GL_EXT_multisampled_render_to_texture extension. Part 2.

For textures that use this extension, a multisampled texture is
implicitly created for the texture.
Upon write or read, the multisampled texture is either return
to be drawn to or resolved and returned as a single sampled texture.

This is the functionality change with end2end tests.

Bug: angleproject:980428
Change-Id: I5776875a132fed7a3f4f00fb02f9e8e250684630
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1773717
Commit-Queue: Rafael Cintron <rafael.cintron@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/tests/gl_tests/MultisampledRenderToTextureTest.cpp b/src/tests/gl_tests/MultisampledRenderToTextureTest.cpp
new file mode 100644
index 0000000..cb90c5b
--- /dev/null
+++ b/src/tests/gl_tests/MultisampledRenderToTextureTest.cpp
@@ -0,0 +1,738 @@
+//
+// Copyright 2019 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.
+//
+
+// MultisampledRenderToTextureTest: Tests of EXT_multisampled_render_to_texture extension
+
+#include "test_utils/ANGLETest.h"
+#include "test_utils/gl_raii.h"
+
+using namespace angle;
+
+namespace
+{
+constexpr char kBasicVertexShader[] =
+    R"(attribute vec3 position;
+void main()
+{
+    gl_Position = vec4(position, 1);
+})";
+
+constexpr char kGreenFragmentShader[] =
+    R"(void main()
+{
+    gl_FragColor = vec4(0, 1, 0, 1);
+})";
+
+constexpr char kRedFragmentShader[] =
+    R"(void main()
+{
+    gl_FragColor = vec4(1, 0, 0, 1);
+})";
+
+constexpr char kVS[] =
+    "precision highp float;\n"
+    "attribute vec4 position;\n"
+    "varying vec2 texcoord;\n"
+    "\n"
+    "void main()\n"
+    "{\n"
+    "    gl_Position = position;\n"
+    "    texcoord = (position.xy * 0.5) + 0.5;\n"
+    "}\n";
+
+constexpr char kFS[] =
+    "precision highp float;\n"
+    "uniform sampler2D tex;\n"
+    "varying vec2 texcoord;\n"
+    "\n"
+    "void main()\n"
+    "{\n"
+    "    gl_FragColor = texture2D(tex, texcoord);\n"
+    "}\n";
+
+class MultisampledRenderToTextureTest : public ANGLETest
+{
+  protected:
+    MultisampledRenderToTextureTest()
+    {
+        setWindowWidth(64);
+        setWindowHeight(64);
+        setConfigRedBits(8);
+        setConfigGreenBits(8);
+        setConfigBlueBits(8);
+        setConfigAlphaBits(8);
+    }
+
+    void testSetUp() override {}
+
+    void testTearDown() override {}
+
+    void setupCopyTexProgram()
+    {
+        mCopyTextureProgram.makeRaster(kVS, kFS);
+        ASSERT_GL_TRUE(mCopyTextureProgram.valid());
+
+        mCopyTextureUniformLocation = glGetUniformLocation(mCopyTextureProgram, "tex");
+
+        ASSERT_GL_NO_ERROR();
+    }
+
+    void verifyResults(GLuint texture,
+                       GLubyte data[4],
+                       GLint fboSize,
+                       GLint xs,
+                       GLint ys,
+                       GLint xe,
+                       GLint ye)
+    {
+        glViewport(0, 0, fboSize, fboSize);
+
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
+        // Draw a quad with the target texture
+        glUseProgram(mCopyTextureProgram);
+        glBindTexture(GL_TEXTURE_2D, texture);
+        glUniform1i(mCopyTextureUniformLocation, 0);
+
+        drawQuad(mCopyTextureProgram, "position", 0.5f);
+
+        // Expect that the rendered quad has the same color as the source texture
+        EXPECT_PIXEL_NEAR(xs, ys, data[0], data[1], data[2], data[3], 1.0);
+        EXPECT_PIXEL_NEAR(xs, ye - 1, data[0], data[1], data[2], data[3], 1.0);
+        EXPECT_PIXEL_NEAR(xe - 1, ys, data[0], data[1], data[2], data[3], 1.0);
+        EXPECT_PIXEL_NEAR(xe - 1, ye - 1, data[0], data[1], data[2], data[3], 1.0);
+        EXPECT_PIXEL_NEAR((xs + xe) / 2, (ys + ye) / 2, data[0], data[1], data[2], data[3], 1.0);
+    }
+
+    void clearAndDrawQuad(GLuint program, GLsizei viewportWidth, GLsizei viewportHeight)
+    {
+        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+        glViewport(0, 0, viewportWidth, viewportHeight);
+        ASSERT_GL_NO_ERROR();
+
+        drawQuad(program, "position", 0.0f);
+    }
+
+    GLProgram mCopyTextureProgram;
+    GLint mCopyTextureUniformLocation = -1;
+};
+
+class MultisampledRenderToTextureES3Test : public MultisampledRenderToTextureTest
+{};
+
+// Checking against invalid parameters for RenderbufferStorageMultisampleEXT.
