swung0x48
ae57d01168
`unaligned-atomic-buffer-range@P7`, `unaligned-storage-buffer-range@P7` and
`unaligned-texel-buffer-range@P7` become named declines (rule I (a)). The two
offset-overflow guards next to them keep their named Fatal under their own words:
those are arithmetic that cannot happen, not shapes an application can bind.
The atomic-counter one is the only member of this cluster an application can
actually reach, and it is a real live gap, not a hypothetical. GL 4.6 core 6.1.1
gives GL_ATOMIC_COUNTER_BUFFER no queryable offset alignment, so
ValidateBufferRangeOffsetAndSize only enforces offset % 4 on it - while glslang
lowers every atomic_uint onto a synthesized storage block whose descriptor offset
must be a multiple of minStorageBufferOffsetAlignment (16 on lavapipe, 64 on
Adreno). `glBindBufferRange(GL_ATOMIC_COUNTER_BUFFER, 0, buf, 4, 4)` is a legal
GL bind that this backend cannot express, and it used to take the session with
it. The plain SSBO and texel halves are unreachable by comparison:
GL_SHADER_STORAGE_BUFFER_OFFSET_ALIGNMENT and GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT
are published from the same Vulkan limits, so the frontend already answers
GL_INVALID_VALUE.
DECLINED RATHER THAN COPIED, and this is the package's one real design choice.
Copying the window into an aligned transient slice reads correctly and then
silently DROPS every shader write. This site cannot tell a writable storage block
from a read-only one - there is no readonly bit in the storage-block reflection,
an atomic counter is written by definition, and MarkWireBufferGpuWritten right
below already assumes any binding here may be written. A correct copy needs a
post-dispatch copy-back from the transient slice to the unaligned source, ordered
with a barrier, and the place to record that is the draw/dispatch tail in
VulkanRenderer.cpp / WireDraw.inc - wave-2 packages B and C, not this file.
Returning stale counters with no error is worse than losing the dispatch with a
named line in the role log. notes/p7/magma-a.md carries the recipe for whoever
holds those files.
The texel half keeps the draw where it safely can: a read-only buffer texture
falls back to the same placeholder view an unbound one gets (zeros, which is what
a missing view gives in monolith), while a writable imageBuffer declines - the
placeholder is shared by every unbound binding, so absorbing real stores into it
would alias other bindings as well as lose the writes. Copying is not available
there either: the transient arena carries no {UNIFORM,STORAGE}_TEXEL_BUFFER
usage, so no VkBufferView can be made over it, and widening a shared per-frame
allocation to buy an unreachable path is the wrong trade.
red-once (R-16), a reachable case this time, all three Magma two-process arms:
DirectVulkan.{Split,Spawn,Tcp}.Buffers.F1WireScenario.UnalignedAtomicCounterRangeDeclinesAndTheSessionLives
before Subprocess aborted - Fatal{UnmigratedVerb, "Magma:unaligned-atomic-buffer-range@P7"}
after 3/3 Passed, and the role log carries
"block 'gl_AtomicCounterBlock_0' is bound at offset 4, which is not a
multiple of this device's minStorageBufferOffsetAlignment (16);
atomic-counter ranges cannot be expressed as a descriptor ... DECLINED
(unaligned-atomic-buffer-range)"
The case pins the decline's whole observable: the bind raises no GL error, the
dispatch does not run, every byte of the counter buffer is unchanged, and the
context still serves ordinary work afterwards. A future copy-back turns one
EXPECT into seed[1] + 1 and leaves the rest standing.
Lanes: integration-magma-split 75/75, -spawn 54/54, -tcp 56/56,
integration-magma-buffers 21/21.
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.