swung0x48
43f8b47088
- Track H subsystem 4 (P2 brief D12.4, ARCHITECTURE.md 9.5), behind
kMGPipeSubsystemMagmaVertexInput.
- VertexInputStateFactory::ComputeHash's buffer identity component becomes the buffer's
{slot, gen} - "lifetimeId -> gen mixed into every server-side content hash". Both are
equally ABA-proof (the allocator maps one onto the other and bumps Gen only on slot
REUSE); what changes is that the hash now carries the identity the SERVER will be handed
once buffers travel as handles, instead of a number only the client can mint.
- LookupVaoDrawMemo becomes a direct slot index: the slot IS the index, and the whole
validation is one handle compare. Gone with the re-key are the Fibonacci mix of the VAO's
address, the two-way probe, the frame-serial eviction choice and the (pointer, lifetime
id) pair - slots are dense by construction, so consecutive VAOs land in consecutive
entries and the collision the address hash existed to spread does not arise below the
table size.
- The table stays FIXED at 2048 entries and the slot index wraps, where the brief calls
for a grow-on-demand vector. Reason, and it is a tree fact the brief does not carry:
nothing in P2 frees a VertexElementsCso slot. The frontend death notification is Espryt
0b's e2 and it covers Espryt's six kinds; buffers are the only kind with an OnDestroy
hook today. A grow-on-demand table would therefore hold one ~1 KB VaoDrawMemo per VAO
EVER created, which on a chunk-cycling Minecraft frame is tens of megabytes. Above the
table size this degrades to a direct-mapped cache validated by the full {slot, gen}:
never wrong, only colder, and strictly better than the address hash it replaces.
Revisit when object deletion reaches the client allocator.
- SetupDrawSnapshot's VAO identity collapses to the same handle - one compare instead of
(address, lifetime id) - so the snapshot and the draw memo cannot disagree about whether
the VAO moved. The config version stays: it answers a different question.
- Handle acquisition sits behind a one-entry memo in the renderer. Acquiring is a hash
probe into the allocator's lifetimeId -> slot map and LookupVaoDrawMemo runs per draw, so
without it the arm would have swapped the address hash it deletes for another probe; a
run of draws over one VAO now pays a single Uint64 compare. Magma acquires the handles
itself because the tracker does not emit object-class state in P2 (it emits for dirty
bits 0-4 only); when it does, these become reads of what the client already sent.
- Negative control C (MOBILEGL_PIPE_HANDLE_ABA_CONTROL, brief D18) is implemented here
because the two guards it defeats live here: it makes ComputeHash hash the raw
BufferObject* and makes LookupVaoDrawMemo skip the lifetime-id compare - the exact state
the table was in before the ABA fix. It applies to the PRE-HANDLE arm, which is what
HandleRecycleScenario.AbaControl runs (MOBILEGL_PIPE_PUSH=0), and it is what proves that
scenario's reproducer still reproduces instead of passing for the wrong reason.
- Verification on this tree: ctest -L integration-gpu -R DirectVulkan is 432/432 under the
default bitmask and 432/432 under MOBILEGL_PIPE_PUSH=0, and -L unit is green. Pull build
symbol_report --threshold 0: 0 added / 0 removed / 0 renamed, 4 resized, all four the
contract commit's.
MobileGL
A desktop OpenGL implementation
MobileGL is a free and open-source project that implements a desktop OpenGL API. The goal is to provide a complete desktop OpenGL implementation with a state management layer and multi-backend support.
Note
Status: In development. Parts of the codebase are incomplete. Current short-term target: OpenGL 4.2 (Core Profile).
Project positioning
MobileGL is an implementation of a desktop OpenGL library. It aims to provide:
- Full OpenGL state management.
- A front-end that exposes OpenGL functions.
- Multiple independent backend implementations, where each backend targets a specific graphics API and remains fully isolated from others.
This project is intended as an implementation/translation layer.
Key components
The repository is organized into following top-level modules:
- MG_State — state tracking and management logic for Graphics APIs.
- MG_Impl — front-end implementations of Graphics APIs that interact with
MG_StateandMG_Backend. - MG_Backend — per-backend translation layer that maps front-end Graphics APIs' semantics and state into concrete backend API calls (e.g. OpenGL ES, Vulkan).
- MG_Util and other utility modules.
Third-party components
MobileGL reuses several open-source projects:
- SPIRV-Cross by KhronosGroup - Apache License 2.0: github
- glslang by KhronosGroup - Various Licenses: github
- DiligentCore by Diligent Graphics - Apache License 2.0: github
- flat_hash_map by Malte Skarupke - Boost Software License 1.0: github
Refer to each component's repository for exact license texts. Any bundled third-party code in this repository is included under the upstream project's license.
Compatibility & target
- Short-term target:
OpenGL 4.2 (Core Profile). - Current development focus:
- Performance improvement
MG_StateandMG_ImplforOpenGL 4.2 (Core Profile)Direct (Vulkan)backendDirect (OpenGL ES)backend
Build Instructions
We currently provide no releases and no precompiled binaries.
