[Merge] (DirectGLES, GLState, GLImpl, ShaderTranspiler): land GL43 wave6 and wave7 with the image-uniform naming repair

MobileGL/MG_IntegrationTest/CMakeLists.txt

@@ -87,6 +87,8 @@ add_executable(MobileGLIntegrationTest
     Scenarios/Glsl420DeclarationScenario.cpp
     Scenarios/IoBlockNameCollisionScenario.cpp
     Scenarios/TessellationDrawModeScenario.cpp
+    Scenarios/GeometryDrawModeScenario.cpp
+    Scenarios/FormatlessImageBakeScenario.cpp
     Scenarios/FragmentOutputArrayIndexScenario.cpp
     Scenarios/BufferTextureScenario.cpp
     Scenarios/VertexAttribBindingScenario.cpp

MobileGL/MG_IntegrationTest/Scenarios/FormatlessImageBakeScenario.cpp

@@ -0,0 +1,211 @@
+// MobileGL - MobileGL/MG_IntegrationTest/Scenarios/FormatlessImageBakeScenario.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+//
+// Scenario - A FORMAT-LESS IMAGE UNIFORM WHOSE UNIT HOLDS A NON-CORE FORMAT.
+//
+// GLSL 4.20 lets a write-only image uniform omit its layout format; GLSL ES demands one, so
+// DirectGLES BAKES the format of whatever glBindImageTexture put on the unit into the
+// declaration. When that format is outside the GLSL ES core thirteen, the bake alone is not
+// enough - the baked declaration then has to go through the same channel-widening
+// WidenImageFormatsForEssl gives a DECLARED non-core format (see NonCoreImageFormatScenario for
+// the widening itself).
+//
+// The two routes had different arming. The declared route armed the widening on the format
+// alone; the baked route armed it only when the driver lacked GL_NV_image_formats. That reads
+// like an optimisation and is not one: SPIRV-Cross throws for its is_desktop_only_format set the
+// moment it targets ESSL, whatever the driver would have accepted, so on a driver that HAS the
+// extension the shader half of the widening stayed switched off while TextureImpl's storage/bind
+// half - which keys on SpirvCrossCanPrintEsslImageFormat, not on the driver bit - still ran. The
+// stage threw, the program linked without it, and every dispatch silently did nothing.
+//
+// KHR-GL43.stencil_texturing.functional is where it surfaced: its compute half writes through a
+// format-less `uimage2D` bound to an R8UI texture, and returned zeros for every texel.
+//
+// DISCRIMINATING ONLY WHERE THE DRIVER ADVERTISES GL_NV_image_formats - Mesa does, which is what
+// the software lanes run and where this was found. On Adreno 830 and both Malis the extension is
+// absent, the old code already armed the widening, and these cases pass before and after; they
+// are kept running there as a guard against the opposite mistake.
+
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <vector>
+
+#include "../Harness/HeadlessGL.h"
+#include "../Harness/ScenarioFixture.h"
+
+#ifdef GLAPI
+#undef GLAPI
+#endif
+#define GL_GLEXT_PROTOTYPES
+#include <GL/gl.h>
+#include <GL/glcorearb.h>
+#undef GL_GLEXT_PROTOTYPES
+
+namespace MGITest {
+    namespace {
+
+        constexpr int kExtent = 8;
+
+        // No layout format on uni_image on purpose: that is the whole subject. uni_source is a
+        // plain integer texture so nothing but the image declaration is in play.
