2010-09-09  Kenneth Russell  <kbr@google.com>

        Reviewed by NOBODY (OOPS!).

        Incorporate algorithm for processing paths into GPU-renderable triangle meshes

        https://bugs.webkit.org/show_bug.cgi?id=45521

        Adding an implementation of Loop and Blinn's GPU accelerated path

        rendering algorithm from GPU Gems 3. This implementation pays

        particular attention to the efficiency of the curve subdivision

        phase needed for correct rendering. It utilizes the OpenGL utility

        library tessellator for triangulation of the interior of the

        shape. The regions handled by Loop and Blinn's algorithm are

        handled by the local triangulator previously incorporated.

        No tests yet; pixel tests will eventually be used to verify this

        algorithm and prevent regressions.

        * platform/graphics/gpu/LoopBlinnPathProcessor.cpp: Added.

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::Segment):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::setup):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::kind):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::getPoint):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::next):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::prev):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::setNext):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::setPrev):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::contour):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::subdivide):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::boundingBox):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::numCrossingsForXRay):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::numberOfTriangles):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::getTriangle):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::numberOfInteriorVertices):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::getInteriorVertex):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::markedForSubdivision):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::setMarkedForSubdivision):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::toString):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::computeBoundingBox):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::Contour):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::add):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::subdivide):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::begin):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::end):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::isOrientedCounterClockwise):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::setIsOrientedCounterClockwise):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::boundingBox):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::fillSide):

        (WebCore::LoopBlinnPathProcessorImplementation::Contour::setFillSide):

        (WebCore::LoopBlinnPathProcessorImplementation::Segment::triangulate):

        (WebCore::LoopBlinnPathProcessor::LoopBlinnPathProcessor):

        (WebCore::LoopBlinnPathProcessor::~LoopBlinnPathProcessor):

        (WebCore::LoopBlinnPathProcessor::process):

        (WebCore::LoopBlinnPathProcessor::buildContours):

        (WebCore::LoopBlinnPathProcessor::allSegmentsOverlappingY):

        (WebCore::valueToString):

        (WebCore::LoopBlinnPathProcessor::determineSidesToFill):

        (WebCore::LoopBlinnPathProcessor::determineOrientation):

        (WebCore::SweepData::SweepEvent::SweepEvent):

        (WebCore::SweepData::SweepEvent::setup):

        (WebCore::SweepData::SweepEvent::x):

        (WebCore::SweepData::SweepEvent::entry):

        (WebCore::SweepData::SweepEvent::interval):

        (WebCore::SweepData::SweepEvent::operator<):

        (WebCore::SweepData::trianglesOverlap):

        (WebCore::LoopBlinnPathProcessor::subdivideCurves):

        (WebCore::LoopBlinnPathProcessor::conditionallySubdivide):

        (WebCore::LoopBlinnPathProcessor::subdivideCurvesSlow):

        (WebCore::TessellationState::vertexCallback):

        (WebCore::TessellationState::combineCallback):

        (WebCore::TessellationState::edgeFlagCallback):

        (WebCore::LoopBlinnPathProcessor::tessellateInterior):

        * platform/graphics/gpu/LoopBlinnPathProcessor.h: Added.

/*

 * Copyright (C) 2010 Google Inc. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1.  Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 * 2.  Redistributions in binary form must reproduce the above copyright

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include "LoopBlinnPathProcessor.h"

#include "FloatPoint.h"

#include "FloatRect.h"

#include "LoopBlinnClassifier.h"

#include "LoopBlinnConstants.h"

#include "LoopBlinnLocalTriangulator.h"

#include "LoopBlinnMathUtils.h"

#include "LoopBlinnPathCache.h"

#include "LoopBlinnTextureCoords.h"

#include "PODArena.h"

#include "PODIntervalTree.h"

#include "Path.h"

#include "thirdparty/glu/internal_glu.h"

#include <algorithm>

#include <wtf/Assertions.h>

#if PLATFORM(SKIA)

#include "SkGeometry.h"

#include "SkPath.h"

#include "SkScalar.h"

#else

// Must port to your platform.

#endif

namespace WebCore {

using LoopBlinnMathUtils::XRay;

using LoopBlinnMathUtils::chopCubicAt;

using LoopBlinnMathUtils::numXRayCrossingsForCubic;

using LoopBlinnMathUtils::trianglesOverlap;

using LoopBlinnMathUtils::xRayCrossesLine;

using LoopBlinnPathProcessorImplementation::Contour;

using LoopBlinnPathProcessorImplementation::Segment;

namespace {

#ifndef NDEBUG

inline String valueToString(const FloatRect& arg)

{

    StringBuilder builder;

    builder.append("[FloatRect left=");

    builder.append(String::number(arg.left()));

    builder.append(" top=");

    builder.append(String::number(arg.top()));

    builder.append(" right=");

    builder.append(String::number(arg.right()));

    builder.append(" bottom=");

    builder.append(String::number(arg.bottom()));

    builder.append("]");

    return builder.toString();

}

#endif

} // anonymous namespace

namespace LoopBlinnPathProcessorImplementation {

//----------------------------------------------------------------------

// Segment

//

// Describes a segment of the path: either a cubic or a line segment.

// These are stored in a doubly linked list to speed up curve

// subdivision, which occurs due to either rendering artifacts in the

// loop case or due to overlapping triangles.

class Segment : public Noncopyable {

public:

    enum Kind {

        Cubic,

        Line

    };

    // No-argument constructor allows construction by the PODArena class.

