fix expo-scroll-edge-effect not finding the scrollview

2026-06-26 17:26:57 +02:00
parent 870d899ab2
commit e9b81b303a
4 changed files with 134 additions and 0 deletions
@@ -0,0 +1,44 @@
+# @bsky.app\_\_expo-scroll-edge-effect.patch
+
+Fixes the iOS 26 scroll edge effect (the blur under the status bar) failing to
+attach on the New Architecture (Fabric).
+
+## Why
+
+The native view resolves the target scroll view by React tag:
+`scrollViewTag` (published from JS when the scroll view mounts) ->
+`appContext.findView(withTag:)` -> attach a `UIScrollEdgeElementContainerInteraction`.
+
+On Paper this resolved on the first try, because view-by-tag registration was
+serialized through the single UIManager batch pipeline - by the time the tag
+prop reached native, the scroll view was already in the registry.
+
+On Fabric there is no synchronous tag->view registry. The scroll view's
+`ComponentView` is registered when its mount transaction is applied, which is
+deferred relative to the JS commit that set the tag. So the one-shot
+`resolveScrollView` runs before the view is mounted and returns nil, the
+interaction never attaches, and the blur is lost. (The un-gated case happened to
+work only because the header's `didMoveToWindow` provided a late second attempt;
+a list mounted later - e.g. behind an `isActive` gate - had no such retry.)
+
+## What it does
+
+Makes resolution event-driven and self-healing instead of one-shot:
+
+- When `resolveScrollView` returns nil, it bumps a bounded counter and calls
+  `setNeedsLayout()`; `layoutSubviews()` re-attempts as sibling views mount, so
+  it retries exactly when the scroll view actually appears - no fixed timer.
+- `isAttached` stops re-running once resolved (no teardown/re-attach churn).
+- `resolveAttempts` / `maxResolveAttempts` bound the retries so a
+  permanently-absent scroll view (list not rendered) cannot spin layout forever.
+- The budget is reset on every "fresh" trigger (prop change, entering the
+  window) via `scheduleResolve()`, so each new tag gets a full retry budget.
+
+## Notes
+
+- iOS only; gated behind `#available(iOS 26, *)`.
+- This mirrors how `react-native-screens` handles the same effect on Fabric
+  (resolve from the live view hierarchy and re-apply on mount/layout lifecycle
+  rather than a single tag lookup). A cleaner long-term fix would move
+  resolution to the scroll-view side, but this is the minimal change to the
+  existing tag-based design.