+TEST_P(MultisampledRenderToTextureTest, RenderbufferParameterCheck)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+
+    GLRenderbuffer renderbuffer;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+
+    // Positive test case
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT16, 64, 64);
+    ASSERT_GL_NO_ERROR();
+
+    GLint samples;
+    glGetIntegerv(GL_MAX_SAMPLES_EXT, &samples);
+    ASSERT_GL_NO_ERROR();
+    EXPECT_GE(samples, 1);
+
+    // Samples too large
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, samples + 1, GL_DEPTH_COMPONENT16, 64, 64);
+    ASSERT_GL_ERROR(GL_INVALID_VALUE);
+
+    // Renderbuffer size too large
+    GLint maxSize;
+    glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE, &maxSize);
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 2, GL_DEPTH_COMPONENT16, maxSize + 1,
+                                        maxSize);
+    ASSERT_GL_ERROR(GL_INVALID_VALUE);
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 2, GL_DEPTH_COMPONENT16, maxSize,
+                                        maxSize + 1);
+    ASSERT_GL_ERROR(GL_INVALID_VALUE);
+
+    // Retrieving samples
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT16, 64, 64);
+    GLint param = 0;
+    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_SAMPLES_EXT, &param);
+    // GE because samples may vary base on implementation. Spec says "the resulting value for
+    // RENDERBUFFER_SAMPLES_EXT is guaranteed to be greater than or equal to samples and no more
+    // than the next larger sample count supported by the implementation"
+    EXPECT_GE(param, 4);
+}
+
+// Checking against invalid parameters for FramebufferTexture2DMultisampleEXT.
+TEST_P(MultisampledRenderToTextureTest, Texture2DParameterCheck)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer fbo;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    // Positive test case
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    ASSERT_GL_NO_ERROR();
+
+    // Attachment not COLOR_ATTACHMENT0
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    ASSERT_GL_ERROR(GL_INVALID_ENUM);
+
+    // Target not framebuffer
+    glFramebufferTexture2DMultisampleEXT(GL_RENDERBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    ASSERT_GL_ERROR(GL_INVALID_ENUM);
+
+    GLint samples;
+    glGetIntegerv(GL_MAX_SAMPLES_EXT, &samples);
+    ASSERT_GL_NO_ERROR();
+    EXPECT_GE(samples, 1);
+
+    // Samples too large
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, samples + 1);
+    ASSERT_GL_ERROR(GL_INVALID_VALUE);
+
+    // Retrieving samples
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    GLint param = 0;
+    glGetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                          GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_SAMPLES_EXT, &param);
+    // GE because samples may vary base on implementation. Spec says "the resulting value for
+    // TEXTURE_SAMPLES_EXT is guaranteed to be greater than or equal to samples and no more than the
+    // next larger sample count supported by the implementation"
+    EXPECT_GE(param, 4);
+}
+
+// Checking against invalid parameters for FramebufferTexture2DMultisampleEXT (cubemap).
