/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <math.h>

#include "mozilla/Alignment.h"

#include "cairo.h"

#include "gfxContext.h"

#include "gfxMatrix.h"
#include "gfxUtils.h"
#include "gfxASurface.h"
#include "gfxPattern.h"
#include "gfxPlatform.h"
#include "gfxPrefs.h"
#include "GeckoProfiler.h"
#include "gfx2DGlue.h"
#include "mozilla/gfx/PathHelpers.h"
#include "mozilla/gfx/DrawTargetTiled.h"
#include <algorithm>

#if XP_WIN
#include "gfxWindowsPlatform.h"
#include "mozilla/gfx/DeviceManagerDx.h"
#endif

using namespace mozilla;
using namespace mozilla::gfx;

UserDataKey gfxContext::sDontUseAsSourceKey;


PatternFromState::operator mozilla::gfx::Pattern&()
{
  gfxContext::AzureState &state = mContext->CurrentState();

  if (state.pattern) {
    return *state.pattern->GetPattern(mContext->mDT, state.patternTransformChanged ? &state.patternTransform : nullptr);
  }

  if (state.sourceSurface) {
    Matrix transform = state.surfTransform;

    if (state.patternTransformChanged) {
      Matrix mat = mContext->GetDTTransform();
      if (!mat.Invert()) {
        mPattern = new (mColorPattern.addr())
        ColorPattern(Color()); // transparent black to paint nothing
        return *mPattern;
      }
      transform = transform * state.patternTransform * mat;
    }

    mPattern = new (mSurfacePattern.addr())
    SurfacePattern(state.sourceSurface, ExtendMode::CLAMP, transform);
    return *mPattern;
  }

  mPattern = new (mColorPattern.addr())
  ColorPattern(state.color);
  return *mPattern;
}


gfxContext::gfxContext(DrawTarget *aTarget, const Point& aDeviceOffset)
  : mPathIsRect(false)
  , mTransformChanged(false)
  , mDT(aTarget)
{
  if (!aTarget) {
    gfxCriticalError() << "Don't create a gfxContext without a DrawTarget";
  }

  MOZ_COUNT_CTOR(gfxContext);

  mStateStack.SetLength(1);
  CurrentState().drawTarget = mDT;
  CurrentState().deviceOffset = aDeviceOffset;
  mDT->SetTransform(GetDTTransform());
}

/* static */ already_AddRefed<gfxContext>
gfxContext::CreateOrNull(DrawTarget* aTarget,
                         const mozilla::gfx::Point& aDeviceOffset)
{
  if (!aTarget || !aTarget->IsValid()) {
    gfxCriticalNote << "Invalid target in gfxContext::CreateOrNull " << hexa(aTarget);
    return nullptr;
  }

  RefPtr<gfxContext> result = new gfxContext(aTarget, aDeviceOffset);
  return result.forget();
}

/* static */ already_AddRefed<gfxContext>
gfxContext::CreatePreservingTransformOrNull(DrawTarget* aTarget)
{
  if (!aTarget || !aTarget->IsValid()) {
    gfxCriticalNote << "Invalid target in gfxContext::CreatePreservingTransformOrNull " << hexa(aTarget);
    return nullptr;
  }

  Matrix transform = aTarget->GetTransform();
  RefPtr<gfxContext> result = new gfxContext(aTarget);
  result->SetMatrix(ThebesMatrix(transform));
  return result.forget();
}

gfxContext::~gfxContext()
{
  for (int i = mStateStack.Length() - 1; i >= 0; i--) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      mStateStack[i].drawTarget->PopClip();
    }
  }
  MOZ_COUNT_DTOR(gfxContext);
}

void
gfxContext::Save()
{
  CurrentState().transform = mTransform;
  mStateStack.AppendElement(AzureState(CurrentState()));
  CurrentState().pushedClips.Clear();
}

void
gfxContext::Restore()
{
  for (unsigned int c = 0; c < CurrentState().pushedClips.Length(); c++) {
    mDT->PopClip();
  }

  mStateStack.RemoveElementAt(mStateStack.Length() - 1);

  mDT = CurrentState().drawTarget;

  ChangeTransform(CurrentState().transform, false);
}

// drawing
void
gfxContext::NewPath()
{
  mPath = nullptr;
  mPathBuilder = nullptr;
  mPathIsRect = false;
  mTransformChanged = false;
}

void
gfxContext::ClosePath()
{
  EnsurePathBuilder();
  mPathBuilder->Close();
}

already_AddRefed<Path> gfxContext::GetPath()
{
  EnsurePath();
  RefPtr<Path> path(mPath);
  return path.forget();
}

void gfxContext::SetPath(Path* path)
{
  MOZ_ASSERT(path->GetBackendType() == mDT->GetBackendType() ||
             path->GetBackendType() == BackendType::RECORDING ||
             (mDT->GetBackendType() == BackendType::DIRECT2D1_1 && path->GetBackendType() == BackendType::DIRECT2D));
  mPath = path;
  mPathBuilder = nullptr;
  mPathIsRect = false;
  mTransformChanged = false;
}