    Segment()

         : m_arena(0)

         , m_kind(Cubic)

         , m_prev(0)

         , m_next(0)

         , m_contour(0)

         , m_triangulator(0)

         , m_markedForSubdivision(false)

    {

    }

    // Initializer for cubic curve segments.

    void setup(PODArena* arena,

               Contour* contour,

               FloatPoint cp0,

               FloatPoint cp1,

               FloatPoint cp2,

               FloatPoint cp3)

    {

        m_arena = arena;

        m_contour = contour;

        m_kind = Cubic;

        m_points[0] = cp0;

        m_points[1] = cp1;

        m_points[2] = cp2;

        m_points[3] = cp3;

        computeBoundingBox();

    }

    // Initializer for line segments.

    void setup(PODArena* arena,

               Contour* contour,

               FloatPoint p0,

               FloatPoint p1)

    {

        m_arena = arena;

        m_contour = contour;

        m_kind = Line;

        m_points[0] = p0;

        m_points[1] = p1;

        computeBoundingBox();

    }

    Kind kind() const { return m_kind; }

    // Returns the i'th control point, 0 <= i < 4.

    const FloatPoint& getPoint(int i)

    {

        ASSERT(i >= 0 && i < 4);

        return m_points[i];

    }

    Segment* next() const { return m_next; }

    Segment* prev() const { return m_prev; }

    void setNext(Segment* next) { m_next = next; }

    void setPrev(Segment* prev) { m_prev = prev; }

    // The contour this segment belongs to.

    Contour* contour() const { return m_contour; }

    // Subdivides the current segment at the given parameter value (0 <=

    // t <= 1) and replaces it with the two newly created Segments in

    // the linked list, if possible. Returns a pointer to the leftmost

    // Segment.

    Segment* subdivide(float param)

    {

        FloatPoint dst[7];

        chopCubicAt(m_points, dst, param);

        Segment* left = m_arena->allocateObject<Segment>();

        Segment* right = m_arena->allocateObject<Segment>();

        left->setup(m_arena, m_contour, dst[0], dst[1], dst[2], dst[3]);

        right->setup(m_arena, m_contour, dst[3], dst[4], dst[5], dst[6]);

        left->setNext(right);

        right->setPrev(left);

        // Try to set up a link between "this->prev()" and "left".

        if (prev()) {

            left->setPrev(prev());

            prev()->setNext(left);

        }

        // Try to set up a link between "this->next()" and "right".

        Segment* n = next();

        if (n) {

            right->setNext(n);

            n->setPrev(right);

        }

        // Set up a link between "this" and "left"; this is only to

        // provide a certain amount of continuity during forward iteration.

        setNext(left);

        return left;

    }

    // Subdivides the current segment at the halfway point and replaces

    // it with the two newly created Segments in the linked list, if

    // possible. Returns a pointer to the leftmost Segment.

    Segment* subdivide() { return subdivide(0.5f); }

    const FloatRect& boundingBox() const { return m_boundingBox; }

    // Computes the number of times a query line starting at the given

    // point and extending to x=+infinity crosses this segment. Outgoing

    // "ambiguous" argument indicates whether the query intersected an

    // endpoint or tangent point of the segment, indicating that another

    // query point is preferred.

    int numCrossingsForXRay(const XRay& xRay, bool& ambiguous) const

    {

        if (m_kind == Cubic)

            // Should consider caching the monotonic cubics.

            return numXRayCrossingsForCubic(xRay, m_points, ambiguous);

        return xRayCrossesLine(xRay, m_points, ambiguous) ? 1 : 0;

    }

    // Performs a local triangulation of the control points in this

    // segment. This operation only makes sense for cubic type segments.

    // texCoords may be null when the klm coordinates have not been

    // computed yet.

    void triangulate(LoopBlinnLocalTriangulator::InsideEdgeComputation computeInsideEdges,

                     const LoopBlinnTextureCoords::Result* texCoords);

    // Returns the number of control point triangles associated with

    // this segment.

    int numberOfTriangles() const

    {

        if (!m_triangulator)

            return 0;

        return m_triangulator->numberOfTriangles();

    }

    // Fetches the given control point triangle for this segment.

    LoopBlinnLocalTriangulator::Triangle* getTriangle(int index)

    {

        ASSERT(m_triangulator);

        return m_triangulator->getTriangle(index);

    }

    // Number of vertices along the inside edge of this segment. This

    // can be called either for line or cubic type segments.

    int numberOfInteriorVertices() const

    {

        if (m_kind == Cubic) {

            if (m_triangulator)

                return m_triangulator->numberOfInteriorVertices();

            return 0;

        }

        return 2;

    }

    // Returns the given interior vertex, 0 <= index < numberOfInteriorVertices().

    FloatPoint getInteriorVertex(int index) const

    {

        ASSERT(index >= 0 && index < numberOfInteriorVertices());

        if (m_kind == Cubic) {

            FloatPoint res;

            if (m_triangulator) {

                LoopBlinnLocalTriangulator::Vertex* vertex = m_triangulator->getInteriorVertex(index);

                if (vertex)

                    res.set(vertex->xyCoordinates().x(), vertex->xyCoordinates().y());

            }

            return res;

        }

        return m_points[index];

    }

    // State to assist with curve subdivision.

    bool markedForSubdivision() const { return m_markedForSubdivision; }

    void setMarkedForSubdivision(bool markedForSubdivision) { m_markedForSubdivision = markedForSubdivision; }

#ifndef NDEBUG

    // Suppport for printing Segments.

    String toString() const

    {

        StringBuilder builder;

        builder.append("[Segment kind=");

        builder.append(kind() == Line ? "line" : "cubic");

        builder.append(" boundingBox=");

        builder.append(valueToString(boundingBox()));

        builder.append(" contour=0x");

        builder.append(String::format("%p", contour()));

        builder.append(" markedForSubdivision=");

        builder.append(markedForSubdivision() ? "true" : "false");

        builder.append("]");

        return builder.toString();

    }

#endif

 private:

    // Computes the bounding box of this Segment.

    void computeBoundingBox()

    {

        switch (m_kind) {

        case Cubic:

            m_boundingBox.fitToPoints(m_points[0], m_points[1], m_points[2], m_points[3]);

            break;

        case Line:

            m_boundingBox.fitToPoints(m_points[0], m_points[1]);

            break;

        }

    }

    PODArena* m_arena;

    Kind m_kind;

    FloatPoint m_points[4];

    Segment* m_prev;

