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The last piece of state ownership this phase owed: the eight DirectGLES twin
tables resolved a handle process-wide, so two contexts of one session that do
NOT share a share group - which have independent name spaces, so the same
{slot, gen} in both is legal - were handed the SAME twin, driver ids,
persistent map and pooled store included. Two contexts that DO share a group
were served by whichever of them twinned first. Design and per-slice shape:
docs/Disaggregated/design/11-state-ownership.md (S6).
Key: DirectGLES.h's TwinKey{SessionKey, ShareGroupKey} - the same two words
the applier's object records are filed under, with the group derived by
MGPipeApplierShareGroupKeyFor so a record and the twin describing it can never
land in different buckets. Session is in the key because a twin names a driver
id and no driver id crosses a connection.
Resolution: SessionRuntime.cpp's ResolveThreadTwinKey, installed by
InstallSessionRuntimeHooks beside the S2 PipeInputs probe, the S4 native
tuple key and the S5 applier key. It reads the ThreadSessionScope's session
and CurrentContextToken() - apply-thread state only, never MG_State, so the
frontend-keyed-lookup prohibition on the apply thread still holds. A thread
that belongs to no session answers {0, 0}, which is the process singleton this
replaces; the monolith and every unit case are unchanged by construction.
Shape: SlotTables.h's SlotTableRegistry holds one SharedPtr bucket per key,
with a thread-local last-key memo. It forwards every handle-keyed entry -
GetOrCreate, FindByHandle, LiveGenAt, HandleOf, StateForHandle,
NoteStateForHandle, ReleaseByHandle, ForEachLive, the counters - to the
CALLING THREAD's bucket, so the ~150 call sites in Managers.cpp and
DirectGLES.cpp are literally unchanged. The holder list stays process-wide: a
death notice is about an object, not a bucket, and each shared holder is one
bucket. ForEachLive now walks the calling thread's bucket (what a context can
see is its own group); the death and diagnostic walks take the new
ForEachBucket.
DropEveryTwinForEndedServerSession is session-scoped: it runs on the apply
thread of the session that is ending, while S2 lets neighbour sessions keep
rendering in the same process. No session on the thread keeps the old
process-wide drop verbatim. Managers.h's "a texture is owned by exactly one
context (share groups are not implemented)" is corrected: a texture belongs to
a share group and its sibling contexts legitimately mutate it.
Tests: MG_Test/Wire/TwinOwnershipTest.cpp, five cases driving the real twin
tables with no EGL and no wire - the same handle in two nonshared groups is
two twins and neither overwrites the other; two contexts of one group resolve
ONE twin; a per-session drop takes only that session's; a thread with no
session still gets the process-wide table; and the six-registry template
repeats the first three. Negative control run and reverted: making the
registry answer a single {0, 0} bucket turns four of the five red.
Full host ctest against a stashed baseline, compared by test name: 0 new
failures. The one name in the difference set
(LogForwardChannel.APeerThatStopsReadingCostsWarnLinesNotTheCallersTime) is a
pre-existing flake, failing on the baseline too with the identical assertion.
The 103-case acceptance set plus the five new cases is 108/108 green.
Remaining debts (documented): the unit shadows (g_activeTextureUnit,
g_boundTexturesCache, g_boundSamplersCache) are still process-global; the
driver-level glIsBuffer probe is still not usable on this host, so sharing is
proven at the twin layer (the twin IS the object holding the driver id); the
backend context/sync generations are still process-wide; the per-record
ContextSlot is still S1's edge declaration.
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_MAGMA_MAX_DRAWS_PER_COMMAND_BUFFER |
Draws and dispatches Magma records into one command buffer before it submits the buffer mid-frame and continues on a fresh one. 0 never splits. |
Integer 0–16777216 |
16384 |
MOBILEGL_MAGMA_DESCRIPTOR_TRIM_FRAMES |
Frames a frame slot's descriptor pools must stay under a quarter full before Magma frees the slot's cached descriptor sets and grown pools. 0 never trims. |
Integer 0–1048576 |
120 |
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.