+        const char* const kComputeSource = R"(#version 430 core
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+writeonly uniform uimage2D uni_image;
+uniform usampler2D uni_source;
+void main()
+{
+    ivec2 at = ivec2(gl_GlobalInvocationID.xy);
+    imageStore(uni_image, at, uvec4(texelFetch(uni_source, at, 0).r, 0u, 0u, 0u));
+}
+)";
+
+        class FormatlessImageBakeScenario : public ScenarioTest {
+        protected:
+            void SetUp() override {
+                ScenarioTest::SetUp();
+                if (!Ready()) return;
+                if (!BackendHostsCompute()) {
+                    GTEST_SKIP() << "no compute stage on " << Gl().BackendName() << " ("
+                                 << Gl().RendererString() << ")";
+                }
+            }
+
+            static bool BackendHostsCompute() {
+                GLint maxImageUnits = 0;
+                glGetIntegerv(GL_MAX_IMAGE_UNITS, &maxImageUnits);
+                DrainErrors();
+                return maxImageUnits >= 2;
+            }
+
+            static void DrainErrors() {
+                for (int i = 0; i < 16 && glGetError() != GL_NO_ERROR; ++i) {
+                }
+            }
+
+            static GLuint BuildCompute(const char* source, std::string& log) {
+                const GLuint cs = glCreateShader(GL_COMPUTE_SHADER);
+                glShaderSource(cs, 1, &source, nullptr);
+                glCompileShader(cs);
+                GLint ok = 0;
+                glGetShaderiv(cs, GL_COMPILE_STATUS, &ok);
+                if (!ok) {
+                    char buffer[2048] = "";
+                    glGetShaderInfoLog(cs, sizeof(buffer), nullptr, buffer);
+                    log = buffer;
+                    glDeleteShader(cs);
+                    return 0;
+                }
+                const GLuint program = glCreateProgram();
+                glAttachShader(program, cs);
+                glLinkProgram(program);
+                glGetProgramiv(program, GL_LINK_STATUS, &ok);
+                glDeleteShader(cs);
+                if (!ok) {
+                    char buffer[2048] = "";
+                    glGetProgramInfoLog(program, sizeof(buffer), nullptr, buffer);
+                    log = buffer;
+                    glDeleteProgram(program);
+                    return 0;
+                }
+                return program;
+            }
+
+            // internalFormat is the NON-CORE image format under test; the destination texture and
+            // the glBindImageTexture argument both use it, and the shader declares nothing.
+            void RunCopy(GLenum internalFormat, GLenum uploadFormat, GLenum uploadType) {
+                std::vector<GLuint> expected(kExtent * kExtent);
+                for (int i = 0; i < kExtent * kExtent; ++i) {
+                    expected[i] = static_cast<GLuint>(1 + i);
+                }
+
+                // Source: a core-format integer texture holding 1..64.
+                std::vector<GLubyte> sourceBytes(kExtent * kExtent);
+                for (int i = 0; i < kExtent * kExtent; ++i) {
+                    sourceBytes[i] = static_cast<GLubyte>(expected[i]);
+                }
+                GLuint sourceTexture = 0;
+                glGenTextures(1, &sourceTexture);
+                glBindTexture(GL_TEXTURE_2D, sourceTexture);
+                glTexStorage2D(GL_TEXTURE_2D, 1, GL_R8UI, kExtent, kExtent);
+                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, kExtent, kExtent, GL_RED_INTEGER, GL_UNSIGNED_BYTE,
+                                sourceBytes.data());
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+                // Destination: the format under test, zero-filled so "the dispatch did nothing"
+                // and "the dispatch wrote zeros" are the same observation the CTS made.
