swung0x48
d40f753983
GL 3.3 Core: a shader input whose generic attribute array is disabled reads that
attribute's current value (per-context state, default (0,0,0,1)). Four defects made
that path non-conformant, three of them silently.
* Out-of-bounds current-value reads. m_currentVertexAttributes held 16 entries while
the DirectVulkan draw path walked shader input locations 0..31 and GL_MAX_VERTEX_ATTRIBS
was advertised straight from the device (commonly 32). The only guard was MOBILEGL_ASSERT,
which expands to nothing outside debug builds. Grow the storage capacity to 32, advertise
min(device limit, capacity), validate against that dynamic limit, and give the accessors
real runtime bounds checks. Replace the literal 32 loops with the constant, and pin
MAX_VERTEX_ATTRIBS to the Uint32 mask width and to vertexInputTypes' bound with
static_asserts so the two can no longer drift apart -- that drift was the bug.
* DirectGLES never fed current values to the driver. Values were stored in MG_State only,
so a disabled attribute always rendered as the ES driver's own untouched (0,0,0,1) while
DirectVulkan rendered it correctly: identical GL code, different pixels per backend.
Add SyncCurrentVertexAttributeValues() to the draw prologue, and hoist the
glType -> (base type, component count) dispatch into MG_State::GLState so both backends
resolve the semantics from one place instead of it living inside VulkanRenderer.
* Enabled arrays the backend could not map were silently demoted to the current value.
ToVkVertexFormat had no DataType::Float16 case, so a GL_HALF_FLOAT array fell to
VK_FORMAT_UNDEFINED, dropped out of the vertex input state, and became indistinguishable
from a disabled array: the geometry rendered a constant colour with GL_NO_ERROR. Add the
Float16 mapping, track an unsupportedAttribMask, and hard-fail the draw before pipeline
creation so no synthetic attribute is baked into a cached VkPipeline.
* glGetVertexAttrib{fv,iv,Iiv,Iuiv}(GL_CURRENT_VERTEX_ATTRIB) returned before any index
validation, reading past the array instead of raising GL_INVALID_VALUE.
Also resolve ProgramObject::DoReflection's "TODO: get from backend" 16-location clamp,
which capped the new DirectGLES sync at locations 0..15; report GL_MAX_VERTEX_ATTRIBS
through the same helper the validators use, so the clamp cannot be bypassed; and bound
vertex binding indices by the same dynamic limit, since the default attribute -> binding
mapping is the identity.
Add a "Vertex attributes" driver POST row to both backends: FAIL below the GL 3.3 Core
minimum of 16, WARN above MobileGL's storage capacity (clamped, extra attributes unusable),
PASS in between -- making the driver/host mismatch that caused the out-of-bounds read
visible instead of silently swallowed.
Covered by 7 new regression tests (each verified to fail against the previous behaviour).
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 3.3 (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 3.3 (Core Profile). - Current development focus:
MG_StateandMG_ImplforOpenGL 3.3 (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 |
VK_ICD_FILENAMES |
Select the Vulkan ICD used by the Vulkan loader. | Path to an ICD JSON file | Loader default |
Notice
- MobileGL is not production-ready currently.
- Some
OpenGL 3.3 (Core Profile)features are still missing or under development.
License
This project is distributed under GNU LGPL v3.0. See the LICENSE file in the repository for detailed information.