[Fix] (MG_Backend, MG_Impl/GLImpl, MG_Util): make anisotropic filtering actually reachable - advertise GL_EXT/ARB_texture_filter_anisotropic only where the host driver or the samplerAnisotropy device feature supports it, answer GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT from the backend limit, and honor the sampler state on DirectVulkan (feature enable, limit clamp, LINEAR-only gate, resolved value in the sampler cache key)

MobileGL/MG_Backend/BackendObject.h

@@ -232,6 +232,9 @@ namespace MobileGL {
 
         struct DynamicBackendParameters {
             SizeT UniformBufferOffsetAlignment = 256;
+            // GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT. 1.0 means the backend cannot filter anisotropically,
+            // which is also why the extension is not advertised in that case.
+            Float MaxTextureMaxAnisotropy = 1.0f;
             Float AliasedLineWidthRangeMin = 1.0f;
             Float AliasedLineWidthRangeMax = 1.0f;
             Float SmoothLineWidthRangeMin = 1.0f;

MobileGL/MG_Backend/DirectGLES/BackendObject_DirectGLES.cpp

@@ -605,9 +605,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
                     {
                         .TargetGLVersion = {3, 3, 0},   // Target OpenGL Version
                         .TargetGLSLVersion = {4, 6, 0}, // Target Shading Language Version
-                        // Baseline advertisement (no timer queries yet); reconciled once
-                        // the ES capabilities exist, see UpdateAdvertisedTimerQueryExtension.
-                        .Extensions = BuildAdvertisedExtensions(false),
+                        // Baseline advertisement (no timer queries / anisotropy yet); reconciled
+                        // once the ES capabilities exist, see UpdateAdvertisedCapabilityExtensions.
+                        .Extensions = BuildAdvertisedExtensions(false, false),
                         .IsCompatibilityProfile = false // Is Compatibility Profile
                     },
                 .StaticBackendCapability = {.AllowVSOnlyPrograms = false} // Backend Capability
@@ -627,8 +627,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
         // thread can only observe the extension string after the
         // advertisement for its context has settled; rebuilding the whole
         // list keeps the re-run after a context recreation idempotent.
-        void UpdateAdvertisedTimerQueryExtension() {
-            MutableRendererInfo().RendererGLInfo.Extensions = BuildAdvertisedExtensions(AreTimerQueriesSupported());
+        void UpdateAdvertisedCapabilityExtensions(Bool anisotropicFilteringSupported) {
+            MutableRendererInfo().RendererGLInfo.Extensions =
+                BuildAdvertisedExtensions(AreTimerQueriesSupported(), anisotropicFilteringSupported);
         }
     } // namespace
 
@@ -672,11 +673,11 @@ namespace MobileGL::MG_Backend::DirectGLES {
             return false;
         }
         DirectGLES::SetGLESCapabilities(m_GLESCapabilities);
-        // Now that g_GLESCapabilities knows about GL_EXT_disjoint_timer_query,
-        // reconcile the E_GL_ARB_timer_query advertisement (see the comment on
-        // UpdateAdvertisedTimerQueryExtension for why it cannot happen when
-        // the extension list is first built).
-        UpdateAdvertisedTimerQueryExtension();
+        // Now that g_GLESCapabilities knows about GL_EXT_disjoint_timer_query and
+        // GL_EXT_texture_filter_anisotropic, reconcile the advertisement (see the comment on
+        // UpdateAdvertisedCapabilityExtensions for why it cannot happen when the extension
+        // list is first built).
+        UpdateAdvertisedCapabilityExtensions(m_GLESCapabilities.SupportsTextureFilterAnisotropy);
         UpdateDynamicBackendParameters();
         PopulateFormatCapabilities(m_GLESFunctions, m_GLESCapabilities, MutableFormatCapabilities());
         PrintFormatCapabilities(GetFormatCapabilities());
@@ -818,7 +819,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
         return MutableRendererInfo();
     }
 
-    Vector<GLExtension> BuildAdvertisedExtensions(Bool timerQueriesSupported) {
+    Vector<GLExtension> BuildAdvertisedExtensions(Bool timerQueriesSupported, Bool anisotropicFilteringSupported) {
         Vector<GLExtension> extensions = {V_OpenGL30, V_OpenGL31, V_OpenGL32,
                                           V_OpenGL33, E_GL_ARB_draw_buffers_blend, E_GL_ARB_compute_shader,
                                           E_GL_ARB_shader_storage_buffer_object, E_GL_ARB_shader_image_load_store,
@@ -836,6 +837,14 @@ namespace MobileGL::MG_Backend::DirectGLES {
         if (timerQueriesSupported && !MG_Config::Features.DisableTimerQuery) {
             extensions.push_back(E_GL_ARB_timer_query);
         }
+        // Only advertised when the host ES driver actually filters anisotropically: the sampler
+        // state is accepted regardless, but forwarding it would be a no-op without the extension,
+        // and an app that trusts the string (LWJGL builds GLCapabilities from it) would silently
+        // get plain trilinear.
+        if (anisotropicFilteringSupported) {
+            extensions.push_back(E_GL_EXT_texture_filter_anisotropic);
+            extensions.push_back(E_GL_ARB_texture_filter_anisotropic);
+        }
         return extensions;
     }
 