    Segment* m_next;

    Contour* m_contour;

    FloatRect m_boundingBox;

    LoopBlinnLocalTriangulator* m_triangulator;

    bool m_markedForSubdivision;

};

//----------------------------------------------------------------------

// Contour

//

// Describes a closed contour of the path.

class Contour : public Noncopyable {

public:

    Contour()

    {

        m_first = &m_sentinel;

        m_first->setNext(m_first);

        m_first->setPrev(m_first);

        m_isOrientedCounterClockwise = true;

        m_boundingBoxDirty = false;

        m_fillSide = LoopBlinnConstants::RightSide;

    }

    void add(Segment* segment)

    {

        if (m_first == &m_sentinel) {

            // First element is the sentinel. Replace it with the incoming

            // segment.

            segment->setNext(m_first);

            segment->setPrev(m_first);

            m_first->setNext(segment);

            m_first->setPrev(segment);

            m_first = segment;

        } else {

            // m_first->prev() is the sentinel.

            Segment* sentinel = m_first->prev();

            Segment* last = sentinel->prev();

            last->setNext(segment);

            segment->setPrev(last);

            segment->setNext(sentinel);

            sentinel->setPrev(segment);

        }

        m_boundingBoxDirty = true;

    }

    // Subdivides the given segment at the given parametric value.

    // Returns a pointer to the first of the two portions of the

    // subdivided segment.

    Segment* subdivide(Segment* segment, float param)

    {

        Segment* left = segment->subdivide(param);

        if (m_first == segment)

            m_first = left;

        return left;

    }

    // Subdivides the given segment at the halfway point. Returns a

    // pointer to the first of the two portions of the subdivided

    // segment.

    Segment* subdivide(Segment* segment)

    {

        Segment* left = segment->subdivide();

        if (m_first == segment)

            m_first = left;

        return left;

    }

    // Returns the first segment in the contour for iteration.

    Segment* begin() const { return m_first; }

    // Returns the last segment in the contour for iteration. Callers

    // should not iterate over this segment. In other words:

    //  for (Segment* cur = contour->begin();

    //       cur != contour->end();

    //       cur = cur->next()) {

    //    // .. process cur ...

    //  }

    Segment* end() const { return m_first->prev(); }

    bool isOrientedCounterClockwise() const { return m_isOrientedCounterClockwise; }

    void setIsOrientedCounterClockwise(bool isOrientedCounterClockwise) { m_isOrientedCounterClockwise = isOrientedCounterClockwise; }

    const FloatRect& boundingBox() const

    {

        if (m_boundingBoxDirty) {

            bool first = true;

            for (Segment* cur = begin(); cur != end(); cur = cur->next()) {

                if (first)

                    m_boundingBox = cur->boundingBox();

                else

                    m_boundingBox.unite(cur->boundingBox());

                first = false;

            }

            m_boundingBoxDirty = false;

        }

        return m_boundingBox;

    }

    // Returns which side of this contour is filled.

    LoopBlinnConstants::FillSide fillSide() const

    {

        return m_fillSide;

    }

    void setFillSide(LoopBlinnConstants::FillSide fillSide)

    {

        m_fillSide = fillSide;

    }

private:

    // The start of the segment chain. The segments are kept in a

    // circular doubly linked list for rapid access to the beginning and

    // end.

    Segment* m_first;

    // The sentinel element at the end of the chain, needed for

    // reasonable iteration semantics.

    Segment m_sentinel;

    bool m_isOrientedCounterClockwise;

    mutable FloatRect m_boundingBox;

    mutable bool m_boundingBoxDirty;

    // Which side of this contour should be filled.

    LoopBlinnConstants::FillSide m_fillSide;

};

//----------------------------------------------------------------------

// Segment

//

// Definition of Segment::triangulate(), which must come after

// declaration of Contour.

void Segment::triangulate(LoopBlinnLocalTriangulator::InsideEdgeComputation computeInsideEdges,

                          const LoopBlinnTextureCoords::Result* texCoords)

{

    ASSERT(m_kind == Cubic);

    if (!m_triangulator)

        m_triangulator = m_arena->allocateObject<LoopBlinnLocalTriangulator>();

    m_triangulator->reset();

    for (int i = 0; i < 4; i++) {

        LoopBlinnLocalTriangulator::Vertex* vertex = m_triangulator->getVertex(i);

        if (texCoords) {

            vertex->set(getPoint(i).x(),

                        getPoint(i).y(),

                        texCoords->klmCoordinates[i].x(),

                        texCoords->klmCoordinates[i].y(),

                        texCoords->klmCoordinates[i].z());

        } else {

            vertex->set(getPoint(i).x(),

                        getPoint(i).y(),

                        // No texture coordinates yet

                        0, 0, 0);

        }

    }

    m_triangulator->triangulate(computeInsideEdges, contour()->fillSide());

}

} // namespace LoopBlinnPathProcessorImplementation

//----------------------------------------------------------------------

// LoopBlinnPathProcessor

//

LoopBlinnPathProcessor::LoopBlinnPathProcessor()

    : m_arena(PODArena::create())

#ifndef NDEBUG

    , m_verboseLogging(false)

#endif

{

}

LoopBlinnPathProcessor::LoopBlinnPathProcessor(PassRefPtr<PODArena> arena)

    : m_arena(arena)

#ifndef NDEBUG

    , m_verboseLogging(false)

#endif

{

}

LoopBlinnPathProcessor::~LoopBlinnPathProcessor()

{

}

void LoopBlinnPathProcessor::process(const Path& path, LoopBlinnPathCache& cache)

{

    buildContours(path);

    // Run plane-sweep algorithm to determine overlaps of control point

    // curves and subdivide curves appropriately.

    subdivideCurves();

    // Determine orientations of countours. Based on orientation and the

    // number of curve crossings at a random point on the contour,

    // determine whether to fill the left or right side of the contour.

    determineSidesToFill();

    // Classify curves, compute texture coordinates and subdivide as

    // necessary to eliminate rendering artifacts. Do the final

    // triangulation of the curve segments, determining the path along

    // the interior of the shape.

