Summary: X-link: https://github.com/facebook/react-native/pull/42688 We are planning on overhauling NodeToString to output JSON instead of HTML for the purposes of better benchmarking and capturing trees in JSON format to benchmark later. This gives us a bit of a headache as we have to revise several build files to ensure this new library works, ensure that it is only included in certain debug builds, and deal with the benchmark <-> internal cross boundary that arises as the benchmark code (which is a separate binary) tries to interact with it. On top of it all this is really not used at all. The plan is to rip out this functionality and just put it in a separate binary that one can include if they really want to debug. That means that it cannot exist in the public API, so I am removing it here. Private internals come next Changelog: [Internal] Reviewed By: NickGerleman Differential Revision: D53137544
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 If the version is out of date, please create an issue or pull request on the vcpkg repository.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 install
to install dependencies for the test generator. - Run
yarn gentest
in theyoga
directory.
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).