@@ -940,6 +949,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
 
     void BackendObject_DirectGLES::UpdateDynamicBackendParameters() {
         m_dynamicParameters.UniformBufferOffsetAlignment = m_GLESCapabilities.UniformBufferOffsetAlignment;
+        m_dynamicParameters.MaxTextureMaxAnisotropy = m_GLESCapabilities.MaxTextureMaxAnisotropy;
         m_dynamicParameters.AliasedLineWidthRangeMin = m_GLESCapabilities.AliasedLineWidthRangeMin;
         m_dynamicParameters.AliasedLineWidthRangeMax = m_GLESCapabilities.AliasedLineWidthRangeMax;
         m_dynamicParameters.SmoothLineWidthRangeMin = m_GLESCapabilities.SmoothLineWidthRangeMin;

MobileGL/MG_Backend/DirectGLES/BackendObject_DirectGLES.h

@@ -66,9 +66,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
     const RendererInfo& GetRendererIdentity();
 
     // The full OpenGL extension list Espryt advertises (glGetString(GL_EXTENSIONS))
-    // for a device whose timer queries are (or are not) usable. The
-    // MOBILEGL_DISABLE_TIMERQUERY escape hatch is applied inside.
-    Vector<GLExtension> BuildAdvertisedExtensions(Bool timerQueriesSupported);
+    // for a device whose timer queries / anisotropic filtering are (or are not) usable.
+    // The MOBILEGL_DISABLE_TIMERQUERY escape hatch is applied inside.
+    Vector<GLExtension> BuildAdvertisedExtensions(Bool timerQueriesSupported, Bool anisotropicFilteringSupported);
 
     // Format: <OpenGL ES Renderer>, OpenGL ES <Major>.<Minor> — the exact string an
     // initialized backend returns from GetBackendAPIVersionString (and that ends up

MobileGL/MG_Backend/DirectVulkan/BackendObject_DirectVulkan.cpp

@@ -488,14 +488,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                     .TargetGLSLVersion = {4, 6, 0},
                     // Baseline advertisement (no shader subgroup, no timer queries); a
                     // live backend reconciles its copy in UpdateAdvertisedExtensions.
-                    .Extensions = BuildAdvertisedExtensions(false, false),
+                    .Extensions = BuildAdvertisedExtensions(false, false, false),
                     .IsCompatibilityProfile = false
                 },
             .StaticBackendCapability = {.AllowVSOnlyPrograms = false}};
         return rendererInfo;
     }
 
-    Vector<GLExtension> BuildAdvertisedExtensions(Bool shaderSubgroupSupported, Bool timerQueriesSupported) {
+    Vector<GLExtension> BuildAdvertisedExtensions(Bool shaderSubgroupSupported, Bool timerQueriesSupported,
+                                                  Bool anisotropicFilteringSupported) {
         Vector<GLExtension> extensions = {V_OpenGL30, V_OpenGL31, V_OpenGL32,
                                           V_OpenGL33, E_GL_ARB_draw_buffers_blend, E_GL_ARB_compute_shader,
                                           E_GL_ARB_shader_storage_buffer_object, E_GL_ARB_shader_image_load_store,
@@ -516,6 +517,13 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         if (timerQueriesSupported && !MG_Config::Features.DisableTimerQuery) {
             extensions.push_back(E_GL_ARB_timer_query);
         }
+        // Only advertised when the samplerAnisotropy device feature was granted: without it the
+        // sampler state is accepted but never applied, and an app trusting the string (LWJGL builds
+        // GLCapabilities from it) would think it enabled anisotropic filtering.
+        if (anisotropicFilteringSupported) {
+            extensions.push_back(E_GL_EXT_texture_filter_anisotropic);
+            extensions.push_back(E_GL_ARB_texture_filter_anisotropic);
+        }
         return extensions;
     }
 
