layout/base/DisplayPortUtils.cpp
author Botond Ballo <botond@mozilla.com>
Sun, 24 Jan 2021 04:08:00 +0000
changeset 564410 e65982f456435928e5ed52db9a96d12836663e7a
parent 561554 b7973553b72310024b31fb374f082762b1d7abc5
child 565976 544291ca47c142982819190163f65f79da134dea
permissions -rw-r--r--
Bug 1682919 - Avoid creating a new DisplayPortMargins object as a side effect of querying the displayport. r=tnikkel DisplayPortMargins objects are only meant to be created when setting display port margins, not when querying them, because the object's constructor records the visual and layout scroll offsets at the time of construction to use for adjusting the margins to be layout-relative. Differential Revision: https://phabricator.services.mozilla.com/D102075

/* -*- 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 "DisplayPortUtils.h"

#include "FrameMetrics.h"
#include "Layers.h"
#include "mozilla/dom/Document.h"
#include "mozilla/gfx/gfxVars.h"
#include "mozilla/gfx/Point.h"
#include "mozilla/layers/APZCCallbackHelper.h"
#include "mozilla/layers/APZPublicUtils.h"
#include "mozilla/layers/CompositorBridgeChild.h"
#include "mozilla/layers/PAPZ.h"
#include "mozilla/layers/RepaintRequest.h"
#include "mozilla/PresShell.h"
#include "mozilla/StaticPrefs_layers.h"
#include "nsDeckFrame.h"
#include "nsIScrollableFrame.h"
#include "nsLayoutUtils.h"
#include "nsPlaceholderFrame.h"
#include "nsSubDocumentFrame.h"
#include "RetainedDisplayListBuilder.h"

#include <ostream>

namespace mozilla {

using gfx::gfxVars;
using gfx::IntSize;

using layers::APZCCallbackHelper;
using layers::FrameMetrics;
using layers::LayerManager;
using layers::RepaintRequest;
using layers::ScrollableLayerGuid;

typedef ScrollableLayerGuid::ViewID ViewID;

static LazyLogModule sDisplayportLog("apz.displayport");

/* static */
DisplayPortMargins DisplayPortMargins::FromAPZ(
    const ScreenMargin& aMargins, const CSSPoint& aVisualOffset,
    const CSSPoint& aLayoutOffset, const CSSToScreenScale2D& aScale) {
  return DisplayPortMargins{aMargins, aVisualOffset, aLayoutOffset, aScale};
}

CSSToScreenScale2D ComputeDisplayportScale(nsIScrollableFrame* aScrollFrame) {
  // The calculation here is equivalent to
  // CalculateBasicFrameMetrics(aScrollFrame).DisplayportPixelsPerCSSPixel(),
  // but we don't calculate the entire frame metrics.
  if (!aScrollFrame) {
    return CSSToScreenScale2D(1.0, 1.0);
  }
  nsIFrame* frame = do_QueryFrame(aScrollFrame);
  MOZ_ASSERT(frame);
  nsPresContext* presContext = frame->PresContext();
  PresShell* presShell = presContext->PresShell();
  return presContext->CSSToDevPixelScale() *
         LayoutDeviceToLayerScale2D(
             presShell->GetCumulativeResolution() *
             nsLayoutUtils::GetTransformToAncestorScale(frame)) *
         LayerToScreenScale2D(1.0, 1.0);
}

/* static */
DisplayPortMargins DisplayPortMargins::ForScrollFrame(
    nsIScrollableFrame* aScrollFrame, const ScreenMargin& aMargins,
    const Maybe<CSSToScreenScale2D>& aScale) {
  CSSPoint visualOffset;
  CSSPoint layoutOffset;
  if (aScrollFrame) {
    nsIFrame* scrollFrame = do_QueryFrame(aScrollFrame);
    PresShell* presShell = scrollFrame->PresShell();
    layoutOffset = CSSPoint::FromAppUnits(aScrollFrame->GetScrollPosition());
    if (aScrollFrame->IsRootScrollFrameOfDocument() &&
        presShell->IsVisualViewportOffsetSet()) {
      visualOffset =
          CSSPoint::FromAppUnits(presShell->GetVisualViewportOffset());

    } else {
      visualOffset = layoutOffset;
    }
  }
  return DisplayPortMargins{aMargins, visualOffset, layoutOffset,
                            aScale.valueOrFrom([&] {
                              return ComputeDisplayportScale(aScrollFrame);
                            })};
}

/* static */
DisplayPortMargins DisplayPortMargins::ForContent(
    nsIContent* aContent, const ScreenMargin& aMargins) {
  return ForScrollFrame(
      aContent ? nsLayoutUtils::FindScrollableFrameFor(aContent) : nullptr,
      aMargins, Nothing());
}

ScreenMargin DisplayPortMargins::GetRelativeToLayoutViewport(
    ContentGeometryType aGeometryType,
    nsIScrollableFrame* aScrollableFrame) const {
  // APZ wants |mMargins| applied relative to the visual viewport.
  // The main-thread painting code applies margins relative to
  // the layout viewport. To get the main thread to paint the
  // area APZ wants, apply a translation between the two. The
  // magnitude of the translation depends on whether we are
  // applying the displayport to scrolled or fixed content.
  CSSPoint scrollDeltaCss =
      ComputeAsyncTranslation(aGeometryType, aScrollableFrame);
  ScreenPoint scrollDelta = scrollDeltaCss * mScale;
  ScreenMargin margins = mMargins;
  margins.left -= scrollDelta.x;
  margins.right += scrollDelta.x;
  margins.top -= scrollDelta.y;
  margins.bottom += scrollDelta.y;
  return margins;
}

std::ostream& operator<<(std::ostream& aOs,
                         const DisplayPortMargins& aMargins) {
  if (aMargins.mVisualOffset == CSSPoint() &&
      aMargins.mLayoutOffset == CSSPoint()) {
    aOs << aMargins.mMargins;
  } else {
    aOs << "{" << aMargins.mMargins << "," << aMargins.mVisualOffset << ","
        << aMargins.mLayoutOffset << "}";
  }
  return aOs;
}

