292e2f3944
Summary: X-link: https://github.com/facebook/react-native/pull/42645 We want to be able to capture Yoga trees in production. To do this we need to serialize and deserialize the in-memory representation of a tree. We have a way to turn a tree into html using NodeToString.cpp but that outputs html, which is going to be hard to deserialize. So, I added the [nlohmann json library](https://github.com/nlohmann/json/tree/develop?tab=readme-ov-file) so that we can serialize into JSON instead. Then we need to change the inner workings of NodeToString.cpp to use this library instead of its html. One of the bigger structural changes I made was standardizing the checks need to append something to the string. What we want is to only add something if it is not the default style. The existing logic does that but bears the burden of knowing what the default of certain styles actually is. This just calls the getter on a new node to obtain that value, which should simplify things a bit. Reviewed By: NickGerleman Differential Revision: D52929268
Yoga 
Yoga is an embeddable and performant flexbox layout engine with bindings for multiple languages.
Building
Yoga's main implementation targets C++ 20 with accompanying build logic in CMake. A wrapper is provided to build the main library and run unit tests.
./unit_tests <Debug|Release>
While not required, this script will use ninja if it is installed for faster builds.
Yoga is additionally part of the vcpkg collection of ports maintained by Microsoft and community contributors. If the version is out of date, please create an issue or pull request on the vcpkg repository.
Adding Tests
Many of Yoga's tests are automatically generated, using HTML fixtures describing node structure. These are rendered in Chrome to generate an expected layout result for the tree. New fixtures can be added to gentest/fixtures.
<div id="my_test" style="width: 100px; height: 100px; align-items: center;">
<div style="width: 50px; height: 50px;"></div>
</div>
To generate new tests from added fixtures:
- Ensure you have yarn classic installed.
- Run
yarn installto install dependencies for the test generator. - Run
yarn gentestin theyogadirectory.
Debugging
Yoga provides a VSCode "launch.json" configuration which allows debugging unit tests. Simply add your breakpoints, and run "Debug C++ Unit tests (lldb)" (or "Debug C++ Unit tests (vsdbg)" on Windows).