@@ -630,7 +638,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // run without a renderer; no timer query is advertised then. Rebuilding
         // the whole list keeps re-runs idempotent.
         m_rendererInfo.RendererGLInfo.Extensions = BuildAdvertisedExtensions(
-            m_vulkanCaps.SupportsShaderSubgroup, pVulkanRenderer && pVulkanRenderer->IsTimerQuerySupported());
+            m_vulkanCaps.SupportsShaderSubgroup, pVulkanRenderer && pVulkanRenderer->IsTimerQuerySupported(),
+            pVulkanRenderer && pVulkanRenderer->IsSamplerAnisotropySupported());
     }
 
     void BackendObject_DirectVulkan::UpdateDynamicBackendParameters() {
@@ -680,6 +689,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         m_dynamicParameters.UniformBufferOffsetAlignment = m_vulkanCaps.UniformBufferOffsetAlignment;
         m_dynamicParameters.AliasedLineWidthRangeMin = m_vulkanCaps.AliasedLineWidthRangeMin;
         m_dynamicParameters.AliasedLineWidthRangeMax = m_vulkanCaps.AliasedLineWidthRangeMax;
+        // Without the samplerAnisotropy feature the limit is unusable, so report 1.0 (no anisotropy)
+        // rather than a maximum the sampler manager will never apply.
+        m_dynamicParameters.MaxTextureMaxAnisotropy =
+            (pVulkanRenderer && pVulkanRenderer->IsSamplerAnisotropySupported()) ? m_vulkanCaps.MaxSamplerAnisotropy
+                                                                                : 1.0f;
         m_dynamicParameters.SmoothLineWidthRangeMin = m_vulkanCaps.SmoothLineWidthRangeMin;
         m_dynamicParameters.SmoothLineWidthRangeMax = m_vulkanCaps.SmoothLineWidthRangeMax;
         m_dynamicParameters.SmoothLineWidthGranularity = m_vulkanCaps.SmoothLineWidthGranularity;

MobileGL/MG_Backend/DirectVulkan/BackendObject_DirectVulkan.h

@@ -73,7 +73,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
     // a device with the given raw capabilities. The MOBILEGL_DISABLE_SUBGROUP and
     // MOBILEGL_DISABLE_TIMERQUERY escape hatches are applied inside, so callers pass
     // the detected device support (passing an already-gated value is harmless).
-    Vector<GLExtension> BuildAdvertisedExtensions(Bool shaderSubgroupSupported, Bool timerQueriesSupported);
+    Vector<GLExtension> BuildAdvertisedExtensions(Bool shaderSubgroupSupported, Bool timerQueriesSupported,
+                                                  Bool anisotropicFilteringSupported);
 
     // Format: <GPU Name>, Vulkan <Vulkan Version>, Driver <Driver Version> — the exact
     // string an initialized backend returns from GetBackendAPIVersionString (and that

MobileGL/MG_Backend/DirectVulkan/Renderer/VkSamplerManager.cpp

@@ -58,11 +58,24 @@ namespace MobileGL::MG_Backend::DirectVulkan {
 
         m_device = initInfo.device;
         m_config = initInfo.config;
+        m_samplerAnisotropySupported = initInfo.samplerAnisotropySupported;
+        m_maxSamplerAnisotropy = std::max(initInfo.maxSamplerAnisotropy, 1.0f);
         MOBILEGL_ASSERT(m_device != VK_NULL_HANDLE && m_config != nullptr,
                         "VkSamplerManager::Initialize failed: invalid initialization info");
         return true;
     }
 