CSSPoint DisplayPortMargins::ComputeAsyncTranslation(
    ContentGeometryType aGeometryType,
    nsIScrollableFrame* aScrollableFrame) const {
  // If we are applying the displayport to scrolled content, the
  // translation is the entire difference between the visual and
  // layout offsets.
  if (aGeometryType == ContentGeometryType::Scrolled) {
    return mVisualOffset - mLayoutOffset;
  }

  // If we are applying the displayport to fixed content, only
  // part of the difference between the visual and layout offsets
  // should be applied. This is because fixed content remains fixed
  // to the layout viewport, and some of the async delta between
  // the visual and layout offsets can drag the layout viewport
  // with it. We want only the remaining delta, i.e. the offset of
  // the visual viewport relative to the (async-scrolled) layout
  // viewport.
  if (!aScrollableFrame) {
    // Displayport on a non-scrolling frame for some reason.
    // There will be no divergence between the two viewports.
    return CSSPoint();
  }
  // Fixed content is always fixed to an RSF.
  MOZ_ASSERT(aScrollableFrame->IsRootScrollFrameOfDocument());
  nsIFrame* scrollFrame = do_QueryFrame(aScrollableFrame);
  if (!scrollFrame->PresShell()->IsVisualViewportSizeSet()) {
    // Zooming is disabled, so the layout viewport tracks the
    // visual viewport completely.
    return CSSPoint();
  }
  // Use KeepLayoutViewportEnclosingViewportVisual() to compute
  // an async layout viewport the way APZ would.
  const CSSRect visualViewport{
      mVisualOffset,
      // TODO: There are probably some edge cases here around async zooming
      // that are not currently being handled properly. For proper handling,
      // we'd likely need to save APZ's async zoom when populating
      // mVisualOffset, and using it to adjust the visual viewport size here.
      // Note that any incorrectness caused by this will only occur transiently
      // during async zooming.
      CSSSize::FromAppUnits(scrollFrame->PresShell()->GetVisualViewportSize())};
  const CSSRect scrollableRect = CSSRect::FromAppUnits(
      nsLayoutUtils::CalculateExpandedScrollableRect(scrollFrame));
  CSSRect asyncLayoutViewport{
      mLayoutOffset,
      CSSSize::FromAppUnits(aScrollableFrame->GetScrollPortRect().Size())};
  FrameMetrics::KeepLayoutViewportEnclosingVisualViewport(
      visualViewport, scrollableRect, /* out */ asyncLayoutViewport);
  return mVisualOffset - asyncLayoutViewport.TopLeft();
}

// Return the maximum displayport size, based on the LayerManager's maximum
// supported texture size. The result is in app units.
static nscoord GetMaxDisplayPortSize(nsIContent* aContent,
                                     nsPresContext* aFallbackPrescontext) {
  MOZ_ASSERT(!StaticPrefs::layers_enable_tiles_AtStartup(),
             "Do not clamp displayports if tiling is enabled");

  // Pick a safe maximum displayport size for sanity purposes. This is the
  // lowest maximum texture size on tileless-platforms (Windows, D3D10).
  // If the gfx.max-texture-size pref is set, further restrict the displayport
  // size to fit within that, because the compositor won't upload stuff larger
  // than this size.
  nscoord safeMaximum = aFallbackPrescontext
                            ? aFallbackPrescontext->DevPixelsToAppUnits(
                                  std::min(8192, gfxPlatform::MaxTextureSize()))
                            : nscoord_MAX;

  nsIFrame* frame = aContent->GetPrimaryFrame();
  if (!frame) {
    return safeMaximum;
  }
  frame = nsLayoutUtils::GetDisplayRootFrame(frame);

  nsIWidget* widget = frame->GetNearestWidget();
  if (!widget) {
    return safeMaximum;
  }
  LayerManager* lm = widget->GetLayerManager();
  if (!lm) {
    return safeMaximum;
  }
  nsPresContext* presContext = frame->PresContext();

  int32_t maxSizeInDevPixels = lm->GetMaxTextureSize();
  if (maxSizeInDevPixels < 0 || maxSizeInDevPixels == INT_MAX) {
    return safeMaximum;
  }
  maxSizeInDevPixels =
      std::min(maxSizeInDevPixels, gfxPlatform::MaxTextureSize());
  return presContext->DevPixelsToAppUnits(maxSizeInDevPixels);
}

static nsRect ApplyRectMultiplier(nsRect aRect, float aMultiplier) {
  if (aMultiplier == 1.0f) {
    return aRect;
  }
  float newWidth = aRect.width * aMultiplier;
  float newHeight = aRect.height * aMultiplier;
  float newX = aRect.x - ((newWidth - aRect.width) / 2.0f);
  float newY = aRect.y - ((newHeight - aRect.height) / 2.0f);
  // Rounding doesn't matter too much here, do a round-in
  return nsRect(ceil(newX), ceil(newY), floor(newWidth), floor(newHeight));
}

static nsRect GetDisplayPortFromRectData(nsIContent* aContent,
                                         DisplayPortPropertyData* aRectData,
                                         float aMultiplier) {
  // In the case where the displayport is set as a rect, we assume it is
  // already aligned and clamped as necessary. The burden to do that is
  // on the setter of the displayport. In practice very few places set the
  // displayport directly as a rect (mostly tests). We still do need to
  // expand it by the multiplier though.
  return ApplyRectMultiplier(aRectData->mRect, aMultiplier);
}

static nsRect GetDisplayPortFromMarginsData(
    nsIContent* aContent, DisplayPortMarginsPropertyData* aMarginsData,
    float aMultiplier, const DisplayPortOptions& aOptions) {
  // In the case where the displayport is set via margins, we apply the margins
  // to a base rect. Then we align the expanded rect based on the alignment
  // requested, further expand the rect by the multiplier, and finally, clamp it
  // to the size of the scrollable rect.

