src/shaders/gradients/SkRadialGradient.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#include "src/shaders/gradients/SkRadialGradient.h"

#include "include/core/SkColor.h"
#include "include/core/SkColorSpace.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkShader.h"
#include "include/effects/SkGradientShader.h"
#include "include/private/base/SkTArray.h"
#include "src/core/SkRasterPipeline.h"
#include "src/core/SkRasterPipelineOpList.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkWriteBuffer.h"
#include "src/shaders/SkLocalMatrixShader.h"
#include "src/shaders/SkShaderBase.h"
#include "src/shaders/gradients/SkGradientBaseShader.h"

#if defined(SK_GRAPHITE)
#include "src/gpu/graphite/KeyContext.h"
#include "src/gpu/graphite/KeyHelpers.h"
#include "src/gpu/graphite/PaintParamsKey.h"
#endif

#include <cstdint>
#include <utility>

class SkArenaAlloc;
enum class SkTileMode;

static SkMatrix rad_to_unit_matrix(const SkPoint& center, SkScalar radius) {
    SkScalar inv = SkScalarInvert(radius);

    SkMatrix matrix;
    matrix.setTranslate(-center.fX, -center.fY);
    matrix.postScale(inv, inv);
    return matrix;
}

SkRadialGradient::SkRadialGradient(const SkPoint& center, SkScalar radius, const Descriptor& desc)
        : SkGradientBaseShader(desc, rad_to_unit_matrix(center, radius))
        , fCenter(center)
        , fRadius(radius) {}

SkShaderBase::GradientType SkRadialGradient::asGradient(GradientInfo* info,
                                                        SkMatrix* localMatrix) const {
    if (info) {
        commonAsAGradient(info);
        info->fPoint[0] = fCenter;
        info->fRadius[0] = fRadius;
    }
    if (localMatrix) {
        *localMatrix = SkMatrix::I();
    }
    return GradientType::kRadial;
}

sk_sp<SkFlattenable> SkRadialGradient::CreateProc(SkReadBuffer& buffer) {
    DescriptorScope desc;
    SkMatrix legacyLocalMatrix;
    if (!desc.unflatten(buffer, &legacyLocalMatrix)) {
        return nullptr;
    }
    const SkPoint center = buffer.readPoint();
    const SkScalar radius = buffer.readScalar();
    return SkGradientShader::MakeRadial(center,
                                        radius,
                                        desc.fColors,
                                        std::move(desc.fColorSpace),
                                        desc.fPositions,
                                        desc.fColorCount,
                                        desc.fTileMode,
                                        desc.fInterpolation,
                                        &legacyLocalMatrix);
}

void SkRadialGradient::flatten(SkWriteBuffer& buffer) const {
    this->SkGradientBaseShader::flatten(buffer);
    buffer.writePoint(fCenter);
    buffer.writeScalar(fRadius);
}

void SkRadialGradient::appendGradientStages(SkArenaAlloc*, SkRasterPipeline* p,
                                            SkRasterPipeline*) const {
    p->append(SkRasterPipelineOp::xy_to_radius);
}

#if defined(SK_ENABLE_SKVM)
skvm::F32 SkRadialGradient::transformT(skvm::Builder* p, skvm::Uniforms*,
                                       skvm::Coord coord, skvm::I32* mask) const {
    return sqrt(coord.x*coord.x + coord.y*coord.y);
}
#endif

#if defined(SK_GRAPHITE)
void SkRadialGradient::addToKey(const skgpu::graphite::KeyContext& keyContext,
                                skgpu::graphite::PaintParamsKeyBuilder* builder,
                                skgpu::graphite::PipelineDataGatherer* gatherer) const {
    this->addToKeyCommon(keyContext, builder, gatherer,
                         GradientType::kRadial,
                         fCenter, { 0.0f, 0.0f },
                         fRadius, 0.0f,
                         0.0f, 0.0f);
}
#endif

sk_sp<SkShader> SkGradientShader::MakeRadial(const SkPoint& center, SkScalar radius,
                                             const SkColor4f colors[],
                                             sk_sp<SkColorSpace> colorSpace,
                                             const SkScalar pos[],
                                             int colorCount,
                                             SkTileMode mode,
                                             const Interpolation& interpolation,
                                             const SkMatrix* localMatrix) {
    if (radius < 0) {
        return nullptr;
    }
    if (!SkGradientBaseShader::ValidGradient(colors, colorCount, mode, interpolation)) {
        return nullptr;
    }
    if (1 == colorCount) {
        return SkShaders::Color(colors[0], std::move(colorSpace));
    }
    if (localMatrix && !localMatrix->invert(nullptr)) {
        return nullptr;
    }

    if (SkScalarNearlyZero(radius, SkGradientBaseShader::kDegenerateThreshold)) {
        // Degenerate gradient optimization, and no special logic needed for clamped radial gradient
        return SkGradientBaseShader::MakeDegenerateGradient(
                colors, pos, colorCount, std::move(colorSpace), mode);
    }

    SkGradientBaseShader::ColorStopOptimizer opt(colors, pos, colorCount, mode);

    SkGradientBaseShader::Descriptor desc(
            opt.fColors, std::move(colorSpace), opt.fPos, opt.fCount, mode, interpolation);
    return SkLocalMatrixShader::MakeWrapped<SkRadialGradient>(localMatrix, center, radius, desc);
}

sk_sp<SkShader> SkGradientShader::MakeRadial(const SkPoint& center, SkScalar radius,
                                             const SkColor colors[],
                                             const SkScalar pos[],
                                             int colorCount,
                                             SkTileMode mode,
                                             uint32_t flags,
                                             const SkMatrix* localMatrix) {
    SkColorConverter converter(colors, colorCount);
    return MakeRadial(center, radius, converter.fColors4f.begin(), nullptr, pos, colorCount, mode,
                      flags, localMatrix);
}

void SkRegisterRadialGradientShaderFlattenable() {
    SK_REGISTER_FLATTENABLE(SkRadialGradient);
}