+                GLuint destTexture = 0;
+                glGenTextures(1, &destTexture);
+                glBindTexture(GL_TEXTURE_2D, destTexture);
+                glTexStorage2D(GL_TEXTURE_2D, 1, internalFormat, kExtent, kExtent);
+                const std::vector<GLubyte> zeros(static_cast<std::size_t>(kExtent) * kExtent * 8, 0);
+                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, kExtent, kExtent, uploadFormat, uploadType, zeros.data());
+                ASSERT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR)) << "destination storage";
+
+                std::string log;
+                const GLuint program = BuildCompute(kComputeSource, log);
+                ASSERT_NE(program, 0u) << "the format-less image program did not build: " << log;
+
+                glUseProgram(program);
+                glBindImageTexture(1, destTexture, 0, GL_FALSE, 0, GL_WRITE_ONLY, internalFormat);
+                glUniform1i(glGetUniformLocation(program, "uni_image"), 1);
+                glActiveTexture(GL_TEXTURE1);
+                glBindTexture(GL_TEXTURE_2D, sourceTexture);
+                glUniform1i(glGetUniformLocation(program, "uni_source"), 1);
+                ASSERT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR)) << "binding";
+
+                glDispatchCompute(kExtent, kExtent, 1);
+                glMemoryBarrier(GL_ALL_BARRIER_BITS);
+                EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR)) << "dispatch";
+
+                std::vector<GLuint> readback(kExtent * kExtent, 0xFFFFFFFFu);
+                glActiveTexture(GL_TEXTURE0);
+                glBindTexture(GL_TEXTURE_2D, destTexture);
+                glGetTexImage(GL_TEXTURE_2D, 0, GL_RED_INTEGER, GL_UNSIGNED_INT, readback.data());
+                EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR)) << "readback";
+
+                int offenders = 0;
+                for (int i = 0; i < kExtent * kExtent; ++i) {
+                    if (readback[i] != expected[i]) ++offenders;
+                }
+                EXPECT_EQ(offenders, 0) << "the dispatch wrote " << offenders << " of "
+                                        << (kExtent * kExtent) << " texels wrongly; texel 0 was "
+                                        << readback[0] << ", expected " << expected[0]
+                                        << ". A whole stage lost to the ESSL emitter looks exactly like this.";
+
+                glUseProgram(0);
+                glDeleteProgram(program);
+                glDeleteTextures(1, &sourceTexture);
+                glDeleteTextures(1, &destTexture);
+                DrainErrors();
+            }
+        };
+
+        // R8UI: one of the seven formats GLSL ES reaches only through GL_NV_image_formats AND one
+        // SPIRV-Cross refuses to print for ESSL, so it needs the widening in both driver modes.
+        TEST_F(FormatlessImageBakeScenario, R8uiBakedFromTheBoundUnitStillReachesTheDriver) {
+            if (!Ready()) GTEST_SKIP();
+            RunCopy(GL_R8UI, GL_RED_INTEGER, GL_UNSIGNED_BYTE);
+        }
+
+        // R16UI, from the same set, carried in RGBA16UI: the fix must not be R8UI-shaped.
+        TEST_F(FormatlessImageBakeScenario, R16uiBakedFromTheBoundUnitStillReachesTheDriver) {
+            if (!Ready()) GTEST_SKIP();
+            RunCopy(GL_R16UI, GL_RED_INTEGER, GL_UNSIGNED_SHORT);
+        }
+
+        // The control: R32UI is in the GLSL ES core thirteen, so it is baked and never widened.
+        // It passed before the fix and has to keep passing.
+        TEST_F(FormatlessImageBakeScenario, CoreFormatBakedFromTheBoundUnitIsUnaffected) {
+            if (!Ready()) GTEST_SKIP();
+            RunCopy(GL_R32UI, GL_RED_INTEGER, GL_UNSIGNED_INT);
+        }
+
+    } // namespace
+} // namespace MGITest

MobileGL/MG_IntegrationTest/Scenarios/GeometryDrawModeScenario.cpp

@@ -0,0 +1,298 @@
+// MobileGL - MobileGL/MG_IntegrationTest/Scenarios/GeometryDrawModeScenario.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+//
+// Scenario - A GEOMETRY SHADER'S INPUT PRIMITIVE CONSTRAINS THE DRAW MODE, AND
+// GL_NONE IS NOT A USABLE "NO GEOMETRY SHADER" SENTINEL.
