swung0x48
452d33b578
CONTRACT-P7 §3.2's `multisample-blit-shape@P7`. The name covered two halves that
are not the same question.
The half with an arm: a multisample colour blit whose destination rectangle is a
different size from its source. vkCmdResolveImage carries one extent and one
offset per side, so it can express neither the scale nor the flip - which is why
this arm already resolved into a single-sample scratch at raw offsets and blitted
THAT for the flip. The two `width != |dx1-dx0|` clauses were the only thing
keeping the scale out of the same route, and the monolith arm reaches it the same
way (VulkanRenderer.cpp's `regionWasTransformed` branch). They are gone; the
scratch is still sized by the SOURCE rect, so only the second leg sees the scale.
The filter only started mattering with that scale - at 1:1 LINEAR and NEAREST read
the same texel - so the second leg now asks whether the format can be filtered
before it passes VK_FILTER_LINEAR, which is undefined behaviour on a format whose
optimalTilingFeatures lack SAMPLED_IMAGE_FILTER_LINEAR. GL ignores filter for a
multisample resolve anyway, so the fallback is NEAREST and not a refusal.
The half with no arm: a MULTISAMPLE DESTINATION. vkCmdCopyImage is the only
command that writes one, it takes a single extent, and GL 4.6 core 18.3.1 makes a
blit whose rectangles differ in size INVALID_OPERATION when either framebuffer is
multisampled. There is no picture to get right, so rule I (a): MGLOG_E_ONCE with
both rectangles and both sample counts, the error GL names, the destination left
alone, the session kept.
Two entries on each of the three Magma arms (`MsBlit.`), split-only because the
monolith arm drops the scale (its vkCmdResolveImage lands 1:1 at the destination
offset), so an equality between the arms would assert that the wire arm is as
wrong. The scale and the flip share one case over one source: dropping the scale
lands an 8x4 band in a 4x2 attachment, dropping the flip returns the right two
colours in the wrong order, and the second blit's expectation is the first's with
the rows swapped.
Red once (R-16, executed and reverted), twice:
* restore the two size-equality clauses ->
DirectVulkan.Split.MsBlit.…ScalesAndFlipsThroughTheResolveScratch dies as
Fatal{UnmigratedVerb, "Magma:multisample-resolve-region"};
* restore MagmaWireFatal("multisample-blit-shape@P7") ->
DirectVulkan.Split.MsBlit.…DeclinesAndKeepsTheSession dies by that name.
Reverted, 6/6 green on the three arms.
Measured on the way in: the decline's GL error reaches the client with a LATER
reply, not with the blit call, so the case's glFinish is load-bearing - without it
the INVALID_OPERATION surfaced attached to the 1:1 resolve twenty lines down.
Gates: integration-magma-split 90 (+2), -spawn 69 (+2), -tcp 71 (+2),
integration-magma-full-split 523 (+2), ctest -L unit 2420, all green;
fatal_census 79 abort sites / 44 family words / 0 unmarked; link_ratchet
--assert-monotone unchanged at 186; G1 pull .text 0xa52203 with an nm
--defined-only list identical to p7-before/pull-syms.txt (30570 lines, 0 diffs) -
every line of this commit is inside WireFramebuffer.inc's
`#if MOBILEGL_BUILD_DISAGGREGATED` or in the test tree.
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.