Don't expose non-conformant multisampling modes on GL

src/libANGLE/Caps.cpp

@@ -71,6 +71,15 @@ TextureCaps GenerateMinimumTextureCaps(GLenum sizedInternalFormat,
     caps.filterable = internalFormatInfo.filterSupport(clientVersion, extensions);
 
     caps.sampleCounts.insert(0);
+    if (internalFormatInfo.isRequiredRenderbufferFormat(clientVersion))
+    {
+        if ((clientVersion.major >= 3 && clientVersion.minor >= 1) ||
+            (clientVersion.major >= 3 && internalFormatInfo.componentType != GL_UNSIGNED_INT &&
+             internalFormatInfo.componentType != GL_INT))
+        {
+            caps.sampleCounts.insert(4);
+        }
+    }
 
     return caps;
 }

src/libANGLE/Context.cpp

@@ -2726,12 +2726,58 @@ void Context::updateCaps()
 
         // OpenGL ES does not support multisampling with non-rendererable formats
         // OpenGL ES 3.0 or prior does not support multisampling with integer formats
-        if (!formatInfo.renderSupport ||
+        if (!formatCaps.renderable ||
             (getClientVersion() < ES_3_1 &&
              (formatInfo.componentType == GL_INT || formatInfo.componentType == GL_UNSIGNED_INT)))
         {
             formatCaps.sampleCounts.clear();
         }
+        else
+        {
+            // We may have limited the max samples for some required renderbuffer formats due to
+            // non-conformant formats. In this case MAX_SAMPLES needs to be lowered accordingly.
+            GLuint formatMaxSamples = formatCaps.getMaxSamples();
+
+            // GLES 3.0.5 section 4.4.2.2: "Implementations must support creation of renderbuffers
+            // in these required formats with up to the value of MAX_SAMPLES multisamples, with the
+            // exception of signed and unsigned integer formats."
+            if (formatInfo.componentType != GL_INT && formatInfo.componentType != GL_UNSIGNED_INT &&
+                formatInfo.isRequiredRenderbufferFormat(getClientVersion()))
+            {
+                ASSERT(getClientVersion() < ES_3_0 || formatMaxSamples >= 4);
+                mCaps.maxSamples = std::min(mCaps.maxSamples, formatMaxSamples);
+            }
+
+            // Handle GLES 3.1 MAX_*_SAMPLES values similarly to MAX_SAMPLES.
+            if (getClientVersion() >= ES_3_1)
+            {
+                // GLES 3.1 section 9.2.5: "Implementations must support creation of renderbuffers
+                // in these required formats with up to the value of MAX_SAMPLES multisamples, with
+                // the exception that the signed and unsigned integer formats are required only to
+                // support creation of renderbuffers with up to the value of MAX_INTEGER_SAMPLES
+                // multisamples, which must be at least one."
+                if (formatInfo.componentType == GL_INT ||
+                    formatInfo.componentType == GL_UNSIGNED_INT)
+                {
+                    mCaps.maxIntegerSamples = std::min(mCaps.maxIntegerSamples, formatMaxSamples);
+                }
+
+                // GLES 3.1 section 19.3.1.
+                if (formatCaps.texturable)
+                {
+                    if (formatInfo.depthBits > 0)
+                    {
+                        mCaps.maxDepthTextureSamples =
+                            std::min(mCaps.maxDepthTextureSamples, formatMaxSamples);
+                    }
+                    else if (formatInfo.redBits > 0)
+                    {
+                        mCaps.maxColorTextureSamples =
+                            std::min(mCaps.maxColorTextureSamples, formatMaxSamples);
+                    }
+                }
+            }
+        }
 
