHint_UpdateOpacityLayer,
                     "should only return UpdateUsesOpacity hint "
                     "when also returning UpdateOpacityLayer hint");
        // When an internal table part (including cells) changes between
        // having opacity 1 and non-1, it changes whether its
        // backgrounds (and those of table parts inside of it) are
        // painted as part of the table's nsDisplayTableBorderBackground
        // display item, or part of its own display item.  That requires
        // invalidation, so change UpdateOpacityLayer to RepaintFrame.
        hint &= ~nsChangeHint_UpdateOpacityLayer;
        hint |= nsChangeHint_RepaintFrame;
      }

      // Opacity disables preserve-3d, so if we toggle it, then we also need
      // to update the overflow areas of all potentially affected frames.
      if ((hint & nsChangeHint_UpdateUsesOpacity) &&
          frame->StyleDisplay()->mTransformStyle == NS_STYLE_TRANSFORM_STYLE_PRESERVE_3D) {
        hint |= nsChangeHint_UpdateSubtreeOverflow;
      }

      if (hint & nsChangeHint_UpdateBackgroundPosition) {
        // For most frame types, DLBI can detect background position changes,
        // so we only need to schedule a paint.
        hint |= nsChangeHint_SchedulePaint;
        if (frame->IsFrameOfType(nsIFrame::eTablePart) ||
            frame->IsFrameOfType(nsIFrame::eMathML)) {
          // Table parts and MathML frames don't build display items for their
          // backgrounds, so DLBI can't detect background-position changes for
          // these frames. Repaint the whole frame.
          hint |= nsChangeHint_RepaintFrame;
        }
      }

      if (hint & (nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView |
                  nsChangeHint_UpdateOpacityLayer | nsChangeHint_UpdateTransformLayer |
                  nsChangeHint_ChildrenOnlyTransform | nsChangeHint_SchedulePaint)) {
        ApplyRenderingChangeToTree(presContext->PresShell(), frame, hint);
      }
      if ((hint & nsChangeHint_RecomputePosition) && !didReflowThisFrame) {
        ActiveLayerTracker::NotifyOffsetRestyle(frame);
        // It is possible for this to fall back to a reflow
        if (!RecomputePosition(frame)) {
          didReflowThisFrame = true;
        }
      }
      NS_ASSERTION(!(hint & nsChangeHint_ChildrenOnlyTransform) ||
                   (hint & nsChangeHint_UpdateOverflow),
                   "nsChangeHint_UpdateOverflow should be passed too");
      if (!didReflowThisFrame &&
          (hint & (nsChangeHint_UpdateOverflow |
                   nsChangeHint_UpdatePostTransformOverflow |
                   nsChangeHint_UpdateParentOverflow |
                   nsChangeHint_UpdateSubtreeOverflow))) {
        if (hint & nsChangeHint_UpdateSubtreeOverflow) {
          for (nsIFrame* cont = frame; cont; cont =
                 nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
            AddSubtreeToOverflowTracker(cont, mOverflowChangedTracker);
          }
          // The work we just did in AddSubtreeToOverflowTracker
          // subsumes some of the other hints:
          hint &= ~(nsChangeHint_UpdateOverflow |
                    nsChangeHint_UpdatePostTransformOverflow);
        }
        if (hint & nsChangeHint_ChildrenOnlyTransform) {
          // The overflow areas of the child frames need to be updated:
          nsIFrame* hintFrame = GetFrameForChildrenOnlyTransformHint(frame);
          nsIFrame* childFrame = hintFrame->PrincipalChildList().FirstChild();
          NS_ASSERTION(!nsLayoutUtils::GetNextContinuationOrIBSplitSibling(frame),
                       "SVG frames should not have continuations "
                       "or ib-split siblings");
          NS_ASSERTION(!nsLayoutUtils::GetNextContinuationOrIBSplitSibling(hintFrame),
                       "SVG frames should not have continuations "
                       "or ib-split siblings");
          for ( ; childFrame; childFrame = childFrame->GetNextSibling()) {
            MOZ_ASSERT(childFrame->IsFrameOfType(nsIFrame::eSVG),
                       "Not expecting non-SVG children");
            // If |childFrame| is dirty or has dirty children, we don't bother
            // updating overflows since that will happen when it's reflowed.
            if (!(childFrame->GetStateBits() &
                  (NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN))) {
              mOverflowChangedTracker.AddFrame(childFrame,
                                        OverflowChangedTracker::CHILDREN_CHANGED);
            }
            NS_ASSERTION(!nsLayoutUtils::GetNextContinuationOrIBSplitSibling(childFrame),
                         "SVG frames should not have continuations "
                         "or ib-split siblings");
            NS_ASSERTION(childFrame->GetParent() == hintFrame,
                         "SVG child frame not expected to have different parent");
          }
        }
        // If |frame| is dirty or has dirty children, we don't bother updating
        // overflows since that will happen when it's reflowed.
        if (!(frame->GetStateBits() &
              (NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN))) {
          if (hint & (nsChangeHint_UpdateOverflow |
                      nsChangeHint_UpdatePostTransformOverflow)) {
            OverflowChangedTracker::ChangeKind changeKind;
            // If we have both nsChangeHint_UpdateOverflow and
            // nsChangeHint_UpdatePostTransformOverflow,
            // CHILDREN_CHANGED is selected as it is
            // strictly stronger.
            if (hint & nsChangeHint_UpdateOverflow) {
              changeKind = OverflowChangedTracker::CHILDREN_CHANGED;
            } else {
              changeKind = OverflowChangedTracker::TRANSFORM_CHANGED;
            }
            for (nsIFrame* cont = frame; cont; cont =
                   nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
              mOverflowChangedTracker.AddFrame(cont, changeKind);
            }
          }
          // UpdateParentOverflow hints need to be processed in addition
          // to the above, since if the processing of the above hints
          // yields no change, the update will not propagate to the
          // parent.
          if (hint & nsChangeHint_UpdateParentOverflow) {
            MOZ_ASSERT(frame->GetParent(),
                       "shouldn't get style hints for the root frame");
            for (nsIFrame* cont = frame; cont; cont =
                   nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
              mOverflowChangedTracker.AddFrame(cont->GetParent(),
                                   OverflowChangedTracker::CHILDREN_CHANGED);
            }
          }
        }
      }
      if ((hint & nsChangeHint_UpdateCursor) && !didUpdateCursor) {
        presContext->PresShell()->SynthesizeMouseMove(false);
        didUpdateCursor = true;
      }
      if (hint & nsChangeHint_UpdateWidgetProperties) {
        frame->UpdateWidgetProperties();
      }
      if (hint & nsChangeHint_UpdateTableCellSpans) {
        frameConstructor->UpdateTableCellSpans(content);
      }
    }
  }

