0908d3a173
Summary: Adds a data structure that holds a series of values that can be *borrowed* for exclusive writing. That means, that only a single consumer can write to any value owned by the data structure. In addition, the data structure exposes read access via iteration over all contained values. A typical use case would be a counter with thread-local values that are accumulated by readers in other parts of a programm. The design carefully avoids the use of atomics or locks for reading and writing. This approach avoids cache flushes and bus sync between cores. Borrowing and returning a value go through a central lock to guarantee the consistency of the underlying data structure. Values are allocated in a `std::forward_list`, which typically should avoid two values in the same cache line -- in that case, writing to one value would still cause cache flushing on other cores. An alternative approach would be to allocate values continuously on cache line boundaries (with padding between them). We can still change the code if the current approach turns out to be too naive (non-deterministic). Reviewed By: SidharthGuglani Differential Revision: D15535018 fbshipit-source-id: 212ac88bba9682a4c9d4326b46de0ee2fb5d9a7e
Yoga 
Building
Yoga builds with buck. Make sure you install buck before contributing to Yoga. Yoga's main implementation is in C, with bindings to supported languages and frameworks. When making changes to Yoga please ensure the changes are also propagated to these bindings when applicable.
Testing
For testing we rely on gtest as a submodule. After cloning Yoga run git submodule init followed by git submodule update.
For any changes you make you should ensure that all the tests are passing. In case you make any fixes or additions to the library please also add tests for that change to ensure we don't break anything in the future. Tests are located in the tests directory. Run the tests by executing buck test //:yoga.
Instead of manually writing a test which ensures parity with web implementations of Flexbox you can run gentest/gentest.rb to generate a test for you. You can write html which you want to verify in Yoga, in gentest/fixtures folder, such as the following.
<div id="my_test" style="width: 100px; height: 100px; align-items: center;">
<div style="width: 50px; height: 50px;"></div>
</div>
Run gentest/gentest.rb to generate test code and re-run buck test //:yoga to validate the behavior. One test case will be generated for every root div in the input html.
You may need to install the latest watir-webdriver gem (gem install watir-webdriver) and ChromeDriver to run gentest/gentest.rb Ruby script.
.NET
.NET testing is not integrated in buck yet, you might need to set up .NET testing environment. We have a script which to launch C# test on macOS, csharp/tests/Facebook.Yoga/test_macos.sh.
Benchmarks
Benchmarks are located in benchmark/YGBenchmark.c and can be run with buck run //benchmark:benchmark. If you think your change has affected performance please run this before and after your change to validate that nothing has regressed. Benchmarks are run on every commit in CI.
JavaScript
Installing through NPM
npm install yoga-layout
By default this will install the library and try to build for all platforms (node, browser asm, and standalone webpack). You may receive errors if you do not have the required platform development tools already installed. To preset the platform you'd like to build for you can set a .npmrc property first.
npm config set yoga-layout:platform standalone
This will now only run the standalone webpack build upon install.
Build Platforms
| name | description |
|---|---|
| all (default) | Builds all of these platforms. |
| browser | Builds asm js browser version. |
| node | Builds node js version. |
| standalone | Runs webpack. |
| none | Does nothing. You can use the prepackaged libs. |