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Capture didExceedMaxLines after doing text layout with constraints (#9457)

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Subsequent operations like debugAssertDoesMeetConstraints() may do layout
operations that alter _textPainter's state.

Fixes https://github.com/flutter/flutter/issues/9372
This commit is contained in:
Jason Simmons 2017-04-19 16:04:47 -07:00 committed by GitHub
parent ab1aa07e8f
commit a657428b5c
2 changed files with 14 additions and 1 deletions
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7
packages/flutter/lib/src/rendering/paragraph.dart
View file

@ -6,6 +6,7 @@ import 'dart:ui' as ui;
import 'package:flutter/gestures.dart';
import 'package:flutter/services.dart';
import 'package:meta/meta.dart';
import 'box.dart';
import 'debug.dart';
@ -189,17 +190,21 @@ class RenderParagraph extends RenderBox {
bool _hasVisualOverflow = false;
ui.Shader _overflowShader;
@visibleForTesting
bool get debugHasOverflowShader => _overflowShader != null;
@override
void performLayout() {
_layoutTextWithConstraints(constraints);
// We grab _textPainter.size here because assigning to `size` will trigger
// us to validate our intrinsic sizes, which will change _textPainter's
// layout because the intrinsic size calculations are destructive.
// Other _textPainter state like didExceedMaxLines will also be affected.
final Size textSize = _textPainter.size;
final bool didOverflowHeight = _textPainter.didExceedMaxLines;
size = constraints.constrain(textSize);
final bool didOverflowWidth = size.width < textSize.width;
final bool didOverflowHeight = _textPainter.didExceedMaxLines;
// TODO(abarth): We're only measuring the sizes of the line boxes here. If
// the glyphs draw outside the line boxes, we might think that there isn't
// visual overflow when there actually is visual overflow. This can become

8
packages/flutter/test/rendering/paragraph_test.dart
View file

@ -135,5 +135,13 @@ void main() {
relayoutWith(maxLines: null, softWrap: false, overflow: TextOverflow.ellipsis);
expect(paragraph.size.height, equals(2 * lineHeight));
// Test presence of the fade effect.
relayoutWith(maxLines: 3, softWrap: true, overflow: TextOverflow.fade);
expect(paragraph.debugHasOverflowShader, isTrue);
relayoutWith(maxLines: 100, softWrap: true, overflow: TextOverflow.fade);
expect(paragraph.debugHasOverflowShader, isFalse);
});
}