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:
After fixing `calculateShadowViewMutationsForNewTree` I realized that it will be even better to test Stacking Context and mutation instructions infra using both functions: `calculateShadowViewMutationsForNewTree` (used for testing) and the Differentiator itself. This diff implements it.
Now we have two similarly working functions with different implementations that we can use for testing Differentiator and other parts of the infra.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: sammy-SC
Differential Revision: D25576922
fbshipit-source-id: 7922e9ebfb9d6ef1792566554ba0c4a14f835ae2
Summary:
The test covers most props that must generate views.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: sammy-SC
Differential Revision: D25576921
fbshipit-source-id: df5bedb8f6d409b5142e472ca2edcb1953bee4e1
Summary:
The "reparenting differ" has been the default differ for several months; ship it by removing config and the old differ.
Some functions can't be deleted yet because unit testing relies on it heavily; this can be refactored in the future if we care a lot.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D25257205
fbshipit-source-id: 6f1dcc490bb1efe3d12506addf5f0843ca48c5c6
Summary:
Changelog: [internal]
Background executor performs unnecessary operations when second `completeRoot` message from React arrives before first `completeRoot` was finished. This produces unnecessary `ShadowViewMutations`.
Mechanism:
Everytime `completeRoot` is received, before the call is dispatched on the background queue, `completeRootEventCounter_DO_NOT_USE_` is incremented.
Inside `ShadowTree::tryCommit` we check if the value has been incremented to determine if another `completeRoot` is queued.
Reviewed By: JoshuaGross
Differential Revision: D24419160
fbshipit-source-id: 11e19026feca01db6c8981b093a691a6b58a006f
Summary:
See additional assertion. Tests still pass, so no other change was necessary.
Changelog: [Internal]
Differential Revision: D23775553
fbshipit-source-id: 57d3191f25dd55ab4da189207f6d201a31b175e0
Summary:
We don't need a shared_ptr here and without it the code will be faster and simpler.
This change is aligned with any clone-line callbacks we have in the Core which accepts a `const &` and return `shared_ptr<>`.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: JoshuaGross, sammy-SC
Differential Revision: D23725687
fbshipit-source-id: 1cd959f4273913175d342302e2f12752f0114768
Summary:
Previously, to get a current root shadow node for a shadow tree, we called `tryCommit` method and stole a pointer from this. That was not a very straightforward method to get things done, and most importantly we need to do this to change the shape of the ShadowTreeCommitTransaction signature (remove a shared pointer from the callback) to make it simpler, faster and allow future improvements (see the next diff).
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: JoshuaGross, sammy-SC
Differential Revision: D23725689
fbshipit-source-id: 51950b843a0e401828b6c6a38e5e2aaaf21ec166
Summary:
In `StateReconciliationTest`, the way initializer lists are used to create null `ShadowNode`s causes this error on Visual Studio 2017 on Windows:
```cpp
auto result = (ShadowNode const *){nullptr};
```
---
```
StateReconciliationTest.cpp(35): error C4576: a parenthesized type followed by an init
ializer list is a non-standard explicit type conversion syntax
```
This change allows this test to compile in Visual Studio 2017, and the effected tests successfully compile and pass on Windows. They also compile and pass on Linux and macOS (both built with Clang)
## Changelog
Changelog: [Internal][Changed] - Fabric Tests: Change null ShadowNode creation in StateReconciliationTest
Pull Request resolved: https://github.com/facebook/react-native/pull/29899
Test Plan: The Fabric test suite passes on Windows after this change is made. I also tested it under macOS and Linux built with Clang and they both pass with this change made.
Reviewed By: sammy-SC
Differential Revision: D23592007
Pulled By: shergin
fbshipit-source-id: 7c6131736d478a0bf29d6c9475ef9149b7602dd6
Summary:
Just renaming, nothing more.
The idea of MountingTelemetry already grown to something bigger than just mounting telemetry, so we are renaming it.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: mdvacca
Differential Revision: D23374947
fbshipit-source-id: f60ce38b75d1ce77498b84688e59598314c69a78
Summary:
Now we store a revision number of a Shadow Tree that leads to a transaction for which the concrete instance of MountingTelemetry corresponds. This is useful to understand how many actual transactions were skipped during a mounting phase (a mounting transaction does not directly correspond to a commit operation).