+TEST_P(MultisampledRenderToTextureTest, TextureCubeMapParameterCheck)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_CUBE_MAP, texture);
+    for (GLenum face = 0; face < 6; face++)
+    {
+        glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, GL_RGBA, 64, 64, 0, GL_RGBA,
+                     GL_UNSIGNED_BYTE, nullptr);
+        ASSERT_GL_NO_ERROR();
+    }
+
+    GLint samples;
+    glGetIntegerv(GL_MAX_SAMPLES_EXT, &samples);
+    ASSERT_GL_NO_ERROR();
+    EXPECT_GE(samples, 1);
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    for (GLenum face = 0; face < 6; face++)
+    {
+        // Positive test case
+        glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture, 0, 4);
+        ASSERT_GL_NO_ERROR();
+
+        // Attachment not COLOR_ATTACHMENT0
+        glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
+                                             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture, 0, 4);
+        ASSERT_GL_ERROR(GL_INVALID_ENUM);
+
+        // Target not framebuffer
+        glFramebufferTexture2DMultisampleEXT(GL_RENDERBUFFER, GL_COLOR_ATTACHMENT0,
+                                             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture, 0, 4);
+        ASSERT_GL_ERROR(GL_INVALID_ENUM);
+
+        // Samples too large
+        glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture, 0,
+                                             samples + 1);
+        ASSERT_GL_ERROR(GL_INVALID_VALUE);
+
+        // Retrieving samples
+        glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                             GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture, 0, 4);
+        GLint param = 0;
+        glGetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                              GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_SAMPLES_EXT,
+                                              &param);
+        // GE because samples may vary base on implementation. Spec says "the resulting value for
+        // TEXTURE_SAMPLES_EXT is guaranteed to be greater than or equal to samples and no more than
+        // the next larger sample count supported by the implementation"
+        EXPECT_GE(param, 4);
+    }
+}
+
+// Checking for framebuffer completeness using extension methods.
+TEST_P(MultisampledRenderToTextureTest, FramebufferCompleteness)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+
+    // Checking that Renderbuffer and texture2d having different number of samples results
+    // in a FRAMEBUFFER_INCOMPLETE_MULTISAMPLE
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    EXPECT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    GLRenderbuffer renderbuffer;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 8, GL_DEPTH_COMPONENT16, 64, 64);
+    ASSERT_GL_NO_ERROR();
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderbuffer);
+    EXPECT_GLENUM_EQ(GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE,
+                     glCheckFramebufferStatus(GL_FRAMEBUFFER));
+}
+
+// Draw test with color attachment only.
+TEST_P(MultisampledRenderToTextureTest, 2DColorAttachmentMultisampleDrawTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    // Set up texture and bind to FBO
+    GLsizei size = 6;
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    EXPECT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    // Set viewport and clear to black
+    glViewport(0, 0, size, size);
+    glClearColor(0.0, 0.0, 0.0, 1.0);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // Set up Green square program
+    ANGLE_GL_PROGRAM(program, kBasicVertexShader, kGreenFragmentShader);
+    glUseProgram(program);
+    GLint positionLocation = glGetAttribLocation(program, "position");
+    ASSERT_NE(-1, positionLocation);
+
+    setupQuadVertexBuffer(0.5f, 0.5f);
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);
+    glEnableVertexAttribArray(positionLocation);
+
+    // Draw green square
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    ASSERT_GL_NO_ERROR();
+
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::black);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::green);
+
+    // Set up Red square program
+    ANGLE_GL_PROGRAM(program2, kBasicVertexShader, kRedFragmentShader);
+    glUseProgram(program2);
+    GLint positionLocation2 = glGetAttribLocation(program2, "position");
+    ASSERT_NE(-1, positionLocation2);
+
+    setupQuadVertexBuffer(0.5f, 0.75f);
+    glVertexAttribPointer(positionLocation2, 3, GL_FLOAT, GL_FALSE, 0, 0);
+
+    // Draw red square
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    ASSERT_GL_NO_ERROR();
+
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::black);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::red);
+
+    glDisableVertexAttribArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+}
+
+// Draw test using both color and depth attachments.
