[Fix] (MG_Backend/DirectGLES, MG_Impl/GLImpl): ReadPixels - fall back to wide-format conversion when the ES driver rejects a legacy native read combo (Adreno errors on e.g. GL_RED/GL_UNSIGNED_INT and leaves the buffer untouched), and enforce packed-type/format pairing at the state layer via shared ValidateClientFormatTypePairing (GL_RED + GL_UNSIGNED_SHORT_5_6_5 now raises GL_INVALID_OPERATION)

MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp

@@ -3760,7 +3760,30 @@ namespace MobileGL::MG_Backend::DirectGLES {
         }
 
         MGLOG_D("ReadPixels: glReadPixels()");
+        DrainESErrors();
         g_GLESFuncs.glReadPixels(x, y, width, height, format, type, pixels);
+        const GLenum nativeReadError = g_GLESFuncs.glGetError();
+        if (nativeReadError != GL_NO_ERROR) {
+            // ES drivers only guarantee GL_RGBA/GL_UNSIGNED_BYTE, GL_RGBA_INTEGER/(U)INT, float RGBA and one
+            // implementation-defined pair; legacy combos like GL_RED/GL_UNSIGNED_INT are rejected by e.g.
+            // Adreno with a GL error and an untouched destination (GL CTS packed_pixels r8_format_red). The
+            // failed read wrote nothing (client memory and PBO alike), so re-service the request through the
+            // wide-format conversion path before any PBO writeback can capture stale contents. The conversion
+            // helper saves/restores the ES pixel-pack binding and handles the state-layer PBO itself.
+            DrainESErrors();
+            MGLOG_D("ReadPixels: native read of %s/%s failed (%s), retrying via client-format conversion",
+                    MG_Util::ConvertGLEnumToString(format).c_str(), MG_Util::ConvertGLEnumToString(type).c_str(),
+                    MG_Util::ConvertGLEnumToString(nativeReadError).c_str());
+            if (ReadPixelsViaFormatConversion(x, y, width, height, format, type, pixels)) {
+                MGLOG_D("ReadPixels: finished via client-format conversion after native failure");
+                return;
+            }
+            MGLOG_E("ReadPixels: native read of %s/%s failed (%s) and no conversion path covers it, "
+                    "skipping readback",
+                    MG_Util::ConvertGLEnumToString(format).c_str(), MG_Util::ConvertGLEnumToString(type).c_str(),
+                    MG_Util::ConvertGLEnumToString(nativeReadError).c_str());
+            return;
+        }
         if (usePBO) {
             // pull back to client memory if PBO is used
             MGLOG_D("ReadPixels: PBO used, mapping buffer to client memory");

MobileGL/MG_Impl/GLImpl/Framebuffer/GL_Framebuffer.cpp

@@ -1681,6 +1681,13 @@ namespace MobileGL::MG_Impl::GLImpl {
             }
         }
 
+        // Packed-type/format pairing (GL CTS packed_pixels: e.g. GL_RED with GL_UNSIGNED_SHORT_5_6_5 must
+        // raise an error instead of reaching the backend). Shared with the TexImage/GetTexImage validators;
+        // runs after the depth-stencil branch above so DEPTH_STENCIL with a wrong type keeps GL_INVALID_ENUM.
+        if (!TextureImpl::ValidateClientFormatTypePairing(textureInputFormat, texturePixelDataType)) {
+            return false;
+        }
+
         // Check PBO state
         const auto& pixelPackBufferObject =
             MG_State::pGLContext->GetBufferBindingSlot(BufferTarget::PixelPack).GetBoundObject();

MobileGL/MG_Impl/GLImpl/Texture/Validators.cpp

@@ -235,17 +235,15 @@ namespace MobileGL::MG_Impl::GLImpl::TextureImpl {
                format == TextureInputFormat::StencilIndex;
     }
 
-    // Mirrors the desktop-GL validity matrix used by GL CTS packed_pixels (glcPackedPixelsTests
-    // isFormatValid, INPUT_TEXIMAGE): packed-type/format pairing, depth-vs-color mismatch, and
-    // integer-ness matching all raise GL_INVALID_OPERATION instead of reaching the upload path.
-    Bool ValidateTextureInternalFormatCompatibleWithInput(TextureInputFormat format,
-                                                          TextureInternalFormat internalFormat,
-                                                          TexturePixelDataType type) {
+    // Client-memory format<->type pairing rules shared by pixel uploads (TexImage*) and readbacks
+    // (ReadPixels, GetTexImage). Mirrors the desktop-GL validity matrix used by GL CTS packed_pixels
+    // (glcPackedPixelsTests isFormatValid): packed types constrain the formats they may pair with, and
+    // integer formats reject floating-point types; violations raise GL_INVALID_OPERATION.
+    Bool ValidateClientFormatTypePairing(TextureInputFormat format, TexturePixelDataType type) {
         const auto recordInvalidOperation = [](const char* message) {
             MG_State::pGLContext->RecordError(
                 ErrorCode::InvalidOperation,
-                MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", "ValidateTextureInternalFormatCompatibleWithInput",
-                                             message));
+                MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", "ValidateClientFormatTypePairing", message));
             return false;
         };
 