  nsRect base;
  if (nsRect* baseData = static_cast<nsRect*>(
          aContent->GetProperty(nsGkAtoms::DisplayPortBase))) {
    base = *baseData;
  } else {
    // In theory we shouldn't get here, but we do sometimes (see bug 1212136).
    // Fall through for graceful handling.
  }

  nsIFrame* frame = nsLayoutUtils::GetScrollFrameFromContent(aContent);
  if (!frame) {
    // Turns out we can't really compute it. Oops. We still should return
    // something sane. Note that since we can't clamp the rect without a
    // frame, we don't apply the multiplier either as it can cause the result
    // to leak outside the scrollable area.
    NS_WARNING(
        "Attempting to get a displayport from a content with no primary "
        "frame!");
    return base;
  }

  bool isRoot = false;
  if (aContent->OwnerDoc()->GetRootElement() == aContent) {
    isRoot = true;
  }

  nsIScrollableFrame* scrollableFrame = frame->GetScrollTargetFrame();
  nsPoint scrollPos;
  if (scrollableFrame) {
    scrollPos = scrollableFrame->GetScrollPosition();
  }

  nsPresContext* presContext = frame->PresContext();
  int32_t auPerDevPixel = presContext->AppUnitsPerDevPixel();

  LayoutDeviceToScreenScale2D res(
      presContext->PresShell()->GetCumulativeResolution() *
      nsLayoutUtils::GetTransformToAncestorScale(frame));

  // Calculate the expanded scrollable rect, which we'll be clamping the
  // displayport to.
  nsRect expandedScrollableRect =
      nsLayoutUtils::CalculateExpandedScrollableRect(frame);

  // GetTransformToAncestorScale() can return 0. In this case, just return the
  // base rect (clamped to the expanded scrollable rect), as other calculations
  // would run into divisions by zero.
  if (res == LayoutDeviceToScreenScale2D(0, 0)) {
    // Make sure the displayport remains within the scrollable rect.
    return base.MoveInsideAndClamp(expandedScrollableRect - scrollPos);
  }

  // First convert the base rect to screen pixels
  LayoutDeviceToScreenScale2D parentRes = res;
  if (isRoot) {
    // the base rect for root scroll frames is specified in the parent document
    // coordinate space, so it doesn't include the local resolution.
    float localRes = presContext->PresShell()->GetResolution();
    parentRes.xScale /= localRes;
    parentRes.yScale /= localRes;
  }
  ScreenRect screenRect =
      LayoutDeviceRect::FromAppUnits(base, auPerDevPixel) * parentRes;

  // Note on the correctness of applying the alignment in Screen space:
  //   The correct space to apply the alignment in would be Layer space, but
  //   we don't necessarily know the scale to convert to Layer space at this
  //   point because Layout may not yet have chosen the resolution at which to
  //   render (it chooses that in FrameLayerBuilder, but this can be called
  //   during display list building). Therefore, we perform the alignment in
  //   Screen space, which basically assumes that Layout chose to render at
  //   screen resolution; since this is what Layout does most of the time,
  //   this is a good approximation. A proper solution would involve moving
  //   the choosing of the resolution to display-list building time.
  ScreenSize alignment;

  PresShell* presShell = presContext->PresShell();
  MOZ_ASSERT(presShell);

  bool useWebRender = gfxVars::UseWebRender();

  ScreenMargin margins = aMarginsData->mMargins.GetRelativeToLayoutViewport(
      aOptions.mGeometryType, scrollableFrame);

  if (presShell->IsDisplayportSuppressed()) {
    alignment = ScreenSize(1, 1);
  } else if (useWebRender) {
    // Moving the displayport is relatively expensive with WR so we use a larger
    // alignment that causes the displayport to move less frequently. The
    // alignment scales up with the size of the base rect so larger scrollframes
    // use a larger alignment, but we clamp the alignment to a power of two
    // between 128 and 1024 (inclusive).
    // This naturally also increases the size of the displayport compared to
    // always using a 128 alignment, so the displayport multipliers are also
    // correspondingly smaller when WR is enabled to prevent the displayport
    // from becoming too big.
    IntSize multiplier =
        layers::apz::GetDisplayportAlignmentMultiplier(screenRect.Size());
    alignment = ScreenSize(128 * multiplier.width, 128 * multiplier.height);
  } else if (StaticPrefs::layers_enable_tiles_AtStartup()) {
    // Don't align to tiles if they are too large, because we could expand
    // the displayport by a lot which can take more paint time. It's a tradeoff
    // though because if we don't align to tiles we have more waste on upload.
    IntSize tileSize = gfxVars::TileSize();
    alignment = ScreenSize(std::min(256, tileSize.width),
                           std::min(256, tileSize.height));
  } else {
    // If we're not drawing with tiles then we need to be careful about not
    // hitting the max texture size and we only need 1 draw call per layer
    // so we can align to a smaller multiple.
    alignment = ScreenSize(128, 128);
  }

  // Avoid division by zero.
  if (alignment.width == 0) {
    alignment.width = 128;
  }
  if (alignment.height == 0) {
    alignment.height = 128;
  }

  if (StaticPrefs::layers_enable_tiles_AtStartup() || useWebRender) {
    // Expand the rect by the margins
    screenRect.Inflate(margins);
  } else {
    // Calculate the displayport to make sure we fit within the max texture size
    // when not tiling.
    nscoord maxSizeAppUnits = GetMaxDisplayPortSize(aContent, presContext);
    MOZ_ASSERT(maxSizeAppUnits < nscoord_MAX);

    // The alignment code can round up to 3 tiles, we want to make sure
    // that the displayport can grow by up to 3 tiles without going
    // over the max texture size.
    const int MAX_ALIGN_ROUNDING = 3;

    // Find the maximum size in screen pixels.
    int32_t maxSizeDevPx = presContext->AppUnitsToDevPixels(maxSizeAppUnits);
    int32_t maxWidthScreenPx = floor(double(maxSizeDevPx) * res.xScale) -
                               MAX_ALIGN_ROUNDING * alignment.width;
    int32_t maxHeightScreenPx = floor(double(maxSizeDevPx) * res.yScale) -
                                MAX_ALIGN_ROUNDING * alignment.height;