+TEST_P(MultisampledRenderToTextureTest, 2DColorDepthMultisampleDrawTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    GLsizei size = 6;
+    // create complete framebuffer with depth buffer
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+
+    GLRenderbuffer renderbuffer;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT16, size, size);
+    ASSERT_GL_NO_ERROR();
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderbuffer);
+    EXPECT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    // Set viewport and clear framebuffer
+    glViewport(0, 0, size, size);
+    glClearColor(0.0, 0.0, 0.0, 1.0);
+    glClearDepthf(0.5f);
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    // Draw first green square
+    ANGLE_GL_PROGRAM(program, kBasicVertexShader, kGreenFragmentShader);
+    glEnable(GL_DEPTH_TEST);
+    glDepthFunc(GL_GREATER);
+    glUseProgram(program);
+    GLint positionLocation = glGetAttribLocation(program, "position");
+    ASSERT_NE(-1, positionLocation);
+
+    setupQuadVertexBuffer(0.8f, 0.5f);
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, 0);
+    glEnableVertexAttribArray(positionLocation);
+
+    // Tests that TRIANGLES works.
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    ASSERT_GL_NO_ERROR();
+
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::black);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::green);
+
+    // Draw red square behind green square
+    ANGLE_GL_PROGRAM(program2, kBasicVertexShader, kRedFragmentShader);
+    glUseProgram(program2);
+    GLint positionLocation2 = glGetAttribLocation(program2, "position");
+    ASSERT_NE(-1, positionLocation2);
+
+    setupQuadVertexBuffer(0.7f, 1.0f);
+    glVertexAttribPointer(positionLocation2, 3, GL_FLOAT, GL_FALSE, 0, 0);
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    ASSERT_GL_NO_ERROR();
+    glDisable(GL_DEPTH_TEST);
+
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::green);
+
+    glDisableVertexAttribArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+}
+
+// Read pixels with pack buffer. ES3+.
+TEST_P(MultisampledRenderToTextureES3Test, MultisampleReadPixelsTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+
+    // PBO only available ES3 and above
+    ANGLE_SKIP_TEST_IF(getClientMajorVersion() < 3);
+    GLsizei size = 6;
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, size, size);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    EXPECT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    // Set viewport and clear to red
+    glViewport(0, 0, size, size);
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    // Bind Pack Pixel Buffer and read to it
+    GLBuffer PBO;
+    glBindBuffer(GL_PIXEL_PACK_BUFFER, PBO);
+    glBufferData(GL_PIXEL_PACK_BUFFER, 4 * size * size, nullptr, GL_STATIC_DRAW);
+    glReadPixels(0, 0, size, size, GL_RGBA, GL_UNSIGNED_BYTE, 0);
+    ASSERT_GL_NO_ERROR();
+
+    // Retrieving pixel color
+    void *mappedPtr    = glMapBufferRange(GL_PIXEL_PACK_BUFFER, 0, 32, GL_MAP_READ_BIT);
+    GLColor *dataColor = static_cast<GLColor *>(mappedPtr);
+    EXPECT_GL_NO_ERROR();
+
+    EXPECT_EQ(GLColor::red, dataColor[0]);
+
+    glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
+    EXPECT_GL_NO_ERROR();
+}
+
+// CopyTexImage from a multisampled texture functionality test.
+TEST_P(MultisampledRenderToTextureTest, MultisampleCopyTexImageTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    GLsizei size = 16;
+
+    setupCopyTexProgram();
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    // Disable mipmapping
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+
+    // Set color for framebuffer
+    glClearColor(0.25f, 1.0f, 0.75f, 0.5f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    GLTexture copyToTex;
+    glBindTexture(GL_TEXTURE_2D, copyToTex);
+
+    // Disable mipmapping
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 0, 0, size, size, 0);
+    ASSERT_GL_NO_ERROR();
+
+    GLubyte expected[4] = {64, 255, 191, 255};
+    verifyResults(copyToTex, expected, size, 0, 0, size, size);
+}
+
+// CopyTexSubImage from a multisampled texture functionality test.
