ganesh/ops/QuadPerEdgeAA.h

/*
 * Copyright 2018 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef QuadPerEdgeAA_DEFINED
#define QuadPerEdgeAA_DEFINED

#include "include/core/SkPoint.h"
#include "include/core/SkPoint3.h"
#include "include/private/gpu/ganesh/GrTypesPriv.h"
#include "src/gpu/BufferWriter.h"
#include "src/gpu/ganesh/GrBuffer.h"
#include "src/gpu/ganesh/GrColor.h"
#include "src/gpu/ganesh/GrGeometryProcessor.h"
#include "src/gpu/ganesh/GrSamplerState.h"
#include "src/gpu/ganesh/geometry/GrQuad.h"
#include "src/gpu/ganesh/geometry/GrQuadUtils.h"
#include "src/gpu/ganesh/ops/TextureOp.h"

class GrCaps;
class GrColorSpaceXform;
class GrMeshDrawTarget;
struct GrShaderCaps;
struct VertexWriter;

namespace skgpu::ganesh::QuadPerEdgeAA {
using Saturate = skgpu::ganesh::TextureOp::Saturate;

enum class CoverageMode { kNone, kWithPosition, kWithColor };
enum class Subset : bool { kNo = false, kYes = true };
enum class ColorType { kNone, kByte, kFloat, kLast = kFloat };
static const int kColorTypeCount = static_cast<int>(ColorType::kLast) + 1;

enum class IndexBufferOption {
    kPictureFramed,  // geometrically AA'd   -> 8 verts/quad + an index buffer
    kIndexedRects,   // non-AA'd but indexed -> 4 verts/quad + an index buffer
    kTriStrips,      // non-AA'd             -> 4 verts/quad but no index buffer
    kLast = kTriStrips
};
static const int kIndexBufferOptionCount = static_cast<int>(IndexBufferOption::kLast) + 1;

IndexBufferOption CalcIndexBufferOption(GrAAType aa, int numQuads);

// Gets the minimum ColorType that can represent a color.
ColorType MinColorType(SkPMColor4f);

// Specifies the vertex configuration for an op that renders per-edge AA quads. The vertex
// order (when enabled) is device position, color, local position, subset, aa edge equations.
// This order matches the constructor argument order of VertexSpec and is the order that
// GPAttributes maintains. If hasLocalCoords is false, then the local quad type can be ignored.
struct VertexSpec {
public:
    VertexSpec()
            : fDeviceQuadType(0)     // kAxisAligned
            , fLocalQuadType(0)      // kAxisAligned
            , fIndexBufferOption(0)  // kPictureFramed
            , fHasLocalCoords(false)
            , fColorType(0)  // kNone
            , fHasSubset(false)
            , fUsesCoverageAA(false)
            , fCompatibleWithCoverageAsAlpha(false)
            , fRequiresGeometrySubset(false) {}

    VertexSpec(GrQuad::Type deviceQuadType,
               ColorType colorType,
               GrQuad::Type localQuadType,
               bool hasLocalCoords,
               Subset subset,
               GrAAType aa,
               bool coverageAsAlpha,
               IndexBufferOption indexBufferOption)
            : fDeviceQuadType(static_cast<unsigned>(deviceQuadType))
            , fLocalQuadType(static_cast<unsigned>(localQuadType))
            , fIndexBufferOption(static_cast<unsigned>(indexBufferOption))
            , fHasLocalCoords(hasLocalCoords)
            , fColorType(static_cast<unsigned>(colorType))
            , fHasSubset(static_cast<unsigned>(subset))
            , fUsesCoverageAA(aa == GrAAType::kCoverage)
            , fCompatibleWithCoverageAsAlpha(coverageAsAlpha)
            , fRequiresGeometrySubset(aa == GrAAType::kCoverage &&
                                      deviceQuadType > GrQuad::Type::kRectilinear) {}

    GrQuad::Type deviceQuadType() const { return static_cast<GrQuad::Type>(fDeviceQuadType); }
    GrQuad::Type localQuadType() const { return static_cast<GrQuad::Type>(fLocalQuadType); }
    IndexBufferOption indexBufferOption() const {
        return static_cast<IndexBufferOption>(fIndexBufferOption);
    }
    bool hasLocalCoords() const { return fHasLocalCoords; }
    ColorType colorType() const { return static_cast<ColorType>(fColorType); }
    bool hasVertexColors() const { return ColorType::kNone != this->colorType(); }
    bool hasSubset() const { return fHasSubset; }
    bool usesCoverageAA() const { return fUsesCoverageAA; }
    bool compatibleWithCoverageAsAlpha() const { return fCompatibleWithCoverageAsAlpha; }
    bool requiresGeometrySubset() const { return fRequiresGeometrySubset; }
    // Will always be 2 or 3
    int deviceDimensionality() const;
    // Will always be 0 if hasLocalCoords is false, otherwise will be 2 or 3
    int localDimensionality() const;

    int verticesPerQuad() const { return fUsesCoverageAA ? 8 : 4; }

    CoverageMode coverageMode() const;
    size_t vertexSize() const;

    bool needsIndexBuffer() const {
        return this->indexBufferOption() != IndexBufferOption::kTriStrips;
    }