+//
+// GL 4.6 core 11.3.1: mode must be one of the primitive types that decomposes into the
+// geometry shader's declared input primitive, or the draw is GL_INVALID_OPERATION. The
+// validator asked "is there a geometry stage?" by comparing the REFLECTED INPUT PRIMITIVE
+// against GL_NONE - and GL_NONE and GL_POINTS are both 0, so a `layout(points) in` geometry
+// shader answered "no geometry stage" and every mode sailed through. The rule was therefore
+// dead for exactly the geometry shaders whose input primitive rejects the most modes.
+//
+// KHR-GL43.transform_feedback.api_errors_test is where it showed: it draws a points-in
+// geometry program with GL_LINES through glDrawTransformFeedbackInstanced and requires
+// INVALID_OPERATION. The bug is not specific to that entry point - every draw shares this
+// validator - so the ordinary glDrawArrays spelling is pinned here too, and the lines-in
+// program is the control that proves the rule was not simply widened.
+//
+// Needs a real context: the validator returns before this rule when no backend object is
+// active, so the GPU-free negative-API suite cannot reach it.
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "../Harness/HeadlessGL.h"
+#include "../Harness/ScenarioFixture.h"
+
+#ifdef GLAPI
+#undef GLAPI
+#endif
+#define GL_GLEXT_PROTOTYPES
+#include <GL/gl.h>
+#include <GL/glcorearb.h>
+#undef GL_GLEXT_PROTOTYPES
+
+namespace MGITest {
+    namespace {
+
+        const char* const kVertexSource = R"(#version 420 core
+void main()
+{
+    gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
+}
+)";
+
+        // The input primitive the CTS case uses, and the one the GL_NONE sentinel erased.
+        // `result` is here so the same program can be captured with transform feedback.
+        const char* const kPointsInGeometrySource = R"(#version 420 core
+layout(points) in;
+layout(points, max_vertices = 1) out;
+out float result;
+void main()
+{
+    gl_Position = gl_in[0].gl_Position;
+    result = 1.0;
+    EmitVertex();
+}
+)";
+
+        const char* const kLinesInGeometrySource = R"(#version 420 core
+layout(lines) in;
+layout(points, max_vertices = 1) out;
+void main()
+{
+    gl_Position = gl_in[0].gl_Position;
+    EmitVertex();
+}
+)";
+
+        const char* const kFragmentSource = R"(#version 420 core
+out vec4 fragColor;
+void main()
+{
+    fragColor = vec4(0.0, 1.0, 0.0, 1.0);
+}
+)";
+
+        class GeometryDrawModeScenario : public ScenarioTest {
+        protected:
+            void SetUp() override {
+                ScenarioTest::SetUp();
+                if (!Ready()) return;
+                glGenVertexArrays(1, &m_vao);
+                glBindVertexArray(m_vao);
+                if (!BackendHostsGeometry()) {
+                    GTEST_SKIP() << "no geometry stage on " << Gl().BackendName() << " ("
+                                 << Gl().RendererString() << "); there is no input primitive to validate";
+                }
+            }
+
+            void TearDown() override {
+                if (!Ready()) return;
+                glUseProgram(0);
+                for (const GLuint program : m_programs) {
+                    glDeleteProgram(program);
+                }
+                m_programs.clear();
+                glBindVertexArray(0);
+                if (m_vao != 0) glDeleteVertexArrays(1, &m_vao);
+                m_vao = 0;
+            }
+
+            // The same real-backend probe IoBlockNameCollisionScenario uses: 0 on a DirectGLES
+            // driver without GL_EXT_geometry_shader and on a DirectVulkan device without the
+            // geometryShader feature.
