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kc3-lang/angle/src/tests/gl_tests/ClearTest.cpp

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  • Author : Joonatan Saarhelo
    Date : 2018-10-17 20:49:06
    Hash : 945dea36
    Message : Clamp glClearDepthf and glDepthRangef BUG=angleproject:2884 Change-Id: Ib1867fbd4c2ea3c3b29d2f987d384762f5851e8f Reviewed-on: https://chromium-review.googlesource.com/c/1276585 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>

  • src/tests/gl_tests/ClearTest.cpp
  • //
    // Copyright 2015 The ANGLE Project Authors. All rights reserved.
    // Use of this source code is governed by a BSD-style license that can be
    // found in the LICENSE file.
    //
    
    #include "test_utils/ANGLETest.h"
    
    #include "random_utils.h"
    #include "shader_utils.h"
    #include "test_utils/gl_raii.h"
    
    using namespace angle;
    
    namespace
    {
    
    Vector4 RandomVec4(int seed, float minValue, float maxValue)
    {
        RNG rng(seed);
        srand(seed);
        return Vector4(
            rng.randomFloatBetween(minValue, maxValue), rng.randomFloatBetween(minValue, maxValue),
            rng.randomFloatBetween(minValue, maxValue), rng.randomFloatBetween(minValue, maxValue));
    }
    
    GLColor Vec4ToColor(const Vector4 &vec)
    {
        GLColor color;
        color.R = static_cast<uint8_t>(vec.x() * 255.0f);
        color.G = static_cast<uint8_t>(vec.y() * 255.0f);
        color.B = static_cast<uint8_t>(vec.z() * 255.0f);
        color.A = static_cast<uint8_t>(vec.w() * 255.0f);
        return color;
    };
    
    class ClearTestBase : public ANGLETest
    {
      protected:
        ClearTestBase()
        {
            setWindowWidth(128);
            setWindowHeight(128);
            setConfigRedBits(8);
            setConfigGreenBits(8);
            setConfigBlueBits(8);
            setConfigAlphaBits(8);
            setConfigDepthBits(24);
        }
    
        void SetUp() override
        {
            ANGLETest::SetUp();
    
            mFBOs.resize(2, 0);
            glGenFramebuffers(2, mFBOs.data());
    
            ASSERT_GL_NO_ERROR();
        }
    
        void TearDown() override
        {
            if (!mFBOs.empty())
            {
                glDeleteFramebuffers(static_cast<GLsizei>(mFBOs.size()), mFBOs.data());
            }
    
            if (!mTextures.empty())
            {
                glDeleteTextures(static_cast<GLsizei>(mTextures.size()), mTextures.data());
            }
    
            ANGLETest::TearDown();
        }
    
        std::vector<GLuint> mFBOs;
        std::vector<GLuint> mTextures;
    };
    
    class ClearTest : public ClearTestBase
    {
    };
    class ClearTestES3 : public ClearTestBase
    {
    };
    
    class ClearTestRGB : public ANGLETest
    {
      protected:
        ClearTestRGB()
        {
            setWindowWidth(128);
            setWindowHeight(128);
            setConfigRedBits(8);
            setConfigGreenBits(8);
            setConfigBlueBits(8);
        }
    };
    
    // Test clearing the default framebuffer
    TEST_P(ClearTest, DefaultFramebuffer)
    {
        glClearColor(0.25f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
        EXPECT_PIXEL_NEAR(0, 0, 64, 128, 128, 128, 1.0);
    }
    
    // Test clearing the RGB default framebuffer and verify that the alpha channel is not cleared
    TEST_P(ClearTestRGB, DefaultFramebufferRGB)
    {
        glClearColor(0.25f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
        EXPECT_PIXEL_NEAR(0, 0, 64, 128, 128, 255, 1.0);
    }
    
    // Test clearing a RGBA8 Framebuffer
    TEST_P(ClearTest, RGBA8Framebuffer)
    {
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture texture;
    
