gecko-dev/layout/generic/nsSplittableFrame.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/. */

/*
 * base class for rendering objects that can be split across lines,
 * columns, or pages
 */

#include "nsSplittableFrame.h"
#include "nsContainerFrame.h"
#include "nsFieldSetFrame.h"
#include "nsIFrameInlines.h"

using namespace mozilla;

void nsSplittableFrame::Init(nsIContent* aContent, nsContainerFrame* aParent,
                             nsIFrame* aPrevInFlow) {
  if (aPrevInFlow) {
    // Hook the frame into the flow
    SetPrevInFlow(aPrevInFlow);
    aPrevInFlow->SetNextInFlow(this);
  }
  nsFrame::Init(aContent, aParent, aPrevInFlow);
}

void nsSplittableFrame::DestroyFrom(nsIFrame* aDestructRoot,
                                    PostDestroyData& aPostDestroyData) {
  // Disconnect from the flow list
  if (mPrevContinuation || mNextContinuation) {
    RemoveFromFlow(this);
  }

  // Let the base class destroy the frame
  nsFrame::DestroyFrom(aDestructRoot, aPostDestroyData);
}

nsIFrame* nsSplittableFrame::GetPrevContinuation() const {
  return mPrevContinuation;
}

void nsSplittableFrame::SetPrevContinuation(nsIFrame* aFrame) {
  NS_ASSERTION(!aFrame || Type() == aFrame->Type(),
               "setting a prev continuation with incorrect type!");
  NS_ASSERTION(!IsInPrevContinuationChain(aFrame, this),
               "creating a loop in continuation chain!");
  mPrevContinuation = aFrame;
  RemoveStateBits(NS_FRAME_IS_FLUID_CONTINUATION);
}

nsIFrame* nsSplittableFrame::GetNextContinuation() const {
  return mNextContinuation;
}

void nsSplittableFrame::SetNextContinuation(nsIFrame* aFrame) {
  NS_ASSERTION(!aFrame || Type() == aFrame->Type(),
               "setting a next continuation with incorrect type!");
  NS_ASSERTION(!IsInNextContinuationChain(aFrame, this),
               "creating a loop in continuation chain!");
  mNextContinuation = aFrame;
  if (aFrame) aFrame->RemoveStateBits(NS_FRAME_IS_FLUID_CONTINUATION);
}

nsIFrame* nsSplittableFrame::FirstContinuation() const {
  nsSplittableFrame* firstContinuation = const_cast<nsSplittableFrame*>(this);
  while (firstContinuation->mPrevContinuation) {
    firstContinuation =
        static_cast<nsSplittableFrame*>(firstContinuation->mPrevContinuation);
  }
  MOZ_ASSERT(firstContinuation, "post-condition failed");
  return firstContinuation;
}

nsIFrame* nsSplittableFrame::LastContinuation() const {
  nsSplittableFrame* lastContinuation = const_cast<nsSplittableFrame*>(this);
  while (lastContinuation->mNextContinuation) {
    lastContinuation =
        static_cast<nsSplittableFrame*>(lastContinuation->mNextContinuation);
  }
  MOZ_ASSERT(lastContinuation, "post-condition failed");
  return lastContinuation;
}

#ifdef DEBUG
bool nsSplittableFrame::IsInPrevContinuationChain(nsIFrame* aFrame1,
                                                  nsIFrame* aFrame2) {
  int32_t iterations = 0;
  while (aFrame1 && iterations < 10) {
    // Bail out after 10 iterations so we don't bog down debug builds too much
    if (aFrame1 == aFrame2) return true;
    aFrame1 = aFrame1->GetPrevContinuation();
    ++iterations;
  }
  return false;
}

bool nsSplittableFrame::IsInNextContinuationChain(nsIFrame* aFrame1,
                                                  nsIFrame* aFrame2) {
  int32_t iterations = 0;
  while (aFrame1 && iterations < 10) {
    // Bail out after 10 iterations so we don't bog down debug builds too much
    if (aFrame1 == aFrame2) return true;
    aFrame1 = aFrame1->GetNextContinuation();
    ++iterations;
  }
  return false;
}
#endif

nsIFrame* nsSplittableFrame::GetPrevInFlow() const {
  return (GetStateBits() & NS_FRAME_IS_FLUID_CONTINUATION) ? mPrevContinuation
                                                           : nullptr;
}

void nsSplittableFrame::SetPrevInFlow(nsIFrame* aFrame) {
  NS_ASSERTION(!aFrame || Type() == aFrame->Type(),
               "setting a prev in flow with incorrect type!");
  NS_ASSERTION(!IsInPrevContinuationChain(aFrame, this),
               "creating a loop in continuation chain!");
  mPrevContinuation = aFrame;
  AddStateBits(NS_FRAME_IS_FLUID_CONTINUATION);
}

nsIFrame* nsSplittableFrame::GetNextInFlow() const {
  return mNextContinuation && (mNextContinuation->GetStateBits() &
                               NS_FRAME_IS_FLUID_CONTINUATION)
             ? mNextContinuation
             : nullptr;
}

void nsSplittableFrame::SetNextInFlow(nsIFrame* aFrame) {
  NS_ASSERTION(!aFrame || Type() == aFrame->Type(),
               "setting a next in flow with incorrect type!");
  NS_ASSERTION(!IsInNextContinuationChain(aFrame, this),
               "creating a loop in continuation chain!");
  mNextContinuation = aFrame;
  if (aFrame) aFrame->AddStateBits(NS_FRAME_IS_FLUID_CONTINUATION);
}

nsIFrame* nsSplittableFrame::FirstInFlow() const {
  nsSplittableFrame* firstInFlow = const_cast<nsSplittableFrame*>(this);
  while (nsIFrame* prev = firstInFlow->GetPrevInFlow()) {
    firstInFlow = static_cast<nsSplittableFrame*>(prev);
  }
  MOZ_ASSERT(firstInFlow, "post-condition failed");
  return firstInFlow;
}

nsIFrame* nsSplittableFrame::LastInFlow() const {
  nsSplittableFrame* lastInFlow = const_cast<nsSplittableFrame*>(this);
  while (nsIFrame* next = lastInFlow->GetNextInFlow()) {
    lastInFlow = static_cast<nsSplittableFrame*>(next);
  }
  MOZ_ASSERT(lastInFlow, "post-condition failed");
  return lastInFlow;
}

