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* 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 SkSLSampleMatrix_DEFINED
#define SkSLSampleMatrix_DEFINED
#include <string>
namespace SkSL {
* Represents the matrix applied to a fragment processor by its parent's sample(child, matrix) call.
struct SampleMatrix {
enum class Kind {
// No sample(child, matrix) call affects the FP.
// The FP is sampled with a matrix whose value is fixed and based only on constants or
// uniforms, and thus the transform can be hoisted to the vertex shader (assuming that
// its parent can also be hoisted, i.e. not sampled explicitly).
// The FP is sampled with a non-constant/uniform value, or sampled multiple times, and
// thus the transform cannot be hoisted to the vertex shader.
// Make a SampleMatrix with kNone for its kind. Will not have an expression or have perspective.
// Represents sample(child, color) and sample(child, color, float2) calls.
: fKind(Kind::kNone)
, fHasPerspective(false) {}
// This corresponds to sample(child, color, matrix) calls where every call site in the FP has
// the same constant or uniform.
static SampleMatrix MakeConstUniform(std::string expression, bool hasPerspective=true) {
return SampleMatrix(Kind::kConstantOrUniform, std::move(expression), hasPerspective);
// This corresponds to sample(child, color, matrix) where the 3rd argument is an expression,
// or where the constants/uniforms are not the same at all call sites in the FP.
static SampleMatrix MakeVariable(bool hasPerspective=true) {
return SampleMatrix(Kind::kVariable, "", hasPerspective);
SampleMatrix merge(const SampleMatrix& other);
bool operator==(const SampleMatrix& other) const {
return fKind == other.fKind && fExpression == other.fExpression &&
fHasPerspective == other.fHasPerspective;
bool isNoOp() const { return fKind == Kind::kNone; }
bool isConstUniform() const { return fKind == Kind::kConstantOrUniform; }
bool isVariable() const { return fKind == Kind::kVariable; }
Kind fKind;
// The constant or uniform expression representing the matrix (will be the empty string when
// kind == kNone or kVariable)
std::string fExpression;
// FIXME: We can expand this to track a more general matrix type to allow for optimizations on
// identity or scale+translate matrices too.
bool fHasPerspective;
SampleMatrix(Kind kind, std::string expression, bool hasPerspective)
: fKind(kind)
, fExpression(expression)
, fHasPerspective(hasPerspective) {}
} // namespace