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            if (seg->kind() == Segment::Cubic) {

                LoopBlinnClassifier::Result classification = LoopBlinnClassifier::classify(seg->getPoint(0),

                                                                                           seg->getPoint(1),

                                                                                           seg->getPoint(2),

                                                                                           seg->getPoint(3));

#ifndef NDEBUG

                if (m_verboseLogging)

                    LOG_ERROR("Classification: %d", (int) classification.curveType);

#endif

                LoopBlinnTextureCoords::Result texCoords =

                    LoopBlinnTextureCoords::compute(classification, cur->fillSide());

                if (texCoords.hasRenderingArtifact) {

                    // FIXME: there is a problem where the algorithm

                    // sometimes fails to converge when splitting at the

                    // subdivision parameter value. For the time being,

                    // split halfway.

                    cur->subdivide(seg);

                    // Next iteration will handle the newly subdivided curves

                } else {

                    if (!texCoords.isLineOrPoint) {

                        seg->triangulate(LoopBlinnLocalTriangulator::ComputeInsideEdges, &texCoords);

                        for (int i = 0; i < seg->numberOfTriangles(); i++) {

                            LoopBlinnLocalTriangulator::Triangle* triangle = seg->getTriangle(i);

                            for (int j = 0; j < 3; j++) {

                                LoopBlinnLocalTriangulator::Vertex* vert = triangle->getVertex(j);

                                cache.addVertex(vert->xyCoordinates().x(),

                                                vert->xyCoordinates().y(),

                                                vert->klmCoordinates().x(),

                                                vert->klmCoordinates().y(),

                                                vert->klmCoordinates().z());

                            }

                        }

#ifdef LOOP_BLINN_PATH_CACHE_DEBUG_INTERIOR_EDGES

                        // Show the end user the interior edges as well

                        for (int i = 1; i < seg->numberOfInteriorVertices(); i++) {

                            FloatPoint vert = seg->getInteriorVertex(i);

                            // Duplicate previous vertex to be able to draw GL_LINES

                            FloatPoint prev = seg->getInteriorVertex(i - 1);

                            cache.addInteriorEdgeVertex(prev.x(), prev.y());

                            cache.addInteriorEdgeVertex(vert.x(), vert.y());

                        }

#endif // LOOP_BLINN_PATH_CACHE_DEBUG_INTERIOR_EDGES

                    }

                }

            }

        }

    }

    // Run the interior paths through a tessellation algorithm

    // supporting multiple contours.

    tessellateInterior(cache);

}

void LoopBlinnPathProcessor::buildContours(const Path& path)

{

    // Clear out the contours

    m_contours.clear();

#if PLATFORM(SKIA)

    SkPath::Iter iter(*path.platformPath(), false);

    SkPoint points[4];

    SkPath::Verb verb;

    Contour* contour = 0;

    SkPoint curPoint = { 0 };

    SkPoint moveToPoint = { 0 };

    do {

        verb = iter.next(points);

        if (verb != SkPath::kMove_Verb) {

            if (!contour) {

                contour = m_arena->allocateObject<Contour>();

                m_contours.append(contour);

            }

        }

        switch (verb) {

        case SkPath::kMove_Verb: {

            contour = m_arena->allocateObject<Contour>();

            m_contours.append(contour);

            curPoint = points[0];

            moveToPoint = points[0];

#ifndef NDEBUG

            if (m_verboseLogging)

                LOG_ERROR("MoveTo (%f, %f)", points[0].fX, points[0].fY);

#endif

            break;

        }

        case SkPath::kLine_Verb: {

            Segment* segment = m_arena->allocateObject<Segment>();

            if (iter.isCloseLine()) {

                segment->setup(m_arena.get(), contour, curPoint, points[1]);

#ifndef NDEBUG

                if (m_verboseLogging)

                    LOG_ERROR("CloseLineTo (%f, %f), (%f, %f)", curPoint.fX, curPoint.fY, points[1].fX, points[1].fY);

#endif

                contour->add(segment);

                contour = 0;

            } else {

                segment->setup(m_arena.get(), contour, points[0], points[1]);

#ifndef NDEBUG

                if (m_verboseLogging)

                    LOG_ERROR("LineTo (%f, %f), (%f, %f)", points[0].fX, points[0].fY, points[1].fX, points[1].fY);

#endif

                contour->add(segment);

                curPoint = points[1];

            }

            break;

        }

        case SkPath::kQuad_Verb: {

            // Need to degree elevate the quadratic into a cubic

            SkPoint cubic[4];

            SkConvertQuadToCubic(points, cubic);

            Segment* segment = m_arena->allocateObject<Segment>();

            segment->setup(m_arena.get(), contour,

                           cubic[0], cubic[1], cubic[2], cubic[3]);

#ifndef NDEBUG

            if (m_verboseLogging)

                LOG_ERROR("Quad->CubicTo (%f, %f), (%f, %f), (%f, %f), (%f, %f)", cubic[0].fX, cubic[0].fY, cubic[1].fX, cubic[1].fY, cubic[2].fX, cubic[2].fY, cubic[3].fX, cubic[3].fY);

#endif

            contour->add(segment);

            curPoint = cubic[3];

            break;

        }

        case SkPath::kCubic_Verb: {

            Segment* segment = m_arena->allocateObject<Segment>();

            segment->setup(m_arena.get(), contour, points[0], points[1], points[2], points[3]);

#ifndef NDEBUG

            if (m_verboseLogging)

                LOG_ERROR("CubicTo (%f, %f), (%f, %f), (%f, %f), (%f, %f)", points[0].fX, points[0].fY, points[1].fX, points[1].fY, points[2].fX, points[2].fY, points[3].fX, points[3].fY);

#endif

            contour->add(segment);

            curPoint = points[3];

            break;

        }

        case SkPath::kClose_Verb: {

            Segment* segment = m_arena->allocateObject<Segment>();

            segment->setup(m_arena.get(), contour, curPoint, moveToPoint);

#ifndef NDEBUG

            if (m_verboseLogging)

                LOG_ERROR("Close (%f, %f) -> (%f, %f)", curPoint.fX, curPoint.fY, moveToPoint.fX, moveToPoint.fY);

#endif

            contour->add(segment);

            contour = 0;

        }

        case SkPath::kDone_Verb:

            break;

        }

    } while (verb != SkPath::kDone_Verb);

#else // !PLATFORM(SKIA)

    // Must port to your platform.