@@ -288,6 +286,27 @@ namespace MobileGL::MG_Impl::GLImpl::TextureImpl {
             return recordInvalidOperation("Integer format cannot be used with a floating-point type");
         }
 
+        return true;
+    }
+
+    // Mirrors the desktop-GL validity matrix used by GL CTS packed_pixels (glcPackedPixelsTests
+    // isFormatValid, INPUT_TEXIMAGE): packed-type/format pairing, depth-vs-color mismatch, and
+    // integer-ness matching all raise GL_INVALID_OPERATION instead of reaching the upload path.
+    Bool ValidateTextureInternalFormatCompatibleWithInput(TextureInputFormat format,
+                                                          TextureInternalFormat internalFormat,
+                                                          TexturePixelDataType type) {
+        const auto recordInvalidOperation = [](const char* message) {
+            MG_State::pGLContext->RecordError(
+                ErrorCode::InvalidOperation,
+                MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", "ValidateTextureInternalFormatCompatibleWithInput",
+                                             message));
+            return false;
+        };
+
+        if (!ValidateClientFormatTypePairing(format, type)) {
+            return false;
+        }
+
         // TexImage in core 3.3 has no stencil-only upload path (that arrived with GL 4.4).
         if (format == TextureInputFormat::StencilIndex) {
             return recordInvalidOperation("STENCIL_INDEX is not a valid texture upload format");

MobileGL/MG_Impl/GLImpl/Texture/Validators.h

@@ -23,6 +23,7 @@ namespace MobileGL::MG_Impl::GLImpl::TextureImpl {
     Bool ValidateTextureSizeRange(Int width, Int height, Int depth);
     Bool ValidateTextureInternalFormat(TextureInternalFormat format);
     Bool ValidateTextureBorderNumber(Int border);
+    Bool ValidateClientFormatTypePairing(TextureInputFormat format, TexturePixelDataType type);
     Bool ValidateTextureInternalFormatCompatibleWithInput(TextureInputFormat format,
                                                           TextureInternalFormat internalFormat,
                                                           TexturePixelDataType type);

MobileGL/MG_Test/Framebuffer/FramebufferTest.cpp

@@ -221,6 +221,40 @@ TEST_F(FramebufferTest, ReadPixelsAllowsPersistentMappedPixelPackBuffer) {
     EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
 }
 
+TEST_F(FramebufferTest, ReadPixelsRejectsMismatchedPackedTypeFormatPairs) {
+    GLuint framebuffer = 0;
+    GLuint texture = 0;
+    MG_Impl::GLImpl::CreateFramebuffers(1, &framebuffer);
+    MG_Impl::GLImpl::CreateTextures(GL_TEXTURE_2D, 1, &texture);
+    MG_Impl::GLImpl::TextureStorage2D(texture, 1, GL_RGBA8, 4, 4);
+    MG_Impl::GLImpl::NamedFramebufferTexture(framebuffer, GL_COLOR_ATTACHMENT0, texture, 0);
+    MG_Impl::GLImpl::BindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
+
+    MG_Backend::gBackendFunctionsTable.GL.ReadPixels = RecordReadPixels;
+    Uint8 pixelStorage[4 * 4 * 4] = {};
+
+    // Packed RGB type with a non-RGB format must never reach the backend (GL CTS packed_pixels
+    // reads GL_RED with GL_UNSIGNED_SHORT_5_6_5 and expects an error).
+    MG_Impl::GLImpl::ReadPixels(0, 0, 4, 4, GL_RED, GL_UNSIGNED_SHORT_5_6_5, pixelStorage);
+    EXPECT_EQ(g_readPixelsCallCount, 0);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_INVALID_OPERATION);
+
+    // Packed RGBA type with a non-RGBA/BGRA format is rejected as well.
+    MG_Impl::GLImpl::ReadPixels(0, 0, 4, 4, GL_RGB, GL_UNSIGNED_INT_8_8_8_8, pixelStorage);
+    EXPECT_EQ(g_readPixelsCallCount, 0);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_INVALID_OPERATION);
+
+    // Packed depth-stencil type requires the DEPTH_STENCIL format.
+    MG_Impl::GLImpl::ReadPixels(0, 0, 4, 4, GL_RGBA, GL_UNSIGNED_INT_24_8, pixelStorage);
+    EXPECT_EQ(g_readPixelsCallCount, 0);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_INVALID_OPERATION);
+
+    // A plain RGBA/UNSIGNED_BYTE readback keeps working.
+    MG_Impl::GLImpl::ReadPixels(0, 0, 4, 4, GL_RGBA, GL_UNSIGNED_BYTE, pixelStorage);
+    EXPECT_EQ(g_readPixelsCallCount, 1);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
 TEST_F(FramebufferTest, NamedRenderbufferStorageAndFramebufferAttachDoNotChangeBindings) {
     GLuint framebuffer = 0;
     GLuint renderbuffer = 0;