path: root/gfx/thebes/gfxContext.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 <math.h>

#include "mozilla/Alignment.h"

#include "cairo.h"

#include "gfxContext.h"

#include "gfxMatrix.h"
#include "gfxUtils.h"
#include "gfxPattern.h"
#include "gfxPlatform.h"

#include "gfx2DGlue.h"
#include "mozilla/gfx/PathHelpers.h"
#include "mozilla/ProfilerLabels.h"
#include <algorithm>
#include "TextDrawTarget.h"

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

using namespace mozilla;
using namespace mozilla::gfx;

#ifdef DEBUG
#  define CURRENTSTATE_CHANGED() mAzureState.mContentChanged = true;
#else
#  define CURRENTSTATE_CHANGED()
#endif

PatternFromState::operator Pattern&() {
  const gfxContext::AzureState& state = mContext->mAzureState;

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

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

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

  return MakeUnique<gfxContext>(aTarget, aDeviceOffset);
}

gfxContext::~gfxContext() {
  while (!mSavedStates.IsEmpty()) {
    Restore();
  }
  for (unsigned int c = 0; c < mAzureState.pushedClips.Length(); c++) {
    mDT->PopClip();
  }
}

mozilla::layout::TextDrawTarget* gfxContext::GetTextDrawer() const {
  if (mDT->GetBackendType() == BackendType::WEBRENDER_TEXT) {
    return static_cast<mozilla::layout::TextDrawTarget*>(&*mDT);
  }
  return nullptr;
}

void gfxContext::Save() {
  mSavedStates.AppendElement(mAzureState);
  mAzureState.pushedClips.Clear();
#ifdef DEBUG
  mAzureState.mContentChanged = false;
#endif
}

void gfxContext::Restore() {
#ifdef DEBUG
  // gfxContext::Restore is used to restore AzureState. We need to restore it
  // only if it was altered. The following APIs do change the content of
  // AzureState, a user should save the state before using them and restore it
  // after finishing painting:
  // 1. APIs to setup how to paint, such as SetColor()/SetAntialiasMode(). All
  //    gfxContext SetXXXX public functions belong to this category, except
  //    gfxContext::SetPath & gfxContext::SetMatrix.
  // 2. Clip functions, such as Clip() or PopClip(). You may call PopClip()
  //    directly instead of using gfxContext::Save if the clip region is the
  //    only thing that you altered in the target context.
  // 3. Function of setup transform matrix, such as Multiply() and
  //    SetMatrix(). Using gfxContextMatrixAutoSaveRestore is more recommended
  //    if transform data is the only thing that you are going to alter.
  //
  // You will hit the assertion message below if there is no above functions
  // been used between a pair of gfxContext::Save and gfxContext::Restore.
  // Considerate to remove that pair of Save/Restore if hitting that assertion.
  //
  // In the other hand, the following APIs do not alter the content of the
  // current AzureState, therefore, there is no need to save & restore
  // AzureState:
  // 1. constant member functions of gfxContext.
  // 2. Paint calls, such as Line()/Rectangle()/Fill(). Those APIs change the
  //    content of drawing buffer, which is not part of AzureState.
  // 3. Path building APIs, such as SetPath()/MoveTo()/LineTo()/NewPath().
  //    Surprisingly, path information is not stored in AzureState either.
  // Save current AzureState before using these type of APIs does nothing but
  // make performance worse.
  NS_ASSERTION(
      mAzureState.mContentChanged || mAzureState.pushedClips.Length() > 0,
      "The context of the current AzureState is not altered after "
      "Save() been called. you may consider to remove this pair of "
      "gfxContext::Save/Restore.");
#endif

  for (unsigned int c = 0; c < mAzureState.pushedClips.Length(); c++) {
    mDT->PopClip();
  }

  mAzureState = mSavedStates.PopLastElement();

  ChangeTransform(mAzureState.transform, false);
}

// drawing

void gfxContext::Fill(const Pattern& aPattern) {
  AUTO_PROFILER_LABEL("gfxContext::Fill", GRAPHICS);

  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(1.0f));
    } else {
      mDT->FillRect(mRect, aPattern, DrawOptions(1.0f, op, mAzureState.aaMode));
    }
  } else {
    EnsurePath();
    mDT->Fill(mPath, aPattern, DrawOptions(1.0f, op, mAzureState.aaMode));
  }
}

// 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, SnapOption::IgnoreScale)) {
      gfxMatrix mat = CurrentMatrixDouble();
      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();
}

void gfxContext::SnappedClip(const gfxRect& rect) {
  Rect rec = ToRect(rect);

  gfxRect newRect(rect);
  if (UserToDevicePixelSnapped(newRect, SnapOption::IgnoreScale)) {
    gfxMatrix mat = CurrentMatrixDouble();
    if (mat.Invert()) {
      // We need the user space rect.
      rec = ToRect(mat.TransformBounds(newRect));
    } else {
      rec = Rect();
    }
  }

  Clip(rec);
}

bool gfxContext::UserToDevicePixelSnapped(gfxRect& rect,
                                          SnapOptions aOptions) 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 = mAzureState.transform;
  if (!aOptions.contains(SnapOption::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))) {
    return false;
  }

  if (aOptions.contains(SnapOption::PrioritizeSize)) {
    // Snap the dimensions of the rect, to minimize distortion; only after that
    // will we snap its position. In particular, this guarantees that a square
    // remains square after snapping, which may not be the case if each edge is
    // independently snapped to device pixels.

