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fix a RenderBox.size access exception#74402

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fluttergithubbot merged 4 commits into
flutter:masterfrom
xu-baolin:0121size
Jan 26, 2021
Merged

fix a RenderBox.size access exception#74402
fluttergithubbot merged 4 commits into
flutter:masterfrom
xu-baolin:0121size

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@xu-baolin

@xu-baolin xu-baolin commented Jan 21, 2021 •
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Why does the exception happen

The EditableTextState will access RenderBox.size during rebuilding.
So, if the LayoutBuilder.builder returns a TextFormField widget, it will trigger the exception as follow when _RenderLayoutBuilder.performLayout is running,

I think this type of access is legal and we can use the RenderObject._doingThisLayoutWithCallback to distinguish this scenario.

======== Exception caught by widgets library =======================================================
The following assertion was thrown building UnmanagedRestorationScope:
RenderBox.size accessed beyond the scope of resize, layout, or permitted parent access. RenderBox can always access its own size, otherwise, the only object that is allowed to read RenderBox.size is its parent, if they have said they will. It you hit this assert trying to access a child's size, pass "parentUsesSize: true" to that child's layout().
'package:flutter/src/rendering/box.dart':
Failed assertion: line 1947 pos 13: 'debugDoingThisResize || debugDoingThisLayout || _computingThisDryLayout ||
              (RenderObject.debugActiveLayout == parent && _size._canBeUsedByParent)'


Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=2_bug.md

The relevant error-causing widget was: 
  TextFormField file:///D:/My%20Documents/Desktop/flutter_app_test/lib/main.dart:84:13
To inspect this widget in Flutter DevTools, visit: http://127.0.0.1:58353/#/inspector?uri=http%3A%2F%2F127.0.0.1%3A58350%2F4G1hfjZhevY%3D%2F&inspectorRef=inspector-0
When the exception was thrown, this was the stack: 
#2      RenderBox.size.<anonymous closure> (package:flutter/src/rendering/box.dart:1947:13)
#3      RenderBox.size (package:flutter/src/rendering/box.dart:1960:6)
#4      EditableTextState._updateSizeAndTransform (package:flutter/src/widgets/editable_text.dart:2410:40)
#5      EditableTextState._openInputConnection (package:flutter/src/widgets/editable_text.dart:2016:7)
#6      EditableTextState.didUpdateWidget (package:flutter/src/widgets/editable_text.dart:1611:9)
...
====================================================================================================

Steps to reproduce

See the unit test for details.

Fixes #73676

@flutter-dashboard flutter-dashboard Bot added the framework flutter/packages/flutter repository. See also f: labels. label Jan 21, 2021
@google-cla google-cla Bot added the cla: yes label Jan 21, 2021
@xu-baolin
xu-baolin requested a review from chunhtai January 21, 2021 13:45
chunhtai
chunhtai reviewed Jan 21, 2021
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Comment thread packages/flutter/lib/src/rendering/box.dart Outdated
debugDoingThisResize || debugDoingThisLayout || _computingThisDryLayout ||
(RenderObject.debugActiveLayout == parent && _size._canBeUsedByParent),
(RenderObject.debugActiveLayout == parent && _size._canBeUsedByParent) ||
RenderObject.debugActiveLayout!.debugDoingThisLayoutWithCallback,

@chunhtai chunhtai Jan 21, 2021

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can you move this into the if case in line 1945? This is more like something we want to short-circuit than checking in assert

@xu-baolin xu-baolin Jan 22, 2021

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done

Comment thread packages/flutter/test/widgets/layout_builder_test.dart
buildCount++;
if (buildCount > 1) {
final _RenderLayoutSpy spy = tester.renderObject(find.byType(_LayoutSpy));
childSize = spy.size;

@chunhtai chunhtai Jan 21, 2021

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what happen if we try to access the size in the first build? we should make sure this situation will throw.

@xu-baolin xu-baolin Jan 21, 2021

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The RO is null when first build and we can not access size by it.

chunhtai
chunhtai approved these changes Jan 22, 2021
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LGTM, except for indent issue

Comment thread packages/flutter/lib/src/rendering/box.dart Outdated
);
}
if (RenderObject.debugActiveLayout != null &&
!RenderObject.debugActiveLayout!.debugDoingThisLayoutWithCallback) {

@chunhtai chunhtai Jan 22, 2021

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indent seems to be off.

@xu-baolin xu-baolin Jan 25, 2021

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Shouldn't it be indented by two spaces?

@xu-baolin xu-baolin Jan 25, 2021

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Got it now!

Comment thread packages/flutter/lib/src/rendering/box.dart Outdated
if (RenderObject.debugActiveLayout != null &&
!RenderObject.debugActiveLayout!.debugDoingThisLayoutWithCallback) {
assert(
debugDoingThisResize || debugDoingThisLayout || _computingThisDryLayout ||

@chunhtai chunhtai Jan 22, 2021

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same here

@fluttergithubbot
fluttergithubbot merged commit 1e7f395 into flutter:master Jan 26, 2021
This was referenced Jun 14, 2023
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@LongCatIsLooong LongCatIsLooong mentioned this pull request Jul 8, 2026
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Framework assertion in flutter/src/rendering/box.dart when using LayoutBuilder

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