    // For each axis, inflate the margins up to the maximum size.
    if (screenRect.height < maxHeightScreenPx) {
      int32_t budget = maxHeightScreenPx - screenRect.height;
      // Scale the margins down to fit into the budget if necessary, maintaining
      // their relative ratio.
      float scale = 1.0f;
      if (float(budget) < margins.TopBottom()) {
        scale = float(budget) / margins.TopBottom();
      }
      float top = margins.top * scale;
      float bottom = margins.bottom * scale;
      screenRect.y -= top;
      screenRect.height += top + bottom;
    }
    if (screenRect.width < maxWidthScreenPx) {
      int32_t budget = maxWidthScreenPx - screenRect.width;
      float scale = 1.0f;
      if (float(budget) < margins.LeftRight()) {
        scale = float(budget) / margins.LeftRight();
      }
      float left = margins.left * scale;
      float right = margins.right * scale;
      screenRect.x -= left;
      screenRect.width += left + right;
    }
  }

  ScreenPoint scrollPosScreen =
      LayoutDevicePoint::FromAppUnits(scrollPos, auPerDevPixel) * res;

  // Align the display port.
  screenRect += scrollPosScreen;
  float x = alignment.width * floor(screenRect.x / alignment.width);
  float y = alignment.height * floor(screenRect.y / alignment.height);
  float w = alignment.width * ceil(screenRect.width / alignment.width + 1);
  float h = alignment.height * ceil(screenRect.height / alignment.height + 1);
  screenRect = ScreenRect(x, y, w, h);
  screenRect -= scrollPosScreen;

  // Convert the aligned rect back into app units.
  nsRect result = LayoutDeviceRect::ToAppUnits(screenRect / res, auPerDevPixel);

  // If we have non-zero margins, expand the displayport for the low-res buffer
  // if that's what we're drawing. If we have zero margins, we want the
  // displayport to reflect the scrollport.
  if (margins != ScreenMargin()) {
    result = ApplyRectMultiplier(result, aMultiplier);
  }

  // Make sure the displayport remains within the scrollable rect.
  result = result.MoveInsideAndClamp(expandedScrollableRect - scrollPos);

  return result;
}

static bool GetDisplayPortData(
    nsIContent* aContent, DisplayPortPropertyData** aOutRectData,
    DisplayPortMarginsPropertyData** aOutMarginsData) {
  MOZ_ASSERT(aOutRectData && aOutMarginsData);

  *aOutRectData = static_cast<DisplayPortPropertyData*>(
      aContent->GetProperty(nsGkAtoms::DisplayPort));
  *aOutMarginsData = static_cast<DisplayPortMarginsPropertyData*>(
      aContent->GetProperty(nsGkAtoms::DisplayPortMargins));

  if (!*aOutRectData && !*aOutMarginsData) {
    // This content element has no displayport data at all
    return false;
  }

  if (*aOutRectData && *aOutMarginsData) {
    // choose margins if equal priority
    if ((*aOutRectData)->mPriority > (*aOutMarginsData)->mPriority) {
      *aOutMarginsData = nullptr;
    } else {
      *aOutRectData = nullptr;
    }
  }

  NS_ASSERTION((*aOutRectData == nullptr) != (*aOutMarginsData == nullptr),
               "Only one of aOutRectData or aOutMarginsData should be set!");

  return true;
}

static bool GetWasDisplayPortPainted(nsIContent* aContent) {
  DisplayPortPropertyData* rectData = nullptr;
  DisplayPortMarginsPropertyData* marginsData = nullptr;

  if (!GetDisplayPortData(aContent, &rectData, &marginsData)) {
    return false;
  }

  return rectData ? rectData->mPainted : marginsData->mPainted;
}

bool DisplayPortUtils::IsMissingDisplayPortBaseRect(nsIContent* aContent) {
  DisplayPortPropertyData* rectData = nullptr;
  DisplayPortMarginsPropertyData* marginsData = nullptr;

  if (GetDisplayPortData(aContent, &rectData, &marginsData) && marginsData) {
    return !aContent->GetProperty(nsGkAtoms::DisplayPortBase);
  }

  return false;
}

static void TranslateFromScrollPortToScrollFrame(nsIContent* aContent,
                                                 nsRect* aRect) {
  MOZ_ASSERT(aRect);
  if (nsIScrollableFrame* scrollableFrame =
          nsLayoutUtils::FindScrollableFrameFor(aContent)) {
    *aRect += scrollableFrame->GetScrollPortRect().TopLeft();
  }
}

static bool GetDisplayPortImpl(nsIContent* aContent, nsRect* aResult,
                               float aMultiplier,
                               const DisplayPortOptions& aOptions) {
  DisplayPortPropertyData* rectData = nullptr;
  DisplayPortMarginsPropertyData* marginsData = nullptr;

  if (!GetDisplayPortData(aContent, &rectData, &marginsData)) {
    return false;
  }

  nsIFrame* frame = aContent->GetPrimaryFrame();
  if (frame && !frame->PresShell()->AsyncPanZoomEnabled()) {
    return false;
  }

  if (!aResult) {
    // We have displayport data, but the caller doesn't want the actual
    // rect, so we don't need to actually compute it.
    return true;
  }

  bool isDisplayportSuppressed = false;

  if (frame) {
    nsPresContext* presContext = frame->PresContext();
    MOZ_ASSERT(presContext);
    PresShell* presShell = presContext->PresShell();
    MOZ_ASSERT(presShell);
    isDisplayportSuppressed = presShell->IsDisplayportSuppressed();
  }

  nsRect result;
  if (rectData) {
    result = GetDisplayPortFromRectData(aContent, rectData, aMultiplier);
  } else if (isDisplayportSuppressed ||
             nsLayoutUtils::ShouldDisableApzForElement(aContent)) {
    // Make a copy of the margins data but set the margins to empty.
    // Do not create a new DisplayPortMargins object with
    // DisplayPortMargins::Empty(), because that will record the visual
    // and layout scroll offsets in place right now on the DisplayPortMargins,
    // and those are only meant to be recorded when the margins are stored.
    DisplayPortMarginsPropertyData noMargins = *marginsData;
    noMargins.mMargins.mMargins = ScreenMargin();
    result = GetDisplayPortFromMarginsData(aContent, &noMargins, aMultiplier,
                                           aOptions);
  } else {
    result = GetDisplayPortFromMarginsData(aContent, marginsData, aMultiplier,
                                           aOptions);
  }