If you want to try the project right now, you’ll need to build it yourself:
-
Clone the repository:
git clone https://github.com/MobileGL-Dev/MobileGL.git -
Initialize and update all submodules recursively:
git submodule update --init --recursive -
Follow glslang’s own documentation for its required initiation.
-
Configure and build the project with CMake:
cmake -B build cmake --build buildor do it in a modern way:
cmake -S . -B build -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ cmake --build buildAlternatively, you can use platform-specific build commands as needed.
Build For macOS
On macOS, MobileGL can be built as a dylib that exposes the normal OpenGL/CGL/NSOpenGL entry points and routes them to the DirectVulkan backend. This is useful for running applications such as Minecraft through their stock GLFW/LWJGL OpenGL path while MobileGL is injected before context creation.
Prerequisites:
- macOS with Clang and Ninja.
- Vulkan loader and MoltenVK installed. With Homebrew, the MoltenVK ICD is commonly located at
/opt/homebrew/etc/vulkan/icd.d/MoltenVK_icd.json.
Configure and build:
cmake -S . -B build-macos-magma \
-G Ninja \
-DCMAKE_BUILD_TYPE=Release \
-DMOBILEGL_BACKEND_TYPE=DirectVulkan \
-DMOBILEGL_BUILD_TEST=OFF \
-DMOBILEGL_BUILD_BENCHMARK=OFF
cmake --build build-macos-magma --target MobileGL -j8
The dylib will be generated at:
build-macos-magma/libMobileGL.dylib
To run Minecraft by MobileGL from a launcher like PrismLauncher, keep the stock LWJGL/GLFW natives and add a wrapper command to the instance settings:
env DYLD_INSERT_LIBRARIES=/absolute/path/to/MobileGL/build-macos-magma/libMobileGL.dylib MOBILEGL_BACKEND_TYPE=DirectVulkan VK_ICD_FILENAMES=/opt/homebrew/etc/vulkan/icd.d/MoltenVK_icd.json
Also make sure the JVM arguments include:
-XstartOnFirstThread
DYLD_INSERT_LIBRARIES must be active before GLFW creates its OpenGL context. After startup, the Minecraft F3 screen should report MobileGL and the Direct (Vulkan) backend if the injection worked.
Build Options
| Option | Description | Default |
|---|---|---|
MOBILEGL_BUILD_TEST |
Build MobileGL tests (requires Clang) | ON |
MOBILEGL_BUILD_BENCHMARK |
Build MobileGL benchmarks (requires Clang) | ON |
MOBILEGL_FORCE_RELEASE_OPT |
Enable O3 and LTO in Debug build | ON |
MOBILEGL_ENABLE_TRACY |
Enable Tracy profiler for performance analysis | OFF |
Notes:
- The project requires C++23.
MG_TestandMG_Benchmarkcan only be built with Clang, not GCC. To enforce Clang, add-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++to your command.- On Android, tests and benchmarks are always disabled.
Environment Variables
MobileGL supports runtime configuration via environment variables.
Supported Keys
| Variable | Description | Allowed Values | Default |
|---|---|---|---|
MOBILEGL_BACKEND_TYPE |
Select active backend implementation at startup. | DirectGLES, DirectVulkan |
DirectGLES |
MOBILEGL_DISABLE_TIMERQUERY |
Disable GPU timer-query exposure and use. | 0, 1 |
0 |
MOBILEGL_ESPRYT_USE_ANGLE |
Load ANGLE EGL/GLES libraries. | 0, 1 |
0 |
MOBILEGL_MAGMA_DISABLE_SUBGROUP |
Disable Vulkan shader subgroup support. | 0, 1 |
0 |
MOBILEGL_ADVERTISE_FP64 |
Advertise GL_ARB_gpu_shader_fp64. GLSL double/dvec/dmat compile and run either way - they are narrowed to 32 bits - so this only changes whether an application is told it has 64-bit precision, which it does not. |
0, 1 |
0 |
MOBILEGL_MAGMA_R11G11B10F_FALLBACK |
Use Magma's R11G11B10F format fallback. | 0, 1 |
0 |
MOBILEGL_MAGMA_FRAMESINFLIGHT |
Set Magma frames in flight. | Integer 1–64 |
3 |
MOBILEGL_ESPRYT_AVOID_SAMPLER_MIPMAP_MIN_FILTER |
Avoid sampler mipmap minification filters. | 0, 1 |
0 |
MOBILEGL_COHERENT_AS_FLUSH |
Treat persistent GL_MAP_FLUSH_EXPLICIT_BIT maps as coherent (app-compat for engines like Flywheel that never flush them). |
0, 1 |
0 |
MOBILEGL_ESPRYT_FORCE_DS_READBACK_EMULATION |
Always emulate depth/stencil glReadPixels/glGetTexImage by shader sampling on Espryt, instead of using the driver's own depth/stencil readback where it has one. |
0, 1 |
0 |
VK_ICD_FILENAMES |
Select the Vulkan ICD used by the Vulkan loader. | Path to an ICD JSON file | Loader default |
License
This project is distributed under GNU LGPL v3.0. See the LICENSE file in the repository for detailed information.