src/gpu/graphite/sparse_strips/SparseStripsConfig.h

/*
 * Copyright 2026 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef skgpu_graphite_SparseStripConfig_DEFINED
#define skgpu_graphite_SparseStripConfig_DEFINED

#include "include/core/SkColorType.h"

#include <array>
#include <cstddef>
#include <cstdint>

namespace skgpu::graphite {

// Tunable compile-time paramters that control various aspects of SparseStrips behavior
struct SparseStripConfig {
    // These control the size, in pixels, of the tiles generated by polylines.
    static constexpr uint16_t kTileWidth  = 8;
    static constexpr uint16_t kTileHeight = 8;
    static_assert(kTileWidth == kTileHeight);

    // The tile dimensions MUST match the hard coded constant in the fragment shader. If that value
    // changes, this must be updated.
    static_assert(kTileWidth == 8);

    // These control the AlphaAtlasManager
    static constexpr SkColorType kColorType       = SkColorType::kRGBA_8888_SkColorType;
    static constexpr int32_t kAtlasBytesPerTexel  = 4;
    static_assert(kColorType == SkColorType::kRGBA_8888_SkColorType);

    static constexpr int32_t kAtlasWidth          = 8192;
    static constexpr int32_t kAtlasWidthBytes     = kAtlasWidth * kAtlasBytesPerTexel;
    static constexpr int32_t kInitialAtlasRows    = 1;
    static constexpr int32_t kMaxAtlasRows        = 8192;
    static constexpr int32_t kMaxAtlasBytes       = kAtlasWidth * kMaxAtlasRows *
                                                    kAtlasBytesPerTexel;
    static constexpr int32_t kMaxTexturePages     = 2;

    // The AlphaAtlasManager uses a flipflopping allocation system that will break if the page count
    // is increased beyond 2.
    static_assert(kMaxTexturePages == 2);
    // To avoid uploading the texture width, and to avoid a costly divide and mod in the shader, we
    // assume that the atlas width is always fixed.
    static_assert(kAtlasWidth == 8192);

    // The number of MSAA SubSamples in SparseStrips rendering. We currently only support 8.
    using SubSampleType                           = uint8_t;
    static constexpr int32_t   kNumSubSamples     = sizeof(SubSampleType) * 8;
    static_assert(!((kNumSubSamples & (kNumSubSamples - 1))));
    static_assert(sizeof(SubSampleType) * 8 == kNumSubSamples);

    static constexpr int32_t kLUTMaskWidth        = 64;
    static constexpr int32_t kLUTMaskHeight       = 64;
    static constexpr int32_t kLUTMaskWidthExcl    = kLUTMaskWidth - 1;
    static constexpr int32_t kLUTMaskHeightExcl   = kLUTMaskHeight - 1;
    static constexpr float   kLUTMaskWidthF       = static_cast<float>(kLUTMaskWidth);
    static constexpr float   kLUTMaskHeightF      = static_cast<float>(kLUTMaskHeight);
    static constexpr size_t  kLUTSize             = kLUTMaskWidth * kLUTMaskHeight;

    using LUTArray                                = std::array<SubSampleType, kLUTSize>;

    static constexpr float kStripEpsilon          = 1e-5f;
};

}  // namespace skgpu::graphite

#endif  // skgpu_graphite_SparseStripConfig_DEFINED