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@felangel felangel commented Nov 20, 2023

chore: roll engine to a902c222680d63925b55c47cff7b3c6cab3326b7

@felangel felangel self-assigned this Nov 20, 2023
@felangel felangel changed the title chore: roll engine to 121c4fa469 chore: roll engine to 5850edc69ef1e892a5401b9de60a6db1139187e6 Dec 8, 2023
@felangel felangel changed the title chore: roll engine to 5850edc69ef1e892a5401b9de60a6db1139187e6 chore: roll engine to 5850edc69 Dec 8, 2023
@felangel felangel changed the title chore: roll engine to 5850edc69 chore: roll engine to a902c22268 Dec 8, 2023
@felangel felangel merged commit 447487a into shorebird/dev Dec 8, 2023
@felangel felangel deleted the chore/roll-engine branch December 8, 2023 20:15
felangel pushed a commit that referenced this pull request Dec 11, 2023
This is a follow up to the following pull requests:
- flutter#124514

I was finally able to reproduce this bug and found out why it was happening. Consider this code:

```dart
GestureDetector(
  behavior: HitTestBehavior.translucent,
  // Note: Make sure onTap is not null to ensure events
  // are captured by `GestureDetector`
  onTap: () {},
  child: _shouldShowSlider
    ? Slider(value: _value, onChanged: _handleSlide)
    : const SizedBox.shrink().
)
```

Runtime exception happens when:

1. User taps and holds the Slider (drag callback captured by `GestureDetector`)
2. `_shouldShowSlider` changes to false, Slider disappears and unmounts, and unregisters `_handleSlide`. But the callback is still registered by `GestureDetector`
3. Users moves finger as if Slider were still there
4. Drag callback is invoked, `_SliderState.showValueIndicator` is called
5. Exception - Slider is already disposed

This pull request fixes it by adding a mounted check inside `_SliderState.showValueIndicator` to ensure the Slider is actually mounted at the time of invoking drag event callback. I've added a unit test that will fail without this change.

The error stack trace is:

```
The following assertion was thrown while handling a gesture:
This widget has been unmounted, so the State no longer has a context (and should be considered
defunct).
Consider canceling any active work during "dispose" or using the "mounted" getter to determine if
the State is still active.

When the exception was thrown, this was the stack:
#0      State.context.<anonymous closure> (package:flutter/src/widgets/framework.dart:950:9)
#1      State.context (package:flutter/src/widgets/framework.dart:956:6)
#2      _SliderState.showValueIndicator (package:flutter/src/material/slider.dart:968:18)
#3      _RenderSlider._startInteraction (package:flutter/src/material/slider.dart:1487:12)
#4      _RenderSlider._handleDragStart (package:flutter/src/material/slider.dart:1541:5)
#5      DragGestureRecognizer._checkStart.<anonymous closure> (package:flutter/src/gestures/monodrag.dart:531:53)
#6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:275:24)
#7      DragGestureRecognizer._checkStart (package:flutter/src/gestures/monodrag.dart:531:7)
#8      DragGestureRecognizer._checkDrag (package:flutter/src/gestures/monodrag.dart:498:5)
#9      DragGestureRecognizer.acceptGesture (package:flutter/src/gestures/monodrag.dart:431:7)
#10     _CombiningGestureArenaMember.acceptGesture (package:flutter/src/gestures/team.dart:45:14)
#11     GestureArenaManager._resolveInFavorOf (package:flutter/src/gestures/arena.dart:281:12)
#12     GestureArenaManager._resolve (package:flutter/src/gestures/arena.dart:239:9)
#13     GestureArenaEntry.resolve (package:flutter/src/gestures/arena.dart:53:12)
#14     _CombiningGestureArenaMember._resolve (package:flutter/src/gestures/team.dart:85:15)
#15     _CombiningGestureArenaEntry.resolve (package:flutter/src/gestures/team.dart:19:15)
#16     OneSequenceGestureRecognizer.resolve (package:flutter/src/gestures/recognizer.dart:375:13)
#17     DragGestureRecognizer.handleEvent (package:flutter/src/gestures/monodrag.dart:414:13)
#18     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:98:12)
#19     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:143:9)
#20     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:625:13)
#21     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:141:18)
#22     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:127:7)
#23     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:488:19)
#24     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:468:22)
#25     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:439:11)
#26     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:413:7)
#27     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:376:5)
#28     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:323:7)
#29     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:292:9)
#30     _invoke1 (dart:ui/hooks.dart:186:13)
#31     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:433:7)
#32     _dispatchPointerDataPacket (dart:ui/hooks.dart:119:31)

Handler: "onStart"
Recognizer:
  HorizontalDragGestureRecognizer#a5df2
```

*List which issues are fixed by this PR. You must list at least one issue.*

Internal bug: b/273666179, b/192329942

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*
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3 participants