gfxPoint
gfxContext::CurrentPoint()
{
  EnsurePathBuilder();
  return ThebesPoint(mPathBuilder->CurrentPoint());
}

void
gfxContext::Fill()
{
  Fill(PatternFromState(this));
}

void
gfxContext::Fill(const Pattern& aPattern)
{
  PROFILER_LABEL("gfxContext", "Fill",
    js::ProfileEntry::Category::GRAPHICS);
  FillAzure(aPattern, 1.0f);
}

void
gfxContext::MoveTo(const gfxPoint& pt)
{
  EnsurePathBuilder();
  mPathBuilder->MoveTo(ToPoint(pt));
}

void
gfxContext::LineTo(const gfxPoint& pt)
{
  EnsurePathBuilder();
  mPathBuilder->LineTo(ToPoint(pt));
}

void
gfxContext::Line(const gfxPoint& start, const gfxPoint& end)
{
  EnsurePathBuilder();
  mPathBuilder->MoveTo(ToPoint(start));
  mPathBuilder->LineTo(ToPoint(end));
}

// XXX snapToPixels is only valid when snapping for filled
// rectangles and for even-width stroked rectangles.
// For odd-width stroked rectangles, we need to offset x/y by
// 0.5...
void
gfxContext::Rectangle(const gfxRect& rect, bool snapToPixels)
{
  Rect rec = ToRect(rect);

  if (snapToPixels) {
    gfxRect newRect(rect);
    if (UserToDevicePixelSnapped(newRect, true)) {
      gfxMatrix mat = ThebesMatrix(mTransform);
      if (mat.Invert()) {
        // We need the user space rect.
        rec = ToRect(mat.TransformBounds(newRect));
      } else {
        rec = Rect();
      }
    }
  }

  if (!mPathBuilder && !mPathIsRect) {
    mPathIsRect = true;
    mRect = rec;
    return;
  }

  EnsurePathBuilder();

  mPathBuilder->MoveTo(rec.TopLeft());
  mPathBuilder->LineTo(rec.TopRight());
  mPathBuilder->LineTo(rec.BottomRight());
  mPathBuilder->LineTo(rec.BottomLeft());
  mPathBuilder->Close();
}

// transform stuff
void
gfxContext::Multiply(const gfxMatrix& matrix)
{
  ChangeTransform(ToMatrix(matrix) * mTransform);
}

void
gfxContext::SetMatrix(const gfxMatrix& matrix)
{
  ChangeTransform(ToMatrix(matrix));
}

gfxMatrix
gfxContext::CurrentMatrix() const
{
  return ThebesMatrix(mTransform);
}

gfxPoint
gfxContext::DeviceToUser(const gfxPoint& point) const
{
  return ThebesPoint(mTransform.Inverse().TransformPoint(ToPoint(point)));
}

Size
gfxContext::DeviceToUser(const Size& size) const
{
  return mTransform.Inverse().TransformSize(size);
}

gfxRect
gfxContext::DeviceToUser(const gfxRect& rect) const
{
  return ThebesRect(mTransform.Inverse().TransformBounds(ToRect(rect)));
}

gfxPoint
gfxContext::UserToDevice(const gfxPoint& point) const
{
  return ThebesPoint(mTransform.TransformPoint(ToPoint(point)));
}

Size
gfxContext::UserToDevice(const Size& size) const
{
  const Matrix &matrix = mTransform;

  Size newSize;
  newSize.width = size.width * matrix._11 + size.height * matrix._12;
  newSize.height = size.width * matrix._21 + size.height * matrix._22;
  return newSize;
}

gfxRect
gfxContext::UserToDevice(const gfxRect& rect) const
{
  const Matrix &matrix = mTransform;
  return ThebesRect(matrix.TransformBounds(ToRect(rect)));
}

bool
gfxContext::UserToDevicePixelSnapped(gfxRect& rect, bool ignoreScale) const
{
  if (mDT->GetUserData(&sDisablePixelSnapping))
      return false;

  // if we're not at 1.0 scale, don't snap, unless we're
  // ignoring the scale.  If we're not -just- a scale,
  // never snap.
  const gfxFloat epsilon = 0.0000001;
#define WITHIN_E(a,b) (fabs((a)-(b)) < epsilon)
  Matrix mat = mTransform;
  if (!ignoreScale &&
      (!WITHIN_E(mat._11,1.0) || !WITHIN_E(mat._22,1.0) ||
        !WITHIN_E(mat._12,0.0) || !WITHIN_E(mat._21,0.0)))
      return false;
#undef WITHIN_E

  gfxPoint p1 = UserToDevice(rect.TopLeft());
  gfxPoint p2 = UserToDevice(rect.TopRight());
  gfxPoint p3 = UserToDevice(rect.BottomRight());

