Summary:
This changes Clang format config to enforce left pointer alignment instead of right, in accordance with https://www.internalfb.com/intern/wiki/Cpp/CppStyle/
Changelog: [Internal]
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Reviewed By: sammy-SC
Differential Revision: D48952040
fbshipit-source-id: 108329b2f11d2041a31dee3334c7801d69a3f1ad
Summary:
(reland of D48761722)
Pull Request resolved: https://github.com/facebook/react-native/pull/39217
React Native uses an inconsistent mix of "west const" and "east const". E.g. `const auto &` in 74 files, but `auto const &` in 60. Sometimes they are mixed from one line to the next: {F1079102436}
Clang format 14 adds a QualifierAlignment option, but fbsource is still on 12, so we cannot use it in our config until the [world is updated]()https://fb.workplace.com/groups/toolchain.fndn/posts/24006558685624673/?comment_id=24009214565359085&reply_comment_id=24009455088668366. This diff just runs a local version of Clang format locally first to fix QualifierAlignment, then reformats with the fbsource version, to fix any other output differences unrelated to that. This will not continually enforce a style, but will make the world more consistent, and hopefully encourage a consistent style until we can set it.
West const seems more popular in `//xplat` so I just picked left alignment somewhat arbitrarily, but we could also maybe take a poll on this.
Changelog: [Internal]
bypass-github-export-checks
Reviewed By: shwanton
Differential Revision: D48852450
fbshipit-source-id: 1789aa0db43948169f482188cb8b5e8f0f0246b8
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/37853
This adds a basic implementation of `IntersectionObserver`. This will not be available yet and is only compatible with the new React Native architecture. This shouldn't show up in the changelog until we're ready to enable this in some form.
Changelog: [Internal]
## Context
This implements a basic version of the `IntersectionObserver` API (as defined on the Web) for React Native.
The motivation for this is supporting several use cases that are not possible in React Native at the moment, most importantly:
* Tracking paint times for elements in the screen.
* Tracking precise visibility of elements in the screen outside the context of a `VirtualizedList` (with an even better precision and control).
## Implementation details
This API is implemented as a native module that registers a mount hook in Fabric. Whenever there's a mount (an update to the UI of the host platform) we check for intersections in the shadow tree. The shadow tree contains information about the representation of the UI in a given time (including scroll position), which we use as source of truth for this in a cross-platform fashion. We rely on the fact that scroll position is updated regularly in the shadow tree to provide an up-to-date view into the UI.
**This implementation is completely cross-platform.** The only platform-specific part is the report of mounts in mount hooks from the host platform to Fabric.
This API uses a centralized entity in JS and native to handle registration of observers and dispatch of notifications. The dispatch the notifications for all observers in the same callback so we can easily change the sequencing of events easily (for example, we can change this to use microtasks when they're available in RN).
## Known limitations
* Timestamps are generally accurate for paint (as we report mounts right after they happen in the host platform), but **state updates (like scroll) are reported with a slight delay**.
* In regular rendering, we first update the shadow tree and then mount it (paint), which is generally precise. In state updates, the UI is updated first and then the shadow tree is updated. In this case, we're not correctly reporting the timestamp of the scroll event (which we should be using) but the timestamp of when the update is processed. We'll fix this in a following diff.
* The IntersectionObserver API has a concept of initial notification. This is a mechanism to report the initial state of an observed target. If we start observing a target when it's added to the tree but before it's painted, this initial notification is supposed to provide initial paint time (which is important for performance measurements). This implements some logic to handle that correctly (we check if there is a pending transaction) but it's currently unreliable:
* React Native does not currently block paint on microtasks or layout effects, so setting up an observer in these stages could have race conditions with actual mount. If mount happens before the observation is started, the initial notification doesn't report initial time but observation time. If mount happens after, the initial notification should be fine (except in some cases on Android, see the next point).
* On Android, we have a push model to send mutations to the host platform, we means we consume transactions after commit, not immediately before mount. This breaks this logic and we need to figure out a solution in a following diff.
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Reviewed By: sammy-SC, rshest
Differential Revision: D45278720
fbshipit-source-id: de350388c6325128f1cf73328779a9d3577a258a
Nick GerlemanandFacebook GitHub Bot
Rubén NorteandFacebook GitHub Bot