stroke_cap.dart

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';

import 'package:flutter/material.dart';

import 'diagram_step.dart';

const double _kFontSize = 14.0;

class StrokeCapDescription extends CustomPainter {
  StrokeCapDescription({this.filename, required this.cap})
    : _capPainter = _createLabelPainter(cap.toString());

  static const EdgeInsets padding = EdgeInsets.all(3.0);

  final String? filename;
  final StrokeCap cap;
  final TextPainter _capPainter;

  Widget get widget {
    return ConstrainedBox(
      constraints: const BoxConstraints(maxWidth: 130.0),
      child: AspectRatio(
        aspectRatio: 1.0,
        child: Padding(
          padding: const EdgeInsets.all(3.0),
          child: CustomPaint(painter: this),
        ),
      ),
    );
  }

  static TextPainter _createLabelPainter(
    String label, {
    FontStyle style = FontStyle.normal,
  }) {
    final TextPainter result = TextPainter(
      textDirection: TextDirection.ltr,
      text: TextSpan(
        text: label,
        style: TextStyle(
          color: Colors.black,
          fontStyle: style,
          fontSize: _kFontSize,
        ),
      ),
    );
    result.layout();
    return result;
  }

  @override
  void paint(Canvas canvas, Size size) {
    assert(size != Size.zero);
    final Offset center = Offset(
      size.width / 2.0,
      (size.height - _capPainter.height - padding.vertical) / 2.0,
    );
    final Offset start = Offset(0.0, center.dy);
    final Offset middle = Offset(size.width / 2.0, center.dy);

    final Paint startPaint =
        Paint()
          ..color = Colors.grey
          ..style = PaintingStyle.stroke
          ..strokeCap = StrokeCap.square
          ..strokeWidth = 20.0;
    final Paint linePaint =
        Paint()
          ..color = Colors.grey
          ..style = PaintingStyle.stroke
          ..strokeCap = cap
          ..strokeWidth = 20.0;
    final Paint endPaint =
        Paint()
          ..color = Colors.deepPurpleAccent
          ..style = PaintingStyle.stroke
          ..strokeCap = cap
          ..strokeWidth = 20.0;

    Path line =
        Path() // Line
          ..moveTo(start.dx, start.dy)
          ..lineTo(middle.dx, middle.dy);
    canvas.drawPath(line, linePaint);
    line =
        Path() // Start point, so that it doesn't show the starting end cap.
          ..moveTo(start.dx, start.dy)
          ..lineTo(start.dx, start.dy);
    canvas.drawPath(line, startPaint);
    line =
        Path() // End point, a different color to highlight the cap.
          ..moveTo(middle.dx, middle.dy)
          ..lineTo(middle.dx, middle.dy);
    canvas.drawPath(line, endPaint);
    _capPainter.paint(
      canvas,
      Offset(
        padding.left,
        size.height - (padding.bottom + 3.0 + _capPainter.height),
      ),
    );
  }

  @override
  bool shouldRepaint(StrokeCapDescription oldDelegate) {
    return cap != oldDelegate.cap;
  }
}

class StrokeCapDiagram extends StatelessWidget with DiagramMetadata {
  const StrokeCapDiagram({
    required this.name,
    this.cap = StrokeCap.round,
    super.key,
  });

  @override
  final String name;
  final StrokeCap cap;

  @override
  Widget build(BuildContext context) {
    final StrokeCapDescription description = StrokeCapDescription(cap: cap);

    return ConstrainedBox(
      key: UniqueKey(),
      constraints: BoxConstraints.tight(const Size(150.0, 100.0)),
      child: Container(
        padding: const EdgeInsets.all(18.0),
        color: Colors.white,
        child: CustomPaint(painter: description),
      ),
    );
  }
}

class StrokeCapDiagramStep extends DiagramStep {
  @override
  final String category = 'dart-ui';

  final List<StrokeCapDiagram> _diagrams = const <StrokeCapDiagram>[
    StrokeCapDiagram(name: 'butt_cap', cap: StrokeCap.butt),
    StrokeCapDiagram(name: 'round_cap'),
    StrokeCapDiagram(name: 'square_cap', cap: StrokeCap.square),
  ];

  @override
  Future<List<StrokeCapDiagram>> get diagrams async => _diagrams;
}