  if (!StaticPrefs::layers_enable_tiles_AtStartup()) {
    // Perform the desired error handling if the displayport dimensions
    // exceeds the maximum allowed size
    nscoord maxSize = GetMaxDisplayPortSize(aContent, nullptr);
    if (result.width > maxSize || result.height > maxSize) {
      switch (aOptions.mMaxSizeExceededBehaviour) {
        case MaxSizeExceededBehaviour::Assert:
          NS_ASSERTION(false, "Displayport must be a valid texture size");
          break;
        case MaxSizeExceededBehaviour::Drop:
          return false;
      }
    }
  }

  if (aOptions.mRelativeTo == DisplayportRelativeTo::ScrollFrame) {
    TranslateFromScrollPortToScrollFrame(aContent, &result);
  }

  *aResult = result;
  return true;
}

bool DisplayPortUtils::GetDisplayPort(nsIContent* aContent, nsRect* aResult,
                                      const DisplayPortOptions& aOptions) {
  float multiplier = StaticPrefs::layers_low_precision_buffer()
                         ? 1.0f / StaticPrefs::layers_low_precision_resolution()
                         : 1.0f;
  return GetDisplayPortImpl(aContent, aResult, multiplier, aOptions);
}

bool DisplayPortUtils::HasDisplayPort(nsIContent* aContent) {
  return GetDisplayPort(aContent, nullptr);
}

bool DisplayPortUtils::HasPaintedDisplayPort(nsIContent* aContent) {
  DisplayPortPropertyData* rectData = nullptr;
  DisplayPortMarginsPropertyData* marginsData = nullptr;
  GetDisplayPortData(aContent, &rectData, &marginsData);
  if (rectData) {
    return rectData->mPainted;
  }
  if (marginsData) {
    return marginsData->mPainted;
  }
  return false;
}

void DisplayPortUtils::MarkDisplayPortAsPainted(nsIContent* aContent) {
  DisplayPortPropertyData* rectData = nullptr;
  DisplayPortMarginsPropertyData* marginsData = nullptr;
  GetDisplayPortData(aContent, &rectData, &marginsData);
  MOZ_ASSERT(rectData || marginsData,
             "MarkDisplayPortAsPainted should only be called for an element "
             "with a displayport");
  if (rectData) {
    rectData->mPainted = true;
  }
  if (marginsData) {
    marginsData->mPainted = true;
  }
}

/* static */
bool DisplayPortUtils::GetDisplayPortForVisibilityTesting(nsIContent* aContent,
                                                          nsRect* aResult) {
  MOZ_ASSERT(aResult);
  // Since the base rect might not have been updated very recently, it's
  // possible to end up with an extra-large displayport at this point, if the
  // zoom level is changed by a lot. Instead of using the default behaviour of
  // asserting, we can just ignore the displayport if that happens, as this
  // call site is best-effort.
  return GetDisplayPortImpl(aContent, aResult, 1.0f,
                            DisplayPortOptions()
                                .With(MaxSizeExceededBehaviour::Drop)
                                .With(DisplayportRelativeTo::ScrollFrame));
}

void DisplayPortUtils::InvalidateForDisplayPortChange(
    nsIContent* aContent, bool aHadDisplayPort, const nsRect& aOldDisplayPort,
    const nsRect& aNewDisplayPort, RepaintMode aRepaintMode) {
  if (aRepaintMode != RepaintMode::Repaint) {
    return;
  }

  bool changed =
      !aHadDisplayPort || !aOldDisplayPort.IsEqualEdges(aNewDisplayPort);

  nsIFrame* frame = nsLayoutUtils::GetScrollFrameFromContent(aContent);
  if (frame) {
    frame = do_QueryFrame(frame->GetScrollTargetFrame());
  }

  if (changed && frame) {
    // It is important to call SchedulePaint on the same frame that we set the
    // dirty rect properties on so we can find the frame later to remove the
    // properties.
    frame->SchedulePaint();

    if (!nsLayoutUtils::AreRetainedDisplayListsEnabled() ||
        !nsLayoutUtils::DisplayRootHasRetainedDisplayListBuilder(frame)) {
      return;
    }

    bool found;
    nsRect* rect = frame->GetProperty(
        nsDisplayListBuilder::DisplayListBuildingDisplayPortRect(), &found);

    if (!found) {
      rect = new nsRect();
      frame->AddProperty(
          nsDisplayListBuilder::DisplayListBuildingDisplayPortRect(), rect);
      frame->SetHasOverrideDirtyRegion(true);

      nsIFrame* rootFrame = frame->PresShell()->GetRootFrame();
      MOZ_ASSERT(rootFrame);

      RetainedDisplayListData* data =
          GetOrSetRetainedDisplayListData(rootFrame);
      data->Flags(frame) |= RetainedDisplayListData::FrameFlags::HasProps;
    } else {
      MOZ_ASSERT(rect, "this property should only store non-null values");
    }

    if (aHadDisplayPort) {
      // We only need to build a display list for any new areas added
      nsRegion newRegion(aNewDisplayPort);
      newRegion.SubOut(aOldDisplayPort);
      rect->UnionRect(*rect, newRegion.GetBounds());
    } else {
      rect->UnionRect(*rect, aNewDisplayPort);
    }
  }
}

bool DisplayPortUtils::SetDisplayPortMargins(nsIContent* aContent,
                                             PresShell* aPresShell,
                                             const DisplayPortMargins& aMargins,
                                             uint32_t aPriority,
                                             RepaintMode aRepaintMode) {
  MOZ_ASSERT(aContent);
  MOZ_ASSERT(aContent->GetComposedDoc() == aPresShell->GetDocument());

