TextField toggle a11y off/on crashes on iOS #43795

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1. mehmetf

   added

   c: crashStack traces logged to the consoleStack traces logged to the console

   platform-iosiOS applications specificallyiOS applications specifically

   a: accessibilityAccessibility, e.g. VoiceOver or TalkBack. (aka a11y)Accessibility, e.g. VoiceOver or TalkBack. (aka a11y)

   customer: fun (g3)

   on Oct 30, 2019
2. HansMuller

   added

   p: material_uimaterial_ui package in flutter/packagesmaterial_ui package in flutter/packages

   frameworkflutter/packages/flutter repository. See also f: labels.flutter/packages/flutter repository. See also f: labels.

   on Oct 30, 2019
3. HansMuller commented on Oct 30, 2019

   

   HansMuller

   on Oct 30, 2019

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   CC @darrenaustin
4. mehmetf

   added

   severe: customer critical

   on Oct 31, 2019
5. darrenaustin commented on Oct 31, 2019

   

   darrenaustin

   on Oct 31, 2019

   Last edited by darrenaustin

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   I am able to reproduce the problem with the given test and instructions. Needs more investigation, but it looks like a problem in the engine.

   Here is the stack trace for future reference:

   #0	0x00000001033538c8 in flutter::AccessibilityBridge::textInputView() ()
   #1	0x00000001033558b8 in -[TextInputSemanticsObject textInputSurrogate] ()
   #2	0x000000010335599c in -[TextInputSemanticsObject accessibilityElementDidLoseFocus] ()
   
6. darrenaustin

   added

   engineflutter/engine related. See also e: labels.flutter/engine related. See also e: labels.

   on Oct 31, 2019
7. darrenaustin

   self-assigned this

   on Nov 1, 2019
8. darrenaustin

   added this to the December 2019 milestone on Nov 1, 2019
9. darrenaustin commented on Nov 6, 2019

   

   darrenaustin

   on Nov 6, 2019

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   So I think I understand what is going on here. The AccessibilityBridge constructs a mirror SemanticObject tree that it hands to the system for VoiceOver to navigate. When a text field is focused in the semantic tree a TextInputSemanticsObject object is constructed with a weak pointer back to the bridge.

   When VoiceOver is turned off the bridge is destroyed and the semantic objects are released. However, it appears that something in the system is still holding onto a reference to the TextInputSemanticsObject, as it isn't dealloc'd at this time. When VoiceOver is turned back on, the system sends a accessibilityElementDidLoseFocus message to the text input object. In response it tries to dereference the weak pointer to the now defunct bridge and it crashes.

   Not sure why or what part of the system is holding on to the text input object, as we have shut down the bridge and reset all the accessibility elements on the main view. I can fix this with a guard against the weak reference being dead, but that feels more like a bandaid. I would like to understand why the system is still referencing this after VoiceOver is shutdown and preferably find a way to reset set it completely.
10. darrenaustin

    closed this as completedin flutter-team-archive/engine#13857on Nov 14, 2019
11. github-actions commented on Aug 25, 2021

    

    github-actionsbot

    on Aug 25, 2021

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    This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.
12. github-actions

    locked as resolved and limited conversation to collaborators on Aug 25, 2021