    GrPrimitiveType primitiveType() const {
        switch (this->indexBufferOption()) {
            case IndexBufferOption::kPictureFramed:
                return GrPrimitiveType::kTriangles;
            case IndexBufferOption::kIndexedRects:
                return GrPrimitiveType::kTriangles;
            case IndexBufferOption::kTriStrips:
                return GrPrimitiveType::kTriangleStrip;
        }

        SkUNREACHABLE;
    }

private:
    static_assert(GrQuad::kTypeCount <= 4, "GrQuad::Type doesn't fit in 2 bits");
    static_assert(kColorTypeCount <= 4, "Color doesn't fit in 2 bits");
    static_assert(kIndexBufferOptionCount <= 4, "IndexBufferOption doesn't fit in 2 bits");

    unsigned fDeviceQuadType : 2;
    unsigned fLocalQuadType : 2;
    unsigned fIndexBufferOption : 2;
    unsigned fHasLocalCoords : 1;
    unsigned fColorType : 2;
    unsigned fHasSubset : 1;
    unsigned fUsesCoverageAA : 1;
    unsigned fCompatibleWithCoverageAsAlpha : 1;
    // The geometry subset serves to clip off pixels touched by quads with sharp corners that
    // would otherwise exceed the miter limit for the AA-outset geometry.
    unsigned fRequiresGeometrySubset : 1;
    };

    // A Tessellator is responsible for processing a series of device+local GrQuads into a VBO,
    // as specified by a VertexSpec. This vertex data can then be processed by a GP created with
    // MakeProcessor and/or MakeTexturedProcessor.
    class Tessellator {
    public:
        explicit Tessellator(const VertexSpec& spec, char* vertices);

        // Calculates (as needed) inset and outset geometry for anti-aliasing, and appends all
        // necessary position and vertex attributes required by this Tessellator's VertexSpec into
        // the 'vertices' the Tessellator was called with. The insetting and outsetting may
        // damage the provided GrQuads (as this is intended to work with GrQuadBuffer::Iter).
        // 'localQuad' can be null if the VertexSpec does not use local coords.
        void append(GrQuad* deviceQuad, GrQuad* localQuad,
                    const SkPMColor4f& color, const SkRect& uvSubset, GrQuadAAFlags aaFlags);

        SkDEBUGCODE(skgpu::BufferWriter::Mark vertexMark() const { return fVertexWriter.mark(); })

    private:
        // VertexSpec defines many unique ways to write vertex attributes, which can be handled
        // generically by branching per-quad based on the VertexSpec. However, there are several
        // specs that appear in the wild far more frequently, so they use explicit WriteQuadProcs
        // that have no branches.
        typedef void (*WriteQuadProc)(VertexWriter* vertices, const VertexSpec& spec,
                                      const GrQuad* deviceQuad, const GrQuad* localQuad,
                                      const float coverage[4], const SkPMColor4f& color,
                                      const SkRect& geomSubset, const SkRect& texSubset);
        static WriteQuadProc GetWriteQuadProc(const VertexSpec& spec);

        GrQuadUtils::TessellationHelper fAAHelper;
        VertexSpec                      fVertexSpec;
        VertexWriter                    fVertexWriter;
        WriteQuadProc                   fWriteProc;
    };

    GrGeometryProcessor* MakeProcessor(SkArenaAlloc*, const VertexSpec&);

    GrGeometryProcessor* MakeTexturedProcessor(SkArenaAlloc*,
                                               const VertexSpec&,
                                               const GrShaderCaps&,
                                               const GrBackendFormat&,
                                               GrSamplerState,
                                               const skgpu::Swizzle&,
                                               sk_sp<GrColorSpaceXform> textureColorSpaceXform,
                                               Saturate);

    // This method will return the correct index buffer for the specified indexBufferOption.
    // It will, correctly, return nullptr if the indexBufferOption is kTriStrips.
    sk_sp<const GrBuffer> GetIndexBuffer(GrMeshDrawTarget*, IndexBufferOption);

    // What is the maximum number of quads allowed for the specified indexBuffer option?
    int QuadLimit(IndexBufferOption);

    // This method will issue the draw call on the provided GrOpsRenderPass, as specified by the
    // indexing method in vertexSpec. It is up to the calling code to allocate, fill in, and bind a
    // vertex buffer, and to acquire and bind the correct index buffer (if needed) with
    // GrPrimitiveRestart::kNo.
    //
    // @param runningQuadCount  the number of quads already stored in 'vertexBuffer' and
    //                          'indexBuffer' e.g., different GrMeshes have already been placed in
    //                          the buffers to allow dynamic state changes.
    // @param quadCount         the number of quads that will be drawn by the provided 'mesh'.
    //                          A subsequent ConfigureMesh call would the use
    //                          'runningQuadCount' + 'quadCount' for its new 'runningQuadCount'.
    void IssueDraw(const GrCaps&, GrOpsRenderPass*, const VertexSpec&, int runningQuadCount,
                   int quadCount, int maxVerts, int absVertBufferOffset);

    }  // namespace skgpu::ganesh::QuadPerEdgeAA

#endif // QuadPerEdgeAA_DEFINED