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: mdvacca
Differential Revision: D23364663
fbshipit-source-id: 32b86bcdfc1ae97d8fff3b97a8615cc5a5b4d4a9
Summary:
With this change, we now collect the number of text measurements that we perform during the layout phase of the commit. Text measurements are the most expensive layout operations which pretty much responsible for the vast majority of time spent in the layout phase.
Changelog: [Internal] Fabric-specific internal change.
Reviewed By: mdvacca
Differential Revision: D23364664
fbshipit-source-id: 19514b93166b4053c2f3be37e79507f2c5248000
Summary:
# What is this?
For a very long time, we've discussed the possibility of detecting Node Reparenting in the Fabric Differ. Practically, from the developer perspective, ReactJS and React Native do not allow reparenting: nodes cannot be reparented, only deleted and then recreated with entirely new tags.
However, Fabric introduced the idea of View Flattening where views deemed unnecessary would be removed from the View hierarchy entirely. This is great and improves memory usage, except for one issue: if a View becomes unflattened, or becomes flattened, the entire tree underneath it must be rebuilt.
In a past diff we introduced a mechanism to detect sibling reordering cleverly, and produce a minimal instruction set. This diff is very similar: we know the invariants around flattening and unflattening of views and we take advantage of them to produce an optimal set of instructions efficiently.
# What's different from previous attempts?
No global maps! Those are slow!
This seems to work and (hopefully) might even improve performance, since way less work is being done on the UI thread in cases when views are (un)flattened.
This *only* does extra work when flattening/unflattening happens, which gives product engineers a little more control over perf.
# So, how's it work?
This algorithm is intuitively simple (I think) but tricky to pull off, because there are lots of edge-cases.
In short: In the past, that information was hidden from the Differ: the differ didn't know if views were being reparented, it would see them
as entirely new views or as views being deleted if a View was flattened or unflattened. We very subtly change the information given to the differ:
all nodes are visible to the differ, but marked as Flattened or Unflattened. Thus, when the differ compares two nodes in the "old" and "new" tree,
it can tell not just if there are updates to the node but if it has been unflattened or flattened as well.
For example, take this tree, where * indicates that a View is flattened:
```
A
+
+----+---+
B* X
+ +
| |
+---+--+ +
E F Y
```
When the Differ asks for the children of A, in the past it would get a list `[E, F, X]`. That is, B* and X are both its children, but since B is flattened, it is omitted entirely from the list and
its children are substituted.
Now, when the Differ asks for the children of A, we give it this list instead: `[B*, E, F, X]`. That is: we give it a list which includes B, but B is marked as flattened.
Another wrinkle: A node `X` could have its children flattened, but still be a concrete view: so flattening/unflattening is a different operation from making a view "concrete" or "unconcrete", which can change independently of flattening.
There is one additional wrinkle: because of zIndex/stacking order, the children of `B` might not actually appear after `B` in the list. Depending on zIndex, a tree that looks like this:
```
A
+
+------+------+
B* C*
+ +
| |
+--+--+ +--+--+
D E F G
```
Could actually be linearized as: `[D G B* F C* E]` (as an extreme example; but basically all permutations as possible).
This is the reason, and the *only* reason that the inner Flattener/Unflattener
## The cases we need to handle
There are 7 cases/edge-cases of flattening and unflattening that we need to handle. Practically, all cases of reordering + flattening/unflattening, and taking recursive cases into account:
1. View A and A' (A in the old tree, A' in the new tree) are matched in the differ, and A* has been flattened or unflattened. These two cases are the easiest to handle.
2. View A' has been reordered with its siblings, and has been flattened or unflattened. These cases are slightly trickier to handle.
3. While flattening or unflattening, we encounter a child that has also been unflattened or flattened. So we need to handle four cases here in total: Flatten-Flatten, Flatten-Unflatten, Unflatten-Flatten, and Unflatten-Unflatten.
Other things to think about, also covered above:
1. Ordering. Views can be reordered and flattened/unflattened at the same time.
2. zIndex ordering: children in a certain order from the ShadowNode perspective may be stacked differently from a View perspective. We use the zIndex ordering for everything in the differ, and this prevents us from performing certain optimizations (see above: we cannot assume that children come after their parent in a list; they may come before, may be interwoven with children from other parents, etc).