         if (formatCaps.texturable && formatInfo.compressed)
         {

src/libANGLE/formatutils.cpp

@@ -327,6 +327,110 @@ GLenum InternalFormat::getReadPixelsType() const
     }
 }
 
+bool InternalFormat::isRequiredRenderbufferFormat(const Version &version) const
+{
+    // GLES 3.0.5 section 4.4.2.2:
+    // "Implementations are required to support the same internal formats for renderbuffers as the
+    // required formats for textures enumerated in section 3.8.3.1, with the exception of the color
+    // formats labelled "texture-only"."
+    if (!sized || compressed)
+    {
+        return false;
+    }
+
+    // Luma formats.
+    if (isLUMA())
+    {
+        return false;
+    }
+
+    // Depth/stencil formats.
+    if (depthBits > 0 || stencilBits > 0)
+    {
+        // GLES 2.0.25 table 4.5.
+        // GLES 3.0.5 section 3.8.3.1.
+        // GLES 3.1 table 8.14.
+
+        // Required formats in all versions.
+        switch (internalFormat)
+        {
+            case GL_DEPTH_COMPONENT16:
+            case GL_STENCIL_INDEX8:
+                // Note that STENCIL_INDEX8 is not mentioned in GLES 3.0.5 section 3.8.3.1, but it
+                // is in section 4.4.2.2.
+                return true;
+            default:
+                break;
+        }
+        if (version.major < 3)
+        {
+            return false;
+        }
+        // Required formats in GLES 3.0 and up.
+        switch (internalFormat)
+        {
+            case GL_DEPTH_COMPONENT32F:
+            case GL_DEPTH_COMPONENT24:
+            case GL_DEPTH32F_STENCIL8:
+            case GL_DEPTH24_STENCIL8:
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    // RGBA formats.
+    // GLES 2.0.25 table 4.5.
+    // GLES 3.0.5 section 3.8.3.1.
+    // GLES 3.1 table 8.13.
+
+    // Required formats in all versions.
+    switch (internalFormat)
+    {
+        case GL_RGBA4:
+        case GL_RGB5_A1:
+        case GL_RGB565:
+            return true;
+        default:
+            break;
+    }
+    if (version.major < 3)
+    {
+        return false;
+    }
+
+    if (format == GL_BGRA_EXT)
+    {
+        return false;
+    }
+
+    switch (componentType)
+    {
+        case GL_SIGNED_NORMALIZED:
+        case GL_FLOAT:
+            return false;
+        case GL_UNSIGNED_INT:
+        case GL_INT:
+            // Integer RGB formats are not required renderbuffer formats.
+            if (alphaBits == 0 && greenBits != 0)
+            {
+                return false;
+            }
+            // All integer R and RG formats are required.
+            // Integer RGBA formats including RGB10_A2_UI are required.
+            return true;
+        case GL_UNSIGNED_NORMALIZED:
+            if (internalFormat == GL_SRGB8)
+            {
+                return false;
+            }
+            return true;
+        default:
+            UNREACHABLE();
+            return false;
+    }
+}
+
 Format::Format(GLenum internalFormat) : Format(GetSizedInternalFormatInfo(internalFormat))
 {
 }

src/libANGLE/formatutils.h

@@ -85,6 +85,12 @@ struct InternalFormat
     GLenum getReadPixelsFormat() const;
     GLenum getReadPixelsType() const;
 
+    // Return true if the format is a required renderbuffer format in the given version of the core
+    // spec. Note that it isn't always clear whether all the rules that apply to core required
+    // renderbuffer formats also apply to additional formats added by extensions. Because of this
+    // extension formats are conservatively not included.
+    bool isRequiredRenderbufferFormat(const Version &version) const;
+
     bool operator==(const InternalFormat &other) const;
     bool operator!=(const InternalFormat &other) const;
 

src/libANGLE/renderer/gl/FunctionsGL.cpp

@@ -789,7 +789,8 @@ FunctionsGL::FunctionsGL()
       primitiveBoundingBox(nullptr),
       eglImageTargetRenderbufferStorageOES(nullptr),
       eglImageTargetTexture2DOES(nullptr),
-      discardFramebuffer(nullptr)
+      discardFramebuffer(nullptr),
+      getInternalformatSampleivNV(nullptr)
 {
 }
 
@@ -848,6 +849,9 @@ void FunctionsGL::initializeProcsDesktopGL()
     // Even though extensions are written against specific versions of GL, many drivers expose the extensions
     // in even older versions.  Always try loading the extensions regardless of GL version.
 