    ASSERT_NOT_REACHED();

#endif

}

Vector<Segment*> LoopBlinnPathProcessor::allSegmentsOverlappingY(Contour* queryContour, float x, float y)

{

    Vector<Segment*> res;

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            const FloatRect& boundingBox = seg->boundingBox();

            if (boundingBox.top() <= y && y <= boundingBox.bottom())

                res.append(seg);

        }

    }

    return res;

}

// Uncomment this to debug the orientation computation.

// #define GPU_PATH_PROCESSOR_DEBUG_ORIENTATION

#ifndef NDEBUG

// Routines needed to print the types of IntervalNodes we instantiate

// in this file.

inline String valueToString(const float& value)

{

    return String::number(value);

}

inline String valueToString(void* const& value)

{

    return String::format("0x%p", value);

}

#endif

void LoopBlinnPathProcessor::determineSidesToFill()

{

    // Loop and Blinn's algorithm can only easily emulate the even/odd

    // fill rule, and only for non-intersecting curves. We can determine

    // which side of each curve segment to fill based on its

    // clockwise/counterclockwise orientation and how many other

    // contours surround it.

    // To optimize the query of all curve segments intersecting a

    // horizontal line going to x=+infinity, we build up an interval

    // tree whose keys are the y extents of the segments.

    PODIntervalTree<float, Segment*> tree(m_arena);

    typedef PODIntervalTree<float, Segment*>::IntervalType IntervalType;

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        determineOrientation(cur);

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            const FloatRect& boundingBox = seg->boundingBox();

            tree.add(tree.createInterval(boundingBox.top(), boundingBox.bottom(), seg));

        }

    }

    // Now iterate through the contours and pick a random segment (in

    // this case we use the first) and a random point on that segment.

    // Find all segments from other contours which intersect this one

    // and count the number of crossings a horizontal line to

    // x=+infinity makes with those contours. This combined with the

    // orientation of the curve tells us which side to fill -- again,

    // assuming an even/odd fill rule, which is all we can easily

    // handle.

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        bool ambiguous = true;

        int numCrossings = 0;

        // For each contour, attempt to find a point on the contour which,

        // when we cast an XRay, does not intersect the other contours at

        // an ambiguous point (the junction between two curves or at a

        // tangent point). Ambiguous points make the determination of

        // whether this contour is contained within another fragile. Note

        // that this loop is only an approximation to the selection of a

        // good casting point. We could as well evaluate a segment to

        // determine a point upon it.

        for (Segment* seg = cur->begin();

             ambiguous && seg != cur->end();

             seg = seg->next()) {

            numCrossings = 0;

            // We use a zero-sized vertical interval for the query.

            Vector<IntervalType> overlaps = tree.allOverlaps(tree.createInterval(seg->getPoint(0).y(),

                                                                                 seg->getPoint(0).y(),

                                                                                 0));

#if defined(GPU_PATH_PROCESSOR_DEBUG_ORIENTATION) && !defined(NDEBUG)

            Vector<Segment*> slowOverlaps = allSegmentsOverlappingY(cur, seg->getPoint(0).x(), seg->getPoint(0).y());

            if (overlaps.size() != slowOverlaps.size()) {

                LOG_ERROR("For query point (%f, %f) on contour 0x%p:", seg->getPoint(0).x(), seg->getPoint(0).y(), cur);

                LOG_ERROR(" overlaps:");

                for (size_t i = 0; i < overlaps.size(); i++)

                    LOG_ERROR("  %d: %s", i+1, overlaps[i].data()->toString().ascii().data());

                LOG_ERROR(" slowOverlaps:");

                for (size_t i = 0; i < slowOverlaps.size(); i++)

                    LOG_ERROR("  %d: %s", (i+1) slowOverlaps[i]->toString());

                LOG_ERROR("Interval tree:");

                tree.dump();

            }

            ASSERT(overlaps.size() == slowOverlaps.size());

#endif // defined(GPU_PATH_PROCESSOR_DEBUG_ORIENTATION) && !defined(NDEBUG)

            for (Vector<IntervalType>::iterator iter = overlaps.begin();

                 iter != overlaps.end();

                 iter++) {

                const IntervalType& interval = *iter;

                Segment* querySegment = interval.data();

                // Ignore segments coming from the same contour.

                if (querySegment->contour() != cur) {

                    // Only perform queries that can affect the computation.

                    const FloatRect& boundingBox = querySegment->contour()->boundingBox();

                    if (seg->getPoint(0).x() >= boundingBox.left()

                        && seg->getPoint(0).x() <= boundingBox.right()) {

                        numCrossings += querySegment->numCrossingsForXRay(seg->getPoint(0),

                                                                          ambiguous);

                        if (ambiguous) {

#ifndef NDEBUG

                            if (m_verboseLogging) {

                                LOG_ERROR("Ambiguous intersection query at point (%f, %f)", seg->getPoint(0).x(), seg->getPoint(0).y());

                                LOG_ERROR("Query segment: %s", querySegment->toString().ascii().data());

                            }

#endif

                            break; // Abort iteration over overlaps.

                        }

                    }

                }

            }

        } // for (Segment* seg = cur->begin(); ...

        cur->setFillSide((cur->isOrientedCounterClockwise() ^ (numCrossings & 1)) ? LoopBlinnConstants::LeftSide : LoopBlinnConstants::RightSide);

    }

}

void LoopBlinnPathProcessor::determineOrientation(Contour* contour)

{

    // Determine signed area of the polygon represented by the points

    // along the segments. Consider this an approximation to the true

    // orientation of the polygon; it probably won't handle

    // self-intersecting curves correctly.

