third_party/angle/src/tests/gl_tests/ProvokingVertexTest.cpp - cobalt - Git at Google

 //
 // 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.
 //
 // ProvkingVertexTest:
 //   Tests on the conformance of the provoking vertex, which applies to flat
 //   shading and compatibility with D3D. See the section on 'flatshading'
 //   in the ES 3 specs.
 //

 #include "test_utils/ANGLETest.h"

 using namespace angle;

 namespace
 {

 class ProvokingVertexTest : public ANGLETest
 {
   protected:
     ProvokingVertexTest()
         : mProgram(0),
           mFramebuffer(0),
           mTexture(0),
           mTransformFeedback(0),
           mBuffer(0),
           mIntAttribLocation(-1)
     {
         setWindowWidth(64);
         setWindowHeight(64);
         setConfigRedBits(8);
         setConfigGreenBits(8);
         setConfigBlueBits(8);
         setConfigAlphaBits(8);
         setConfigDepthBits(24);
     }

     void testSetUp() override
     {
         constexpr char kVS[] =
             "#version 300 es\n"
             "in int intAttrib;\n"
             "in vec2 position;\n"
             "flat out int attrib;\n"
             "void main() {\n"
             "  gl_Position = vec4(position, 0, 1);\n"
             "  attrib = intAttrib;\n"
             "}";

         constexpr char kFS[] =
             "#version 300 es\n"
             "flat in int attrib;\n"
             "out int fragColor;\n"
             "void main() {\n"
             "  fragColor = attrib;\n"
             "}";

         std::vector<std::string> tfVaryings;
         tfVaryings.push_back("attrib");
         mProgram = CompileProgramWithTransformFeedback(kVS, kFS, tfVaryings, GL_SEPARATE_ATTRIBS);
         ASSERT_NE(0u, mProgram);

         glGenTextures(1, &mTexture);
         glBindTexture(GL_TEXTURE_2D, mTexture);
         glTexStorage2D(GL_TEXTURE_2D, 1, GL_R32I, getWindowWidth(), getWindowHeight());

         glGenFramebuffers(1, &mFramebuffer);
         glBindFramebuffer(GL_FRAMEBUFFER, mFramebuffer);
         glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, mTexture, 0);

         mIntAttribLocation = glGetAttribLocation(mProgram, "intAttrib");
         ASSERT_NE(-1, mIntAttribLocation);
         glEnableVertexAttribArray(mIntAttribLocation);

         ASSERT_GL_NO_ERROR();
     }

     void testTearDown() override
     {
         if (mProgram != 0)
         {
             glDeleteProgram(mProgram);
             mProgram = 0;
         }

         if (mFramebuffer != 0)
         {
             glDeleteFramebuffers(1, &mFramebuffer);
             mFramebuffer = 0;
         }

         if (mTexture != 0)
         {
             glDeleteTextures(1, &mTexture);
             mTexture = 0;
         }

         if (mTransformFeedback != 0)
         {
             glDeleteTransformFeedbacks(1, &mTransformFeedback);
             mTransformFeedback = 0;
         }

         if (mBuffer != 0)
         {
             glDeleteBuffers(1, &mBuffer);
             mBuffer = 0;
         }
     }

     GLuint mProgram;
     GLuint mFramebuffer;
     GLuint mTexture;
     GLuint mTransformFeedback;
     GLuint mBuffer;
     GLint mIntAttribLocation;
 };

 // Test drawing a simple triangle with flat shading, and different valued vertices.
 TEST_P(ProvokingVertexTest, FlatTriangle)
 {
     GLint vertexData[] = {1, 2, 3, 1, 2, 3};
     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     drawQuad(mProgram, "position", 0.5f);

     GLint pixelValue = 0;
     glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

     ASSERT_GL_NO_ERROR();
     EXPECT_EQ(vertexData[2], pixelValue);
 }

 // Ensure that any provoking vertex shenanigans still gives correct vertex streams.
 TEST_P(ProvokingVertexTest, FlatTriWithTransformFeedback)
 {
     // http://anglebug.com/4092
     ANGLE_SKIP_TEST_IF(IsAndroid() && IsVulkan());

