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// Copyright 2014 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 'basic.dart';
import 'framework.dart';
class _GridPaperPainter extends CustomPainter {
const _GridPaperPainter({
required this.color,
required this.interval,
required this.divisions,
required this.subdivisions,
});
final Color color;
final double interval;
final int divisions;
final int subdivisions;
@override
void paint(Canvas canvas, Size size) {
final Paint linePaint = Paint()
..color = color;
final double allDivisions = (divisions * subdivisions).toDouble();
for (double x = 0.0; x <= size.width; x += interval / allDivisions) {
linePaint.strokeWidth = (x % interval == 0.0) ? 1.0 : (x % (interval / subdivisions) == 0.0) ? 0.5 : 0.25;
canvas.drawLine(Offset(x, 0.0), Offset(x, size.height), linePaint);
}
for (double y = 0.0; y <= size.height; y += interval / allDivisions) {
linePaint.strokeWidth = (y % interval == 0.0) ? 1.0 : (y % (interval / subdivisions) == 0.0) ? 0.5 : 0.25;
canvas.drawLine(Offset(0.0, y), Offset(size.width, y), linePaint);
}
}
@override
bool shouldRepaint(_GridPaperPainter oldPainter) {
return oldPainter.color != color
|| oldPainter.interval != interval
|| oldPainter.divisions != divisions
|| oldPainter.subdivisions != subdivisions;
}
@override
bool hitTest(Offset position) => false;
}
/// A widget that draws a rectilinear grid of lines one pixel wide.
///
/// Useful with a [Stack] for visualizing your layout along a grid.
///
/// 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.
class GridPaper extends StatelessWidget {
/// Creates a widget that draws a rectilinear grid of 1-pixel-wide lines.
const GridPaper({
super.key,
this.color = const Color(0x7FC3E8F3),
this.interval = 100.0,
this.divisions = 2,
this.subdivisions = 5,
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.'),
assert(subdivisions > 0, 'The "subdivisions" property must be greater than zero. If there were no subdivisions, the grid paper would not paint anything.');
/// The color to draw the lines in the grid.
///
/// Defaults to a light blue commonly seen on traditional grid paper.
final Color color;
/// The distance between the primary lines in the grid, in logical pixels.
///
/// Each primary line is one logical pixel wide.
final double interval;
/// The number of major divisions within each primary grid cell.
///
/// 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]).
final int divisions;
/// 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;
/// The widget below this widget in the tree.
///
/// {@macro flutter.widgets.ProxyWidget.child}
final Widget? child;
@override
Widget build(BuildContext context) {
return CustomPaint(
foregroundPainter: _GridPaperPainter(
color: color,
interval: interval,
divisions: divisions,
subdivisions: subdivisions,
),
child: child,
);
}
}