  DisplayPortMarginsPropertyData* currentData =
      static_cast<DisplayPortMarginsPropertyData*>(
          aContent->GetProperty(nsGkAtoms::DisplayPortMargins));
  if (currentData && currentData->mPriority > aPriority) {
    return false;
  }

  if (currentData && currentData->mMargins.mVisualOffset != CSSPoint() &&
      aMargins.mVisualOffset == CSSPoint()) {
    // If we hit this, then it's possible that we're setting a displayport
    // that is wrong because the old one had a layout/visual adjustment and
    // the new one does not.
    MOZ_LOG(sDisplayportLog, LogLevel::Warning,
            ("Dropping visual offset %s",
             ToString(currentData->mMargins.mVisualOffset).c_str()));
  }

  nsIFrame* scrollFrame = nsLayoutUtils::GetScrollFrameFromContent(aContent);

  nsRect oldDisplayPort;
  bool hadDisplayPort = false;
  bool wasPainted = GetWasDisplayPortPainted(aContent);
  if (scrollFrame) {
    // We only use the two return values from this function to call
    // InvalidateForDisplayPortChange. InvalidateForDisplayPortChange does
    // nothing if aContent does not have a frame. So getting the displayport is
    // useless if the content has no frame, so we avoid calling this to avoid
    // triggering a warning about not having a frame.
    hadDisplayPort = GetHighResolutionDisplayPort(aContent, &oldDisplayPort);
  }

  aContent->SetProperty(
      nsGkAtoms::DisplayPortMargins,
      new DisplayPortMarginsPropertyData(aMargins, aPriority, wasPainted),
      nsINode::DeleteProperty<DisplayPortMarginsPropertyData>);

  nsIScrollableFrame* scrollableFrame =
      scrollFrame ? scrollFrame->GetScrollTargetFrame() : nullptr;
  if (!scrollableFrame) {
    return true;
  }

  nsRect newDisplayPort;
  DebugOnly<bool> hasDisplayPort =
      GetHighResolutionDisplayPort(aContent, &newDisplayPort);
  MOZ_ASSERT(hasDisplayPort);

  if (MOZ_LOG_TEST(sDisplayportLog, LogLevel::Debug)) {
    mozilla::layers::ScrollableLayerGuid::ViewID viewID =
        mozilla::layers::ScrollableLayerGuid::NULL_SCROLL_ID;
    nsLayoutUtils::FindIDFor(aContent, &viewID);
    if (!hadDisplayPort) {
      MOZ_LOG(sDisplayportLog, LogLevel::Debug,
              ("SetDisplayPortMargins %s on scrollId=%" PRIu64 ", newDp=%s\n",
               ToString(aMargins).c_str(), viewID,
               ToString(newDisplayPort).c_str()));
    } else {
      // Use verbose level logging for when an existing displayport got its
      // margins updated.
      MOZ_LOG(sDisplayportLog, LogLevel::Verbose,
              ("SetDisplayPortMargins %s on scrollId=%" PRIu64 ", newDp=%s\n",
               ToString(aMargins).c_str(), viewID,
               ToString(newDisplayPort).c_str()));
    }
  }

  InvalidateForDisplayPortChange(aContent, hadDisplayPort, oldDisplayPort,
                                 newDisplayPort, aRepaintMode);

  scrollableFrame->TriggerDisplayPortExpiration();

  // Display port margins changing means that the set of visible frames may
  // have drastically changed. Check if we should schedule an update.
  hadDisplayPort =
      scrollableFrame->GetDisplayPortAtLastApproximateFrameVisibilityUpdate(
          &oldDisplayPort);

  bool needVisibilityUpdate = !hadDisplayPort;
  // Check if the total size has changed by a large factor.
  if (!needVisibilityUpdate) {
    if ((newDisplayPort.width > 2 * oldDisplayPort.width) ||
        (oldDisplayPort.width > 2 * newDisplayPort.width) ||
        (newDisplayPort.height > 2 * oldDisplayPort.height) ||
        (oldDisplayPort.height > 2 * newDisplayPort.height)) {
      needVisibilityUpdate = true;
    }
  }
  // Check if it's moved by a significant amount.
  if (!needVisibilityUpdate) {
    if (nsRect* baseData = static_cast<nsRect*>(
            aContent->GetProperty(nsGkAtoms::DisplayPortBase))) {
      nsRect base = *baseData;
      if ((std::abs(newDisplayPort.X() - oldDisplayPort.X()) > base.width) ||
          (std::abs(newDisplayPort.XMost() - oldDisplayPort.XMost()) >
           base.width) ||
          (std::abs(newDisplayPort.Y() - oldDisplayPort.Y()) > base.height) ||
          (std::abs(newDisplayPort.YMost() - oldDisplayPort.YMost()) >
           base.height)) {
        needVisibilityUpdate = true;
      }
    }
  }
  if (needVisibilityUpdate) {
    aPresShell->ScheduleApproximateFrameVisibilityUpdateNow();
  }

  return true;
}

void DisplayPortUtils::SetDisplayPortBase(nsIContent* aContent,
                                          const nsRect& aBase) {
  if (MOZ_LOG_TEST(sDisplayportLog, LogLevel::Verbose)) {
    ViewID viewId = nsLayoutUtils::FindOrCreateIDFor(aContent);
    MOZ_LOG(sDisplayportLog, LogLevel::Verbose,
            ("Setting base rect %s for scrollId=%" PRIu64 "\n",
             ToString(aBase).c_str(), viewId));
  }
  aContent->SetProperty(nsGkAtoms::DisplayPortBase, new nsRect(aBase),
                        nsINode::DeleteProperty<nsRect>);
}

void DisplayPortUtils::SetDisplayPortBaseIfNotSet(nsIContent* aContent,
                                                  const nsRect& aBase) {
  if (!aContent->GetProperty(nsGkAtoms::DisplayPortBase)) {
    SetDisplayPortBase(aContent, aBase);
  }
}

bool DisplayPortUtils::GetCriticalDisplayPort(
    nsIContent* aContent, nsRect* aResult, const DisplayPortOptions& aOptions) {
  if (StaticPrefs::layers_low_precision_buffer()) {
    return GetDisplayPortImpl(aContent, aResult, 1.0f, aOptions);
  }
  return false;
}

