Dat Vu
44 lines
1.8 KiB
Markdown
44 lines
1.8 KiB
Markdown
# 0075. Fix load more not triggered on iOS when fast scrolling to bottom
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Date: 2026-03-31
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## Status
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- Issues:
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- [TF-4425 Bug: load more is not working](https://github.com/linagora/tmail-flutter/issues/TF-4425)
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## Context
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On iOS, `handleLoadMoreEmailsRequest()` was never triggered when users scrolled to the bottom of the email list. The original condition used exact equality:
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```dart
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scrollInfo.metrics.pixels == scrollInfo.metrics.maxScrollExtent
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```
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**Root cause:** iOS uses `BouncingScrollPhysics` (spring-based simulation), which causes `pixels` to either overshoot or settle slightly short of `maxScrollExtent` depending on scroll speed and device performance. In both cases, `ScrollEndNotification` fires when `pixels != maxScrollExtent`, so the condition is never satisfied.
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This behavior is device-dependent — newer/faster devices (iPhone 13 Pro Max, iOS 18) are less affected, while older/slower devices (iPhone 7, iOS 15) exhibit larger deviations. Android is unaffected because `ClampingScrollPhysics` clamps `pixels` exactly within `[0, maxScrollExtent]`.
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## Decision
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Apply `ClampingScrollPhysics` on iOS only, and replace `==` with `>=`:
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```dart
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// physics
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physics: PlatformInfo.isIOS
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? const ClampingScrollPhysics()
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: const AlwaysScrollableScrollPhysics(),
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// condition
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scrollInfo.metrics.pixels >= scrollInfo.metrics.maxScrollExtent
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```
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`ClampingScrollPhysics` ensures `pixels` is clamped exactly to `maxScrollExtent` at the boundary, making the condition deterministic. The `>=` adds a defensive guard for any residual edge cases.
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## Consequences
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- Load more works correctly across all iOS versions and device generations.
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- No behavior change on Android or Web.
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- iOS loses the native bounce feel at list boundaries. Acceptable for an email list UI.
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- No risk of duplicate requests due to the existing `isRunning` guard.
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