+    Float VkSamplerManager::ResolveEffectiveMaxAnisotropy(const MG_State::GLState::SamplerObject& sampler) const {
+        if (!m_samplerAnisotropySupported) return 1.0f;
+        // VUID-VkSamplerCreateInfo-anisotropyEnable-01071/01072: anisotropy requires both filters to
+        // be LINEAR and the value to sit within [1, limits.maxSamplerAnisotropy].
+        if (sampler.GetMinFilter() != SamplerFilterMode::Linear ||
+            sampler.GetMagFilter() != SamplerFilterMode::Linear) {
+            return 1.0f;
+        }
+        return std::clamp(sampler.GetMaxAnisotropy(), 1.0f, m_maxSamplerAnisotropy);
+    }
+
     void VkSamplerManager::Shutdown() {
         for (auto& [_, sampler] : m_samplers) {
             if (m_device != VK_NULL_HANDLE && sampler.handle != VK_NULL_HANDLE) {
@@ -99,9 +112,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         XXHASH_VERIFY(XXH64_update(m_hashState, &maxLod, sizeof(maxLod)));
         const auto lodBias = sampler.GetLodBias();
         XXHASH_VERIFY(XXH64_update(m_hashState, &lodBias, sizeof(lodBias)));
-        // Anisotropy is currently an accepted frontend-only state on DirectVulkan.
-        // Keep it out of the key so changing this no-op does not manufacture duplicate
-        // VkSamplers while sampler versioning still exposes the new frontend value.
+        // The RESOLVED value, not the GL request: samplers that only differ in an anisotropy Vulkan
+        // will not apply (NEAREST filtering, or requests past the device limit) must still share one
+        // VkSampler, while two samplers that really do differ must not collide onto the first one's.
+        const auto maxAnisotropy = ResolveEffectiveMaxAnisotropy(sampler);
+        XXHASH_VERIFY(XXH64_update(m_hashState, &maxAnisotropy, sizeof(maxAnisotropy)));
         const auto compareMode = sampler.GetCompareMode();
         XXHASH_VERIFY(XXH64_update(m_hashState, &compareMode, sizeof(compareMode)));
         const auto compareFunc = ResolveCompareFunc(sampler, texture);
@@ -128,10 +143,11 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         samplerInfo.addressModeV = ToVkAddressMode(sampler.GetWrapT());
         samplerInfo.addressModeW = ToVkAddressMode(sampler.GetWrapR());
         samplerInfo.mipLodBias = sampler.GetLodBias();
-        // DirectVulkan does not yet plumb samplerAnisotropy feature/limit discovery;
-        // preserve the accepted frontend state without requesting an unsupported feature.
-        samplerInfo.anisotropyEnable = VK_FALSE;
-        samplerInfo.maxAnisotropy = 1.0f;
+        // Must use the same resolver as BuildSamplerKey - a divergence would either collide two
+        // different samplers or silently create duplicates.
+        const Float maxAnisotropy = ResolveEffectiveMaxAnisotropy(sampler);
+        samplerInfo.anisotropyEnable = maxAnisotropy > 1.0f ? VK_TRUE : VK_FALSE;
+        samplerInfo.maxAnisotropy = maxAnisotropy;
         samplerInfo.compareEnable = sampler.GetCompareMode() == SamplerCompareMode::CompareToTexture ? VK_TRUE : VK_FALSE;
         samplerInfo.compareOp = ToVkCompareOp(ResolveCompareFunc(sampler, texture));
         samplerInfo.maxLod = ResolveEffectiveMaxLod(sampler);

MobileGL/MG_Backend/DirectVulkan/Renderer/VkSamplerManager.h

@@ -24,6 +24,10 @@ public:
     struct InitInfo {
         VkDevice device = VK_NULL_HANDLE;
         const VulkanRendererConfig* config = nullptr;
+        // The samplerAnisotropy device feature was requested and granted at vkCreateDevice.
+        Bool samplerAnisotropySupported = false;
+        // VkPhysicalDeviceLimits::maxSamplerAnisotropy.
+        Float maxSamplerAnisotropy = 1.0f;
     };
 
     Bool Initialize(const InitInfo& initInfo);
@@ -49,9 +53,16 @@ private:
                                                  const MG_State::GLState::ITextureObject& texture);
     static VkBorderColor ResolveVkBorderColor(const MG_State::GLState::SamplerObject& sampler,
                                               const MG_State::GLState::ITextureObject& texture);
+    // The anisotropy Vulkan will actually apply: 1.0 (i.e. disabled) unless the feature is on and
+    // the sampler filters linearly both ways, otherwise the GL request clamped to the device limit.
+    // GL happily carries GL_TEXTURE_MAX_ANISOTROPY on a NEAREST sampler (Blaze3D's blocks do exactly
+    // that) while Vulkan forbids anisotropyEnable there, so the GL value must never be forwarded raw.
+    Float ResolveEffectiveMaxAnisotropy(const MG_State::GLState::SamplerObject& sampler) const;
 
     VkDevice m_device = VK_NULL_HANDLE;
     const VulkanRendererConfig* m_config = nullptr;
+    Bool m_samplerAnisotropySupported = false;
+    Float m_maxSamplerAnisotropy = 1.0f;
     UnorderedMap<Uint64, SamplerCacheEntry> m_samplers;
     static inline XXH64_state_t* m_hashState = XXH64_createState();
 };