  // Check that the rectangle is axis-aligned. For an axis-aligned rectangle,
  // two opposite corners define the entire rectangle. So check if
  // the axis-aligned rectangle with opposite corners p1 and p3
  // define an axis-aligned rectangle whose other corners are p2 and p4.
  // We actually only need to check one of p2 and p4, since an affine
  // transform maps parallelograms to parallelograms.
  if (p2 == gfxPoint(p1.x, p3.y) || p2 == gfxPoint(p3.x, p1.y)) {
      p1.Round();
      p3.Round();

      rect.MoveTo(gfxPoint(std::min(p1.x, p3.x), std::min(p1.y, p3.y)));
      rect.SizeTo(gfxSize(std::max(p1.x, p3.x) - rect.X(),
                          std::max(p1.y, p3.y) - rect.Y()));
      return true;
  }

  return false;
}

bool
gfxContext::UserToDevicePixelSnapped(gfxPoint& pt, bool ignoreScale) const
{
  if (mDT->GetUserData(&sDisablePixelSnapping))
      return false;

  // if we're not at 1.0 scale, don't snap, unless we're
  // ignoring the scale.  If we're not -just- a scale,
  // never snap.
  const gfxFloat epsilon = 0.0000001;
#define WITHIN_E(a,b) (fabs((a)-(b)) < epsilon)
  Matrix mat = mTransform;
  if (!ignoreScale &&
      (!WITHIN_E(mat._11,1.0) || !WITHIN_E(mat._22,1.0) ||
        !WITHIN_E(mat._12,0.0) || !WITHIN_E(mat._21,0.0)))
      return false;
#undef WITHIN_E

  pt = UserToDevice(pt);
  pt.Round();
  return true;
}

void
gfxContext::SetAntialiasMode(AntialiasMode mode)
{
  CurrentState().aaMode = mode;
}

AntialiasMode
gfxContext::CurrentAntialiasMode() const
{
  return CurrentState().aaMode;
}

void
gfxContext::SetDash(gfxFloat *dashes, int ndash, gfxFloat offset)
{
  AzureState &state = CurrentState();

  state.dashPattern.SetLength(ndash);
  for (int i = 0; i < ndash; i++) {
    state.dashPattern[i] = Float(dashes[i]);
  }
  state.strokeOptions.mDashLength = ndash;
  state.strokeOptions.mDashOffset = Float(offset);
  state.strokeOptions.mDashPattern = ndash ? state.dashPattern.Elements()
                                           : nullptr;
}

bool
gfxContext::CurrentDash(FallibleTArray<gfxFloat>& dashes, gfxFloat* offset) const
{
  const AzureState &state = CurrentState();
  int count = state.strokeOptions.mDashLength;

  if (count <= 0 || !dashes.SetLength(count, fallible)) {
    return false;
  }

  for (int i = 0; i < count; i++) {
    dashes[i] = state.dashPattern[i];
  }

  *offset = state.strokeOptions.mDashOffset;

  return true;
}

gfxFloat
gfxContext::CurrentDashOffset() const
{
  return CurrentState().strokeOptions.mDashOffset;
}

void
gfxContext::SetLineWidth(gfxFloat width)
{
  CurrentState().strokeOptions.mLineWidth = Float(width);
}

gfxFloat
gfxContext::CurrentLineWidth() const
{
  return CurrentState().strokeOptions.mLineWidth;
}

void
gfxContext::SetOp(CompositionOp aOp)
{
  CurrentState().op = aOp;
}

CompositionOp
gfxContext::CurrentOp() const
{
  return CurrentState().op;
}

void
gfxContext::SetLineCap(CapStyle cap)
{
  CurrentState().strokeOptions.mLineCap = cap;
}

CapStyle
gfxContext::CurrentLineCap() const
{
  return CurrentState().strokeOptions.mLineCap;
}

void
gfxContext::SetLineJoin(JoinStyle join)
{
  CurrentState().strokeOptions.mLineJoin = join;
}

JoinStyle
gfxContext::CurrentLineJoin() const
{
  return CurrentState().strokeOptions.mLineJoin;
}

void
gfxContext::SetMiterLimit(gfxFloat limit)
{
  CurrentState().strokeOptions.mMiterLimit = Float(limit);
}

gfxFloat
gfxContext::CurrentMiterLimit() const
{
  return CurrentState().strokeOptions.mMiterLimit;
}

// clipping
void
gfxContext::Clip(const Rect& rect)
{
  AzureState::PushedClip clip = { nullptr, rect, mTransform };
  CurrentState().pushedClips.AppendElement(clip);
  mDT->PushClipRect(rect);
  NewPath();
}

void
gfxContext::Clip(const gfxRect& rect)
{
  Clip(ToRect(rect));
}

void
gfxContext::Clip(Path* aPath)
{
  mDT->PushClip(aPath);
  AzureState::PushedClip clip = { aPath, Rect(), mTransform };
  CurrentState().pushedClips.AppendElement(clip);
}

void
gfxContext::Clip()
{
  if (mPathIsRect) {
    MOZ_ASSERT(!mTransformChanged);