+            static bool BackendHostsGeometry() {
+                GLint maxGeometryOutputVertices = 0;
+                glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES, &maxGeometryOutputVertices);
+                DrainErrors();
+                return maxGeometryOutputVertices >= 4;
+            }
+
+            static void DrainErrors() {
+                for (int i = 0; i < 16 && glGetError() != GL_NO_ERROR; ++i) {
+                }
+            }
+
+            GLuint BuildProgram(const char* geometrySource, const char* capturedVarying = nullptr) {
+                const std::vector<std::pair<GLenum, const char*>> stages = {
+                    {GL_VERTEX_SHADER, kVertexSource},
+                    {GL_GEOMETRY_SHADER, geometrySource},
+                    {GL_FRAGMENT_SHADER, kFragmentSource}};
+
+                std::vector<GLuint> shaders;
+                bool ok = true;
+                for (const auto& [stage, source] : stages) {
+                    const GLuint shader = glCreateShader(stage);
+                    glShaderSource(shader, 1, &source, nullptr);
+                    glCompileShader(shader);
+                    GLint compiled = 0;
+                    glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+                    shaders.push_back(shader);
+                    if (!compiled) {
+                        m_buildLog = InfoLog(shader, true);
+                        ok = false;
+                        break;
+                    }
+                }
+                if (!ok) {
+                    for (const GLuint shader : shaders) glDeleteShader(shader);
+                    return 0;
+                }
+
+                const GLuint program = glCreateProgram();
+                for (const GLuint shader : shaders) glAttachShader(program, shader);
+                if (capturedVarying != nullptr) {
+                    glTransformFeedbackVaryings(program, 1, &capturedVarying, GL_INTERLEAVED_ATTRIBS);
+                }
+                glLinkProgram(program);
+                GLint linked = 0;
+                glGetProgramiv(program, GL_LINK_STATUS, &linked);
+                for (const GLuint shader : shaders) glDeleteShader(shader);
+                if (!linked) {
+                    m_buildLog = InfoLog(program, false);
+                    glDeleteProgram(program);
+                    return 0;
+                }
+                m_programs.push_back(program);
+                return program;
+            }
+
+            static std::string InfoLog(GLuint object, bool isShader) {
+                GLint length = 0;
+                if (isShader) {
+                    glGetShaderiv(object, GL_INFO_LOG_LENGTH, &length);
+                } else {
+                    glGetProgramiv(object, GL_INFO_LOG_LENGTH, &length);
+                }
+                std::vector<char> buffer(static_cast<std::size_t>(length) + 1, '\0');
+                if (isShader) {
+                    glGetShaderInfoLog(object, length + 1, nullptr, buffer.data());
+                } else {
+                    glGetProgramInfoLog(object, length + 1, nullptr, buffer.data());
+                }
+                return buffer.data();
+            }
+
+            const std::string& BuildLog() const { return m_buildLog; }
+
+            GLuint m_vao = 0;
+            std::vector<GLuint> m_programs;
+            std::string m_buildLog;
+        };
+
+        // GL_POINTS is the only mode that decomposes into a points input primitive.
+        TEST_F(GeometryDrawModeScenario, PointsInGeometryProgramRejectsEveryOtherMode) {
+            if (!Ready()) GTEST_SKIP();
+
+            const GLuint program = BuildProgram(kPointsInGeometrySource);
+            ASSERT_NE(program, 0u) << "the points-in geometry program did not build: " << BuildLog();
+
+            glUseProgram(program);
+            DrainErrors();
+
+            for (const GLenum mode :
+                 {static_cast<GLenum>(GL_LINES), static_cast<GLenum>(GL_LINE_STRIP),
+                  static_cast<GLenum>(GL_TRIANGLES), static_cast<GLenum>(GL_TRIANGLE_STRIP)}) {
+                glDrawArrays(mode, 0, 3);
+                EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_INVALID_OPERATION))
+                    << "mode " << mode << " does not decompose into the geometry shader's points input";
+                DrainErrors();
+            }
+
+            // The one mode that IS compatible still draws.
+            glDrawArrays(GL_POINTS, 0, 1);
+            EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR));
+            DrainErrors();
+        }
+
+        // The same rule reached through glDrawTransformFeedback*, which is the spelling the CTS
+        // case asks about. The capture span is really completed first, so GL_POINTS comes back
+        // GL_NO_ERROR: without that the draw would report INVALID_OPERATION for the
+        // never-ended-a-span reason instead and the case could not tell the two apart.