// Remove this frame from the flow. Connects prev in flow and next in flow
void nsSplittableFrame::RemoveFromFlow(nsIFrame* aFrame) {
  nsIFrame* prevContinuation = aFrame->GetPrevContinuation();
  nsIFrame* nextContinuation = aFrame->GetNextContinuation();

  // The new continuation is fluid only if the continuation on both sides
  // of the removed frame was fluid
  if (aFrame->GetPrevInFlow() && aFrame->GetNextInFlow()) {
    if (prevContinuation) {
      prevContinuation->SetNextInFlow(nextContinuation);
    }
    if (nextContinuation) {
      nextContinuation->SetPrevInFlow(prevContinuation);
    }
  } else {
    if (prevContinuation) {
      prevContinuation->SetNextContinuation(nextContinuation);
    }
    if (nextContinuation) {
      nextContinuation->SetPrevContinuation(prevContinuation);
    }
  }

  aFrame->SetPrevInFlow(nullptr);
  aFrame->SetNextInFlow(nullptr);
}

nscoord nsSplittableFrame::ConsumedBSize(WritingMode aWM) const {
  nscoord bSize = 0;

  for (nsIFrame* prev = GetPrevContinuation(); prev;
       prev = prev->GetPrevContinuation()) {
    bSize += prev->ContentBSize(aWM);
  }
  return bSize;
}

nscoord nsSplittableFrame::GetEffectiveComputedBSize(
    const ReflowInput& aReflowInput, nscoord aConsumedBSize) const {
  nscoord bSize = aReflowInput.ComputedBSize();
  if (bSize == NS_UNCONSTRAINEDSIZE) {
    return NS_UNCONSTRAINEDSIZE;
  }

  if (aConsumedBSize == NS_UNCONSTRAINEDSIZE) {
    aConsumedBSize = ConsumedBSize(aReflowInput.GetWritingMode());
  }

  bSize -= aConsumedBSize;

  // nsFieldSetFrame's inner frames are special since some of their content-box
  // BSize may be consumed by positioning it below the legend.  So we always
  // report zero for true overflow containers here.
  // XXXmats: hmm, can we fix this so that the sizes actually adds up instead?
  if (IS_TRUE_OVERFLOW_CONTAINER(this) &&
      Style()->GetPseudoType() == PseudoStyleType::fieldsetContent) {
    for (nsFieldSetFrame* fieldset = do_QueryFrame(GetParent()); fieldset;
         fieldset = static_cast<nsFieldSetFrame*>(fieldset->GetPrevInFlow())) {
      bSize -= fieldset->LegendSpace();
    }
  }

  // We may have stretched the frame beyond its computed height. Oh well.
  return std::max(0, bSize);
}

nsIFrame::LogicalSides nsSplittableFrame::GetLogicalSkipSides(
    const ReflowInput* aReflowInput) const {
  if (IS_TRUE_OVERFLOW_CONTAINER(this)) {
    return LogicalSides(eLogicalSideBitsBBoth);
  }

  if (MOZ_UNLIKELY(StyleBorder()->mBoxDecorationBreak ==
                   StyleBoxDecorationBreak::Clone)) {
    return LogicalSides();
  }

  LogicalSides skip;
  if (GetPrevContinuation()) {
    skip |= eLogicalSideBitsBStart;
  }

  if (aReflowInput) {
    // We're in the midst of reflow right now, so it's possible that we haven't
    // created a next-in-flow yet. If our content block-size is going to exceed
    // our available block-size, though, then we're going to need a
    // next-in-flow, it just hasn't been created yet.
    if (NS_UNCONSTRAINEDSIZE != aReflowInput->AvailableBSize()) {
      nscoord effectiveBSize = GetEffectiveComputedBSize(*aReflowInput);
      if (effectiveBSize != NS_UNCONSTRAINEDSIZE &&
          effectiveBSize > aReflowInput->AvailableBSize()) {
        // Our computed block-size is going to exceed our available block-size,
        // so we're going to need a next-in-flow.
        skip |= eLogicalSideBitsBEnd;
      }
    }
  } else {
    nsIFrame* nif = GetNextContinuation();
    if (nif && !IS_TRUE_OVERFLOW_CONTAINER(nif)) {
      skip |= eLogicalSideBitsBEnd;
    }
  }

  // Always skip block-end side if we have a *later* sibling across column-span
  // split.
  if (HasColumnSpanSiblings()) {
    skip |= eLogicalSideBitsBEnd;
  }

  return skip;
}

LogicalSides nsSplittableFrame::PreReflowBlockLevelLogicalSkipSides() const {
  if (MOZ_UNLIKELY(IS_TRUE_OVERFLOW_CONTAINER(this))) {
    return LogicalSides(mozilla::eLogicalSideBitsBBoth);
  }
  if (MOZ_LIKELY(StyleBorder()->mBoxDecorationBreak !=
                 StyleBoxDecorationBreak::Clone) &&
      GetPrevInFlow()) {
    return LogicalSides(mozilla::eLogicalSideBitsBStart);
  }
  return LogicalSides();
}