+    // GL_NV_internalformat_sample_query
+    ASSIGN_WITH_EXT("GL_NV_internalformat_sample_query", "glGetInternalformatSampleivNV", getInternalformatSampleivNV);
+
     // GL_ARB_program_interface_query (loading only functions relevant to GL_NV_path_rendering here)
     ASSIGN_WITH_EXT("GL_ARB_program_interface_query", "glGetProgramInterfaceiv", getProgramInterfaceiv);
     ASSIGN_WITH_EXT("GL_ARB_program_interface_query", "glGetProgramResourceName", getProgramResourceName);
@@ -1799,6 +1803,9 @@ void FunctionsGL::initializeProcsGLES()
 
     // clang-format off
 
+    // GL_NV_internalformat_sample_query
+    ASSIGN_WITH_EXT("GL_NV_internalformat_sample_query", "glGetInternalformatSampleivNV", getInternalformatSampleivNV);
+
     // GL_NV_path_rendering
     ASSIGN_WITH_EXT("GL_NV_path_rendering", "glMatrixLoadfEXT", matrixLoadEXT);
     ASSIGN_WITH_EXT("GL_NV_path_rendering", "glGenPathsNV", genPathsNV);

src/libANGLE/renderer/gl/FunctionsGL.h

@@ -782,6 +782,9 @@ class FunctionsGL
     // GL_EXT_discard_framebuffer
     PFNGLDISCARDFRAMEBUFFEREXTPROC discardFramebuffer;
 
+    // GL_NV_internalformat_sample_query
+    PFNGLGETINTERNALFORMATSAMPLEIVNVPROC getInternalformatSampleivNV;
+
   private:
     void initializeProcsDesktopGL();
     void initializeProcsGLES();

src/libANGLE/renderer/gl/formatutilsgl.cpp

@@ -188,9 +188,13 @@ static InternalFormatInfoMap BuildInternalFormatInfoMap()
     InsertFormatMapping(&map, GL_BGRA_EXT,          VersionOrExts(1, 2, "GL_EXT_bgra"),               AlwaysSupported(), VersionOrExts(1, 2, "GL_EXT_bgra"),            ExtsOnly("GL_EXT_texture_format_BGRA8888"), AlwaysSupported(), NeverSupported()                          );
 
