From b7d42faac018662d6314d8333bc4c38cc76b552a Mon Sep 17 00:00:00 2001
From: Swung0x48 <swung0x48@outlook.com>
Date: Mon, 12 Oct 2026 08:01:54 -0400
Subject: [PATCH] [Fix] (GL): answer GL_TEXTURE_BUFFER_DATA_STORE_BINDING in
 glGetTexLevelParameter

---
 .../MG_Impl/GLImpl/Texture/GL_Texture.cpp     | 15 +++++++
 MobileGL/MG_Test/Texture/TextureTest.cpp      | 45 +++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp b/MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp
index f50f5393..25aed3dd 100644
--- a/MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp
+++ b/MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp
@@ -806,6 +806,15 @@ namespace MobileGL::MG_Impl::GLImpl {
             return static_cast<GLint>(std::min(texelCount, maxTexelCount));
         }
 
+        // GL_TEXTURE_BUFFER_DATA_STORE_BINDING: the name of the buffer a buffer texture is attached
+        // to, or 0 when none is - and 0, the state's initial value, for any other storage.
+        GLuint GetBufferTextureDataStoreBinding(MG_State::GLState::ITextureObject* textureObject) {
+            if (textureObject->GetStorageType() != TextureStorageType::Buffer) return 0u;
+            auto* bufferTextureObject = static_cast<MG_State::GLState::TextureObjectBuffer*>(textureObject);
+            const auto& buffer = bufferTextureObject->GetBufferBindingSlot().GetBoundObject();
+            return buffer != nullptr ? buffer->GetExternalIndex() : 0u;
+        }
+
         // glGetTexLevelParameter{i,f}v answers WIDTH/HEIGHT/DEPTH out of the mipmap chain, and (since
         // the buffer-texture arms above) out of the attached buffer range for GL_TEXTURE_BUFFER. This
         // is what is left: a storage class with no level geometry at all. Report it instead of
@@ -3682,6 +3691,9 @@ namespace MobileGL::MG_Impl::GLImpl {
             }
             break;
         }
+        case GL_TEXTURE_BUFFER_DATA_STORE_BINDING:
+            if (params) *params = static_cast<GLint>(GetBufferTextureDataStoreBinding(textureObject.get()));
+            break;
         case GL_TEXTURE_BUFFER_SIZE:
         case GL_TEXTURE_BUFFER_OFFSET: {
             // GL 4.6 core 8.9: both describe the window of the attached buffer a GL_TEXTURE_BUFFER
@@ -3853,6 +3865,9 @@ namespace MobileGL::MG_Impl::GLImpl {
             }
             break;
         }
+        case GL_TEXTURE_BUFFER_DATA_STORE_BINDING:
+            if (params) *params = static_cast<GLfloat>(GetBufferTextureDataStoreBinding(textureObject.get()));
+            break;
         case GL_TEXTURE_BUFFER_SIZE:
         case GL_TEXTURE_BUFFER_OFFSET: {
             // See GetTexLevelParameteriv_State: both describe the attached buffer range of a
diff --git a/MobileGL/MG_Test/Texture/TextureTest.cpp b/MobileGL/MG_Test/Texture/TextureTest.cpp
index c81762e0..9816c420 100644
--- a/MobileGL/MG_Test/Texture/TextureTest.cpp
+++ b/MobileGL/MG_Test/Texture/TextureTest.cpp
@@ -5369,6 +5369,51 @@ TEST_F(TextureTest, GetTexLevelParameterAnswersBufferStorageGeometry) {
     }
 }
 
+// GL 4.6 core 8.11.3: GL_TEXTURE_BUFFER_DATA_STORE_BINDING names the buffer a buffer texture is
+// attached to, 0 once it is detached - and its initial value 0 for any other storage.
+TEST_F(TextureTest, GetTexLevelParameterReportsBufferDataStoreBinding) {
+    GLuint buffer = 0;
+    MG_Impl::GLImpl::CreateBuffers(1, &buffer);
+    MG_Impl::GLImpl::NamedBufferData(buffer, 64, nullptr, GL_STATIC_DRAW);
+    GLuint texture = 0;
+    MG_Impl::GLImpl::CreateTextures(GL_TEXTURE_BUFFER, 1, &texture);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_BUFFER, texture);
+    MG_Impl::GLImpl::TexBuffer(GL_TEXTURE_BUFFER, GL_R8, buffer);
+    ASSERT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+
+    GLint binding = -1;
+    MG_Impl::GLImpl::GetTexLevelParameteriv(GL_TEXTURE_BUFFER, 0, GL_TEXTURE_BUFFER_DATA_STORE_BINDING, &binding);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+    EXPECT_EQ(binding, static_cast<GLint>(buffer));
+    GLfloat bindingFloat = -1.0f;
+    MG_Impl::GLImpl::GetTexLevelParameterfv(GL_TEXTURE_BUFFER, 0, GL_TEXTURE_BUFFER_DATA_STORE_BINDING,
+                                            &bindingFloat);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+    EXPECT_EQ(bindingFloat, static_cast<GLfloat>(buffer));
+
+    MG_Impl::GLImpl::TexBuffer(GL_TEXTURE_BUFFER, GL_R8, 0);
+    MG_Impl::GLImpl::GetTexLevelParameteriv(GL_TEXTURE_BUFFER, 0, GL_TEXTURE_BUFFER_DATA_STORE_BINDING, &binding);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+    EXPECT_EQ(binding, 0);
+
+    GLuint plain = 0;
+    MG_Impl::GLImpl::GenTextures(1, &plain);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, plain);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    ASSERT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+    binding = -1;
+    MG_Impl::GLImpl::GetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_BUFFER_DATA_STORE_BINDING, &binding);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+    EXPECT_EQ(binding, 0);
+
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, 0);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_BUFFER, 0);
+    MG_Impl::GLImpl::DeleteTextures(1, &plain);
+    MG_Impl::GLImpl::DeleteTextures(1, &texture);
+    MG_Impl::GLImpl::DeleteBuffers(1, &buffer);
+    DrainPendingGlErrors();
+}
+
 // Immutable storage plus glCompressedTexSubImage2D is the modern way to upload a compressed
 // texture, so glTexStorage2D has to commit its levels to a specific compressed internalformat
 // exactly as glTexImage2D does. When it did not, the sub-image call found an uncompressed level