    // Use the same rounding approach as gfx::BasePoint::Round.
    rect.SizeTo(std::floor(rect.width + 0.5), std::floor(rect.height + 0.5));

    // Find the top-left corner based on the original center and the snapped
    // size, then snap this new corner to the grid.
    gfxPoint center = (p1 + p3) / 2;
    gfxPoint topLeft = center - gfxPoint(rect.width / 2.0, rect.height / 2.0);
    topLeft.Round();
    rect.MoveTo(topLeft);
  } else {
    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;
}

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 = mAzureState.transform;
  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::SetDash(const Float* dashes, int ndash, Float offset,
                         Float devPxScale) {
  CURRENTSTATE_CHANGED()

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

bool gfxContext::CurrentDash(FallibleTArray<Float>& dashes,
                             Float* offset) const {
  if (mAzureState.strokeOptions.mDashLength == 0 ||
      !dashes.Assign(mAzureState.dashPattern, fallible)) {
    return false;
  }

  *offset = mAzureState.strokeOptions.mDashOffset;

  return true;
}

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

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

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

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

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

  if (rect.IsZeroArea()) {
    return gfxRect(0, 0, 0, 0);
  }

  if (aSpace == eUserSpace) {
    Matrix mat = mAzureState.transform;
    mat.Invert();
    rect = mat.TransformBounds(rect);
  }

  return ThebesRect(rect);
}

bool gfxContext::ExportClip(ClipExporter& aExporter) const {
  ForAllClips([&](const AzureState::PushedClip& aClip) -> void {
    gfx::Matrix transform = aClip.transform;
    transform.PostTranslate(-GetDeviceOffset());

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

  return true;
}

// rendering sources

bool gfxContext::GetDeviceColor(DeviceColor& aColorOut) const {
  if (mAzureState.pattern) {
    return mAzureState.pattern->GetSolidColor(aColorOut);
  }

  aColorOut = mAzureState.color;
  return true;
}

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

  if (mAzureState.pattern) {
    pat = mAzureState.pattern;
  } else {
    pat = new gfxPattern(mAzureState.color);
  }
  return pat.forget();
}

void gfxContext::Paint(Float alpha) const {
  AUTO_PROFILER_LABEL("gfxContext::Paint", GRAPHICS);

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

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

#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 = mAzureState.transform;
      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 = mAzureState.transform;
      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 = mAzureState.transform;
    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;
}

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

  if (mAzureState.pattern) {
    if (mAzureState.pattern->IsOpaque()) {
      return CompositionOp::OP_OVER;
    } else {
      return CompositionOp::OP_SOURCE;
    }
  } else {
    if (mAzureState.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 mAzureState'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) {
  if (aUpdatePatternTransform && (mAzureState.pattern) &&
      !mAzureState.patternTransformChanged) {
    mAzureState.patternTransform = GetDTTransform();
    mAzureState.patternTransformChanged = true;
  }

  if (mPathIsRect) {
    Matrix invMatrix = aNewMatrix;

    invMatrix.Invert();

    Matrix toNewUS = mAzureState.transform * 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 = mAzureState.transform;
  }

  mAzureState.transform = aNewMatrix;

  mDT->SetTransform(GetDTTransform());
}

Rect gfxContext::GetAzureDeviceSpaceClipBounds() const {
  Rect rect(mAzureState.deviceOffset.x + Float(mDT->GetRect().x),
            mAzureState.deviceOffset.y + Float(mDT->GetRect().y),
            Float(mDT->GetSize().width), Float(mDT->GetSize().height));
  ForAllClips([&](const AzureState::PushedClip& aClip) -> void {
    if (aClip.path) {
      rect.IntersectRect(rect, aClip.path->GetBounds(aClip.transform));
    } else {
      rect.IntersectRect(rect, aClip.transform.TransformBounds(aClip.rect));
    }
  });

  return rect;
}

template <typename F>
void gfxContext::ForAllClips(F&& aLambda) const {
  for (const auto& state : mSavedStates) {
    for (const auto& clip : state.pushedClips) {
      aLambda(clip);
    }
  }
  for (const auto& clip : mAzureState.pushedClips) {
    aLambda(clip);
  }
}