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, getWindowWidth(), getWindowHeight(), 0, GL_RGBA,
                     GL_UNSIGNED_BYTE, nullptr);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
    
        glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
    
        EXPECT_PIXEL_NEAR(0, 0, 128, 128, 128, 128, 1.0);
    }
    
    // Test to validate that we can go from an RGBA framebuffer attachment, to an RGB one and still
    // have a correct behavior after.
    TEST_P(ClearTest, ChangeFramebufferAttachmentFromRGBAtoRGB)
    {
        // http://anglebug.com/2689
        ANGLE_SKIP_TEST_IF(IsD3D9() || IsD3D11() || (IsOzone() && IsOpenGLES()));
        ANGLE_SKIP_TEST_IF(IsOSX() && (IsNVIDIA() || IsIntel()) && IsDesktopOpenGL());
        ANGLE_SKIP_TEST_IF(IsAndroid() && IsAdreno() && IsOpenGLES());
    
        ANGLE_GL_PROGRAM(program, angle::essl1_shaders::vs::Simple(),
                         angle::essl1_shaders::fs::UniformColor());
        setupQuadVertexBuffer(0.5f, 1.0f);
        glUseProgram(program);
        GLint positionLocation = glGetAttribLocation(program, angle::essl1_shaders::PositionAttrib());
        ASSERT_NE(positionLocation, -1);
        glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
        glEnableVertexAttribArray(positionLocation);
    
        GLint colorUniformLocation =
            glGetUniformLocation(program, angle::essl1_shaders::ColorUniform());
        ASSERT_NE(colorUniformLocation, -1);
    
        glUniform4f(colorUniformLocation, 1.0f, 1.0f, 1.0f, 0.5f);
    
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture texture;
        glColorMask(GL_TRUE, GL_FALSE, GL_TRUE, GL_TRUE);
    
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, getWindowWidth(), getWindowHeight(), 0, GL_RGBA,
                     GL_UNSIGNED_BYTE, nullptr);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
    
        glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
        ASSERT_GL_NO_ERROR();
    
        // So far so good, we have an RGBA framebuffer that we've cleared to 0.5 everywhere.
        EXPECT_PIXEL_NEAR(0, 0, 128, 0, 128, 128, 1.0);
    
        // In the Vulkan backend, RGB textures are emulated with an RGBA texture format
        // underneath and we keep a special mask to know that we shouldn't touch the alpha
        // channel when we have that emulated texture. This test exists to validate that
        // this mask gets updated correctly when the framebuffer attachment changes.
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, getWindowWidth(), getWindowHeight(), 0, GL_RGB,
                     GL_UNSIGNED_BYTE, nullptr);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
        ASSERT_GL_NO_ERROR();
    
        glDrawArrays(GL_TRIANGLES, 0, 6);
        ASSERT_GL_NO_ERROR();
    
        EXPECT_PIXEL_RECT_EQ(0, 0, getWindowWidth(), getWindowHeight(), GLColor::magenta);
    }
    
    // Test clearing a RGB8 Framebuffer with a color mask.
    TEST_P(ClearTest, RGB8WithMaskFramebuffer)
    {
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture texture;
    
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, getWindowWidth(), getWindowHeight(), 0, GL_RGB,
                     GL_UNSIGNED_BYTE, nullptr);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
    
        glClearColor(0.2f, 0.4f, 0.6f, 0.8f);
        glClear(GL_COLOR_BUFFER_BIT);
    
        // Since there's no alpha, we expect to get 255 back instead of the clear value (204).
        EXPECT_PIXEL_NEAR(0, 0, 51, 102, 153, 255, 1.0);
    
        glColorMask(GL_TRUE, GL_TRUE, GL_FALSE, GL_TRUE);
        glClearColor(0.1f, 0.3f, 0.5f, 0.7f);
        glClear(GL_COLOR_BUFFER_BIT);
    
        // The blue channel was masked so its value should be unchanged.
        EXPECT_PIXEL_NEAR(0, 0, 26, 77, 153, 255, 1.0);
    
        // Restore default.
        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    }
    
    TEST_P(ClearTest, ClearIssue)
    {
        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_LEQUAL);
    
        glClearColor(0.0, 1.0, 0.0, 1.0);
        glClearDepthf(0.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
        EXPECT_GL_NO_ERROR();
    
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLRenderbuffer rbo;
        glBindRenderbuffer(GL_RENDERBUFFER, rbo);
        glRenderbufferStorage(GL_RENDERBUFFER, GL_RGB565, 16, 16);
    
        EXPECT_GL_NO_ERROR();
    
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, rbo);
    