     // TODO(cwallez) figure out why it is broken on AMD on Mac
     ANGLE_SKIP_TEST_IF(IsOSX() && IsAMD());

     glGenTransformFeedbacks(1, &mTransformFeedback);
     glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, mTransformFeedback);

     glGenBuffers(1, &mBuffer);
     glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, mBuffer);
     glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, 128, nullptr, GL_STREAM_DRAW);

     glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, mBuffer);

     GLint vertexData[] = {1, 2, 3, 1, 2, 3};
     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     glUseProgram(mProgram);
     glBeginTransformFeedback(GL_TRIANGLES);
     drawQuad(mProgram, "position", 0.5f);
     glEndTransformFeedback();
     glUseProgram(0);

     GLint pixelValue = 0;
     glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

     ASSERT_GL_NO_ERROR();
     EXPECT_EQ(vertexData[2], pixelValue);

     void *mapPointer =
         glMapBufferRange(GL_TRANSFORM_FEEDBACK_BUFFER, 0, sizeof(int) * 6, GL_MAP_READ_BIT);
     ASSERT_NE(nullptr, mapPointer);

     int *mappedInts = static_cast<int *>(mapPointer);
     for (unsigned int cnt = 0; cnt < 6; ++cnt)
     {
         EXPECT_EQ(vertexData[cnt], mappedInts[cnt]);
     }
 }

 // Test drawing a simple line with flat shading, and different valued vertices.
 TEST_P(ProvokingVertexTest, FlatLine)
 {
     // http://anglebug.com/4092
     ANGLE_SKIP_TEST_IF((IsWindows() || IsLinux()) && IsVulkan());
     GLfloat halfPixel = 1.0f / static_cast<GLfloat>(getWindowWidth());

     GLint vertexData[]     = {1, 2};
     GLfloat positionData[] = {-1.0f + halfPixel, -1.0f, -1.0f + halfPixel, 1.0f};

     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     GLint positionLocation = glGetAttribLocation(mProgram, "position");
     glEnableVertexAttribArray(positionLocation);
     glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

     glUseProgram(mProgram);
     glDrawArrays(GL_LINES, 0, 2);

     GLint pixelValue = 0;
     glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

     ASSERT_GL_NO_ERROR();
     EXPECT_EQ(vertexData[1], pixelValue);
 }

 // Test drawing a simple triangle strip with flat shading, and different valued vertices.
 TEST_P(ProvokingVertexTest, FlatTriStrip)
 {
     GLint vertexData[]     = {1, 2, 3, 4, 5, 6};
     GLfloat positionData[] = {-1.0f, -1.0f, -1.0f, 1.0f,  0.0f, -1.0f,
                               0.0f,  1.0f,  1.0f,  -1.0f, 1.0f, 1.0f};

     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     GLint positionLocation = glGetAttribLocation(mProgram, "position");
     glEnableVertexAttribArray(positionLocation);
     glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

     glUseProgram(mProgram);
     glDrawArrays(GL_TRIANGLE_STRIP, 0, 6);

     std::vector<GLint> pixelBuffer(getWindowWidth() * getWindowHeight(), 0);
     glReadPixels(0, 0, getWindowWidth(), getWindowHeight(), GL_RED_INTEGER, GL_INT,
                  &pixelBuffer[0]);

     ASSERT_GL_NO_ERROR();

     for (unsigned int triIndex = 0; triIndex < 4; ++triIndex)
     {
         GLfloat sumX = positionData[triIndex * 2 + 0] + positionData[triIndex * 2 + 2] +
                        positionData[triIndex * 2 + 4];
         GLfloat sumY = positionData[triIndex * 2 + 1] + positionData[triIndex * 2 + 3] +
                        positionData[triIndex * 2 + 5];

         float centerX = sumX / 3.0f * 0.5f + 0.5f;
         float centerY = sumY / 3.0f * 0.5f + 0.5f;
         unsigned int pixelX =
             static_cast<unsigned int>(centerX * static_cast<GLfloat>(getWindowWidth()));
         unsigned int pixelY =
             static_cast<unsigned int>(centerY * static_cast<GLfloat>(getWindowHeight()));
         unsigned int pixelIndex = pixelY * getWindowWidth() + pixelX;

         unsigned int provokingVertexIndex = triIndex + 2;