    //

    // There is also a pretty basic assumption here that the contour is

    // closed.

    float signedArea = 0;

    for (Segment* seg = contour->begin();

         seg != contour->end();

         seg = seg->next()) {

        int limit = (seg->kind() == Segment::Cubic) ? 4 : 2;

        for (int i = 1; i < limit; i++) {

            const FloatPoint& prevPoint = seg->getPoint(i - 1);

            const FloatPoint& point = seg->getPoint(i);

            float curArea = prevPoint.x() * point.y() - prevPoint.y() * point.x();

#ifndef NDEBUG

            if (m_verboseLogging)

                LOG_ERROR("Adding to signed area (%f, %f) -> (%f, %f) = %f", prevPoint.x(), prevPoint.y(), point.x(), point.y(), curArea);

#endif

            signedArea += curArea;

        }

    }

    if (signedArea > 0)

        contour->setIsOrientedCounterClockwise(true);

    else

        contour->setIsOrientedCounterClockwise(false);

}

namespace {

//----------------------------------------------------------------------

// Classes and typedefs needed for curve subdivision. These can't be scoped

// within the subdivideCurves() method itself, because templates then fail

// to instantiate.

// The user data which is placed in the PODIntervalTree.

struct SweepData {

    SweepData()

        : triangle(0)

        , segment(0)

    {

    }

    // The triangle this interval is associated with

    LoopBlinnLocalTriangulator::Triangle* triangle;

    // The segment the triangle is associated with

    Segment* segment;

};

typedef PODIntervalTree<float, SweepData*> SweepTree;

typedef SweepTree::IntervalType SweepInterval;

// The entry / exit events which occur at the minimum and maximum x

// coordinates of the control point triangles' bounding boxes.

//

// Note that this class requires its copy constructor and assignment

// operator since it needs to be stored in a Vector.

class SweepEvent {

public:

    SweepEvent()

        : m_x(0)

        , m_entry(false)

        , m_interval(0, 0, 0)

    {

    }

    // Initializes the SweepEvent.

    void setup(float x, bool entry, SweepInterval interval)

    {

        m_x = x;

        m_entry = entry;

        m_interval = interval;

    }

    float x() const { return m_x; }

    bool entry() const { return m_entry; }

    const SweepInterval& interval() const { return m_interval; }

    bool operator<(const SweepEvent& other) const

    {

        return m_x < other.m_x;

    }

private:

    float m_x;

    bool m_entry;

    SweepInterval m_interval;

};

bool trianglesOverlap(LoopBlinnLocalTriangulator::Triangle* t0,

                      LoopBlinnLocalTriangulator::Triangle* t1)

{

    return trianglesOverlap(t0->getVertex(0)->xyCoordinates(),

                            t0->getVertex(1)->xyCoordinates(),

                            t0->getVertex(2)->xyCoordinates(),

                            t1->getVertex(0)->xyCoordinates(),

                            t1->getVertex(1)->xyCoordinates(),

                            t1->getVertex(2)->xyCoordinates());

}

} // anonymous namespace

void LoopBlinnPathProcessor::subdivideCurves()

{

    // We need to determine all overlaps of all control point triangles

    // (from different segments, not the same segment) and, if any

    // exist, subdivide the associated curves.

    //

    // The plane-sweep algorithm determines all overlaps of a set of

    // rectangles in the 2D plane. Our problem maps very well to this

    // algorithm and significantly reduces the complexity compared to a

    // naive implementation.

    //

    // Each bounding box of a control point triangle is converted into

    // an "entry" event at its smallest X coordinate and an "exit" event

    // at its largest X coordinate. Each event has an associated

    // one-dimensional interval representing the Y span of the bounding

    // box. We sort these events by increasing X coordinate. We then

    // iterate through them. For each entry event we add the interval to

    // a side interval tree, and query this tree for overlapping

    // intervals. Any overlapping interval corresponds to an overlapping

    // bounding box. For each exit event we remove the associated

    // interval from the interval tree.

    Vector<Segment*> curSegments;

    Vector<Segment*> nextSegments;

    // Start things off by considering all of the segments

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            if (seg->kind() == Segment::Cubic) {

                seg->triangulate(LoopBlinnLocalTriangulator::DontComputeInsideEdges, 0);

                curSegments.append(seg);

            }

        }

    }

    // Subdivide curves at most this many times

    const int MaxIterations = 5;

    Vector<SweepInterval> overlaps;

    for (int currentIteration = 0; currentIteration < MaxIterations; ++currentIteration) {

        if (!curSegments.size())

            // Done

            break;

        Vector<SweepEvent> events;

        SweepTree tree(m_arena);

        for (Vector<Segment*>::iterator iter = curSegments.begin();

             iter != curSegments.end();

             iter++) {

            Segment* seg = *iter;

            if (seg->kind() == Segment::Cubic) {

                for (int i = 0; i < seg->numberOfTriangles(); i++) {

                    LoopBlinnLocalTriangulator::Triangle* triangle = seg->getTriangle(i);

                    FloatRect boundingBox;

                    boundingBox.fitToPoints(triangle->getVertex(0)->xyCoordinates(),

                                     triangle->getVertex(1)->xyCoordinates(),

                                     triangle->getVertex(2)->xyCoordinates());

                    // Ignore zero-width triangles to avoid issues with

                    // coincident entry and exit events for the same triangle

                    if (boundingBox.right() > boundingBox.left()) {

                        SweepData* data = m_arena->allocateObject<SweepData>();

                        data->triangle = triangle;

                        data->segment = seg;

                        SweepInterval interval = tree.createInterval(boundingBox.top(), boundingBox.bottom(), data);

                        // Add entry and exit events

                        SweepEvent event;

                        event.setup(boundingBox.left(), true, interval);

                        events.append(event);

                        event.setup(boundingBox.right(), false, interval);