    AzureState::PushedClip clip = { nullptr, mRect, mTransform };
    CurrentState().pushedClips.AppendElement(clip);
    mDT->PushClipRect(mRect);
  } else {
    EnsurePath();
    mDT->PushClip(mPath);
    AzureState::PushedClip clip = { mPath, Rect(), mTransform };
    CurrentState().pushedClips.AppendElement(clip);
  }
}

void
gfxContext::PopClip()
{
  MOZ_ASSERT(CurrentState().pushedClips.Length() > 0);

  CurrentState().pushedClips.RemoveElementAt(CurrentState().pushedClips.Length() - 1);
  mDT->PopClip();
}

gfxRect
gfxContext::GetClipExtents()
{
  Rect rect = GetAzureDeviceSpaceClipBounds();

  if (rect.width == 0 || rect.height == 0) {
    return gfxRect(0, 0, 0, 0);
  }

  Matrix mat = mTransform;
  mat.Invert();
  rect = mat.TransformBounds(rect);

  return ThebesRect(rect);
}

bool
gfxContext::HasComplexClip() const
{
  for (int i = mStateStack.Length() - 1; i >= 0; i--) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      const AzureState::PushedClip &clip = mStateStack[i].pushedClips[c];
      if (clip.path || !clip.transform.IsRectilinear()) {
        return true;
      }
    }
  }
  return false;
}

bool
gfxContext::ExportClip(ClipExporter& aExporter)
{
  for (unsigned int i = 0; i < mStateStack.Length(); i++) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      AzureState::PushedClip &clip = mStateStack[i].pushedClips[c];
      gfx::Matrix transform = clip.transform;
      transform.PostTranslate(-GetDeviceOffset());

      aExporter.BeginClip(transform);
      if (clip.path) {
        clip.path->StreamToSink(&aExporter);
      } else {
        aExporter.MoveTo(clip.rect.TopLeft());
        aExporter.LineTo(clip.rect.TopRight());
        aExporter.LineTo(clip.rect.BottomRight());
        aExporter.LineTo(clip.rect.BottomLeft());
        aExporter.Close();
      }
      aExporter.EndClip();
    }
  }

  return true;
}

bool
gfxContext::ClipContainsRect(const gfxRect& aRect)
{
  // Since we always return false when the clip list contains a
  // non-rectangular clip or a non-rectilinear transform, our 'total' clip
  // is always a rectangle if we hit the end of this function.
  Rect clipBounds(0, 0, Float(mDT->GetSize().width), Float(mDT->GetSize().height));

  for (unsigned int i = 0; i < mStateStack.Length(); i++) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      AzureState::PushedClip &clip = mStateStack[i].pushedClips[c];
      if (clip.path || !clip.transform.IsRectilinear()) {
        // Cairo behavior is we return false if the clip contains a non-
        // rectangle.
        return false;
      } else {
        Rect clipRect = mTransform.TransformBounds(clip.rect);

        clipBounds.IntersectRect(clipBounds, clipRect);
      }
    }
  }

  return clipBounds.Contains(ToRect(aRect));
}

// rendering sources

void
gfxContext::SetColor(const Color& aColor)
{
  CurrentState().pattern = nullptr;
  CurrentState().sourceSurfCairo = nullptr;
  CurrentState().sourceSurface = nullptr;
  CurrentState().color = ToDeviceColor(aColor);
}

void
gfxContext::SetDeviceColor(const Color& aColor)
{
  CurrentState().pattern = nullptr;
  CurrentState().sourceSurfCairo = nullptr;
  CurrentState().sourceSurface = nullptr;
  CurrentState().color = aColor;
}

bool
gfxContext::GetDeviceColor(Color& aColorOut)
{
  if (CurrentState().sourceSurface) {
    return false;
  }
  if (CurrentState().pattern) {
    return CurrentState().pattern->GetSolidColor(aColorOut);
  }

  aColorOut = CurrentState().color;
  return true;
}

void
gfxContext::SetSource(gfxASurface *surface, const gfxPoint& offset)
{
  CurrentState().surfTransform = Matrix(1.0f, 0, 0, 1.0f, Float(offset.x), Float(offset.y));
  CurrentState().pattern = nullptr;
  CurrentState().patternTransformChanged = false;
  // Keep the underlying cairo surface around while we keep the
  // sourceSurface.
  CurrentState().sourceSurfCairo = surface;
  CurrentState().sourceSurface =
  gfxPlatform::GetPlatform()->GetSourceSurfaceForSurface(mDT, surface);
  CurrentState().color = Color(0, 0, 0, 0);
}

void
gfxContext::SetPattern(gfxPattern *pattern)
{
  CurrentState().sourceSurfCairo = nullptr;
  CurrentState().sourceSurface = nullptr;
  CurrentState().patternTransformChanged = false;
  CurrentState().pattern = pattern;
}

already_AddRefed<gfxPattern>
gfxContext::GetPattern()
{
  RefPtr<gfxPattern> pat;