bool DisplayPortUtils::HasCriticalDisplayPort(nsIContent* aContent) {
  return GetCriticalDisplayPort(aContent, nullptr);
}

bool DisplayPortUtils::GetHighResolutionDisplayPort(
    nsIContent* aContent, nsRect* aResult, const DisplayPortOptions& aOptions) {
  if (StaticPrefs::layers_low_precision_buffer()) {
    return GetCriticalDisplayPort(aContent, aResult, aOptions);
  }
  return GetDisplayPort(aContent, aResult, aOptions);
}

void DisplayPortUtils::RemoveDisplayPort(nsIContent* aContent) {
  aContent->RemoveProperty(nsGkAtoms::DisplayPort);
  aContent->RemoveProperty(nsGkAtoms::DisplayPortMargins);
}

bool DisplayPortUtils::ViewportHasDisplayPort(nsPresContext* aPresContext) {
  nsIFrame* rootScrollFrame = aPresContext->PresShell()->GetRootScrollFrame();
  return rootScrollFrame && HasDisplayPort(rootScrollFrame->GetContent());
}

bool DisplayPortUtils::IsFixedPosFrameInDisplayPort(const nsIFrame* aFrame) {
  // Fixed-pos frames are parented by the viewport frame or the page content
  // frame. We'll assume that printing/print preview don't have displayports for
  // their pages!
  nsIFrame* parent = aFrame->GetParent();
  if (!parent || parent->GetParent() ||
      aFrame->StyleDisplay()->mPosition != StylePositionProperty::Fixed) {
    return false;
  }
  return ViewportHasDisplayPort(aFrame->PresContext());
}

// We want to this return true for the scroll frame, but not the
// scrolled frame (which has the same content).
bool DisplayPortUtils::FrameHasDisplayPort(nsIFrame* aFrame,
                                           const nsIFrame* aScrolledFrame) {
  if (!aFrame->GetContent() || !HasDisplayPort(aFrame->GetContent())) {
    return false;
  }
  nsIScrollableFrame* sf = do_QueryFrame(aFrame);
  if (sf) {
    if (aScrolledFrame && aScrolledFrame != sf->GetScrolledFrame()) {
      return false;
    }
    return true;
  }
  return false;
}

bool DisplayPortUtils::CalculateAndSetDisplayPortMargins(
    nsIScrollableFrame* aScrollFrame, RepaintMode aRepaintMode) {
  nsIFrame* frame = do_QueryFrame(aScrollFrame);
  MOZ_ASSERT(frame);
  nsIContent* content = frame->GetContent();
  MOZ_ASSERT(content);

  FrameMetrics metrics =
      nsLayoutUtils::CalculateBasicFrameMetrics(aScrollFrame);
  ScreenMargin displayportMargins = layers::apz::CalculatePendingDisplayPort(
      metrics, ParentLayerPoint(0.0f, 0.0f));
  PresShell* presShell = frame->PresContext()->GetPresShell();

  DisplayPortMargins margins = DisplayPortMargins::ForScrollFrame(
      aScrollFrame, displayportMargins,
      Some(metrics.DisplayportPixelsPerCSSPixel()));

  return SetDisplayPortMargins(content, presShell, margins, 0, aRepaintMode);
}

bool DisplayPortUtils::MaybeCreateDisplayPort(nsDisplayListBuilder* aBuilder,
                                              nsIFrame* aScrollFrame,
                                              RepaintMode aRepaintMode) {
  nsIContent* content = aScrollFrame->GetContent();
  nsIScrollableFrame* scrollableFrame = do_QueryFrame(aScrollFrame);
  if (!content || !scrollableFrame) {
    return false;
  }

  bool haveDisplayPort = HasDisplayPort(content);

  // We perform an optimization where we ensure that at least one
  // async-scrollable frame (i.e. one that WantsAsyncScroll()) has a
  // displayport. If that's not the case yet, and we are async-scrollable, we
  // will get a displayport.
  if (aBuilder->IsPaintingToWindow() &&
      nsLayoutUtils::AsyncPanZoomEnabled(aScrollFrame) &&
      !aBuilder->HaveScrollableDisplayPort() &&
      scrollableFrame->WantAsyncScroll()) {
    // If we don't already have a displayport, calculate and set one.
    if (!haveDisplayPort) {
      // We only use the viewId for logging purposes, but create it
      // unconditionally to minimize impact of enabling logging. If we don't
      // assign a viewId here it will get assigned later anyway so functionally
      // there should be no difference.
      ViewID viewId = nsLayoutUtils::FindOrCreateIDFor(content);
      MOZ_LOG(
          sDisplayportLog, LogLevel::Debug,
          ("Setting DP on first-encountered scrollId=%" PRIu64 "\n", viewId));

      CalculateAndSetDisplayPortMargins(scrollableFrame, aRepaintMode);
#ifdef DEBUG
      haveDisplayPort = HasDisplayPort(content);
      MOZ_ASSERT(haveDisplayPort,
                 "should have a displayport after having just set it");
#endif
    }