         EXPECT_EQ(vertexData[provokingVertexIndex], pixelBuffer[pixelIndex]);
     }
 }

 // Test drawing an indexed triangle strip with flat shading and primitive restart.
 TEST_P(ProvokingVertexTest, FlatTriStripPrimitiveRestart)
 {
     // TODO(jmadill): Implement on the D3D back-end.
     ANGLE_SKIP_TEST_IF(IsD3D11());

     GLint indexData[]      = {0, 1, 2, -1, 1, 2, 3, 4, -1, 3, 4, 5};
     GLint vertexData[]     = {1, 2, 3, 4, 5, 6};
     GLfloat positionData[] = {-1.0f, -1.0f, -1.0f, 1.0f,  0.0f, -1.0f,
                               0.0f,  1.0f,  1.0f,  -1.0f, 1.0f, 1.0f};

     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     GLint positionLocation = glGetAttribLocation(mProgram, "position");
     glEnableVertexAttribArray(positionLocation);
     glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

     glDisable(GL_CULL_FACE);
     glEnable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
     glUseProgram(mProgram);
     glDrawElements(GL_TRIANGLE_STRIP, 12, GL_UNSIGNED_INT, indexData);

     std::vector<GLint> pixelBuffer(getWindowWidth() * getWindowHeight(), 0);
     glReadPixels(0, 0, getWindowWidth(), getWindowHeight(), GL_RED_INTEGER, GL_INT,
                  &pixelBuffer[0]);

     ASSERT_GL_NO_ERROR();

     // Account for primitive restart when checking the tris.
     GLint triOffsets[] = {0, 4, 5, 9};

     for (unsigned int triIndex = 0; triIndex < 4; ++triIndex)
     {
         GLint vertexA = indexData[triOffsets[triIndex] + 0];
         GLint vertexB = indexData[triOffsets[triIndex] + 1];
         GLint vertexC = indexData[triOffsets[triIndex] + 2];

         GLfloat sumX =
             positionData[vertexA * 2] + positionData[vertexB * 2] + positionData[vertexC * 2];
         GLfloat sumY = positionData[vertexA * 2 + 1] + positionData[vertexB * 2 + 1] +
                        positionData[vertexC * 2 + 1];

         float centerX = sumX / 3.0f * 0.5f + 0.5f;
         float centerY = sumY / 3.0f * 0.5f + 0.5f;
         unsigned int pixelX =
             static_cast<unsigned int>(centerX * static_cast<GLfloat>(getWindowWidth()));
         unsigned int pixelY =
             static_cast<unsigned int>(centerY * static_cast<GLfloat>(getWindowHeight()));
         unsigned int pixelIndex = pixelY * getWindowWidth() + pixelX;

         unsigned int provokingVertexIndex = triIndex + 2;

         EXPECT_EQ(vertexData[provokingVertexIndex], pixelBuffer[pixelIndex]);
     }
 }

 // Test with FRONT_CONVENTION if we have ANGLE_provoking_vertex.
 TEST_P(ProvokingVertexTest, ANGLEProvokingVertex)
 {
     int32_t vertexData[] = {1, 2, 3};
     float positionData[] = {-1.0f, -1.0f, 3.0f, -1.0f, -1.0f, 3.0f};

     glEnableVertexAttribArray(mIntAttribLocation);
     glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

     GLint positionLocation = glGetAttribLocation(mProgram, "position");
     glEnableVertexAttribArray(positionLocation);
     glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

     glUseProgram(mProgram);
     ASSERT_GL_NO_ERROR();

     const auto &fnExpectId = [&](int id) {
         const int32_t zero[4] = {};
         glClearBufferiv(GL_COLOR, 0, zero);
         glDrawArrays(GL_TRIANGLES, 0, 3);

         int32_t pixelValue = 0;
         glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

         ASSERT_GL_NO_ERROR();
         EXPECT_EQ(vertexData[id], pixelValue);
     };

     fnExpectId(2);

     const bool hasExt = IsGLExtensionEnabled("GL_ANGLE_provoking_vertex");
     if (IsD3D11())
     {
         EXPECT_TRUE(hasExt);
     }
     if (hasExt)
     {
         glProvokingVertexANGLE(GL_FIRST_VERTEX_CONVENTION);
         fnExpectId(0);
     }
 }

 ANGLE_INSTANTIATE_TEST(ProvokingVertexTest, ES3_D3D11(), ES3_OPENGL(), ES3_OPENGLES());