     // Floating point formats
+    // Note that GL_EXT_texture_shared_exponent and GL_ARB_color_buffer_float suggest that RGB9_E5
+    // would be renderable, but once support for renderable float textures got rolled into core GL
+    // spec it wasn't intended to be renderable. In practice it's not reliably renderable even
+    // with the extensions, there's a known bug in at least NVIDIA driver version 370.
     //                       | Format              | OpenGL texture support                                       | Filter           | OpenGL render support                                                                  | OpenGL ES texture support                                         | Filter                                                 | OpenGL ES render support                                                        |
     InsertFormatMapping(&map, GL_R11F_G11F_B10F,    VersionOrExts(3, 0, "GL_EXT_packed_float"),                    AlwaysSupported(), VersionOrExts(3, 0, "GL_EXT_packed_float GL_ARB_color_buffer_float"),                    VersionOnly(3, 0),                                                  AlwaysSupported(),                                       ExtsOnly("GL_EXT_color_buffer_float")                                            );
-    InsertFormatMapping(&map, GL_RGB9_E5,           VersionOrExts(3, 0, "GL_EXT_texture_shared_exponent"),         AlwaysSupported(), VersionOrExts(3, 0, "GL_EXT_texture_shared_exponent GL_ARB_color_buffer_float"),         VersionOnly(3, 0),                                                  AlwaysSupported(),                                       NeverSupported()                                                                 );
+    InsertFormatMapping(&map, GL_RGB9_E5,           VersionOrExts(3, 0, "GL_EXT_texture_shared_exponent"),         AlwaysSupported(), NeverSupported(),                                                                        VersionOnly(3, 0),                                                  AlwaysSupported(),                                       NeverSupported()                                                                 );
     InsertFormatMapping(&map, GL_R16F,              VersionOrExts(3, 0, "GL_ARB_texture_rg ARB_texture_float"),    AlwaysSupported(), VersionOrExts(3, 0, "GL_ARB_texture_rg GL_ARB_texture_float GL_ARB_color_buffer_float"), VersionOrExts(3, 0, "GL_OES_texture_half_float GL_EXT_texture_rg"), VersionOrExts(3, 0, "GL_OES_texture_half_float_linear"), VersionOrExtsAndExts(3, 0, "GL_EXT_texture_rg", "GL_EXT_color_buffer_half_float"));
     InsertFormatMapping(&map, GL_RG16F,             VersionOrExts(3, 0, "GL_ARB_texture_rg ARB_texture_float"),    AlwaysSupported(), VersionOrExts(3, 0, "GL_ARB_texture_rg GL_ARB_texture_float GL_ARB_color_buffer_float"), VersionOrExts(3, 0, "GL_OES_texture_half_float GL_EXT_texture_rg"), VersionOrExts(3, 0, "GL_OES_texture_half_float_linear"), VersionOrExtsAndExts(3, 0, "GL_EXT_texture_rg", "GL_EXT_color_buffer_half_float"));
     InsertFormatMapping(&map, GL_RGB16F,            VersionOrExts(3, 0, "GL_ARB_texture_float"),                   AlwaysSupported(), VersionOrExts(3, 0, "GL_ARB_texture_float GL_ARB_color_buffer_float"),                   VersionOrExts(3, 0, "GL_OES_texture_half_float"),                   VersionOrExts(3, 0, "GL_OES_texture_half_float_linear"), ExtsOnly("GL_EXT_color_buffer_half_float")                                       );

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -109,9 +109,34 @@ static gl::TextureCaps GenerateTextureFormatCaps(const FunctionsGL *functions, G
             std::vector<GLint> samples(numSamples);
             functions->getInternalformativ(GL_RENDERBUFFER, internalFormat, GL_SAMPLES,
                                            static_cast<GLsizei>(samples.size()), &samples[0]);
+
+            GLenum queryInternalFormat = internalFormat;
+            if (internalFormat == GL_STENCIL_INDEX8)
+            {
+                // The query below does generates an error with STENCIL_INDEX8 on NVIDIA driver
+                // 382.33. So for now we assume that the same sampling modes are conformant for
+                // STENCIL_INDEX8 as for DEPTH24_STENCIL8. Clean this up once the driver is fixed.
+                // http://anglebug.com/2059
+                queryInternalFormat = GL_DEPTH24_STENCIL8;
+            }
             for (size_t sampleIndex = 0; sampleIndex < samples.size(); sampleIndex++)
             {
-                textureCaps.sampleCounts.insert(samples[sampleIndex]);
+                // Some NVIDIA drivers expose multisampling modes implemented as a combination of
+                // multisampling and supersampling. These are non-conformant and should not be
+                // exposed through ANGLE. Query which formats are conformant from the driver if
+                // supported.
+                GLint conformant = GL_TRUE;
+                if (functions->getInternalformatSampleivNV)
+                {
+                    functions->getInternalformatSampleivNV(GL_RENDERBUFFER, queryInternalFormat,
+                                                           samples[sampleIndex], GL_CONFORMANT_NV,
+                                                           1, &conformant);
+                    ASSERT(functions->getError() == GL_NO_ERROR);
+                }
+                if (conformant == GL_TRUE)
+                {
+                    textureCaps.sampleCounts.insert(samples[sampleIndex]);
+                }
             }
         }
     }