    // Record that the we now have a scrollable display port.
    aBuilder->SetHaveScrollableDisplayPort();
    return true;
  }
  return false;
}
void DisplayPortUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(
    nsIFrame* aFrame) {
  nsIFrame* frame = aFrame;
  while (frame) {
    frame = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(frame);
    if (!frame) {
      break;
    }
    nsIScrollableFrame* scrollAncestor =
        nsLayoutUtils::GetAsyncScrollableAncestorFrame(frame);
    if (!scrollAncestor) {
      break;
    }
    frame = do_QueryFrame(scrollAncestor);
    MOZ_ASSERT(frame);
    MOZ_ASSERT(scrollAncestor->WantAsyncScroll() ||
               frame->PresShell()->GetRootScrollFrame() == frame);
    if (nsLayoutUtils::AsyncPanZoomEnabled(frame) &&
        !HasDisplayPort(frame->GetContent())) {
      SetDisplayPortMargins(frame->GetContent(), frame->PresShell(),
                            DisplayPortMargins::Empty(frame->GetContent()), 0,
                            RepaintMode::Repaint);
    }
  }
}

bool DisplayPortUtils::MaybeCreateDisplayPortInFirstScrollFrameEncountered(
    nsIFrame* aFrame, nsDisplayListBuilder* aBuilder) {
  nsIScrollableFrame* sf = do_QueryFrame(aFrame);
  if (sf) {
    if (MaybeCreateDisplayPort(aBuilder, aFrame, RepaintMode::Repaint)) {
      return true;
    }
  }
  if (aFrame->IsPlaceholderFrame()) {
    nsPlaceholderFrame* placeholder = static_cast<nsPlaceholderFrame*>(aFrame);
    if (MaybeCreateDisplayPortInFirstScrollFrameEncountered(
            placeholder->GetOutOfFlowFrame(), aBuilder)) {
      return true;
    }
  }
  if (aFrame->IsSubDocumentFrame()) {
    PresShell* presShell = static_cast<nsSubDocumentFrame*>(aFrame)
                               ->GetSubdocumentPresShellForPainting(0);
    nsIFrame* root = presShell ? presShell->GetRootFrame() : nullptr;
    if (root) {
      if (MaybeCreateDisplayPortInFirstScrollFrameEncountered(root, aBuilder)) {
        return true;
      }
    }
  }
  if (aFrame->IsDeckFrame()) {
    // only descend the visible card of a decks
    nsIFrame* child = static_cast<nsDeckFrame*>(aFrame)->GetSelectedBox();
    if (child) {
      return MaybeCreateDisplayPortInFirstScrollFrameEncountered(child,
                                                                 aBuilder);
    }
  }

  for (nsIFrame* child : aFrame->PrincipalChildList()) {
    if (MaybeCreateDisplayPortInFirstScrollFrameEncountered(child, aBuilder)) {
      return true;
    }
  }

  return false;
}

void DisplayPortUtils::ExpireDisplayPortOnAsyncScrollableAncestor(
    nsIFrame* aFrame) {
  nsIFrame* frame = aFrame;
  while (frame) {
    frame = nsLayoutUtils::GetCrossDocParentFrame(frame);
    if (!frame) {
      break;
    }
    nsIScrollableFrame* scrollAncestor =
        nsLayoutUtils::GetAsyncScrollableAncestorFrame(frame);
    if (!scrollAncestor) {
      break;
    }
    frame = do_QueryFrame(scrollAncestor);
    MOZ_ASSERT(frame);
    if (!frame) {
      break;
    }
    MOZ_ASSERT(scrollAncestor->WantAsyncScroll() ||
               frame->PresShell()->GetRootScrollFrame() == frame);
    if (HasDisplayPort(frame->GetContent())) {
      scrollAncestor->TriggerDisplayPortExpiration();
      // Stop after the first trigger. If it failed, there's no point in
      // continuing because all the rest of the frames we encounter are going
      // to be ancestors of |scrollAncestor| which will keep its displayport.
      // If the trigger succeeded, we stop because when the trigger executes
      // it will call this function again to trigger the next ancestor up the
      // chain.
      break;
    }
  }
}

static PresShell* GetPresShell(const nsIContent* aContent) {
  if (dom::Document* doc = aContent->GetComposedDoc()) {
    return doc->GetPresShell();
  }
  return nullptr;
}

static void UpdateDisplayPortMarginsForPendingMetrics(
    const RepaintRequest& aMetrics) {
  nsIContent* content = nsLayoutUtils::FindContentFor(aMetrics.GetScrollId());
  if (!content) {
    return;
  }

  RefPtr<PresShell> presShell = GetPresShell(content);
  if (!presShell) {
    return;
  }

  if (nsLayoutUtils::AllowZoomingForDocument(presShell->GetDocument()) &&
      aMetrics.IsRootContent()) {
    // See APZCCallbackHelper::UpdateRootFrame for details.
    float presShellResolution = presShell->GetResolution();
    if (presShellResolution != aMetrics.GetPresShellResolution()) {
      return;
    }
  }

  nsIScrollableFrame* frame =
      nsLayoutUtils::FindScrollableFrameFor(aMetrics.GetScrollId());

  if (!frame) {
    return;
  }

  if (APZCCallbackHelper::IsScrollInProgress(frame)) {
    // If these conditions are true, then the UpdateFrame
    // message may be ignored by the main-thread, so we
    // shouldn't update the displayport based on it.
    return;
  }

  DisplayPortMarginsPropertyData* currentData =
      static_cast<DisplayPortMarginsPropertyData*>(
          content->GetProperty(nsGkAtoms::DisplayPortMargins));
  if (!currentData) {
    return;
  }

  CSSPoint frameScrollOffset =
      CSSPoint::FromAppUnits(frame->GetScrollPosition());

  DisplayPortUtils::SetDisplayPortMargins(
      content, presShell,
      DisplayPortMargins::FromAPZ(
          aMetrics.GetDisplayPortMargins(), aMetrics.GetVisualScrollOffset(),
          frameScrollOffset, aMetrics.DisplayportPixelsPerCSSPixel()),
      0);
}

/* static */
void DisplayPortUtils::UpdateDisplayPortMarginsFromPendingMessages() {
  if (XRE_IsContentProcess() && layers::CompositorBridgeChild::Get() &&
      layers::CompositorBridgeChild::Get()->GetIPCChannel()) {
    layers::CompositorBridgeChild::Get()->GetIPCChannel()->PeekMessages(
        [](const IPC::Message& aMsg) -> bool {
          if (aMsg.type() == layers::PAPZ::Msg_RequestContentRepaint__ID) {
            PickleIterator iter(aMsg);
            RepaintRequest request;
            if (!IPC::ReadParam(&aMsg, &iter, &request)) {
              MOZ_ASSERT(false);
              return true;
            }

            UpdateDisplayPortMarginsForPendingMetrics(request);
          }
          return true;
        });
  }
}

}  // namespace mozilla