        EXPECT_GL_NO_ERROR();
    
        glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
        glClearDepthf(1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
        EXPECT_GL_NO_ERROR();
    
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        glBindBuffer(GL_ARRAY_BUFFER, 0);
    
        ANGLE_GL_PROGRAM(blueProgram, essl1_shaders::vs::Simple(), essl1_shaders::fs::Red());
        drawQuad(blueProgram, essl1_shaders::PositionAttrib(), 0.5f);
    
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
    }
    
    // Regression test for a bug where "glClearDepthf"'s argument was not clamped
    // In GLES 2 they where declared as GLclampf and the behaviour is the same in GLES 3.2
    TEST_P(ClearTest, ClearIsClamped)
    {
        glClearDepthf(5.0f);
    
        GLfloat clear_depth;
        glGetFloatv(GL_DEPTH_CLEAR_VALUE, &clear_depth);
        EXPECT_EQ(1.0f, clear_depth);
    }
    
    // Regression test for a bug where "glDepthRangef"'s arguments were not clamped
    // In GLES 2 they where declared as GLclampf and the behaviour is the same in GLES 3.2
    TEST_P(ClearTest, DepthRangefIsClamped)
    {
        glDepthRangef(1.1f, -4.0f);
    
        GLfloat depth_range[2];
        glGetFloatv(GL_DEPTH_RANGE, depth_range);
        EXPECT_EQ(1.0f, depth_range[0]);
        EXPECT_EQ(0.0f, depth_range[1]);
    }
    
    // Requires ES3
    // This tests a bug where in a masked clear when calling "ClearBuffer", we would
    // mistakenly clear every channel (including the masked-out ones)
    TEST_P(ClearTestES3, MaskedClearBufferBug)
    {
        unsigned char pixelData[] = {255, 255, 255, 255};
    
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture textures[2];
    
        glBindTexture(GL_TEXTURE_2D, textures[0]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixelData);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[0], 0);
    
        glBindTexture(GL_TEXTURE_2D, textures[1]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixelData);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, textures[1], 0);
    
        ASSERT_GL_NO_ERROR();
        EXPECT_PIXEL_EQ(0, 0, 255, 255, 255, 255);
    
        float clearValue[]   = {0, 0.5f, 0.5f, 1.0f};
        GLenum drawBuffers[] = {GL_NONE, GL_COLOR_ATTACHMENT1};
        glDrawBuffers(2, drawBuffers);
        glColorMask(GL_TRUE, GL_TRUE, GL_FALSE, GL_TRUE);
        glClearBufferfv(GL_COLOR, 1, clearValue);
    
        ASSERT_GL_NO_ERROR();
        EXPECT_PIXEL_EQ(0, 0, 255, 255, 255, 255);
    
        glReadBuffer(GL_COLOR_ATTACHMENT1);
        ASSERT_GL_NO_ERROR();
    
        EXPECT_PIXEL_NEAR(0, 0, 0, 127, 255, 255, 1);
    }
    
    TEST_P(ClearTestES3, BadFBOSerialBug)
    {
        // First make a simple framebuffer, and clear it to green
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture textures[2];
    
        glBindTexture(GL_TEXTURE_2D, textures[0]);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, getWindowWidth(), getWindowHeight());
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[0], 0);
    
        GLenum drawBuffers[] = {GL_COLOR_ATTACHMENT0};
        glDrawBuffers(1, drawBuffers);
    
        float clearValues1[] = {0.0f, 1.0f, 0.0f, 1.0f};
        glClearBufferfv(GL_COLOR, 0, clearValues1);
    
        ASSERT_GL_NO_ERROR();
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
    
        // Next make a second framebuffer, and draw it to red
        // (Triggers bad applied render target serial)
        GLFramebuffer fbo2;
        glBindFramebuffer(GL_FRAMEBUFFER, fbo2);
        ASSERT_GL_NO_ERROR();
    
        glBindTexture(GL_TEXTURE_2D, textures[1]);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, getWindowWidth(), getWindowHeight());
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[1], 0);
    
        glDrawBuffers(1, drawBuffers);
    
        ANGLE_GL_PROGRAM(blueProgram, essl1_shaders::vs::Simple(), essl1_shaders::fs::Red());
        drawQuad(blueProgram, essl1_shaders::PositionAttrib(), 0.5f);
    