                        events.append(event);

                    }

                }

            }

        }

        // Sort events by increasing X coordinate

        std::sort(events.begin(), events.end());

#ifndef NDEBUG

        for (size_t ii = 1; ii < events.size(); ++ii)

            ASSERT(events[ii - 1].x() <= events[ii].x());

#endif

        // Now iterate through the events

        for (Vector<SweepEvent>::iterator iter = events.begin();

             iter != events.end();

             iter++) {

            SweepEvent event = *iter;

            if (event.entry()) {

                // Add this interval into the tree

                tree.add(event.interval());

                // See whether the associated segment has been subdivided yet

                if (!event.interval().data()->segment->markedForSubdivision()) {

                    // Query the tree

                    overlaps.clear();

                    tree.allOverlaps(event.interval(), overlaps);

                    // Now see exactly which triangles overlap this one

                    for (Vector<SweepInterval>::iterator iter = overlaps.begin();

                         iter != overlaps.end();

                         iter++) {

                        SweepInterval overlap = *iter;

                        // Only pay attention to overlaps from a different Segment

                        if (event.interval().data()->segment != overlap.data()->segment) {

                            // See whether the triangles actually overlap

                            if (trianglesOverlap(event.interval().data()->triangle,

                                                 overlap.data()->triangle)) {

                                // Actually subdivide the segments.

                                // Each one might already have been subdivided.

                                Segment* seg = event.interval().data()->segment;

                                conditionallySubdivide(seg, nextSegments);

                                seg = overlap.data()->segment;

                                conditionallySubdivide(seg, nextSegments);

                            }

                        }

                    }

                }

            } else {

                // Remove this interval from the tree

                tree.remove(event.interval());

            }

        }

        curSegments = nextSegments;

        nextSegments.clear();

    }

}

void LoopBlinnPathProcessor::conditionallySubdivide(Segment* seg, Vector<Segment*>& nextSegments)

{

    if (!seg->markedForSubdivision()) {

        seg->setMarkedForSubdivision(true);

        Segment* next = seg->contour()->subdivide(seg);

        // Triangulate the newly subdivided segments.

        next->triangulate(LoopBlinnLocalTriangulator::DontComputeInsideEdges, 0);

        next->next()->triangulate(LoopBlinnLocalTriangulator::DontComputeInsideEdges, 0);

        // Add them for the next iteration.

        nextSegments.append(next);

        nextSegments.append(next->next());

    }

}

#ifndef NDEBUG

void LoopBlinnPathProcessor::subdivideCurvesSlow()

{

    // Alternate, significantly slower algorithm for curve subdivision

    // for use in debugging.

    Vector<Segment*> curSegments;

    Vector<Segment*> nextSegments;

    // Start things off by considering all of the segments

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            if (seg->kind() == Segment::Cubic) {

                seg->triangulate(LoopBlinnLocalTriangulator::DontComputeInsideEdges, 0);

                curSegments.append(seg);

            }

        }

    }

    // Subdivide curves at most this many times

    const int MaxIterations = 5;

    for (int currentIteration = 0; currentIteration < MaxIterations; ++currentIteration) {

        if (!curSegments.size())

            // Done

            break;

        for (Vector<Segment*>::iterator iter = curSegments.begin();

             iter != curSegments.end();

             iter++) {

            Segment* seg = *iter;

            if (seg->kind() == Segment::Cubic) {

                for (Vector<Segment*>::iterator iter2 = curSegments.begin();

                     iter2 != curSegments.end();

                     iter2++) {

                    Segment* seg2 = *iter2;

                    if (seg2->kind() == Segment::Cubic && seg != seg2) {

                        for (int i = 0; i < seg->numberOfTriangles(); i++) {

                            LoopBlinnLocalTriangulator::Triangle* triangle = seg->getTriangle(i);

                            for (int j = 0; j < seg2->numberOfTriangles(); j++) {

                                LoopBlinnLocalTriangulator::Triangle* triangle2 = seg2->getTriangle(j);

                                if (trianglesOverlap(triangle, triangle2)) {

                                    conditionallySubdivide(seg, nextSegments);

                                    conditionallySubdivide(seg2, nextSegments);

                                }

                            }

                        }

                    }

                }

            }

        }

        curSegments = nextSegments;

        nextSegments.clear();

    }

}

#endif

namespace {

//----------------------------------------------------------------------

// Structures and callbacks for tessellation of the interior region of

// the contours.

// The user data for the GLU tessellator.

struct TessellationState {

    TessellationState(LoopBlinnPathCache& inputCache)

        : cache(inputCache) { }

    LoopBlinnPathCache& cache;

    Vector<void*> allocatedPointers;

};

static void vertexCallback(void* vertexData, void* data)

{

    TessellationState* state = static_cast<TessellationState*>(data);

    GLdouble* location = static_cast<GLdouble*>(vertexData);

    state->cache.addInteriorVertex(static_cast<float>(location[0]),

                                   static_cast<float>(location[1]));

}

static void combineCallback(GLdouble coords[3], void* vertexData[4],

                            GLfloat weight[4], void** outData,

                            void* polygonData)

{

    TessellationState* state = static_cast<TessellationState*>(polygonData);

    GLdouble* outVertex = static_cast<GLdouble*>(malloc(3 * sizeof(GLdouble)));

    state->allocatedPointers.append(outVertex);

    outVertex[0] = coords[0];

    outVertex[1] = coords[1];

    outVertex[2] = coords[2];

    *outData = outVertex;

}

static void edgeFlagCallback(GLboolean flag)

{

    // No-op just to prevent triangle strips and fans from being passed to us.

}

} // anonymous namespace

void LoopBlinnPathProcessor::tessellateInterior(LoopBlinnPathCache& cache)

{

    // Because the GLU tessellator requires its input in

    // double-precision format, we need to make a separate copy of the

    // data.

