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64a645352c
The input widget scrolls, so it should give its text loose constraints. That way the text ends up being its intrinsic size even if put in a context with tight constraints. Fixes #298
124 lines
3.7 KiB
Dart
124 lines
3.7 KiB
Dart
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/painting.dart';
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import 'box.dart';
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import 'object.dart';
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export 'package:flutter/painting.dart' show
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FontStyle,
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FontWeight,
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PlainTextSpan,
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StyledTextSpan,
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TextAlign,
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TextBaseline,
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TextDecoration,
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TextDecorationStyle,
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TextSpan,
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TextStyle,
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normal,
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bold,
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underline,
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overline,
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lineThrough;
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/// A render object that displays a paragraph of text
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class RenderParagraph extends RenderBox {
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RenderParagraph(
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TextSpan text
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) : textPainter = new TextPainter(text) {
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assert(text != null);
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}
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final TextPainter textPainter;
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BoxConstraints _constraintsForCurrentLayout; // when null, we don't have a current layout
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/// The text to display
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TextSpan get text => textPainter.text;
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void set text(TextSpan value) {
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if (textPainter.text == value)
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return;
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textPainter.text = value;
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_constraintsForCurrentLayout = null;
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markNeedsLayout();
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}
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void layoutText(BoxConstraints constraints) {
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assert(constraints != null);
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if (_constraintsForCurrentLayout == constraints)
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return; // already cached this layout
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textPainter.maxWidth = constraints.maxWidth;
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textPainter.minWidth = constraints.minWidth;
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textPainter.minHeight = constraints.minHeight;
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textPainter.maxHeight = constraints.maxHeight;
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textPainter.layout();
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// By default, we shrinkwrap to the intrinsic width.
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double width = constraints.constrainWidth(textPainter.maxIntrinsicWidth);
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textPainter.minWidth = width;
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textPainter.maxWidth = width;
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textPainter.layout();
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_constraintsForCurrentLayout = constraints;
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}
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double getMinIntrinsicWidth(BoxConstraints constraints) {
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layoutText(constraints);
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return constraints.constrainWidth(textPainter.minIntrinsicWidth);
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}
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double getMaxIntrinsicWidth(BoxConstraints constraints) {
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layoutText(constraints);
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return constraints.constrainWidth(textPainter.maxIntrinsicWidth);
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}
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double _getIntrinsicHeight(BoxConstraints constraints) {
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layoutText(constraints);
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return constraints.constrainHeight(textPainter.size.height);
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}
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double getMinIntrinsicHeight(BoxConstraints constraints) {
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return _getIntrinsicHeight(constraints);
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}
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double getMaxIntrinsicHeight(BoxConstraints constraints) {
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return _getIntrinsicHeight(constraints);
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}
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double computeDistanceToActualBaseline(TextBaseline baseline) {
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assert(!needsLayout);
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layoutText(constraints);
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return textPainter.computeDistanceToActualBaseline(baseline);
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}
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bool hitTestSelf(Point position) => true;
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void performLayout() {
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layoutText(constraints);
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size = constraints.constrain(textPainter.size);
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}
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void paint(PaintingContext context, Offset offset) {
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// Ideally we could compute the min/max intrinsic width/height with a
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// non-destructive operation. However, currently, computing these values
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// will destroy state inside the painter. If that happens, we need to
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// get back the correct state by calling _layout again.
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//
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// TODO(abarth): Make computing the min/max intrinsic width/height
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// a non-destructive operation.
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layoutText(constraints);
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textPainter.paint(context.canvas, offset);
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}
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// we should probably expose a way to do precise (inter-glpyh) hit testing
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String debugDescribeChildren(String prefix) {
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return '$prefix \u2558\u2550\u2566\u2550\u2550 text \u2550\u2550\u2550\n'
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'${text.toString("$prefix \u2551 ")}\n'
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'$prefix \u255A\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n'
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'$prefix\n';
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}
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}
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