+TEST_P(MultisampledRenderToTextureTest, MultisampleCopyTexSubImageTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    GLsizei size = 16;
+
+    setupCopyTexProgram();
+
+    GLTexture texture;
+    // Create texture in copyFBO0 with color (.25, 1, .75, .5)
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    // Disable mipmapping
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+    GLFramebuffer copyFBO0;
+    glBindFramebuffer(GL_FRAMEBUFFER, copyFBO0);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+
+    // Set color for
+    glClearColor(0.25f, 1.0f, 0.75f, 0.5f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    // Create texture in copyFBO[1] with color (1, .75, .5, .25)
+    GLTexture texture1;
+    glBindTexture(GL_TEXTURE_2D, texture1);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    // Disable mipmapping
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+    GLFramebuffer copyFBO1;
+    glBindFramebuffer(GL_FRAMEBUFFER, copyFBO1);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture1, 0, 4);
+
+    // Set color for
+    glClearColor(1.0f, 0.75f, 0.5f, 0.25f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    GLTexture copyToTex;
+    glBindTexture(GL_TEXTURE_2D, copyToTex);
+
+    // Disable mipmapping
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+    // copyFBO0 -> copyToTex
+    // copyToTex should hold what was originally in copyFBO0 : (.25, 1, .75, .5)
+    glBindFramebuffer(GL_FRAMEBUFFER, copyFBO0);
+    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 0, 0, size, size, 0);
+    ASSERT_GL_NO_ERROR();
+
+    GLubyte expected0[4] = {64, 255, 191, 255};
+    verifyResults(copyToTex, expected0, size, 0, 0, size, size);
+
+    // copyFBO[1] - copySubImage -> copyToTex
+    // copyToTex should have subportion what was in copyFBO[1] : (1, .75, .5, .25)
+    // The rest should still be untouched: (.25, 1, .75, .5)
+    GLint half = size / 2;
+    glBindFramebuffer(GL_FRAMEBUFFER, copyFBO1);
+    glCopyTexSubImage2D(GL_TEXTURE_2D, 0, half, half, half, half, half, half);
+    ASSERT_GL_NO_ERROR();
+
+    GLubyte expected1[4] = {255, 191, 127, 255};
+    verifyResults(copyToTex, expected1, size, half, half, size, size);
+
+    // Verify rest is untouched
+    verifyResults(copyToTex, expected0, size, 0, 0, half, half);
+    verifyResults(copyToTex, expected0, size, 0, half, half, size);
+    verifyResults(copyToTex, expected0, size, half, 0, size, half);
+}
+
+// BlitFramebuffer functionality test. ES3+.
+TEST_P(MultisampledRenderToTextureES3Test, MultisampleBlitFramebufferTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    // blitFramebuffer only available ES3 and above
+    ANGLE_SKIP_TEST_IF(getClientMajorVersion() < 3);
+
+    GLsizei size = 16;
+
+    // Create multisampled framebuffer to use as source.
+    GLRenderbuffer depthMS;
+    glBindRenderbuffer(GL_RENDERBUFFER, depthMS.get());
+    glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT24, size, size);
+
+    GLTexture colorMS;
+    glBindTexture(GL_TEXTURE_2D, colorMS);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    GLFramebuffer fboMS;
+    glBindFramebuffer(GL_FRAMEBUFFER, fboMS);
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthMS.get());
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         colorMS, 0, 4);
+    ASSERT_GL_NO_ERROR();
+
+    // Clear depth to 0.5 and color to green.
+    glClearDepthf(0.5f);
+    glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
+    glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
+    glFlush();
+    ASSERT_GL_NO_ERROR();
+
+    // Draw red into the multisampled color buffer.
+    ANGLE_GL_PROGRAM(drawRed, essl1_shaders::vs::Simple(), essl1_shaders::fs::Red());
+    glEnable(GL_DEPTH_TEST);
+    glDepthFunc(GL_EQUAL);
+    drawQuad(drawRed.get(), essl1_shaders::PositionAttrib(), 0.0f);
+    ASSERT_GL_NO_ERROR();
+
+    // Create single sampled framebuffer to use as dest.