        ASSERT_GL_NO_ERROR();
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
    
        // Check that the first framebuffer is still green.
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
    }
    
    // Test that SRGB framebuffers clear to the linearized clear color
    TEST_P(ClearTestES3, SRGBClear)
    {
        // First make a simple framebuffer, and clear it
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture texture;
    
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_SRGB8_ALPHA8, getWindowWidth(), getWindowHeight());
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
    
        glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
    
        EXPECT_PIXEL_NEAR(0, 0, 188, 188, 188, 128, 1.0);
    }
    
    // Test that framebuffers with mixed SRGB/Linear attachments clear to the correct color for each
    // attachment
    TEST_P(ClearTestES3, MixedSRGBClear)
    {
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
    
        GLTexture textures[2];
    
        glBindTexture(GL_TEXTURE_2D, textures[0]);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_SRGB8_ALPHA8, getWindowWidth(), getWindowHeight());
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[0], 0);
    
        glBindTexture(GL_TEXTURE_2D, textures[1]);
        glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, getWindowWidth(), getWindowHeight());
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, textures[1], 0);
    
        GLenum drawBuffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1};
        glDrawBuffers(2, drawBuffers);
    
        // Clear both textures
        glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
        glClear(GL_COLOR_BUFFER_BIT);
    
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 0, 0);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, 0, 0);
    
        // Check value of texture0
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[0], 0);
        EXPECT_PIXEL_NEAR(0, 0, 188, 188, 188, 128, 1.0);
    
        // Check value of texture1
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textures[1], 0);
        EXPECT_PIXEL_NEAR(0, 0, 128, 128, 128, 128, 1.0);
    }
    
    // This test covers a D3D11 bug where calling ClearRenderTargetView sometimes wouldn't sync
    // before a draw call. The test draws small quads to a larger FBO (the default back buffer).
    // Before each blit to the back buffer it clears the quad to a certain color using
    // ClearBufferfv to give a solid color. The sync problem goes away if we insert a call to
    // flush or finish after ClearBufferfv or each draw.
    TEST_P(ClearTestES3, RepeatedClear)
    {
        const std::string &vertexSource =
            "#version 300 es\n"
            "in highp vec2 position;\n"
            "out highp vec2 v_coord;\n"
            "void main(void)\n"
            "{\n"
            "    gl_Position = vec4(position, 0, 1);\n"
            "    vec2 texCoord = (position * 0.5) + 0.5;\n"
            "    v_coord = texCoord;\n"
            "}\n";
    
        const std::string &fragmentSource =
            "#version 300 es\n"
            "in highp vec2 v_coord;\n"
            "out highp vec4 color;\n"
            "uniform sampler2D tex;\n"
            "void main()\n"
            "{\n"
            "    color = texture(tex, v_coord);\n"
            "}\n";
    
        ANGLE_GL_PROGRAM(program, vertexSource, fragmentSource);
    
        mTextures.resize(1, 0);
        glGenTextures(1, mTextures.data());
    
        GLenum format           = GL_RGBA8;
        const int numRowsCols   = 3;
        const int cellSize      = 32;
        const int fboSize       = cellSize;
        const int backFBOSize   = cellSize * numRowsCols;
        const float fmtValueMin = 0.0f;
        const float fmtValueMax = 1.0f;
    
        glBindTexture(GL_TEXTURE_2D, mTextures[0]);
        glTexStorage2D(GL_TEXTURE_2D, 1, format, fboSize, fboSize);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        ASSERT_GL_NO_ERROR();
    
        glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, mTextures[0], 0);
        ASSERT_GL_NO_ERROR();
    
        ASSERT_GLENUM_EQ(GL_FRAMEBUFFER_COMPLETE, glCheckFramebufferStatus(GL_FRAMEBUFFER));
    
        // larger fbo bound -- clear to transparent black
        glUseProgram(program);
        GLint uniLoc = glGetUniformLocation(program, "tex");
        ASSERT_NE(-1, uniLoc);
        glUniform1i(uniLoc, 0);
        glBindTexture(GL_TEXTURE_2D, mTextures[0]);
    