  frameConstructor->EndUpdate();

#ifdef DEBUG
  // Verify the style tree.  Note that this needs to happen once we've
  // processed the whole list, since until then the tree is not in fact in a
  // consistent state.
  for (const nsStyleChangeData& data : aChangeList) {
    // reget frame from content since it may have been regenerated...
    if (data.mContent) {
      nsIFrame* frame = data.mContent->GetPrimaryFrame();
      if (frame) {
        DebugVerifyStyleTree(frame);
      }
    } else if (!data.mFrame || !data.mFrame->IsViewportFrame()) {
      NS_WARNING("Unable to test style tree integrity -- no content node "
                 "(and not a viewport frame)");
    }
  }
#endif

  aChangeList.Clear();
}

/* static */ uint64_t
RestyleManager::GetAnimationGenerationForFrame(nsIFrame* aFrame)
{
  EffectSet* effectSet = EffectSet::GetEffectSet(aFrame);
  return effectSet ? effectSet->GetAnimationGeneration() : 0;
}

void
RestyleManager::IncrementAnimationGeneration()
{
  // We update the animation generation at start of each call to
  // ProcessPendingRestyles so we should ignore any subsequent (redundant)
  // calls that occur while we are still processing restyles.
  if ((IsGecko() && !AsGecko()->IsProcessingRestyles()) ||
      (IsServo() && !mInStyleRefresh)) {
    ++mAnimationGeneration;
  }
}

