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skia学习记录

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windows编译

  1. 需要有python3环境
  2. git代理配置：
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git config --global http.proxy 127.0.0.1:55664
git config --global https.proxy 127.0.0.1:55664
  1. 安装depot_tools到某一目录
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git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

并配置depot_tools目录为环境变量

  1. 安装LLVM，如15.0.7。
  2. 下载skia源码，并切到一个chrome下分支
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git clone https://skia.googlesource.com/skia.git
  1. 下载skia依赖库源码，跳转到别的分支编译，一直到 The changes made to environment variables only apply to the currently running shell instance...
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cd skia
git checkout chrome/m125
python tools/git-sync-deps
  1. 下载 ninja
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python bin/fetch-ninja
  1. PowerShell生成make文件（可选）：
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bin/gn gen out/debug --args/'clang_win=\"D:\LLVM\" cc=\"clang\" cxx=\"clang++\" extra_cflags=[\"/MTd\"] is_official_build=true is_debug=false skia_use_system_expat=false skia_use_system_libjpeg_turbo=false skia_use_system_libpng=false skia_use_system_libwebp=false skia_use_system_zlib=false skia_use_system_harfbuzz=false skia_use_system_icu=false skia_use_icu=false'
  1. 编译静态库（可选）：
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ninja -C out/debug

用于验证所有步骤是否正确，成功则在debug目录下出现.lib文件

  1. PowerShell生成sln工程：
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bin/gn gen build/sln --args'clang_win=\"D:\LLVM\"' --ide=vs

在skia中使用vertex shader

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void HelloWorld::onPaint(SkSurface* surface) {
    auto canvas = surface->getCanvas();
    canvas->save();
    // Clear background
    canvas->clear(SK_ColorWHITE);

    SkPaint paint;
    paint.setColor(SK_ColorRED);

    static constexpr auto kRect = SkRect::MakeLTRB(20, 20, 120, 120);
    static constexpr auto kUV = SkRect::MakeLTRB(0, 0, 20, 20);

    static constexpr ColorVertex kColorQuad[]{
            {0, 0x00FFFF00, {kRect.left(), kUV.left(), kRect.top(), kUV.top()}},
            {0, 0x00FFFFFF, {kRect.right(), kUV.right(), kRect.top(), kUV.top()}},
            {0, 0xFFFF00FF, {kRect.left(), kUV.left(), kRect.bottom(), kUV.bottom()}},
            {0, 0xFFFFFF00, {kRect.right(), kUV.right(), kRect.bottom(), kUV.bottom()}},
    };
    static constexpr ColorVertex kColorIndexedQuad[]{
            {0, 0x00FFFF00, {kRect.left(), kUV.left(), kRect.top(), kUV.top()}},
            {0, 0x00000000, {100.f, 0.f, 100.f, 5.f}},  // unused
            {0, 0x00FFFFFF, {kRect.right(), kUV.right(), kRect.top(), kUV.top()}},
            {0, 0x00000000, {200.f, 10.f, 200.f, 10.f}},  // unused
            {0, 0xFFFF00FF, {kRect.left(), kUV.left(), kRect.bottom(), kUV.bottom()}},
            {0, 0xFFFFFF00, {kRect.right(), kUV.right(), kRect.bottom(), kUV.bottom()}},
    };
    static constexpr size_t kColorIndexedOffset = 2 * sizeof(ColorVertex);
    static constexpr uint16_t kIndices[]{0, 2, 4, 2, 5, 4};
    static constexpr size_t kIndexOffset = 6;

    sk_sp<SkMesh::VertexBuffer> fColorVB =
            SkMeshes::MakeVertexBuffer(kColorQuad, sizeof(kColorQuad));

    auto data = SkData::MakeUninitialized(sizeof(kColorIndexedQuad) + kColorIndexedOffset);
    sk_sp<SkMesh::VertexBuffer> fColorIndexedVB =
            SkMeshes::MakeVertexBuffer(data->data(), data->size());

    static constexpr SkColor kColors[] = {SK_ColorTRANSPARENT, SK_ColorWHITE};

    static const Attribute kAttributes[]{
            {Attribute::Type::kFloat4, 8, SkString{"xuyv"}},
            {Attribute::Type::kUByte4_unorm, 4, SkString{"brag"}},
    };
    static const Varying kVaryings[]{
            {Varying::Type::kHalf4, SkString{"color"}},
            {Varying::Type::kFloat2, SkString{"uv"}},
    };
    static constexpr char kVS[] = R"(
                    half4 unswizzle_color(half4 color) { return color.garb; }

                    Varyings main(const in Attributes attributes) {
                        Varyings varyings;
                        varyings.color    = unswizzle_color(attributes.brag);
                        varyings.uv       = attributes.xuyv.yw;
                        varyings.position = attributes.xuyv.xz;
                        varyings.position.x += 500.0;
                        return varyings;
                    }
            )";
    static constexpr char kFS[] = R"(
                    uniform colorFilter filter;

                    float2 main(const in Varyings varyings, out float4 color) {
                        color = filter.eval(varyings.color);
                        return varyings.uv;
                    }
            )";
    auto [spec, error] = SkMeshSpecification::Make(
            kAttributes, sizeof(ColorVertex), kVaryings, SkString(kVS), SkString(kFS));

    if (!spec) {
        SkDebugf("%s\n", error.c_str());
    }
    sk_sp<SkMeshSpecification> fSpecWithColor = std::move(spec);

    sk_sp<SkShader> fShader =
            SkGradientShader::MakeRadial({10, 10}, 3, kColors, nullptr, 2, SkTileMode::kMirror);
    SkRuntimeEffect::ChildPtr nullChild[1] = {};
    SkMesh::Result result = SkMesh::Make(fSpecWithColor,
                                         SkMesh::Mode::kTriangleStrip,
                                         fColorVB,
                                         /*vertexCount=*/4,
                                         /*vertexOffset=*/0,
                                         /*uniforms=*/nullptr,
                                         /*children=*/nullChild,
                                         kRect);

    if (!result.mesh.isValid()) {
        SkDebugf("Mesh creation failed: %s\n", result.error.c_str());
    }

    paint.setAlpha(0x40);
    canvas->drawMesh(result.mesh, SkBlender::Mode(SkBlendMode::kDst), paint);
    canvas->translate(0, 150);
    canvas->restore();
}