        GLint positionLocation = glGetAttribLocation(program, "position");
        ASSERT_NE(-1, positionLocation);
    
        glUseProgram(program);
    
        for (int cellY = 0; cellY < numRowsCols; cellY++)
        {
            for (int cellX = 0; cellX < numRowsCols; cellX++)
            {
                int seed            = cellX + cellY * numRowsCols;
                const Vector4 color = RandomVec4(seed, fmtValueMin, fmtValueMax);
    
                glBindFramebuffer(GL_FRAMEBUFFER, mFBOs[0]);
                glClearBufferfv(GL_COLOR, 0, color.data());
    
                glBindFramebuffer(GL_FRAMEBUFFER, 0);
    
                // Method 1: Set viewport and draw full-viewport quad
                glViewport(cellX * cellSize, cellY * cellSize, cellSize, cellSize);
                drawQuad(program, "position", 0.5f);
    
                // Uncommenting the glFinish call seems to make the test pass.
                // glFinish();
            }
        }
    
        std::vector<GLColor> pixelData(backFBOSize * backFBOSize);
        glReadPixels(0, 0, backFBOSize, backFBOSize, GL_RGBA, GL_UNSIGNED_BYTE, pixelData.data());
    
        for (int cellY = 0; cellY < numRowsCols; cellY++)
        {
            for (int cellX = 0; cellX < numRowsCols; cellX++)
            {
                int seed              = cellX + cellY * numRowsCols;
                const Vector4 color   = RandomVec4(seed, fmtValueMin, fmtValueMax);
                GLColor expectedColor = Vec4ToColor(color);
    
                int testN = cellX * cellSize + cellY * backFBOSize * cellSize + backFBOSize + 1;
                GLColor actualColor = pixelData[testN];
                EXPECT_NEAR(expectedColor.R, actualColor.R, 1);
                EXPECT_NEAR(expectedColor.G, actualColor.G, 1);
                EXPECT_NEAR(expectedColor.B, actualColor.B, 1);
                EXPECT_NEAR(expectedColor.A, actualColor.A, 1);
            }
        }
    
        ASSERT_GL_NO_ERROR();
    }
    
    class ScissoredClearTest : public ANGLETest
    {
      public:
        ScissoredClearTest()
        {
            setWindowWidth(64);
            setWindowHeight(64);
            setConfigRedBits(8);
            setConfigGreenBits(8);
            setConfigBlueBits(8);
            setConfigAlphaBits(8);
            setConfigDepthBits(24);
            setConfigStencilBits(8);
        }
    };
    
    // Simple scissored clear.
    TEST_P(ScissoredClearTest, BasicScissoredColorClear)
    {
        const int w     = getWindowWidth();
        const int h     = getWindowHeight();
        const int whalf = w >> 1;
        const int hhalf = h >> 1;
    
        // Clear whole region to red.
        glClearColor(1.0, 0.0, 0.0, 1.0);
        glClear(GL_COLOR_BUFFER_BIT);
    
        // Enable scissor and clear to green.
        glEnable(GL_SCISSOR_TEST);
        glScissor(whalf / 2, hhalf / 2, whalf, whalf);
        glClearColor(0.0, 1.0, 0.0, 1.0);
        glClear(GL_COLOR_BUFFER_BIT);
        ASSERT_GL_NO_ERROR();
    
        // Check the four corners for the original clear color, and the middle for the scissored clear
        // color.
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(0, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(whalf, hhalf, GLColor::green) << "in-scissor area should be green";
    }
    
    // Tests combined scissored color+depth clear.
    TEST_P(ScissoredClearTest, ScissoredColorAndDepthClear)
    {
        const int w     = getWindowWidth();
        const int h     = getWindowHeight();
        const int whalf = w >> 1;
        const int hhalf = h >> 1;
    
        // Clear whole region to red/1.0f.
        glClearColor(1.0, 0.0, 0.0, 1.0);
        glClearDepthf(1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
        // Enable scissor and clear to green/0.5f.
        glEnable(GL_SCISSOR_TEST);
        glScissor(whalf / 2, hhalf / 2, whalf, whalf);
        glClearColor(0.0, 1.0, 0.0, 1.0);
        glClearDepthf(0.5f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        ASSERT_GL_NO_ERROR();
    
        // Check the four corners for the original clear color, and the middle for the scissored clear
        // color.
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(0, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(whalf, hhalf, GLColor::green) << "in-scissor area should be green";
    