# Perf Implications?
Practically, there should be very little negative overhead. There is some overhead in actually performing a flattening/unflattening operation, but... not much more than before. We don't use global maps, so the cost of flattening/unflattening is basically `O(number of nodes reparented)` - note that that's direct nodes reparented, *not* descendants.
tl;dr the perf hit should be similar to reordering, which is non-zero, but close to zero, and zero-cost for any diff operations on parts of the tree that don't involve flattening/unflattening. AFAICT this is very close to an ideal solution for that reason (but I wish it was simpler overall).
# In Summary?
I hope this works out and I think it could improve a number of things downstream: perf, LayoutAnimations, Bindings, certain crashes because of platform assumptions about mutations, etc.
Is it worth it? This new implementation is substantially harder to reason about, harder to read, and harder to understand. This is an important consideration. All I can say there is that I trust the test suite I've been using, but
the decreased readability is a big negative. Hopefully we can improve this in the future.
The rest is fiddly implementation details that I sincerely hope can be improved and simplified in the future.
# Followups?
The part that makes this algorithm the most expensive is that because of zIndex ordering, we cannot assume that children are linearized after their parents and so we rely more heavily on maps for the flattening/unflattening. Our TinyMap implementation should make these `find` operations fast enough unless trees' children are constantly being reordered, but it's still worth thinking of ways to make this even faster.
Changelog: [Internal]
Reviewed By: shergin, mdvacca
Differential Revision: D23259341
fbshipit-source-id: 35d9b90caf262d601a31996ea2cb37e329c61ffc
Summary:
Partial backout of D23123575 (https://github.com/facebook/react-native/commit/1e4d8d902daca8e524ba67fc3c1f4b77698c4d08). It's causing some crashes and there is a more efficient way of doing it, which I will land in a future diff.
Leaving unused feature-flags in place for now, they'll be used shortly.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D23198625
fbshipit-source-id: 6e9cbc6b39898a604b8f4dfccf5a6dd238511a68
Summary:
# Summary
In previous diffs earlier in 2020, we made changes to detect and optimize reordering of views when the order of views changed underneath the same parent.
However, until now we have ignored reparenting and there's evidence of issues because of that. Because Fabric flattens views more aggressively, reparenting is also marginally more likely to happen.
This diff introduces a very general Reparenting detection. It will work with view flattening/unflattening, as well as tree grafting - subtrees moved to entirely different parts of the tree, not just a single
parent disappearing or reappearing because of flattening/unflattening.
There is also another consideration: previously, we were generating strictly too many Create+Delete operations that were redundant and could cause consistency issues, crashes, or bugs on platforms that do not handle that gracefully -
especially since the ordering of the Create+Delete is not guaranteed (a reparented view could be created "first" and then the differ could later issue a "delete" for the same view).
Intuition behind how it works: we know the cases where we can detect reparenting: it's when nodes are *not* matched up with another node from the other tree, and we're either trying to delete an entire subtree, or create an entire subtree. For perf reasons, we generate whatever set of operations comes first (say, we generate all the Delete and Remove instructions) and take note in the `ReparentingMetadata` data-structure that Delete and/or Remove have been performed for each tag (if ordering is different, we do the same for Create+Insert if those come first). Then if we later detect a corresponding subtree creation/deletion, we don't generate those mutations and we mark the previous mutations for deletion. This incurs some map lookup cost, but this is only wasteful for commits where a large tree is deleted and a large tree is created, without reparenting.
We may be able to improve perf further for certain edge-cases in the future.
# Why can't we solve this in JS?
Two things:
1. We certainly can avoid reparenting situations in JS, but it's trickier than before because of Fabric's view flattening logic - product engineers would have to think much harder about how to prevent reparenting in the general case.
2. In the case of specific views like BottomSheet that may crash if they're reparented, the solution is to make sure that the BottomSheet and the first child of the BottomSheet is never memoized, so that lifecycle functions and render are called more often; and that in every render, the BottomSheet manually clones its child, so that when the Views are recreated, the child of the BottomSheet has a tag and is an entirely different instance. This is certainly possible to do but feels like an onerous requirement for product teams, and it could be challenging to track down every specific BottomSheet that is memoized and/or hoist them higher in the view hierarchy so they're not reparented as often.
Reviewed By: shergin
Differential Revision: D23123575
fbshipit-source-id: 2fa7e1f026f87b6f0c60cad469a3ba85cdc234de
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
Valentin Shergin
Joshua Gross
Samuel Susla
generatedunixname89002005287564
empyrical
David Vacca