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SyncCurrentFBO has an early-out that compares three memos, and it could never fire. One of the three, g_fboBindVersions, was only ever stamped by ForceBindCurrentFBO - which runs from glBlitFramebuffer and the DSA glClearNamedFramebuffer* paths and nowhere else. An application that touches neither leaves that memo at 0 while the binding slot's version is at least 1 from its first glBindFramebuffer, so the first term mismatched forever and the guard was dead code rather than merely too coarse. Every draw therefore re-walked all 40-odd attachment slots and rebuilt the 8-slot snorm/unorm clamp mask for a framebuffer that had not changed since the previous draw. SyncCurrentFBO now stamps all three memos itself, through one helper, on every path that leaves the target synced - including the default-framebuffer "nothing to do" path, which previously returned without stamping anything. The memo is renamed to say what it now records (a sync, not a bind). Instrumenting a throwaway build put it at 539998 hits against 2 misses, the misses being the first bind of each target; it was 0 hits before. Skipping the sync also skips the Bind() inside it, so all eleven call sites were checked: every one issues its own bind afterwards (PrepareForDraw and the glClearBuffer* paths bind Draw, ReadPixels and the CopyTexSubImage paths bind Read, BlitFramebuffer binds both, GetTexImage uses its own scoped binder). The global snorm/unorm clamp masks written inside the sync stay correct because they can only be stale if a different framebuffer was synced as Draw in between, which moves the pointer or slot version and forces the re-sync that rewrites them. InvalidateFramebufferBindingCache now also clears these memos: both its callers mean the ES context may have been reset, and a live early-out must not survive that. Two smaller items in the same pass. StateBackendObjectRegistry kept the backend twin and its liveness weak_ptr in two maps, so every lookup cost two hash probes and the draw path does ten to twenty of them; they are one map with one entry type now, one probe. The weak_ptr check itself is load-bearing and stays - glDeleteVertexArrays followed by glGenVertexArrays recycles heap addresses readily. And SyncNeccessaryBuffers ran the full EnsureBufferResource check once per enabled vertex attribute, which on an interleaved Minecraft-shaped VAO means four to eight times over the same VBO; it is deduplicated per distinct buffer now. ns per draw, DriverBench on a GTX 1660 SUPER, A/B against a build differing only by this diff: mc_vanilla_draw 1403 -> 1113, mc_ubo_range 983 -> 797, mc_sampler_churn 2309 -> 2003, mc_sodium_multidraw 3232 -> 3023. Against the native driver Espryt is now 4.3x on both the plain draw and the per-draw uniform-range case, from 8.7x and 9.1x at the start of this work. Unit tests 421/421. Also replayed all 38 locally-available DirectGLES trace fixtures against a baseline library: every one produced bit-identical ssim and mismatched-pixel counts, including the improved-transparency OIT trace whose scratch clear framebuffer is exactly the draw-buffer hazard the code comments warn about.
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
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_USE_ANGLE |
Load ANGLE EGL/GLES libraries. | 0, 1 |
0 |
MOBILEGL_DISABLE_SUBGROUP |
Disable Vulkan shader subgroup support. | 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_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 |
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.