/* static */ void
RestyleManager::AddLayerChangesForAnimation(nsIFrame* aFrame,
                                            nsIContent* aContent,
                                            nsStyleChangeList&
                                              aChangeListToProcess)
{
  if (!aFrame || !aContent) {
    return;
  }

  uint64_t frameGeneration =
    RestyleManager::GetAnimationGenerationForFrame(aFrame);

  nsChangeHint hint = nsChangeHint(0);
  for (const LayerAnimationInfo::Record& layerInfo :
         LayerAnimationInfo::sRecords) {
    layers::Layer* layer =
      FrameLayerBuilder::GetDedicatedLayer(aFrame, layerInfo.mLayerType);
    if (layer && frameGeneration != layer->GetAnimationGeneration()) {
      // If we have a transform layer but don't have any transform style, we
      // probably just removed the transform but haven't destroyed the layer
      // yet. In this case we will add the appropriate change hint
      // (nsChangeHint_UpdateContainingBlock) when we compare style contexts
      // so we can skip adding any change hint here. (If we *were* to add
      // nsChangeHint_UpdateTransformLayer, ApplyRenderingChangeToTree would
      // complain that we're updating a transform layer without a transform).
      if (layerInfo.mLayerType == DisplayItemType::TYPE_TRANSFORM &&
          !aFrame->StyleDisplay()->HasTransformStyle()) {
        continue;
      }
      hint |= layerInfo.mChangeHint;
    }

    // We consider it's the first paint for the frame if we have an animation
    // for the property but have no layer.
    // Note that in case of animations which has properties preventing running
    // on the compositor, e.g., width or height, corresponding layer is not
    // created at all, but even in such cases, we normally set valid change
    // hint for such animations in each tick, i.e. restyles in each tick. As
    // a result, we usually do restyles for such animations in every tick on
    // the main-thread.  The only animations which will be affected by this
    // explicit change hint are animations that have opacity/transform but did
    // not have those properies just before. e.g, setting transform by
    // setKeyframes or changing target element from other target which prevents
    // running on the compositor, etc.
    if (!layer &&
        nsLayoutUtils::HasEffectiveAnimation(aFrame, layerInfo.mProperty)) {
      hint |= layerInfo.mChangeHint;
    }
  }

  if (hint) {
    aChangeListToProcess.AppendChange(aFrame, aContent, hint);
  }
}

RestyleManager::AnimationsWithDestroyedFrame::AnimationsWithDestroyedFrame(
                                                RestyleManager* aRestyleManager)
  : mRestyleManager(aRestyleManager)
  , mRestorePointer(mRestyleManager->mAnimationsWithDestroyedFrame)
{
  MOZ_ASSERT(!mRestyleManager->mAnimationsWithDestroyedFrame,
             "shouldn't construct recursively");
  mRestyleManager->mAnimationsWithDestroyedFrame = this;
}

void
RestyleManager::AnimationsWithDestroyedFrame
              ::StopAnimationsForElementsWithoutFrames()
{
  StopAnimationsWithoutFrame(mContents, CSSPseudoElementType::NotPseudo);
  StopAnimationsWithoutFrame(mBeforeContents, CSSPseudoElementType::before);
  StopAnimationsWithoutFrame(mAfterContents, CSSPseudoElementType::after);
}

void
RestyleManager::AnimationsWithDestroyedFrame
              ::StopAnimationsWithoutFrame(
                  nsTArray<RefPtr<nsIContent>>& aArray,
                  CSSPseudoElementType aPseudoType)
{
  nsAnimationManager* animationManager =
    mRestyleManager->PresContext()->AnimationManager();
  nsTransitionManager* transitionManager =
    mRestyleManager->PresContext()->TransitionManager();
  for (nsIContent* content : aArray) {
    if (aPseudoType == CSSPseudoElementType::NotPseudo) {
      if (content->GetPrimaryFrame()) {
        continue;
      }
    } else if (aPseudoType == CSSPseudoElementType::before) {
      if (nsLayoutUtils::GetBeforeFrame(content)) {
        continue;
      }
    } else if (aPseudoType == CSSPseudoElementType::after) {
      if (nsLayoutUtils::GetAfterFrame(content)) {
        continue;
      }
    }
    dom::Element* element = content->AsElement();

    animationManager->StopAnimationsForElement(element, aPseudoType);
    transitionManager->StopAnimationsForElement(element, aPseudoType);

    // All other animations should keep running but not running on the
    // *compositor* at this point.
    EffectSet* effectSet = EffectSet::GetEffectSet(element, aPseudoType);
    if (effectSet) {
      for (KeyframeEffectReadOnly* effect : *effectSet) {
        effect->ResetIsRunningOnCompositor();
      }
    }
  }
}

} // namespace mozilla