 }  // anonymous namespace
	//
	// 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.
	//
	// ProvkingVertexTest:
	// Tests on the conformance of the provoking vertex, which applies to flat
	// shading and compatibility with D3D. See the section on 'flatshading'
	// in the ES 3 specs.
	//

	#include "test_utils/ANGLETest.h"

	using namespace angle;

	namespace
	{

	class ProvokingVertexTest : public ANGLETest
	{
	protected:
	ProvokingVertexTest()
	: mProgram(0),
	mFramebuffer(0),
	mTexture(0),
	mTransformFeedback(0),
	mBuffer(0),
	mIntAttribLocation(-1)
	{
	setWindowWidth(64);
	setWindowHeight(64);
	setConfigRedBits(8);
	setConfigGreenBits(8);
	setConfigBlueBits(8);
	setConfigAlphaBits(8);
	setConfigDepthBits(24);
	}

	void testSetUp() override
	{
	constexpr char kVS[] =
	"#version 300 es\n"
	"in int intAttrib;\n"
	"in vec2 position;\n"
	"flat out int attrib;\n"
	"void main() {\n"
	" gl_Position = vec4(position, 0, 1);\n"
	" attrib = intAttrib;\n"
	"}";

	constexpr char kFS[] =
	"#version 300 es\n"
	"flat in int attrib;\n"
	"out int fragColor;\n"
	"void main() {\n"
	" fragColor = attrib;\n"
	"}";

	std::vector<std::string> tfVaryings;
	tfVaryings.push_back("attrib");
	mProgram = CompileProgramWithTransformFeedback(kVS, kFS, tfVaryings, GL_SEPARATE_ATTRIBS);
	ASSERT_NE(0u, mProgram);

	glGenTextures(1, &mTexture);
	glBindTexture(GL_TEXTURE_2D, mTexture);
	glTexStorage2D(GL_TEXTURE_2D, 1, GL_R32I, getWindowWidth(), getWindowHeight());

	glGenFramebuffers(1, &mFramebuffer);
	glBindFramebuffer(GL_FRAMEBUFFER, mFramebuffer);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, mTexture, 0);

	mIntAttribLocation = glGetAttribLocation(mProgram, "intAttrib");
	ASSERT_NE(-1, mIntAttribLocation);
	glEnableVertexAttribArray(mIntAttribLocation);

	ASSERT_GL_NO_ERROR();
	}

	void testTearDown() override
	{
	if (mProgram != 0)
	{
	glDeleteProgram(mProgram);
	mProgram = 0;
	}

	if (mFramebuffer != 0)
	{
	glDeleteFramebuffers(1, &mFramebuffer);
	mFramebuffer = 0;
	}

	if (mTexture != 0)
	{
	glDeleteTextures(1, &mTexture);
	mTexture = 0;
	}

	if (mTransformFeedback != 0)
	{
	glDeleteTransformFeedbacks(1, &mTransformFeedback);
	mTransformFeedback = 0;
	}

	if (mBuffer != 0)
	{
	glDeleteBuffers(1, &mBuffer);
	mBuffer = 0;
	}
	}

	GLuint mProgram;
	GLuint mFramebuffer;
	GLuint mTexture;
	GLuint mTransformFeedback;
	GLuint mBuffer;
	GLint mIntAttribLocation;
	};

	// Test drawing a simple triangle with flat shading, and different valued vertices.
	TEST_P(ProvokingVertexTest, FlatTriangle)
	{
	GLint vertexData[] = {1, 2, 3, 1, 2, 3};
	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	drawQuad(mProgram, "position", 0.5f);

	GLint pixelValue = 0;
	glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

	ASSERT_GL_NO_ERROR();
	EXPECT_EQ(vertexData[2], pixelValue);
	}

	// Ensure that any provoking vertex shenanigans still gives correct vertex streams.
	TEST_P(ProvokingVertexTest, FlatTriWithTransformFeedback)
	{
	// http://anglebug.com/4092
	ANGLE_SKIP_TEST_IF(IsAndroid() && IsVulkan());

	// TODO(cwallez) figure out why it is broken on AMD on Mac
	ANGLE_SKIP_TEST_IF(IsOSX() && IsAMD());

	glGenTransformFeedbacks(1, &mTransformFeedback);
	glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, mTransformFeedback);

	glGenBuffers(1, &mBuffer);
	glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, mBuffer);
	glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, 128, nullptr, GL_STREAM_DRAW);

	glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, mBuffer);