  AzureState &state = CurrentState();
  if (state.pattern) {
    pat = state.pattern;
  } else if (state.sourceSurface) {
    NS_ASSERTION(false, "Ugh, this isn't good.");
  } else {
    pat = new gfxPattern(state.color);
  }
  return pat.forget();
}

void
gfxContext::SetFontSmoothingBackgroundColor(const Color& aColor)
{
  CurrentState().fontSmoothingBackgroundColor = aColor;
}

Color
gfxContext::GetFontSmoothingBackgroundColor()
{
  return CurrentState().fontSmoothingBackgroundColor;
}

// masking
void
gfxContext::Mask(SourceSurface* aSurface, Float aAlpha, const Matrix& aTransform)
{
  Matrix old = mTransform;
  Matrix mat = aTransform * mTransform;

  ChangeTransform(mat);
  mDT->MaskSurface(PatternFromState(this), aSurface, Point(),
                   DrawOptions(aAlpha, CurrentState().op, CurrentState().aaMode));
  ChangeTransform(old);
}

void
gfxContext::Mask(SourceSurface *surface, float alpha, const Point& offset)
{
  // We clip here to bind to the mask surface bounds, see above.
  mDT->MaskSurface(PatternFromState(this),
            surface,
            offset,
            DrawOptions(alpha, CurrentState().op, CurrentState().aaMode));
}

void
gfxContext::Paint(gfxFloat alpha)
{
  PROFILER_LABEL("gfxContext", "Paint",
    js::ProfileEntry::Category::GRAPHICS);

  AzureState &state = CurrentState();

  if (state.sourceSurface && !state.sourceSurfCairo &&
      !state.patternTransformChanged)
  {
    // This is the case where a PopGroupToSource has been done and this
    // paint is executed without changing the transform or the source.
    Matrix oldMat = mDT->GetTransform();

    IntSize surfSize = state.sourceSurface->GetSize();

    mDT->SetTransform(Matrix::Translation(-state.deviceOffset.x,
                                          -state.deviceOffset.y));

    mDT->DrawSurface(state.sourceSurface,
                     Rect(state.sourceSurfaceDeviceOffset, Size(surfSize.width, surfSize.height)),
                     Rect(Point(), Size(surfSize.width, surfSize.height)),
                     DrawSurfaceOptions(), DrawOptions(alpha, GetOp()));
    mDT->SetTransform(oldMat);
    return;
  }

  Matrix mat = mDT->GetTransform();
  mat.Invert();
  Rect paintRect = mat.TransformBounds(Rect(Point(0, 0), Size(mDT->GetSize())));

  mDT->FillRect(paintRect, PatternFromState(this),
                DrawOptions(Float(alpha), GetOp()));
}

void
gfxContext::PushGroupForBlendBack(gfxContentType content, Float aOpacity, SourceSurface* aMask, const Matrix& aMaskTransform)
{
  if (gfxPrefs::UseNativePushLayer()) {
    Save();
    mDT->PushLayer(content == gfxContentType::COLOR, aOpacity, aMask, aMaskTransform);
  } else {
    DrawTarget* oldDT = mDT;

    PushNewDT(content);

    if (oldDT != mDT) {
      PushClipsToDT(mDT);
    }
    mDT->SetTransform(GetDTTransform());

    CurrentState().mBlendOpacity = aOpacity;
    CurrentState().mBlendMask = aMask;
#ifdef DEBUG
    CurrentState().mWasPushedForBlendBack = true;
#endif
    CurrentState().mBlendMaskTransform = aMaskTransform;
  }
}

static gfxRect
GetRoundOutDeviceClipExtents(gfxContext* aCtx)
{
  gfxContextMatrixAutoSaveRestore save(aCtx);
  aCtx->SetMatrix(gfxMatrix());
  gfxRect r = aCtx->GetClipExtents();
  r.RoundOut();
  return r;
}

void
gfxContext::PushGroupAndCopyBackground(gfxContentType content, Float aOpacity, SourceSurface* aMask, const Matrix& aMaskTransform)
{
  IntRect clipExtents;
  if (mDT->GetFormat() != SurfaceFormat::B8G8R8X8) {
    gfxRect clipRect = GetRoundOutDeviceClipExtents(this);
    clipExtents = IntRect::Truncate(clipRect.x, clipRect.y, clipRect.width, clipRect.height);
  }
  bool pushOpaqueWithCopiedBG = (mDT->GetFormat() == SurfaceFormat::B8G8R8X8 ||
                                 mDT->GetOpaqueRect().Contains(clipExtents)) &&
                                !mDT->GetUserData(&sDontUseAsSourceKey);

