From d6620959b3a2f6626a60efee2620194c65ed36ba Mon Sep 17 00:00:00 2001
From: Swung0x48 <swung0x48@outlook.com>
Date: Sat, 16 Aug 2025 01:10:04 +0800
Subject: [PATCH] [Feat] (MG_State/Program): BindAttribLocation WIP

---
 .../MG_Impl/GLImpl/Program/GL_Program.cpp     | 22 +++++++++++-
 .../GLState/ProgramState/ProgramObject.cpp    | 36 +++++++++++++++++++
 .../GLState/ProgramState/ProgramObject.h      | 10 ++++++
 MobileGL/MG_Test/Program/ProgramTest.cpp      |  3 +-
 4 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp b/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
index a8ba513c..1ec29ee4 100644
--- a/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
+++ b/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
@@ -85,7 +85,27 @@ namespace MobileGL {
         }
 
         void BindAttribLocation_State(GLuint program, GLuint index, const GLchar* name) {
-            THROW_UNIMPL_EXCEPTION;
+            if (index >= MG_State::GLState::VertexArrayObject::MAX_VERTEX_ATTRIBS) {
+                MG_State::pGLContext->RecordError(
+                        ErrorCode::InvalidValue,
+                        MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                     "`index` is greater than or equal to `GL_MAX_VERTEX_ATTRIBS`."));
+                return;
+            }
+
+            if (strncmp(name, "gl_", 3) == 0) {
+                MG_State::pGLContext->RecordError(
+                        ErrorCode::InvalidOperation,
+                        MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                     "`name` starts with the reserved prefix `gl_`."));
+                return;
+            }
+
+            auto programObject = TryToGetProgramObject(program);
+            if (!programObject)
+                return;
+
+            programObject->SetExplicitAttribLocation(index, name);
         }
 
         void CompileShader_State(GLuint shader) {
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
index f4534ed4..f38d2885 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
@@ -89,12 +89,44 @@ namespace MobileGL {
                     m_uniformTypes[location] = uniform.glDefineType;
                 }
 
+                // attributes (pipe in)
                 int inCount = m_program->getNumPipeInputs();
+                m_attribs.resize(inCount);
+
+                // Parse explicit location in shader
                 for (int i = 0; i < inCount; i++) {
                     auto& inVar = m_program->getPipeInput(i);
+                    auto location = inVar.layoutLocation();
                     m_attribInNameMaxLength = std::max(m_attribInNameMaxLength, (Int)inVar.name.length());
+                    // TODO: how to parse location specified in shader?
+                }
+                // Place explicitly set locations
+                for (int i = 0; i < inCount; i++) {
+                    auto& inVar = m_program->getPipeInput(i);
+
+                    auto it = m_explicitAttribLocations.find(inVar.name);
+                    if (it != m_explicitAttribLocations.end()) {
+                        m_attribs[it->second] = inVar.name;
+                    }
+                }
+                // Place yet placed attributes
+                int nextAvailLoc = 0;
+                for (int i = 0; i < inCount; i++) {
+                    auto& inVar = m_program->getPipeInput(i);
+                    auto it = m_explicitAttribLocations.find(inVar.name);
+                    if (it != m_explicitAttribLocations.end()) {
+                        continue;
+                    }
+                    while (nextAvailLoc < inCount && !m_attribs[nextAvailLoc].empty())
+                        ++nextAvailLoc;
+
+                    assert(nextAvailLoc < inCount);
+
+                    m_attribs[nextAvailLoc] = inVar.name;
                 }
 
+
+                // UBO
                 int uboCount = m_program->getNumUniformBlocks();
                 for (int i = 0; i < uboCount; i++) {
                     auto& ubo = m_program->getUniformBlock(i);
@@ -102,6 +134,10 @@ namespace MobileGL {
                 }
             }
 
+            void ProgramObject::SetExplicitAttribLocation(Uint index, const char *name) {
+                m_explicitAttribLocations[name] = index;
+            }
+
             // void ProgramObject::PreLink() {
             //     m_uniforms.clear();
             //     m_uniformOffsets.clear();
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
index 76a65543..9947c633 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
@@ -14,6 +14,9 @@ namespace MobileGL {
                 SizeT DetachShader(SharedPtr<ShaderObject> shader);
                 void Link();
                 void MarkAsDeleted();
+
+                void SetExplicitAttribLocation(Uint index, const char* name);
+
                 Vector<SharedPtr<ShaderObject>>& GetAttachedShaders();
                 const String& GetInfoLog() const { return m_infoLog; }
                 Int GetUniformMaxLength() const { return m_uniformNameMaxLength; }
@@ -48,11 +51,18 @@ namespace MobileGL {
 
                 SharedPtr<glslang::TProgram> m_program;
 
+                // Attributes
+                UnorderedMap<String, Uint> m_explicitAttribLocations;
+                Vector<String> m_attribs;
+
                 // Uniforms
                 // MG_Util::ShaderTranspiler::SpvcMetadata m_metadata;
 
                 UnorderedMap<String, Uint> m_uniformLocations;
+                // Ordered by location,
+                // aka. m_uniformNames[loc] == "name at location `loc`"
                 Vector<String> m_uniformNames;
+                // ditto.
                 Vector<GLenum> m_uniformTypes;
 
                 // Need to be reflected after linking of SPIR-V binary
diff --git a/MobileGL/MG_Test/Program/ProgramTest.cpp b/MobileGL/MG_Test/Program/ProgramTest.cpp
index 6e0cd42a..95118920 100644
--- a/MobileGL/MG_Test/Program/ProgramTest.cpp
+++ b/MobileGL/MG_Test/Program/ProgramTest.cpp
@@ -24,6 +24,7 @@ TEST_F(ProgramTest, Sanity) {
 const char* vsSrc = R"(#version 460
 
 in vec4 Position;
+in float fIn;
 
 layout(location = 0) uniform mat4 ProjMat;
 uniform vec2 InSize;
@@ -36,7 +37,7 @@ void main(){
     vec4 outPos = ProjMat * vec4(Position.xy, 0.0, 1.0);
     gl_Position = vec4(outPos.xy, 0.2, 1.0);
 
-    oneTexel = 1.0 / InSize;
+    oneTexel = (1.0 * fIn) / InSize;
 
     texCoord = Position.xy / OutSize;
 })";