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The shared control page both roles map had a mixed-writer cache line:
{appliedSeq, submittedSeq, retiredSeq, completedFrameSerial, presentAckSerial}
sat together, but submittedSeq is producer-written (Ring.h's "THE FIVE
WATERMARKS") while the other four are consumer-written. That is why no
single-writer progress block could be aliased over it, and it is what this
package fixes: submittedSeq moves up beside cmdHead, the other thing the
producer writes, and the four that remain become a named LinkProgress member -
the struct c6 declared in ILink.h - so a data plane with no shared page can own
the same four values and every wait predicate in SessionRings.h keeps ONE
implementation at source level.
The two event flags deliberately stay in the doorbell group. Promoting them
would put the client's per-drain exchange(0) on eventRingFull (EventRing.h:200)
onto the line the client's own spin predicate reads 1e5-1e6 times a frame.
73 call sites rewritten, 15 in the library and 58 in tests. The rewrite is
receiver-scoped rather than field-scoped, because SplitRuntimePeek.h:77 has its
own struct with a field of the same name and SplitRuntimePeek.cpp:146 has both
on one line - a field-scoped rename would have silently broken the peek struct
that MagmaRunAheadScenario reads nine times.
THE ASSERTS ARE THE PART THAT NEEDED A SECOND PASS. The first revision shipped
four aggregate asserts and an adversarial review broke them by counterexample:
swapping retiredSeq and completedFrameSerial inside LinkProgress compiled
clean, passed all four, and passed the runtime layout test too - because
appliedSeq stays at offset 0. Three wire-visible offsets on a shared page were
pinned by nothing. Nothing else in the tree covers it either: the ABI
fingerprint takes no input from this page, and sizeof(RingControl) is 4096
whatever the members do, because alignas(4096) makes it so.
So the block is now per-field as CONTRACT-P6 §8.3 actually asked, plus a
standard-layout precondition, a tail bound that alignas cannot satisfy for us,
and the LinkEventFlags mirror. Each was run red: the field swap reds the
per-field asserts by name, a fifth member inside LinkProgress reds sizeof.
One of them cannot go red, and Ring.h now says so rather than implying
otherwise. A SMALL member inserted between Progress and serverEpoch lands at
offset 288, inside Progress's own line, and serverEpoch's alignas(64) absorbs
up to 32 bytes of it - so both line asserts still pass. The review's proposed
fix does not catch it either; I tried it. A gate nobody can falsify is worse
than no gate, so the limit is written down beside the asserts.
Also: RingTest.ControlPageLayoutIsTheSharedContract said nothing about the one
field this package moved, and now asserts the producer/consumer separation and
the event flags' exclusion itself rather than borrowing the claim from Ring.h.
Ring.h grew 30 lines, so the Ring.h:NN citations this package and c6 authored
are re-anchored to named blocks instead of line numbers. ARCHITECTURE.md §11.2
is updated for the new layout, and a factual error introduced in the previous
revision of that paragraph - submittedSeq annotated as releasing staging, which
retiredSeq does - is corrected.
Gates: pull 0 added / 0 removed, .text size 10822147 unchanged; split 0/0,
.text size 11681395 unchanged; unit suite 2326/2328 with the same two
pre-existing environmental failures as the baseline. The five edits behind
MGITEST_SPLIT_RUNTIME_PEEK were proven compiled by a red-once, not assumed.
Note on the .text claim: that is a SIZE, not the bytes - field offsets moved,
so immediates moved with them. And this page's layout IS observable across
binaries; what is unobservable is behaviour within one binary. The contract
already books the layout change deliberately, before spawn exists to care.
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.