  if (gfxPrefs::UseNativePushLayer()) {
    Save();

    if (pushOpaqueWithCopiedBG) {
      mDT->PushLayer(true, aOpacity, aMask, aMaskTransform, IntRect(), true);
    } else {
      mDT->PushLayer(content == gfxContentType::COLOR, aOpacity, aMask, aMaskTransform, IntRect(), false);
    }
  } else {
    RefPtr<SourceSurface> source;
    // This snapshot can be nullptr if the DrawTarget is a cairo target that is currently
    // in an error state.
    if (pushOpaqueWithCopiedBG && (source = mDT->Snapshot())) {
      DrawTarget *oldDT = mDT;
      Point oldDeviceOffset = CurrentState().deviceOffset;

      PushNewDT(gfxContentType::COLOR);

      if (oldDT == mDT) {
        // Creating new DT failed.
        return;
      }

      CurrentState().mBlendOpacity = aOpacity;
      CurrentState().mBlendMask = aMask;
#ifdef DEBUG
      CurrentState().mWasPushedForBlendBack = true;
#endif
      CurrentState().mBlendMaskTransform = aMaskTransform;

      Point offset = CurrentState().deviceOffset - oldDeviceOffset;
      Rect surfRect(0, 0, Float(mDT->GetSize().width), Float(mDT->GetSize().height));
      Rect sourceRect = surfRect + offset;

      mDT->SetTransform(Matrix());

      // XXX: It's really sad that we have to do this (for performance).
      // Once DrawTarget gets a PushLayer API we can implement this within
      // DrawTargetTiled.
      if (source->GetType() == SurfaceType::TILED) {
        SnapshotTiled *sourceTiled = static_cast<SnapshotTiled*>(source.get());
        for (uint32_t i = 0; i < sourceTiled->mSnapshots.size(); i++) {
          Rect tileSourceRect = sourceRect.Intersect(Rect(sourceTiled->mOrigins[i].x,
                                                          sourceTiled->mOrigins[i].y,
                                                          sourceTiled->mSnapshots[i]->GetSize().width,
                                                          sourceTiled->mSnapshots[i]->GetSize().height));

          if (tileSourceRect.IsEmpty()) {
            continue;
          }
          Rect tileDestRect = tileSourceRect - offset;
          tileSourceRect -= sourceTiled->mOrigins[i];

          mDT->DrawSurface(sourceTiled->mSnapshots[i], tileDestRect, tileSourceRect);
        }
      } else {
        mDT->DrawSurface(source, surfRect, sourceRect);
      }
      mDT->SetOpaqueRect(oldDT->GetOpaqueRect());

      PushClipsToDT(mDT);
      mDT->SetTransform(GetDTTransform());
      return;
    }
    DrawTarget* oldDT = mDT;

    PushNewDT(content);

    if (oldDT != mDT) {
      PushClipsToDT(mDT);
    }

    mDT->SetTransform(GetDTTransform());
    CurrentState().mBlendOpacity = aOpacity;
    CurrentState().mBlendMask = aMask;
#ifdef DEBUG
    CurrentState().mWasPushedForBlendBack = true;
#endif
    CurrentState().mBlendMaskTransform = aMaskTransform;
  }
}

void
gfxContext::PopGroupAndBlend()
{
  if (gfxPrefs::UseNativePushLayer()) {
    mDT->PopLayer();
    Restore();
  } else {
    MOZ_ASSERT(CurrentState().mWasPushedForBlendBack);
    Float opacity = CurrentState().mBlendOpacity;
    RefPtr<SourceSurface> mask = CurrentState().mBlendMask;
    Matrix maskTransform = CurrentState().mBlendMaskTransform;

    RefPtr<SourceSurface> src = mDT->Snapshot();
    Point deviceOffset = CurrentState().deviceOffset;
    Restore();
    CurrentState().sourceSurfCairo = nullptr;
    CurrentState().sourceSurface = src;
    CurrentState().sourceSurfaceDeviceOffset = deviceOffset;
    CurrentState().pattern = nullptr;
    CurrentState().patternTransformChanged = false;

    Matrix mat = mTransform;
    mat.Invert();
    mat.PreTranslate(deviceOffset.x, deviceOffset.y); // device offset translation

    CurrentState().surfTransform = mat;

    CompositionOp oldOp = GetOp();
    SetOp(CompositionOp::OP_OVER);

    if (mask) {
      if (!maskTransform.HasNonTranslation()) {
        Mask(mask, opacity, Point(maskTransform._31, maskTransform._32));
      } else {
        Mask(mask, opacity, maskTransform);
      }
    } else {
      Paint(opacity);
    }