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp

@@ -1890,7 +1890,8 @@ void main() {
 
         m_samplerManager = MakeUnique<VkSamplerManager>();
         MOBILEGL_ASSERT(m_samplerManager != nullptr, "VkSamplerManager creation failed.");
-        succeeded = m_samplerManager->Initialize({m_device, &m_config});
+        succeeded = m_samplerManager->Initialize({m_device, &m_config, m_samplerAnisotropyFeatureEnabled,
+                                                  m_physicalDevice.properties.limits.maxSamplerAnisotropy});
         MOBILEGL_ASSERT(succeeded, "VkSamplerManager initialization failed.");
         succeeded = InitializeBlitResources();
         MOBILEGL_ASSERT(succeeded, "Blit pipeline resource initialization failed.");
@@ -6508,6 +6509,10 @@ void main() {
         deviceFeatures.multiDrawIndirect = supportedDeviceFeatures.multiDrawIndirect;
         m_multiDrawIndirectFeatureEnabled = deviceFeatures.multiDrawIndirect == VK_TRUE;
         m_logicOpFeatureEnabled = deviceFeatures.logicOp == VK_TRUE;
+        // Backs GL_TEXTURE_MAX_ANISOTROPY_EXT; optional in Vulkan, so the sampler manager falls back
+        // to isotropic filtering (and the extension goes unadvertised) when the device lacks it.
+        deviceFeatures.samplerAnisotropy = supportedDeviceFeatures.samplerAnisotropy;
+        m_samplerAnisotropyFeatureEnabled = deviceFeatures.samplerAnisotropy == VK_TRUE;
 
         VkDeviceCreateInfo deviceCreateInfo{};
         deviceCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.h

@@ -227,6 +227,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // frontend. Timestamp support (queue timestampValidBits > 0 and a
         // non-zero timestampPeriod) is cached at device creation.
         Bool IsTimerQuerySupported() const;
+        // The samplerAnisotropy device feature was granted, so GL_TEXTURE_MAX_ANISOTROPY_EXT is
+        // honored rather than accepted-and-ignored.
+        Bool IsSamplerAnisotropySupported() const { return m_samplerAnisotropyFeatureEnabled; }
         // Ensures the frame command buffer is recording (same lazy pattern as
         // SetupDraw) and writes a bottom-of-pipe timestamp into the current
         // frame's pool. Null when unsupported or the pool is exhausted.
@@ -359,6 +362,7 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         Bool m_indexTypeUint8ExtensionEnabled = false;
         Bool m_logicOpFeatureEnabled = false;
         Bool m_multiDrawIndirectFeatureEnabled = false;
+        Bool m_samplerAnisotropyFeatureEnabled = false;
         Bool m_shaderDrawParametersExtensionEnabled = false;
         Bool m_shaderDrawParametersFeatureEnabled = false;
         // fillModeNonSolid gates VK_POLYGON_MODE_LINE/_POINT (glPolygonMode); independentBlend gates

MobileGL/MG_Impl/GLImpl/Getter/GL_Getter.cpp

@@ -529,6 +529,13 @@ namespace MobileGL::MG_Impl::GLImpl {
             params[1] = dynamicParameters.AliasedLineWidthRangeMax;
             return;
         }
+        case GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT: {
+            // EXT_texture_filter_anisotropic queries this as a float; the integer path below widens
+            // from here, so this case is the authoritative one.
+            const auto& dynamicParameters = MG_Backend::pActiveBackendObject->GetDynamicParameters();
+            params[0] = dynamicParameters.MaxTextureMaxAnisotropy;
+            return;
+        }
         case GL_ALIASED_POINT_SIZE_RANGE:
         case GL_POINT_SIZE_RANGE: {
             const auto& dynamicParameters = MG_Backend::pActiveBackendObject->GetDynamicParameters();
@@ -1955,6 +1962,10 @@ namespace MobileGL::MG_Impl::GLImpl {
         case GL_MAX_SAMPLES:
             *params = std::max(dynamicParameters.MaxSamples, kFrontendMaxSamples);
             break;
+        case GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT:
+            // Float state (see GetFloatv); rounded to nearest for the integer query per GL 3.3 6.1.2.
+            *params = static_cast<GLint>(std::lround(dynamicParameters.MaxTextureMaxAnisotropy));
+            break;
         default:
             MGLOG_E("glGetIntegerv: Invalid enum %s (0x%X)", MG_Util::ConvertGLEnumToString(pname).c_str(), pname);
             MG_State::pGLContext->RecordError(ErrorCode::InvalidEnum,

MobileGL/MG_Test/BackendLoader/BackendLoaderTest.cpp

@@ -12,6 +12,10 @@
 #include <string>
 #include <vector>
 
+#include <algorithm>
+
+#include <MG_Backend/DirectGLES/BackendObject_DirectGLES.h>
+#include <MG_Backend/DirectVulkan/BackendObject_DirectVulkan.h>
 #include <MG_Util/BackendLoaders/OpenGL/Loader.h>
 
 // ProbeIndirectInstanceIdIncludesBaseInstance is driven against a fake GLES driver:
@@ -31,6 +35,11 @@ namespace {
         GLenum pendingError = GL_NO_ERROR;
         std::vector<std::string> extensions;
 
