src/gpu/ccpr/GrCCPRCoverageOp.h

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrCCPRCoverageOp_DEFINED
#define GrCCPRCoverageOp_DEFINED

#include "GrMesh.h"
#include "SkRect.h"
#include "SkRefCnt.h"
#include "ccpr/GrCCPRCoverageProcessor.h"
#include "ccpr/GrCCPRGeometry.h"
#include "ops/GrDrawOp.h"

class GrCCPRCoverageOp;
class GrOnFlushResourceProvider;
class SkMatrix;
class SkPath;

/**
 * This class produces GrCCPRCoverageOps that render coverage count masks and atlases. A path is
 * added to the current op in two steps:
 *
 *   1) parsePath(ScissorMode, viewMatrix, path, &devBounds, &devBounds45);
 *
 *   <client decides where to put the mask within an atlas, if wanted>
 *
 *   2) saveParsedPath(offsetX, offsetY, clipBounds);
 *
 * The client can flush the currently saved paths to a GrCCPRCoverageOp by calling emitOp, and
 * retrieve all emitted ops after calling finalize().
 */
class GrCCPRCoverageOpsBuilder {
public:
    // Indicates whether a path should enforce a scissor clip when rendering its mask. (Specified
    // as an int because these values get used directly as indices into arrays.)
    enum class ScissorMode : int {
        kNonScissored = 0,
        kScissored = 1
    };
    static constexpr int kNumScissorModes = 2;

    GrCCPRCoverageOpsBuilder(int maxTotalPaths, int numSkPoints, int numSkVerbs)
            : fPathsInfo(maxTotalPaths)
            , fGeometry(numSkPoints, numSkVerbs)
            , fTallies{PrimitiveTallies(), PrimitiveTallies()}
            , fScissorBatches(maxTotalPaths) {}

    ~GrCCPRCoverageOpsBuilder() {
        // Enforce the contract that the client always calls saveParsedPath or discardParsedPath.
        SkASSERT(!fParsingPath);
    }

    // Parses an SkPath into a temporary staging area. The path will not yet be included in the next
    // Op unless there is a matching call to saveParsedPath. The user must complement this with a
    // following call to either saveParsedPath or discardParsedPath.
    //
    // Returns two tight bounding boxes: device space and "45 degree" (| 1 -1 | * devCoords) space.
    //                                                                 | 1  1 |
    void parsePath(const SkMatrix&, const SkPath&, SkRect* devBounds, SkRect* devBounds45);

    // Commits the currently-parsed path from staging to the next Op, and specifies whether the mask
    // should be rendered with a scissor clip in effect. Accepts an optional post-device-space
    // translate for placement in an atlas.
    void saveParsedPath(ScissorMode, const SkIRect& clippedDevIBounds,
                        int16_t atlasOffsetX, int16_t atlasOffsetY);
    void discardParsedPath();

    // Flushes all currently-saved paths internally to a GrCCPRCoverageOp.
    //
    // NOTE: if there is a parsed path in the staging area, it will not be included. But the client
    // may still call saveParsedPath to include it in a future Op.
    void emitOp(SkISize drawBounds);

    // Builds GPU buffers and returns the list of GrCCPRCoverageOps as specified by calls to emitOp.
    bool finalize(GrOnFlushResourceProvider*, SkTArray<std::unique_ptr<GrCCPRCoverageOp>>*);

private:
    using PrimitiveTallies = GrCCPRGeometry::PrimitiveTallies;

    // Every kBeginPath verb has a corresponding PathInfo entry.
    struct PathInfo {
        ScissorMode   fScissorMode;
        int32_t       fPackedAtlasOffset; // (offsetY << 16) | (offsetX & 0xffff)
        std::unique_ptr<GrCCPRCoverageOp>  fTerminatingOp;
    };

    // Every PathInfo with a mode of kScissored has a corresponding ScissorBatch.
    struct ScissorBatch {
        PrimitiveTallies   fInstanceCounts;
        SkIRect            fScissor;
    };

    void endContourIfNeeded(bool insideContour);

    // Staging area for the path being parsed.
    SkDEBUGCODE(int                    fParsingPath = false);
    int                                fCurrPathPointsIdx;
    int                                fCurrPathVerbsIdx;
    PrimitiveTallies                   fCurrPathTallies;

    SkSTArray<32, PathInfo, true>      fPathsInfo;

    GrCCPRGeometry                     fGeometry;

    PrimitiveTallies                   fTallies[kNumScissorModes];
    SkTArray<ScissorBatch, true>       fScissorBatches;

    std::unique_ptr<GrCCPRCoverageOp>  fTerminatingOp;

    friend class GrCCPRCoverageOp; // For ScissorBatch.
};

/**
 * This Op renders coverage count masks and atlases. Create it using GrCCPRCoverageOpsBuilder.
 */
class GrCCPRCoverageOp : public GrDrawOp {
public:
    DEFINE_OP_CLASS_ID

    // GrDrawOp interface.
    const char* name() const override { return "GrCCPRCoverageOp"; }
    FixedFunctionFlags fixedFunctionFlags() const override { return FixedFunctionFlags::kNone; }
    RequiresDstTexture finalize(const GrCaps&, const GrAppliedClip*,
                                GrPixelConfigIsClamped) override {
        return RequiresDstTexture::kNo;
    }
    bool onCombineIfPossible(GrOp* other, const GrCaps& caps) override { return false; }
    void onPrepare(GrOpFlushState*) override {}
    void onExecute(GrOpFlushState*) override;

private:
    static constexpr int kNumScissorModes = GrCCPRCoverageOpsBuilder::kNumScissorModes;
    using PrimitiveTallies = GrCCPRGeometry::PrimitiveTallies;
    using ScissorBatch = GrCCPRCoverageOpsBuilder::ScissorBatch;

    GrCCPRCoverageOp(SkTArray<ScissorBatch, true>&& scissorBatches, const SkISize& drawBounds)
        : INHERITED(ClassID())
        , fScissorBatches(std::move(scissorBatches))
        , fDrawBounds(drawBounds) {
        this->setBounds(SkRect::MakeIWH(fDrawBounds.width(), fDrawBounds.height()),
                        GrOp::HasAABloat::kNo, GrOp::IsZeroArea::kNo);
    }

    void setBuffers(sk_sp<GrBuffer> pointsBuffer, sk_sp<GrBuffer> instanceBuffer,
                    const PrimitiveTallies baseInstances[kNumScissorModes],
                    const PrimitiveTallies endInstances[kNumScissorModes]);

    void drawMaskPrimitives(GrOpFlushState*, const GrPipeline&, const GrCCPRCoverageProcessor::Mode,
                            GrPrimitiveType, int vertexCount,
                            int PrimitiveTallies::* instanceType) const;

    sk_sp<GrBuffer>                      fPointsBuffer;
    sk_sp<GrBuffer>                      fInstanceBuffer;
    PrimitiveTallies                     fBaseInstances[kNumScissorModes];
    PrimitiveTallies                     fInstanceCounts[kNumScissorModes];
    const SkTArray<ScissorBatch, true>   fScissorBatches;
    const SkISize                        fDrawBounds;

    mutable SkTArray<GrMesh>                     fMeshesScratchBuffer;
    mutable SkTArray<GrPipeline::DynamicState>   fDynamicStatesScratchBuffer;

    friend class GrCCPRCoverageOpsBuilder;

    typedef GrDrawOp INHERITED;
};

#endif