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- ID-133: escalation (iii) in MGPipeBarriered - a draw_vbo with NumDraws > 1 that is NOT
kDrawIsIndirect is barriered. Espryt's indirect multi-draw tiers reach
MultiDrawImpl::RunIndirect, whose apply reads the client's GL_DRAW_INDIRECT_BUFFER binding
(BoundDrawIndirectBufferId, MultiDraw.cpp:87) - GetBufferBindingSlot, retiring in P8 - and
unbarriered that is Fatal{UnmigratedPipeInput, "GetBufferBindingSlot@DrawArrays"} on 18 lane
entries. Backtrace of the aborting thread, verbatim frames: CountBarrierPull <-
MultiDrawImpl::RunIndirect <- MultiDrawImpl::DrawElementsBatch <- ServerVerbSink::OnDrawVbo
<- PipeWireDecoder::DecodeAndApply <- PipeApplier::ApplyOne.
- TWO PREMISE CORRECTIONS, both measured, both in the report and in the contract. (a) There is
no indirect multi-draw OP: all twenty draw entry points collapse onto draw_vbo, and the tier
is resolved on the server per batch (ResolveTierForBatch), so the escalation cannot be keyed
on the tier and its cost is NOT confined to the opt-in tier lanes - a plain glMultiDraw* now
waits on the auto -> ext default too. NumDraws > 1 is the narrowest wire fact that contains
the reaching set; kDrawIsIndirect is excluded so Sodium's indirect draw, which resolves by
handle and pulls nothing, keeps running ahead. (b) The read is a SAVE/RESTORE of a GL binding
name around the tier's own scratch buffer, not a data dependency - so it can be retired
outright by giving BoundDrawIndirectBufferId the handle arm its neighbour
ResolveBoundIndexBuffer already has, and this escalation withdrawn. That is three lines in
MultiDraw.cpp, which ID-113 gives to mv, so it is reported rather than edited here.
- The client's half is verb-keyed because the fill decision is asked before the record exists:
{MultiDrawArrays, MultiDrawElements, MultiDrawElementsBaseVertex} is exactly the set whose
record can carry NumDraws > 1 without kDrawIsIndirect. The inclusion goes that way round on
purpose - a record the server calls barriered whose fields the client did not fill would be
an ADMITTED pull of a stale value, which is worse than the abort.
- ID-134: the two ClientVertexArrayScenario entries get the label integration-clientarrays-split
and an expected-red CI step that asserts the MARKER, shaped like gl's Magma lane. ID-131 heeded
by COUNTING, not by assuming: -L integration-split 181 -> 179, -L integration-gpu 1359 -> 1357,
the new label selects exactly 2. The step branches on whether run-ahead is actually ARMED,
because kMGPipeP5eRunAheadReady is a BUILD constant: on a head where it is false the refusal is
unreachable and the entries are legitimately green, so an unconditional demand for red would
fail for the one reason that is not a defect. The client says which world it is in in its own
log line; delete the green branch when the flip lands for good.
- CONTRACT-P5E §3.5 amended to the code: "outside a barriered fill" rested on the caller's claim
about the FUTURE, and a guard whose exemption cannot be false on the class it exists for is not
a guard - it never fired on any of the 70 red entries. The landed rule is "not while the applier
is inside, barriered fill or not", with the fill sites taking §2.5's forced wait first, twice
per filling verb because the block is written either side of the emitters.
- AND §3.2 IS MARKED UNLANDED, which nobody had noticed: "the server's stamp is server-private
… never into the shared block" describes storage the applier owns, and
MGPipeServerStampVerbBoundary still writes m_filled / m_currentVerb / m_serverStampedVerb into
gPipeInputs itself. That gap is what made the race possible. Splitting the stamp is the P11
item - but per-role stamps WITHOUT versioning the BARRIER_PULLED values would be worse than
today, because it turns a loud Fatal into a silent stale read.
- §2.1 carries escalation (iii) as a row, per its own rule that a new escalation is a ruling and
a row in the contract rather than a condition at a call site.
- Gate on the flipped head: unit 2256/2256, isplit 179/179 HARD GREEN, gens rc=0, doc citations
rc=0 (the three remaining are CONTRACT-P5.md's and pre-date this branch).
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.