    SetOp(oldOp);
  }
}

#ifdef MOZ_DUMP_PAINTING
void
gfxContext::WriteAsPNG(const char* aFile)
{
  gfxUtils::WriteAsPNG(mDT, aFile);
}

void 
gfxContext::DumpAsDataURI()
{
  gfxUtils::DumpAsDataURI(mDT);
}

void 
gfxContext::CopyAsDataURI()
{
  gfxUtils::CopyAsDataURI(mDT);
}
#endif

void
gfxContext::EnsurePath()
{
  if (mPathBuilder) {
    mPath = mPathBuilder->Finish();
    mPathBuilder = nullptr;
  }

  if (mPath) {
    if (mTransformChanged) {
      Matrix mat = mTransform;
      mat.Invert();
      mat = mPathTransform * mat;
      mPathBuilder = mPath->TransformedCopyToBuilder(mat);
      mPath = mPathBuilder->Finish();
      mPathBuilder = nullptr;

      mTransformChanged = false;
    }
    return;
  }

  EnsurePathBuilder();
  mPath = mPathBuilder->Finish();
  mPathBuilder = nullptr;
}

void
gfxContext::EnsurePathBuilder()
{
  if (mPathBuilder && !mTransformChanged) {
    return;
  }

  if (mPath) {
    if (!mTransformChanged) {
      mPathBuilder = mPath->CopyToBuilder();
      mPath = nullptr;
    } else {
      Matrix invTransform = mTransform;
      invTransform.Invert();
      Matrix toNewUS = mPathTransform * invTransform;
      mPathBuilder = mPath->TransformedCopyToBuilder(toNewUS);
    }
    return;
  }

  DebugOnly<PathBuilder*> oldPath = mPathBuilder.get();

  if (!mPathBuilder) {
    mPathBuilder = mDT->CreatePathBuilder(FillRule::FILL_WINDING);

    if (mPathIsRect) {
      mPathBuilder->MoveTo(mRect.TopLeft());
      mPathBuilder->LineTo(mRect.TopRight());
      mPathBuilder->LineTo(mRect.BottomRight());
      mPathBuilder->LineTo(mRect.BottomLeft());
      mPathBuilder->Close();
    }
  }

  if (mTransformChanged) {
    // This could be an else if since this should never happen when
    // mPathBuilder is nullptr and mPath is nullptr. But this way we can
    // assert if all the state is as expected.
    MOZ_ASSERT(oldPath);
    MOZ_ASSERT(!mPathIsRect);

    Matrix invTransform = mTransform;
    invTransform.Invert();
    Matrix toNewUS = mPathTransform * invTransform;

    RefPtr<Path> path = mPathBuilder->Finish();
    if (!path) {
      gfxCriticalError() << "gfxContext::EnsurePathBuilder failed in PathBuilder::Finish";
    }
    mPathBuilder = path->TransformedCopyToBuilder(toNewUS);
  }

  mPathIsRect = false;
}

void
gfxContext::FillAzure(const Pattern& aPattern, Float aOpacity)
{
  AzureState &state = CurrentState();

  CompositionOp op = GetOp();

  if (mPathIsRect) {
    MOZ_ASSERT(!mTransformChanged);

    if (op == CompositionOp::OP_SOURCE) {
      // Emulate cairo operator source which is bound by mask!
      mDT->ClearRect(mRect);
      mDT->FillRect(mRect, aPattern, DrawOptions(aOpacity));
    } else {
      mDT->FillRect(mRect, aPattern, DrawOptions(aOpacity, op, state.aaMode));
    }
  } else {
    EnsurePath();
    mDT->Fill(mPath, aPattern, DrawOptions(aOpacity, op, state.aaMode));
  }
}

void
gfxContext::PushClipsToDT(DrawTarget *aDT)
{
  // Don't need to save the old transform, we'll be setting a new one soon!

  // Push all clips from the bottom of the stack to the clip before ours.
  for (unsigned int i = 0; i < mStateStack.Length() - 1; i++) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      aDT->SetTransform(mStateStack[i].pushedClips[c].transform * GetDeviceTransform());
      if (mStateStack[i].pushedClips[c].path) {
        aDT->PushClip(mStateStack[i].pushedClips[c].path);
      } else {
        aDT->PushClipRect(mStateStack[i].pushedClips[c].rect);
      }
    }
  }
}

CompositionOp
gfxContext::GetOp()
{
  if (CurrentState().op != CompositionOp::OP_SOURCE) {
    return CurrentState().op;
  }

  AzureState &state = CurrentState();
  if (state.pattern) {
    if (state.pattern->IsOpaque()) {
      return CompositionOp::OP_OVER;
    } else {
      return CompositionOp::OP_SOURCE;
    }
  } else if (state.sourceSurface) {
    if (state.sourceSurface->GetFormat() == SurfaceFormat::B8G8R8X8) {
      return CompositionOp::OP_OVER;
    } else {
      return CompositionOp::OP_SOURCE;
    }
  } else {
    if (state.color.a > 0.999) {
      return CompositionOp::OP_OVER;
    } else {
      return CompositionOp::OP_SOURCE;
    }
  }
}

