Summary:
changelog: [internal]
`useLayoutEffect` has two guarantees which React Native breaks:
- Layout metrics are ready.
- Updates triggered inside `useLayoutEffect` are applied before paint. State between first commit and update is not shown on the screen.
React Native breaks the first guarantee because it uses Background Executor. Background executor moves Yoga layout to another thread. If user core reads layout metrics in `useLayoutEffect` hook, it is a race. The information might be there, or it might not. They can even read partially update information. This diff does not affect this. We already have a way to turn off Background Executor. We haven't done this because it introduces regressions on one screen but we have a solution for that.
React Native breaks the second guarantee. After Fabric's commit phase, Fabric moves to mounting the changes right away. In this diff, we queue the mounting phase and give React a chance to change what is committed to the screen. To do that, we schedule a task with user blocking priority in `RuntimeScheduler`. React, if there is an update in `useLayoutEffect`, schedules a task in the scheduler with higher priority and stops the mounting phase.
We are not delaying mounting, this just gives React a chance to interrupt it.
Fabric commit phase may be triggered by different mechanisms. C++ state update, surface tear down, template update (not used atm), setNativeProps, to name a few. Fabric only needs to block paint if commit originates from React. Otherwise the scheduling is wrong and we will get into undefined behaviour land.
Rollout:
This change is gated behind `react_fabric:block_paint_for_use_layout_effect` and will be rolled out incrementally.
Reviewed By: javache
Differential Revision: D43083051
fbshipit-source-id: bb494cf56a11763e38dce7ba0093c4dafdd8bf43
Summary:
changelog: [internal]
Passing MountingCoordinator argument by value instead of reference. Using reference does not make sense since we eventually take ownership of shared_ptr anyway. This better communicates the intent.
Reviewed By: christophpurrer
Differential Revision: D43082955
fbshipit-source-id: 29e20abb9824c10a5f0d5e0ba1049ff6d67cee98
Summary:
With the change, a new delegate method allows a receiver to alter a new (proposed) shadow tree with another tree by returning the altered tree.
We will it use in future diffs to implement Commit Hooks.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: sammy-SC
Differential Revision: D25221313
fbshipit-source-id: 9f83577d862b713fff71fa365ce660cc1de87c84
Summary:
This diff moves fabric C++ code from ReactCommon/fabric to ReactCommon/react/renderer
As part of this diff I also refactored components, codegen and callsites on CatalystApp, FB4A and venice
Script: P137350694
changelog: [internal] internal refactor
Reviewed By: fkgozali
Differential Revision: D22852139
fbshipit-source-id: f85310ba858b6afd81abfd9cbe6d70b28eca7415
Samuel Susla
Andres Suarez
Valentin Shergin
David Vacca