	GLint vertexData[] = {1, 2, 3, 1, 2, 3};
	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	glUseProgram(mProgram);
	glBeginTransformFeedback(GL_TRIANGLES);
	drawQuad(mProgram, "position", 0.5f);
	glEndTransformFeedback();
	glUseProgram(0);

	GLint pixelValue = 0;
	glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

	ASSERT_GL_NO_ERROR();
	EXPECT_EQ(vertexData[2], pixelValue);

	void *mapPointer =
	glMapBufferRange(GL_TRANSFORM_FEEDBACK_BUFFER, 0, sizeof(int) * 6, GL_MAP_READ_BIT);
	ASSERT_NE(nullptr, mapPointer);

	int mappedInts = static_cast<int >(mapPointer);
	for (unsigned int cnt = 0; cnt < 6; ++cnt)
	{
	EXPECT_EQ(vertexData[cnt], mappedInts[cnt]);
	}
	}

	// Test drawing a simple line with flat shading, and different valued vertices.
	TEST_P(ProvokingVertexTest, FlatLine)
	{
	// http://anglebug.com/4092
	ANGLE_SKIP_TEST_IF((IsWindows() \|\| IsLinux()) && IsVulkan());
	GLfloat halfPixel = 1.0f / static_cast<GLfloat>(getWindowWidth());

	GLint vertexData[] = {1, 2};
	GLfloat positionData[] = {-1.0f + halfPixel, -1.0f, -1.0f + halfPixel, 1.0f};

	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	GLint positionLocation = glGetAttribLocation(mProgram, "position");
	glEnableVertexAttribArray(positionLocation);
	glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

	glUseProgram(mProgram);
	glDrawArrays(GL_LINES, 0, 2);

	GLint pixelValue = 0;
	glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

	ASSERT_GL_NO_ERROR();
	EXPECT_EQ(vertexData[1], pixelValue);
	}

	// Test drawing a simple triangle strip with flat shading, and different valued vertices.
	TEST_P(ProvokingVertexTest, FlatTriStrip)
	{
	GLint vertexData[] = {1, 2, 3, 4, 5, 6};
	GLfloat positionData[] = {-1.0f, -1.0f, -1.0f, 1.0f, 0.0f, -1.0f,
	0.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f};

	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	GLint positionLocation = glGetAttribLocation(mProgram, "position");
	glEnableVertexAttribArray(positionLocation);
	glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

	glUseProgram(mProgram);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 6);

	std::vector<GLint> pixelBuffer(getWindowWidth() * getWindowHeight(), 0);
	glReadPixels(0, 0, getWindowWidth(), getWindowHeight(), GL_RED_INTEGER, GL_INT,
	&pixelBuffer[0]);

	ASSERT_GL_NO_ERROR();

	for (unsigned int triIndex = 0; triIndex < 4; ++triIndex)
	{
	GLfloat sumX = positionData[triIndex * 2 + 0] + positionData[triIndex * 2 + 2] +
	positionData[triIndex * 2 + 4];
	GLfloat sumY = positionData[triIndex * 2 + 1] + positionData[triIndex * 2 + 3] +
	positionData[triIndex * 2 + 5];

	float centerX = sumX / 3.0f * 0.5f + 0.5f;
	float centerY = sumY / 3.0f * 0.5f + 0.5f;
	unsigned int pixelX =
	static_cast<unsigned int>(centerX * static_cast<GLfloat>(getWindowWidth()));
	unsigned int pixelY =
	static_cast<unsigned int>(centerY * static_cast<GLfloat>(getWindowHeight()));
	unsigned int pixelIndex = pixelY * getWindowWidth() + pixelX;

	unsigned int provokingVertexIndex = triIndex + 2;

	EXPECT_EQ(vertexData[provokingVertexIndex], pixelBuffer[pixelIndex]);
	}
	}

	// Test drawing an indexed triangle strip with flat shading and primitive restart.
	TEST_P(ProvokingVertexTest, FlatTriStripPrimitiveRestart)
	{
	// TODO(jmadill): Implement on the D3D back-end.
	ANGLE_SKIP_TEST_IF(IsD3D11());