        // Draw blue with depth 0.5f and depth test enabled - verify only the middle changes.
        glDisable(GL_SCISSOR_TEST);
        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_EQUAL);
        ANGLE_GL_PROGRAM(program, essl1_shaders::vs::Passthrough(), essl1_shaders::fs::Blue());
    
        // OpenGL uses a depth range of [-1,1] so pass in a z value of 0 to get 0.5 depth.
        drawQuad(program, essl1_shaders::PositionAttrib(), 0.0f);
    
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, 0, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(0, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(w - 1, h - 1, GLColor::red) << "out-of-scissor area should be red";
        EXPECT_PIXEL_COLOR_EQ(whalf, hhalf, GLColor::blue) << "in-scissor area should be blue";
    }
    
    // Tests combined color+depth clear.
    TEST_P(ClearTest, MaskedColorAndDepthClear)
    {
        // Flaky on Android Nexus 5x, possible driver bug.
        // TODO(jmadill): Re-enable when possible. http://anglebug.com/2548
        ANGLE_SKIP_TEST_IF(IsOpenGLES() && IsAndroid());
    
        // Clear to a random color and 1.0 depth.
        Vector4 color1(0.1f, 0.2f, 0.3f, 0.4f);
        GLColor color1RGB(color1);
    
        glClearColor(color1[0], color1[1], color1[2], color1[3]);
        glClearDepthf(1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        ASSERT_GL_NO_ERROR();
    
        // Verify color and was cleared correctly.
        EXPECT_PIXEL_COLOR_NEAR(0, 0, color1RGB, 1);
    
        // Use a color mask to clear to a second color and 0.5 depth.
        Vector4 color2(0.2f, 0.4f, 0.6f, 0.8f);
        GLColor color2RGB(color2);
        glClearColor(color2[0], color2[1], color2[2], color2[3]);
        glClearDepthf(0.5f);
        glColorMask(GL_TRUE, GL_FALSE, GL_TRUE, GL_FALSE);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
        ASSERT_GL_NO_ERROR();
    
        // Verify second clear mask worked as expected.
        GLColor color2Masked(color2RGB[0], color1RGB[1], color2RGB[2], color1RGB[3]);
        EXPECT_PIXEL_COLOR_EQ(0, 0, color2Masked);
    
        // We use a small shader to verify depth.
        ANGLE_GL_PROGRAM(depthTestProgram, essl1_shaders::vs::Passthrough(), essl1_shaders::fs::Blue());
        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_EQUAL);
        drawQuad(depthTestProgram, essl1_shaders::PositionAttrib(), 0.0f);
        EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::blue);
        ASSERT_GL_NO_ERROR();
    }
    
    // Test that just clearing a nonexistent drawbuffer of the default framebuffer doesn't cause an
    // assert.
    TEST_P(ClearTestES3, ClearBuffer1OnDefaultFramebufferNoAssert)
    {
        std::vector<GLuint> testUint(4);
        glClearBufferuiv(GL_COLOR, 1, testUint.data());
        std::vector<GLint> testInt(4);
        glClearBufferiv(GL_COLOR, 1, testInt.data());
        std::vector<GLfloat> testFloat(4);
        glClearBufferfv(GL_COLOR, 1, testFloat.data());
        EXPECT_GL_NO_ERROR();
    }
    
    // Use this to select which configurations (e.g. which renderer, which GLES major version) these
    // tests should be run against. Vulkan support disabled because of incomplete implementation.
    ANGLE_INSTANTIATE_TEST(ClearTest,
                           ES2_D3D9(),
                           ES2_D3D11(),
                           ES3_D3D11(),
                           ES2_OPENGL(),
                           ES3_OPENGL(),
                           ES2_OPENGLES(),
                           ES3_OPENGLES(),
                           ES2_VULKAN());
    ANGLE_INSTANTIATE_TEST(ClearTestES3, ES3_D3D11(), ES3_OPENGL(), ES3_OPENGLES());
    ANGLE_INSTANTIATE_TEST(ScissoredClearTest, ES2_D3D11(), ES2_OPENGL(), ES2_VULKAN());
    
    // Not all ANGLE backends support RGB backbuffers
    ANGLE_INSTANTIATE_TEST(ClearTestRGB, ES2_D3D11(), ES3_D3D11(), ES2_VULKAN());
    
    }  // anonymous namespace