    Vector<GLdouble> vertexData;

    Vector<size_t> contourEndings;

    // For avoiding adding coincident vertices.

    float curX = 0, curY = 0;

    for (Vector<Contour*>::iterator iter = m_contours.begin();

         iter != m_contours.end();

         iter++) {

        Contour* cur = *iter;

        bool first = true;

        for (Segment* seg = cur->begin(); seg != cur->end(); seg = seg->next()) {

            int numberOfInteriorVertices = seg->numberOfInteriorVertices();

            for (int i = 0; i < numberOfInteriorVertices - 1; i++) {

                FloatPoint point = seg->getInteriorVertex(i);

                if (first) {

                    first = false;

                    vertexData.append(point.x());

                    vertexData.append(point.y());

                    vertexData.append(0);

                    curX = point.x();

                    curY = point.y();

                } else if (point.x() != curX || point.y() != curY)  {

                    vertexData.append(point.x());

                    vertexData.append(point.y());

                    vertexData.append(0);

                    curX = point.x();

                    curY = point.y();

                }

            }

        }

        contourEndings.append(vertexData.size());

    }

    // Now that we have all of the vertex data in a stable location in

    // memory, call the tessellator.

    GLUtesselator* tess = internal_gluNewTess();

    TessellationState state(cache);

    internal_gluTessCallback(tess, GLU_TESS_VERTEX_DATA,

                             reinterpret_cast<GLvoid (*)()>(vertexCallback));

    internal_gluTessCallback(tess, GLU_TESS_COMBINE_DATA,

                             reinterpret_cast<GLvoid (*)()>(combineCallback));

    internal_gluTessCallback(tess, GLU_TESS_EDGE_FLAG,

                             reinterpret_cast<GLvoid (*)()>(edgeFlagCallback));

    internal_gluTessBeginPolygon(tess, &state);

    internal_gluTessBeginContour(tess);

    GLdouble* base = vertexData.data();

    int contourIndex = 0;

    for (size_t i = 0; i < vertexData.size(); i += 3) {

        if (i == contourEndings[contourIndex]) {

            internal_gluTessEndContour(tess);

            internal_gluTessBeginContour(tess);

            ++contourIndex;

        }

        internal_gluTessVertex(tess, &base[i], &base[i]);

    }

    internal_gluTessEndContour(tess);

    internal_gluTessEndPolygon(tess);

    for (size_t i = 0; i < state.allocatedPointers.size(); i++)

        free(state.allocatedPointers[i]);

    internal_gluDeleteTess(tess);

}

} // namespace WebCore

/*

 * Copyright (C) 2010 Google Inc. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1.  Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 * 2.  Redistributions in binary form must reproduce the above copyright

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

// The main entry point for Loop and Blinn's GPU accelerated curve

// rendering algorithm.

#ifndef LoopBlinnPathProcessor_h

#define LoopBlinnPathProcessor_h

#include <wtf/Noncopyable.h>

#include <wtf/PassRefPtr.h>

#include <wtf/RefPtr.h>

#include <wtf/Vector.h>

namespace WebCore {

// We use a namespace for classes which are simply implementation

// details of the algorithm but which we need to reference from the

// class definition.

namespace LoopBlinnPathProcessorImplementation {

class Contour;

class Segment;

} // namespace LoopBlinnPathProcessorImplementation

class Path;

class LoopBlinnPathCache;

class PODArena;

// The LoopBlinnPathProcessor turns a Path (assumed to contain one or

// more closed regions) into a set of exterior and interior triangles,

// stored in the LoopBlinnPathCache. The exterior triangles have

// associated 3D texture coordinates which are used to evaluate the

// curve's inside/outside function on a per-pixel basis. The interior

// triangles are filled with 100% opacity.

//

// Note that the fill style and management of multiple layers are

// separate concerns, handled at a higher level with shaders and

// polygon offsets.

class LoopBlinnPathProcessor {

public:

    LoopBlinnPathProcessor();

    explicit LoopBlinnPathProcessor(PassRefPtr<PODArena> arena);

    ~LoopBlinnPathProcessor();

    // Transforms the given path into a triangle mesh for rendering

    // using Loop and Blinn's shader, placing the result into the given

    // LoopBlinnPathCache.

    void process(const Path& path, LoopBlinnPathCache& cache);

#ifndef NDEBUG

    // Enables or disables verbose logging in debug mode.

    void setVerboseLogging(bool onOrOff);

#endif

private:

    // Builds a list of contours for the given path.

    void buildContours(const Path& path);

    // Determines whether the left or right side of each contour should

    // be filled.

    void determineSidesToFill();

    // Determines whether the given (closed) contour is oriented

    // clockwise or counterclockwise.

    void determineOrientation(LoopBlinnPathProcessorImplementation::Contour* contour);

    // Subdivides the curves so that there are no overlaps of the

    // triangles associated with the curves' control points.

    void subdivideCurves();

    // Helper function used during curve subdivision.

    void conditionallySubdivide(LoopBlinnPathProcessorImplementation::Segment* seg,

                                Vector<LoopBlinnPathProcessorImplementation::Segment*>& nextSegments);

    // Tessellates the interior regions of the contours.

    void tessellateInterior(LoopBlinnPathCache& cache);

    // For debugging the orientation computation. Returns all of the

    // segments overlapping the given Y coordinate.

    Vector<LoopBlinnPathProcessorImplementation::Segment*> allSegmentsOverlappingY(LoopBlinnPathProcessorImplementation::Contour* queryContour, float x, float y);

#ifndef NDEBUG

    // For debugging the curve subdivision algorithm. Subdivides the

    // curves using an alternate, slow (O(n^3)) algorithm.

    void subdivideCurvesSlow();

#endif

    // PODArena from which to allocate temporary objects.

    RefPtr<PODArena> m_arena;

    // The contours described by the path.

    Vector<LoopBlinnPathProcessorImplementation::Contour*> m_contours;

#ifndef NDEBUG

    // Whether or not to perform verbose logging in debug mode.

    bool m_verboseLogging;

#endif

};

} // namespace WebCore

#endif // LoopBlinnPathProcessor_h