The RenderEditable needs to be laid out before hit testing
Summary
#Instances of RenderEditable
must be laid out before processing hit
testing. Trying to hit-test a RenderEditable
object before layout
results in an assertion such as the following:
Failed assertion: line 123 pos 45: '!debugNeedsLayout': is not true.
Context
#To support gesture recognizers in selectable text, the
RenderEditable
requires the layout information for its
text spans to determine which text span receives the
pointer event. (Before this change, RenderEditable
objects
didn't take their text into account when evaluating hit tests.)
To implement this, layout was made a prerequisite for performing
hit testing on a RenderEditable
object.
In practice, this is rarely an issue. The widget library ensures that layout is performed before any hit test on all render objects. This problem is only likely to be seen in code that directly interacts with render objects, for example in tests of custom render objects.
Migration guide
#If you see the '!debugNeedsLayout': is not true
assertion error while hit testing the RenderEditable
,
lay out the RenderEditable
before doing so.
Code before migration:
import 'package:flutter/rendering.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/material.dart';
void main() {
test('attach and detach correctly handle gesture', () {
final RenderEditable editable = RenderEditable(
textDirection: TextDirection.ltr,
offset: ViewportOffset.zero(),
textSelectionDelegate: FakeEditableTextState(),
startHandleLayerLink: LayerLink(),
endHandleLayerLink: LayerLink(),
);
final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () {});
editable.attach(owner);
// This throws an assertion error because
// the RenderEditable hasn't been laid out.
editable.handleEvent(const PointerDownEvent(),
BoxHitTestEntry(editable, const Offset(10, 10)));
editable.detach();
});
}
class FakeEditableTextState extends TextSelectionDelegate {
@override
TextEditingValue textEditingValue;
@override
void hideToolbar() {}
@override
void bringIntoView(TextPosition position) {}
}
Code after migration:
import 'package:flutter/rendering.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/material.dart';
void main() {
test('attach and detach correctly handle gesture', () {
final RenderEditable editable = RenderEditable(
textDirection: TextDirection.ltr,
offset: ViewportOffset.zero(),
textSelectionDelegate: FakeEditableTextState(),
startHandleLayerLink: LayerLink(),
endHandleLayerLink: LayerLink(),
);
// Lay out the RenderEditable first.
editable.layout(BoxConstraints.loose(const Size(1000.0, 1000.0)));
final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () {});
editable.attach(owner);
editable.handleEvent(const PointerDownEvent(),
BoxHitTestEntry(editable, const Offset(10, 10)));
editable.detach();
});
}
class FakeEditableTextState extends TextSelectionDelegate {
@override
TextEditingValue textEditingValue;
@override
void hideToolbar() {}
@override
void bringIntoView(TextPosition position) {}
}
Timeline
#Landed in version: 1.18.0
In stable release: 1.20
References
#API documentation:
Relevant issue:
- Issue 43494: SelectableText.rich used along with TapGestureRecognizer isn't working
Relevant PR:
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