/* SVG font code can change the transform after having set the pattern on the
 * context. When the pattern is set it is in user space, if the transform is
 * changed after doing so the pattern needs to be converted back into userspace.
 * We just store the old pattern transform here so that we only do the work
 * needed here if the pattern is actually used.
 * We need to avoid doing this when this ChangeTransform comes from a restore,
 * since the current pattern and the current transform are both part of the
 * state we know the new CurrentState()'s values are valid. But if we assume
 * a change they might become invalid since patternTransformChanged is part of
 * the state and might be false for the restored AzureState.
 */
void
gfxContext::ChangeTransform(const Matrix &aNewMatrix, bool aUpdatePatternTransform)
{
  AzureState &state = CurrentState();

  if (aUpdatePatternTransform && (state.pattern || state.sourceSurface)
      && !state.patternTransformChanged) {
    state.patternTransform = GetDTTransform();
    state.patternTransformChanged = true;
  }

  if (mPathIsRect) {
    Matrix invMatrix = aNewMatrix;
    
    invMatrix.Invert();

    Matrix toNewUS = mTransform * invMatrix;

    if (toNewUS.IsRectilinear()) {
      mRect = toNewUS.TransformBounds(mRect);
      mRect.NudgeToIntegers();
    } else {
      mPathBuilder = mDT->CreatePathBuilder(FillRule::FILL_WINDING);

      mPathBuilder->MoveTo(toNewUS.TransformPoint(mRect.TopLeft()));
      mPathBuilder->LineTo(toNewUS.TransformPoint(mRect.TopRight()));
      mPathBuilder->LineTo(toNewUS.TransformPoint(mRect.BottomRight()));
      mPathBuilder->LineTo(toNewUS.TransformPoint(mRect.BottomLeft()));
      mPathBuilder->Close();

      mPathIsRect = false;
    }

    // No need to consider the transform changed now!
    mTransformChanged = false;
  } else if ((mPath || mPathBuilder) && !mTransformChanged) {
    mTransformChanged = true;
    mPathTransform = mTransform;
  }

  mTransform = aNewMatrix;

  mDT->SetTransform(GetDTTransform());
}

Rect
gfxContext::GetAzureDeviceSpaceClipBounds()
{
  Rect rect(CurrentState().deviceOffset.x, CurrentState().deviceOffset.y,
            Float(mDT->GetSize().width), Float(mDT->GetSize().height));
  for (unsigned int i = 0; i < mStateStack.Length(); i++) {
    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
      AzureState::PushedClip &clip = mStateStack[i].pushedClips[c];
      if (clip.path) {
        Rect bounds = clip.path->GetBounds(clip.transform);
        rect.IntersectRect(rect, bounds);
      } else {
        rect.IntersectRect(rect, clip.transform.TransformBounds(clip.rect));
      }
    }
  }

  return rect;
}

Point
gfxContext::GetDeviceOffset() const
{
  return CurrentState().deviceOffset;
}

Matrix
gfxContext::GetDeviceTransform() const
{
  return Matrix::Translation(-CurrentState().deviceOffset.x,
                             -CurrentState().deviceOffset.y);
}

Matrix
gfxContext::GetDTTransform() const
{
  Matrix mat = mTransform;
  mat._31 -= CurrentState().deviceOffset.x;
  mat._32 -= CurrentState().deviceOffset.y;
  return mat;
}

void
gfxContext::PushNewDT(gfxContentType content)
{
  Rect clipBounds = GetAzureDeviceSpaceClipBounds();
  clipBounds.RoundOut();

  clipBounds.width = std::max(1.0f, clipBounds.width);
  clipBounds.height = std::max(1.0f, clipBounds.height);

  SurfaceFormat format = gfxPlatform::GetPlatform()->Optimal2DFormatForContent(content);

  RefPtr<DrawTarget> newDT =
    mDT->CreateSimilarDrawTarget(IntSize(int32_t(clipBounds.width), int32_t(clipBounds.height)),
                                 format);

  if (!newDT) {
    NS_WARNING("Failed to create DrawTarget of sufficient size.");
    newDT = mDT->CreateSimilarDrawTarget(IntSize(64, 64), format);

    if (!newDT) {
      if (!gfxPlatform::GetPlatform()->DidRenderingDeviceReset()
#ifdef XP_WIN
          && !(mDT->GetBackendType() == BackendType::DIRECT2D1_1 &&
               !DeviceManagerDx::Get()->GetContentDevice())
#endif
          ) {
        // If even this fails.. we're most likely just out of memory!
        NS_ABORT_OOM(BytesPerPixel(format) * 64 * 64);
      }
      newDT = CurrentState().drawTarget;
    }
  }

  Save();

  CurrentState().drawTarget = newDT;
  CurrentState().deviceOffset = clipBounds.TopLeft();

  mDT = newDT;
}