+        // GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT the fake reports, and whether it was ever asked:
+        // querying it on a driver without the extension would raise GL_INVALID_ENUM.
+        GLfloat maxTextureMaxAnisotropy = 16.0f;
+        bool maxTextureMaxAnisotropyQueried = false;
+
         GLuint nextBufferId = 1;
         GLuint nextShaderId = 1;
         GLuint nextProgramId = 1;
@@ -122,6 +131,10 @@ namespace {
         };
         funcs.glGetFloatv = [](GLenum pname, GLfloat* data) {
             switch (pname) {
+            case GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT:
+                g_fake.maxTextureMaxAnisotropyQueried = true;
+                data[0] = g_fake.maxTextureMaxAnisotropy;
+                break;
             // Two-component range queries.
             case GL_ALIASED_LINE_WIDTH_RANGE:
             case GL_SMOOTH_LINE_WIDTH_RANGE:
@@ -404,6 +417,51 @@ TEST(IndirectInstanceIdProbe, FillInCapabilitiesWiresProbeResult) {
     ExpectProbeReleasedAllObjects();
 }
 
+// The extension string is what apps gate on (LWJGL builds GLCapabilities from it), so advertising
+// it on a driver that cannot filter anisotropically would leave them silently on trilinear.
+TEST(TextureAnisotropyCapabilities, ExtensionIsAdvertisedOnlyWhenTheHostDriverSupportsIt) {
+    const auto contains = [](const MobileGL::Vector<MobileGL::GLExtension>& extensions,
+                             MobileGL::GLExtension wanted) {
+        return std::find(extensions.begin(), extensions.end(), wanted) != extensions.end();
+    };
+
+    const auto without = MobileGL::MG_Backend::DirectGLES::BuildAdvertisedExtensions(false, false);
+    EXPECT_FALSE(contains(without, MobileGL::E_GL_EXT_texture_filter_anisotropic));
+    EXPECT_FALSE(contains(without, MobileGL::E_GL_ARB_texture_filter_anisotropic));
+
+    const auto with = MobileGL::MG_Backend::DirectGLES::BuildAdvertisedExtensions(false, true);
+    EXPECT_TRUE(contains(with, MobileGL::E_GL_EXT_texture_filter_anisotropic));
+    EXPECT_TRUE(contains(with, MobileGL::E_GL_ARB_texture_filter_anisotropic));
+
+    // Same rule on the Vulkan backend, where the gate is the samplerAnisotropy device feature.
+    const auto vkWithout = MobileGL::MG_Backend::DirectVulkan::BuildAdvertisedExtensions(false, false, false);
+    EXPECT_FALSE(contains(vkWithout, MobileGL::E_GL_EXT_texture_filter_anisotropic));
+    const auto vkWith = MobileGL::MG_Backend::DirectVulkan::BuildAdvertisedExtensions(false, false, true);
+    EXPECT_TRUE(contains(vkWith, MobileGL::E_GL_EXT_texture_filter_anisotropic));
+    EXPECT_TRUE(contains(vkWith, MobileGL::E_GL_ARB_texture_filter_anisotropic));
+}
+
+TEST(TextureAnisotropyCapabilities, MaxAnisotropyIsQueriedOnlyWhenTheExtensionIsPresent) {
+    ResetFakeDriver();
+    g_fake.maxVertexSsboBlocks = 0;
+    const auto funcs = MakeFakeGLESFunctions();
+
+    MobileGL::MG_External::GLESCapabilities absentCaps;
+    ASSERT_TRUE(MobileGL::MG_Util::BackendLoader::FillInGLESCapabilities(absentCaps, funcs));
+    // Never probed (it would be GL_INVALID_ENUM), and reported as "no anisotropy".
+    EXPECT_FALSE(g_fake.maxTextureMaxAnisotropyQueried);
+    EXPECT_FLOAT_EQ(absentCaps.MaxTextureMaxAnisotropy, 1.0f);
+
+    ResetFakeDriver();
+    g_fake.maxVertexSsboBlocks = 0;
+    g_fake.maxTextureMaxAnisotropy = 16.0f;
+    g_fake.extensions.emplace_back("GL_EXT_texture_filter_anisotropic");
+    MobileGL::MG_External::GLESCapabilities presentCaps;
+    ASSERT_TRUE(MobileGL::MG_Util::BackendLoader::FillInGLESCapabilities(presentCaps, funcs));
+    EXPECT_TRUE(g_fake.maxTextureMaxAnisotropyQueried);
+    EXPECT_FLOAT_EQ(presentCaps.MaxTextureMaxAnisotropy, 16.0f);
+}
+
 TEST(TextureAnisotropyCapabilities, ExtensionPresenceIsDetectedExactly) {
     ResetFakeDriver();
     g_fake.maxVertexSsboBlocks = 0;

