BZLZHH
7c822cdc85
An independent review of the one design door the measurement left open (stop sending
the ~51,000 answers nobody reads, so the 8-slot pool stops churning and the create
window becomes collectable). Verdict: feasible, worth doing, and the proposal AS
WRITTEN would disable the thing it exists to enable.
THE CATCH. The windowed create is wantReply=false AND its answer is read -
WireTables.cpp's drain reads exactly those seqs. A bit keyed on "fire-and-forget"
therefore stops the server answering the creates the window is waiting for: the
window goes from "cannot be collected" to "there is nothing to collect", and the
readfail counter that is the only way to diagnose it disappears with it. It fails
silently, not loudly. The predicate has to be per-record "this answer will never be
read" - true of params / respecify-escape / sub-data, false of a windowed create -
carried as a separate input from wantReply (willReadReply), with
willReadReply && !rowCarriesReplySlot rejected rather than ignored.
VERIFIED HERE, not taken on trust (the reviewer's file:line claims, checked):
- the flag space is RingRecordFlags (Ring.h:281-285), bits 0-4 taken, BIT 5 FREE,
and the header's own table (PipeWire.inc:35-65) says "bit 5 kOptional vs (nothing)
no ring counterpart" - so a new ring bit aliases kOptional, which is exactly what
the assert at PipeWireCodec.cpp:142-145 refuses;
- the three static_asserts that will trip are real and deliberate
(PipeWireCodec.cpp:106, :142-145, RingTest.cpp:740);
- WireFingerprint mixes payload-layout, catalogue, render-state digests + OpCount,
none of which a ring bit moves - so no protocol revision bump is required, and
both cross-version directions degrade to today's behaviour. That makes this
"must upgrade both ends to take EFFECT", not "must upgrade both ends not to
BREAK" - one notch cheaper than handoff-2 section 3.2's protocol surface;
- StreamLink.cpp:564-571 is the independent progress flush (>= 64 records or
>= 1 ms) and :577 is PostReply piggybacking SendProgress on the reply - so
skipping replies coarsens progress granularity. Bounded, but unmeasured.
AND IT CORRECTED TWO OF MY OWN NUMBERS. The frame's reply count is 55,903, not
59,673: op 4 ResourceDestroy carries kNone in the catalogue (PipeWire.inc:179) and
PostReply Fatals on a row with no kReplySlot, so it never answers - I had added its
3,770 records to the total. The derived figures move with it (12.3 replies per create,
0.65 of a create of survival, 6,988 pool churns), and every copy is fixed here:
Config.h, ConfigLoader.cpp, WireTables.cpp's section comment, CONTRACT-P5E.md,
CREATE-WINDOW-MEASURED.md.
TWO MORE THINGS THE FOLLOW-UP MUST CARRY, both recorded in the note's section 7:
- LinkMetricsBeginReply counts ownsReplySlot, so once the flag lands by_op 2 falls
to ~0 - and section 1 of the note tells the reader to use by_op 2 to check whether
the window engaged. That check becomes a FALSE GREEN; the flag needs a
server-side "how many times did this op answer" counter beside it.
- the ~112,000 sendmsg/frame the flag removes are on the apply thread, so the
flag's own value is a measurable claim that nobody has measured.
172/172 and 13/13 after the comment corrections.
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.