+    GLFramebuffer fboSS;
+    glBindFramebuffer(GL_FRAMEBUFFER, fboSS);
+    GLTexture colorSS;
+    glBindTexture(GL_TEXTURE_2D, colorSS);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size, size, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, colorSS, 0);
+    ASSERT_GL_NO_ERROR();
+
+    // Bind MS to READ as SS is already bound to DRAW.
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, fboMS.get());
+    glBlitFramebuffer(0, 0, size, size, 0, 0, size, size, GL_COLOR_BUFFER_BIT, GL_NEAREST);
+    ASSERT_GL_NO_ERROR();
+
+    // Bind SS to READ so we can readPixels from it
+    glBindFramebuffer(GL_FRAMEBUFFER, fboSS.get());
+
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+    EXPECT_PIXEL_COLOR_EQ(size - 1, 0, GLColor::red);
+    EXPECT_PIXEL_COLOR_EQ(0, size - 1, GLColor::red);
+    EXPECT_PIXEL_COLOR_EQ(size - 1, size - 1, GLColor::red);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::red);
+    ASSERT_GL_NO_ERROR();
+}
+
+// GenerateMipmap functionality test
+TEST_P(MultisampledRenderToTextureTest, MultisampleGenerateMipmapTest)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_EXT_multisampled_render_to_texture"));
+    GLsizei size = 64;
+    // Vertex Shader source
+    constexpr char kVS[] = R"(attribute vec4 position;
+varying vec2 vTexCoord;
+
+void main()
+{
+    gl_Position = position;
+    vTexCoord   = (position.xy * 0.5) + 0.5;
+})";
+
+    // Fragment Shader source
+    constexpr char kFS[] = R"(precision mediump float;
+uniform sampler2D uTexture;
+varying vec2 vTexCoord;
+
+void main()
+{
+    gl_FragColor = texture2D(uTexture, vTexCoord);
+})";
+
+    GLProgram m2DProgram;
+    m2DProgram.makeRaster(kVS, kFS);
+    ASSERT_GL_TRUE(m2DProgram.valid());
+
+    ASSERT_GL_NO_ERROR();
+
+    // Initialize texture with blue
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, size, size, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+
+    GLFramebuffer FBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
+    glFramebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                         texture, 0, 4);
+    ASSERT_GLENUM_EQ(GL_FRAMEBUFFER_COMPLETE, glCheckFramebufferStatus(GL_FRAMEBUFFER));
+    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    glViewport(0, 0, size, size);
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    ASSERT_GL_NO_ERROR();
+
+    // Generate mipmap
+    glGenerateMipmap(GL_TEXTURE_2D);
+    ASSERT_GL_NO_ERROR();
+
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
+
+    // Now draw the texture to various different sized areas.
+    clearAndDrawQuad(m2DProgram, size, size);
+    EXPECT_PIXEL_COLOR_EQ(size / 2, size / 2, GLColor::blue);
+
+    // Use mip level 1
+    clearAndDrawQuad(m2DProgram, size / 2, size / 2);
+    EXPECT_PIXEL_COLOR_EQ(size / 4, size / 4, GLColor::blue);
+
+    // Use mip level 2
+    clearAndDrawQuad(m2DProgram, size / 4, size / 4);
+    EXPECT_PIXEL_COLOR_EQ(size / 8, size / 8, GLColor::blue);
+
+    ASSERT_GL_NO_ERROR();
+}
+ANGLE_INSTANTIATE_TEST(MultisampledRenderToTextureTest,
+                       ES2_D3D9(),
+                       ES2_D3D11(),
+                       ES3_D3D11(),
+                       ES2_OPENGL(),
+                       ES3_OPENGL(),
+                       ES2_OPENGLES(),
+                       ES3_OPENGLES(),
+                       ES2_VULKAN(),
+                       ES3_VULKAN());
+ANGLE_INSTANTIATE_TEST(MultisampledRenderToTextureES3Test,
+                       ES3_D3D11(),
+                       ES3_OPENGL(),
+                       ES3_OPENGLES(),
+                       ES3_VULKAN());
+}  // namespace