MobileGL/MG_Test/Texture/TextureTest.cpp

@@ -122,6 +122,10 @@ namespace {
             return table;
         }
         const MobileGL::MG_Backend::DynamicBackendParameters& GetDynamicParameters() const override {
+            return MutableDynamicParameters();
+        }
+        // Lets a test stand in a backend limit (e.g. GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT).
+        static MobileGL::MG_Backend::DynamicBackendParameters& MutableDynamicParameters() {
             static MobileGL::MG_Backend::DynamicBackendParameters params = {};
             return params;
         }
@@ -162,6 +166,30 @@ TEST_F(TextureTest, CreateTexturesCreatesObjectsWithoutBinding) {
     EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
 }
 
+// GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT is float state that must answer every numeric query: GetFloatv
+// is authoritative and GetIntegerv would otherwise fall through to its INVALID_ENUM default.
+TEST_F(TextureTest, MaxTextureMaxAnisotropyIsAnsweredFromTheBackendLimit) {
+    auto backend = MakeUnique<FormatCapabilityBackend>();
+    FormatCapabilityBackend::MutableDynamicParameters().MaxTextureMaxAnisotropy = 16.0f;
+    ScopedBackendOverride override(Move(backend));
+
+    GLfloat floatValue = 0.0f;
+    MG_Impl::GLImpl::GetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &floatValue);
+    EXPECT_FLOAT_EQ(floatValue, 16.0f);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+
+    GLint integerValue = 0;
+    MG_Impl::GLImpl::GetIntegerv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &integerValue);
+    EXPECT_EQ(integerValue, 16);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+
+    // A backend without anisotropy reports the no-anisotropy floor rather than erroring.
+    FormatCapabilityBackend::MutableDynamicParameters().MaxTextureMaxAnisotropy = 1.0f;
+    MG_Impl::GLImpl::GetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &floatValue);
+    EXPECT_FLOAT_EQ(floatValue, 1.0f);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
 TEST_F(TextureTest, TextureMaxAnisotropyDefaultsToOneAndRoundTripsWithoutRedundantVersionBumps) {
     GLuint texture = 0;
     MG_Impl::GLImpl::GenTextures(1, &texture);

MobileGL/MG_Util/BackendLoaders/OpenGL/Loader.cpp

@@ -911,6 +911,13 @@ namespace MobileGL::MG_Util::BackendLoader {
         glesFuncs.glGetIntegerv(GL_MAX_VIEWPORTS, &maxViewports);
         glesFuncs.glGetIntegerv(GL_MAX_VIEWPORT_DIMS, maxViewportDims);
         glesFuncs.glGetIntegerv(GL_VIEWPORT_SUBPIXEL_BITS, &viewportSubpixelBits);
+        // Only legal to query once the extension has been seen in the loop above, hence not batched
+        // with the unconditional probes: on a driver without it this raises GL_INVALID_ENUM.
+        if (caps.SupportsTextureFilterAnisotropy) {
+            GLfloat maxTextureMaxAnisotropy = 1.0f;
+            glesFuncs.glGetFloatv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &maxTextureMaxAnisotropy);
+            caps.MaxTextureMaxAnisotropy = std::max(maxTextureMaxAnisotropy, 1.0f);
+        }
         caps.AliasedLineWidthRangeMin = aliasedLineWidthRange[0];
         caps.AliasedLineWidthRangeMax = aliasedLineWidthRange[1];
         caps.SmoothLineWidthRangeMin = smoothLineWidthRange[0];

MobileGL/MG_Util/BackendLoaders/OpenGL/Loader.h

@@ -1034,6 +1034,9 @@ namespace MobileGL {
             // GL_EXT_texture_filter_anisotropic is present, so sampler/texture
             // anisotropy may be forwarded without raising GL_INVALID_ENUM in GLES.
             Bool SupportsTextureFilterAnisotropy = false;
+            // GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT of the host driver; only queried when the
+            // extension above is present, and left at 1.0 (no anisotropy) otherwise.
+            Float MaxTextureMaxAnisotropy = 1.0f;
             Bool SupportsBaseInstance = false;
             // GL_EXT_disjoint_timer_query is present in the extension string.
             Bool SupportsDisjointTimerQuery = false;