+        TEST_F(GeometryDrawModeScenario, PointsInGeometryProgramRejectsNonPointModesOnFeedbackDraws) {
+            if (!Ready()) GTEST_SKIP();
+
+            const GLuint program = BuildProgram(kPointsInGeometrySource, "result");
+            ASSERT_NE(program, 0u) << "the points-in geometry program did not build: " << BuildLog();
+
+            GLuint feedback = 0;
+            glGenTransformFeedbacks(1, &feedback);
+            glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, feedback);
+            GLuint captureBuffer = 0;
+            glGenBuffers(1, &captureBuffer);
+            glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, captureBuffer);
+            glBufferData(GL_TRANSFORM_FEEDBACK_BUFFER, 64, nullptr, GL_STATIC_DRAW);
+            glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, captureBuffer);
+            glUseProgram(program);
+            DrainErrors();
+
+            glBeginTransformFeedback(GL_POINTS);
+            glDrawArrays(GL_POINTS, 0, 1);
+            glEndTransformFeedback();
+            ASSERT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR)) << "the capture span did not complete";
+
+            glDrawTransformFeedbackInstanced(GL_LINES, feedback, 1);
+            EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_INVALID_OPERATION))
+                << "glDrawTransformFeedbackInstanced must honour the geometry input primitive";
+            DrainErrors();
+
+            glDrawTransformFeedbackStreamInstanced(GL_LINES, feedback, 0, 1);
+            EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_INVALID_OPERATION))
+                << "glDrawTransformFeedbackStreamInstanced must honour the geometry input primitive";
+            DrainErrors();
+
+            // The compatible mode replays the captured span with no error at all, which is what
+            // makes the two assertions above about the MODE and not about the span.
+            glDrawTransformFeedbackInstanced(GL_POINTS, feedback, 1);
+            EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR))
+                << "a compatible mode must still replay the captured span";
+            DrainErrors();
+
+            glUseProgram(0);
+            glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, 0);
+            glBindBuffer(GL_TRANSFORM_FEEDBACK_BUFFER, 0);
+            glDeleteBuffers(1, &captureBuffer);
+            glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, 0);
+            glDeleteTransformFeedbacks(1, &feedback);
+            DrainErrors();
+        }
+
+        // The control: a lines-in geometry shader is a NON-zero input primitive, so it exercised
+        // the rule even before the fix. It must still accept the line modes and still reject the
+        // others - a fix that widened the rule instead of repairing its guard breaks this.
+        TEST_F(GeometryDrawModeScenario, LinesInGeometryProgramStillAcceptsLineModesOnly) {
+            if (!Ready()) GTEST_SKIP();
+
+            const GLuint program = BuildProgram(kLinesInGeometrySource);
+            ASSERT_NE(program, 0u) << "the lines-in geometry program did not build: " << BuildLog();
+
+            glUseProgram(program);
+            DrainErrors();
+
+            for (const GLenum mode : {static_cast<GLenum>(GL_LINES), static_cast<GLenum>(GL_LINE_STRIP),
+                                      static_cast<GLenum>(GL_LINE_LOOP)}) {
+                glDrawArrays(mode, 0, 2);
+                EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_NO_ERROR))
+                    << "mode " << mode << " decomposes into lines and must be accepted";
+                DrainErrors();
+            }
+
+            for (const GLenum mode : {static_cast<GLenum>(GL_POINTS), static_cast<GLenum>(GL_TRIANGLES)}) {
+                glDrawArrays(mode, 0, 3);
+                EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_INVALID_OPERATION))
+                    << "mode " << mode << " does not decompose into lines";
+                DrainErrors();
+            }
+        }
+
+    } // namespace
+} // namespace MGITest