	GLint indexData[] = {0, 1, 2, -1, 1, 2, 3, 4, -1, 3, 4, 5};
	GLint vertexData[] = {1, 2, 3, 4, 5, 6};
	GLfloat positionData[] = {-1.0f, -1.0f, -1.0f, 1.0f, 0.0f, -1.0f,
	0.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f};

	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	GLint positionLocation = glGetAttribLocation(mProgram, "position");
	glEnableVertexAttribArray(positionLocation);
	glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

	glDisable(GL_CULL_FACE);
	glEnable(GL_PRIMITIVE_RESTART_FIXED_INDEX);
	glUseProgram(mProgram);
	glDrawElements(GL_TRIANGLE_STRIP, 12, GL_UNSIGNED_INT, indexData);

	std::vector<GLint> pixelBuffer(getWindowWidth() * getWindowHeight(), 0);
	glReadPixels(0, 0, getWindowWidth(), getWindowHeight(), GL_RED_INTEGER, GL_INT,
	&pixelBuffer[0]);

	ASSERT_GL_NO_ERROR();

	// Account for primitive restart when checking the tris.
	GLint triOffsets[] = {0, 4, 5, 9};

	for (unsigned int triIndex = 0; triIndex < 4; ++triIndex)
	{
	GLint vertexA = indexData[triOffsets[triIndex] + 0];
	GLint vertexB = indexData[triOffsets[triIndex] + 1];
	GLint vertexC = indexData[triOffsets[triIndex] + 2];

	GLfloat sumX =
	positionData[vertexA * 2] + positionData[vertexB * 2] + positionData[vertexC * 2];
	GLfloat sumY = positionData[vertexA * 2 + 1] + positionData[vertexB * 2 + 1] +
	positionData[vertexC * 2 + 1];

	float centerX = sumX / 3.0f * 0.5f + 0.5f;
	float centerY = sumY / 3.0f * 0.5f + 0.5f;
	unsigned int pixelX =
	static_cast<unsigned int>(centerX * static_cast<GLfloat>(getWindowWidth()));
	unsigned int pixelY =
	static_cast<unsigned int>(centerY * static_cast<GLfloat>(getWindowHeight()));
	unsigned int pixelIndex = pixelY * getWindowWidth() + pixelX;

	unsigned int provokingVertexIndex = triIndex + 2;

	EXPECT_EQ(vertexData[provokingVertexIndex], pixelBuffer[pixelIndex]);
	}
	}

	// Test with FRONT_CONVENTION if we have ANGLE_provoking_vertex.
	TEST_P(ProvokingVertexTest, ANGLEProvokingVertex)
	{
	int32_t vertexData[] = {1, 2, 3};
	float positionData[] = {-1.0f, -1.0f, 3.0f, -1.0f, -1.0f, 3.0f};

	glEnableVertexAttribArray(mIntAttribLocation);
	glVertexAttribIPointer(mIntAttribLocation, 1, GL_INT, 0, vertexData);

	GLint positionLocation = glGetAttribLocation(mProgram, "position");
	glEnableVertexAttribArray(positionLocation);
	glVertexAttribPointer(positionLocation, 2, GL_FLOAT, GL_FALSE, 0, positionData);

	glUseProgram(mProgram);
	ASSERT_GL_NO_ERROR();

	const auto &fnExpectId = [&](int id) {
	const int32_t zero[4] = {};
	glClearBufferiv(GL_COLOR, 0, zero);
	glDrawArrays(GL_TRIANGLES, 0, 3);

	int32_t pixelValue = 0;
	glReadPixels(0, 0, 1, 1, GL_RED_INTEGER, GL_INT, &pixelValue);

	ASSERT_GL_NO_ERROR();
	EXPECT_EQ(vertexData[id], pixelValue);
	};

	fnExpectId(2);

	const bool hasExt = IsGLExtensionEnabled("GL_ANGLE_provoking_vertex");
	if (IsD3D11())
	{
	EXPECT_TRUE(hasExt);
	}
	if (hasExt)
	{
	glProvokingVertexANGLE(GL_FIRST_VERTEX_CONVENTION);
	fnExpectId(0);
	}
	}

	ANGLE_INSTANTIATE_TEST(ProvokingVertexTest, ES3_D3D11(), ES3_OPENGL(), ES3_OPENGLES());

	} // anonymous namespace