MobileGL/MG_Util/BackendLoaders/Vulkan/Loader.cpp

@@ -124,6 +124,7 @@ namespace MobileGL::MG_Util::BackendLoader {
         caps.UniformBufferOffsetAlignment = static_cast<int>(p.limits.minUniformBufferOffsetAlignment);
         caps.AliasedLineWidthRangeMin = p.limits.lineWidthRange[0];
         caps.AliasedLineWidthRangeMax = p.limits.lineWidthRange[1];
+        caps.MaxSamplerAnisotropy = p.limits.maxSamplerAnisotropy;
         caps.SmoothLineWidthRangeMin = p.limits.lineWidthRange[0];
         caps.SmoothLineWidthRangeMax = p.limits.lineWidthRange[1];
         caps.SmoothLineWidthGranularity = p.limits.lineWidthGranularity;
@@ -208,6 +209,7 @@ namespace MobileGL::MG_Util::BackendLoader {
         caps.UniformBufferOffsetAlignment = static_cast<int>(properties.limits.minUniformBufferOffsetAlignment);
         caps.AliasedLineWidthRangeMin = properties.limits.lineWidthRange[0];
         caps.AliasedLineWidthRangeMax = properties.limits.lineWidthRange[1];
+        caps.MaxSamplerAnisotropy = properties.limits.maxSamplerAnisotropy;
         caps.SmoothLineWidthRangeMin = properties.limits.lineWidthRange[0];
         caps.SmoothLineWidthRangeMax = properties.limits.lineWidthRange[1];
         caps.SmoothLineWidthGranularity = properties.limits.lineWidthGranularity;

MobileGL/MG_Util/BackendLoaders/Vulkan/Loader.h

@@ -18,6 +18,9 @@ namespace MobileGL {
             Int UniformBufferOffsetAlignment = 256;
             Float AliasedLineWidthRangeMin = 1.0f;
             Float AliasedLineWidthRangeMax = 1.0f;
+            // VkPhysicalDeviceLimits::maxSamplerAnisotropy. Whether it can be used at all depends on
+            // the samplerAnisotropy feature, which the renderer decides at device creation.
+            Float MaxSamplerAnisotropy = 1.0f;
             Float SmoothLineWidthRangeMin = 1.0f;
             Float SmoothLineWidthRangeMax = 1.0f;
             Float SmoothLineWidthGranularity = 1.0f;

MobileGL/MG_Util/SelfTest/DriverPost.cpp

@@ -548,8 +548,8 @@ namespace MobileGL::MG_Util::SelfTest {
         if (summary.capsValid) {
             backendApiVersionString = MG_Backend::DirectGLES::FormatBackendAPIVersionString(
                 summary.caps.GLESRendererString, summary.caps.GLESVersion.Major, summary.caps.GLESVersion.Minor);
-            advertisedExtensions = JoinAdvertisedExtensions(
-                MG_Backend::DirectGLES::BuildAdvertisedExtensions(summary.caps.SupportsDisjointTimerQuery));
+            advertisedExtensions = JoinAdvertisedExtensions(MG_Backend::DirectGLES::BuildAdvertisedExtensions(
+                summary.caps.SupportsDisjointTimerQuery, summary.caps.SupportsTextureFilterAnisotropy));
         }
         AppendMobileGLReportedRows(builder, MG_Backend::DirectGLES::GetRendererIdentity(), backendApiVersionString,
                                    advertisedExtensions);
@@ -841,6 +841,7 @@ namespace MobileGL::MG_Util::SelfTest {
             String driverVersionString; // raw hex, vendor-encoded (see RunVulkanDriverPost)
             Bool shaderSubgroupUsable = false;
             Bool timerQueriesSupported = false;
+            Bool samplerAnisotropySupported = false;
         };
     } // namespace
 
@@ -1107,6 +1108,7 @@ namespace MobileGL::MG_Util::SelfTest {
 
         VkPhysicalDeviceFeatures features{};
         vkGetPhysicalDeviceFeaturesFn(physicalDevice, &features);
+        summary.samplerAnisotropySupported = features.samplerAnisotropy == VK_TRUE;
         if (features.multiDrawIndirect == VK_TRUE) {
             builder.Pass("multiDrawIndirect", "indirect multi-draw batches run as single native commands");
         } else {
@@ -1279,7 +1281,7 @@ namespace MobileGL::MG_Util::SelfTest {
             backendApiVersionString = MG_Backend::DirectVulkan::FormatBackendAPIVersionString(
                 summary.deviceName, summary.apiVersionString, summary.driverVersionString);
             advertisedExtensions = JoinAdvertisedExtensions(MG_Backend::DirectVulkan::BuildAdvertisedExtensions(
-                summary.shaderSubgroupUsable, summary.timerQueriesSupported));
+                summary.shaderSubgroupUsable, summary.timerQueriesSupported, summary.samplerAnisotropySupported));
         }
         AppendMobileGLReportedRows(builder, MG_Backend::DirectVulkan::GetRendererIdentity(), backendApiVersionString,
                                    advertisedExtensions);