grid_paper.dart 3.99 KB
Newer Older
Ian Hickson's avatar
Ian Hickson committed
1
// Copyright 2014 The Flutter Authors. All rights reserved.
2 3 4 5 6 7
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'basic.dart';
import 'framework.dart';

8 9
class _GridPaperPainter extends CustomPainter {
  const _GridPaperPainter({
10 11 12 13
    required this.color,
    required this.interval,
    required this.divisions,
    required this.subdivisions,
14 15 16 17
  });

  final Color color;
  final double interval;
Ian Hickson's avatar
Ian Hickson committed
18
  final int divisions;
19
  final int subdivisions;
20

21
  @override
22
  void paint(Canvas canvas, Size size) {
23
    final Paint linePaint = Paint()
24
      ..color = color;
25
    final double allDivisions = (divisions * subdivisions).toDouble();
Ian Hickson's avatar
Ian Hickson committed
26
    for (double x = 0.0; x <= size.width; x += interval / allDivisions) {
27
      linePaint.strokeWidth = (x % interval == 0.0) ? 1.0 : (x % (interval / subdivisions) == 0.0) ? 0.5 : 0.25;
28
      canvas.drawLine(Offset(x, 0.0), Offset(x, size.height), linePaint);
29
    }
Ian Hickson's avatar
Ian Hickson committed
30
    for (double y = 0.0; y <= size.height; y += interval / allDivisions) {
31
      linePaint.strokeWidth = (y % interval == 0.0) ? 1.0 : (y % (interval / subdivisions) == 0.0) ? 0.5 : 0.25;
32
      canvas.drawLine(Offset(0.0, y), Offset(size.width, y), linePaint);
33 34 35
    }
  }

36
  @override
37 38
  bool shouldRepaint(_GridPaperPainter oldPainter) {
    return oldPainter.color != color
Ian Hickson's avatar
Ian Hickson committed
39 40
        || oldPainter.interval != interval
        || oldPainter.divisions != divisions
41
        || oldPainter.subdivisions != subdivisions;
42
  }
Ian Hickson's avatar
Ian Hickson committed
43

44
  @override
45
  bool hitTest(Offset position) => false;
46 47
}

48
/// A widget that draws a rectilinear grid of lines one pixel wide.
49 50
///
/// Useful with a [Stack] for visualizing your layout along a grid.
51 52 53 54 55
///
/// The grid's origin (where the first primary horizontal line and the first
/// primary vertical line intersect) is at the top left of the widget.
///
/// The grid is drawn over the [child] widget.
56
class GridPaper extends StatelessWidget {
57
  /// Creates a widget that draws a rectilinear grid of 1-pixel-wide lines.
58
  const GridPaper({
59
    super.key,
60 61 62 63
    this.color = const Color(0x7FC3E8F3),
    this.interval = 100.0,
    this.divisions = 2,
    this.subdivisions = 5,
64 65
    this.child,
  }) : assert(divisions > 0, 'The "divisions" property must be greater than zero. If there were no divisions, the grid paper would not paint anything.'),
66
       assert(subdivisions > 0, 'The "subdivisions" property must be greater than zero. If there were no subdivisions, the grid paper would not paint anything.');
67

68
  /// The color to draw the lines in the grid.
69
  ///
70
  /// Defaults to a light blue commonly seen on traditional grid paper.
71
  final Color color;
72 73

  /// The distance between the primary lines in the grid, in logical pixels.
74 75
  ///
  /// Each primary line is one logical pixel wide.
76
  final double interval;
77 78

  /// The number of major divisions within each primary grid cell.
79 80 81 82 83 84 85 86 87 88
  ///
  /// This is the number of major divisions per [interval], including the
  /// primary grid's line.
  ///
  /// The lines after the first are half a logical pixel wide.
  ///
  /// If this is set to 2 (the default), then for each [interval] there will be
  /// a 1-pixel line on the left, a half-pixel line in the middle, and a 1-pixel
  /// line on the right (the latter being the 1-pixel line on the left of the
  /// next [interval]).
Ian Hickson's avatar
Ian Hickson committed
89
  final int divisions;
90

91 92 93 94 95 96 97 98
  /// The number of minor divisions within each major division, including the
  /// major division itself.
  ///
  /// If [subdivisions] is 5 (the default), it means that there will be four
  /// lines between each major ([divisions]) line.
  ///
  /// The subdivision lines after the first are a quarter of a logical pixel wide.
  final int subdivisions;
99

100
  /// The widget below this widget in the tree.
101
  ///
102
  /// {@macro flutter.widgets.ProxyWidget.child}
103
  final Widget? child;
104

105
  @override
106
  Widget build(BuildContext context) {
107 108
    return CustomPaint(
      foregroundPainter: _GridPaperPainter(
Ian Hickson's avatar
Ian Hickson committed
109 110 111
        color: color,
        interval: interval,
        divisions: divisions,
112
        subdivisions: subdivisions,
Ian Hickson's avatar
Ian Hickson committed
113
      ),
114
      child: child,
115 116 117
    );
  }
}