skia2/include/private/SkSLSampleUsage.h

/*
 * Copyright 2020 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkSLSampleUsage_DEFINED
#define SkSLSampleUsage_DEFINED

#include "include/core/SkTypes.h"

#include <string>

namespace SkSL {

/**
 * Represents all of the ways that a fragment processor is sampled by its parent.
 */
class SampleUsage {
public:
    enum class Kind {
        // Child is never sampled
        kNone,
        // Child is only sampled at the same coordinates as the parent
        kPassThrough,
        // Child is sampled with a matrix whose value is uniform
        kUniformMatrix,
        // Child is sampled with sk_FragCoord.xy
        kFragCoord,
        // Child is sampled using explicit coordinates
        kExplicit,
    };

    // Make a SampleUsage that corresponds to no sampling of the child at all
    SampleUsage() = default;

    SampleUsage(Kind kind, bool hasPerspective) : fKind(kind), fHasPerspective(hasPerspective) {
        if (kind != Kind::kUniformMatrix) {
            SkASSERT(!fHasPerspective);
        }
    }

    // Child is sampled with a matrix whose value is uniform. The name is fixed.
    static SampleUsage UniformMatrix(bool hasPerspective) {
        return SampleUsage(Kind::kUniformMatrix, hasPerspective);
    }

    static SampleUsage Explicit() {
        return SampleUsage(Kind::kExplicit, false);
    }

    static SampleUsage PassThrough() {
        return SampleUsage(Kind::kPassThrough, false);
    }

    static SampleUsage FragCoord() { return SampleUsage(Kind::kFragCoord, false); }

    bool operator==(const SampleUsage& that) const {
        return fKind == that.fKind && fHasPerspective == that.fHasPerspective;
    }

    bool operator!=(const SampleUsage& that) const { return !(*this == that); }

    // Arbitrary name used by all uniform sampling matrices
    static const char* MatrixUniformName() { return "matrix"; }

    SampleUsage merge(const SampleUsage& other);

    Kind kind() const { return fKind; }

    bool hasPerspective() const { return fHasPerspective; }

    bool isSampled()       const { return fKind != Kind::kNone; }
    bool isPassThrough()   const { return fKind == Kind::kPassThrough; }
    bool isExplicit()      const { return fKind == Kind::kExplicit; }
    bool isUniformMatrix() const { return fKind == Kind::kUniformMatrix; }
    bool isFragCoord()     const { return fKind == Kind::kFragCoord; }

    std::string constructor() const;

private:
    Kind fKind = Kind::kNone;
    bool fHasPerspective = false;  // Only valid if fKind is kUniformMatrix
};

}  // namespace SkSL

#endif