JavaScript preprocessors can help make authoring JavaScript easier and more convenient.
Babel includes JSX processing.
Search for and use JavaScript packages from npm here. By selecting a package, an import
statement will be added to the top of the JavaScript editor for this package.
Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import
usage.
All packages are different, so refer to their docs for how they work.
If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.
If active, Pens will autosave every 30 seconds after being saved once.
If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.
If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.
Visit your global Editor Settings.
import 'dart:async';
import 'dart:math';
import 'dart:ui';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
///
/// 7. colors
///
void main() {
runApp(MaterialApp(
home: Scaffold(body: Board()),
debugShowCheckedModeBanner: false,
));
}
final size = window.physicalSize / window.devicePixelRatio;
const maxPoints = 99;
const force = Offset(0, 1);
const acceleration = 1.1;
const fillColor = Colors.cyan;
const fillRed = Color(0xffff0000);
final strokeColor = Colors.cyan[700];
extension on Color {
HSLColor get hsl => HSLColor.fromColor(this);
double get lightness => hsl.lightness;
Color withLightness(double value) =>
hsl.withLightness(hsl.lightness * .98).toColor();
}
class Point {
final Offset offset;
final Offset force;
final bool active;
static const zero = Point(Offset.zero, Offset.zero, false);
const Point(this.offset, this.force, [this.active = true]);
Point update() => active
? Point(offset + force, force * acceleration, offset.dy < size.height)
: zero;
Offset up(double value) => offset + Offset(0, -value);
Offset down(double value) => offset + Offset(0, value);
@override
bool operator ==(Object other) =>
identical(this, other) ||
other is Point &&
runtimeType == other.runtimeType &&
offset == other.offset &&
force == other.force &&
active == other.active;
@override
int get hashCode => offset.hashCode ^ force.hashCode ^ active.hashCode;
}
class Segment {
final Point point1;
final Point point2;
final Color strokeColor;
final Color fillColor;
Offset get offset1 => point1.offset;
Offset get offset2 => point2.offset;
const Segment(this.point1, this.point2, {this.strokeColor, this.fillColor});
bool get active => point1.active && point2.active;
List<Offset> get corners => [
point1.up(50),
point2.up(50),
point2.down(50),
point1.down(50),
];
Segment update() {
final newFillColor = fillColor.lightness > 0
? fillColor.withLightness(min(1, fillColor.lightness * .98))
: fillColor;
return Segment(
point1.update(),
point2.update(),
strokeColor: strokeColor,
fillColor: newFillColor,
);
}
}
class Board extends StatefulWidget {
@override
_BoardState createState() => _BoardState();
}
class _BoardState extends State<Board> with SingleTickerProviderStateMixin {
List<Segment> _segments = [];
StreamController<List<Segment>> _streamer;
Stream<List<Segment>> get _point$ => _streamer.stream;
@override
void initState() {
_streamer = StreamController<List<Segment>>()..add(<Segment>[]);
AnimationController.unbounded(vsync: this, duration: Duration(seconds: 1))
..repeat()
..addListener(_updateSegments);
super.initState();
}
@override
Widget build(BuildContext context) => MouseRegion(
onHover: (details) => _addSegment(details.position),
child: StreamBuilder<List<Segment>>(
initialData: <Segment>[],
stream: _point$,
builder: (_, stream) =>
CustomPaint(size: size, painter: Painter(stream.data)),
),
);
void _addSegment(Offset offset) {
_segments
..add(
Segment(
_segments.isEmpty ? Point(offset, force) : _segments.last.point2,
Point(offset, force),
strokeColor: strokeColor,
fillColor: fillColor,
),
);
}
void _updateSegments() {
_segments = _segments
.where((element) => element.active)
.map((element) => element.update())
.toList();
_streamer.add(_segments);
}
}
class Painter extends CustomPainter {
static final fill = Paint()..color = fillColor;
static final stroke = Paint()
..color = Colors.grey
..style = PaintingStyle.stroke;
final List<Segment> segments;
const Painter(this.segments);
@override
void paint(Canvas canvas, Size size) {
if (segments.isEmpty) return;
for (final segment in segments.where((element) => element.active)) {
final path = Path()
..moveTo(segment.corners[0].dx, segment.corners[0].dy)
..lineTo(segment.corners[1].dx, segment.corners[1].dy)
..lineTo(segment.corners[2].dx, segment.corners[2].dy)
..lineTo(segment.corners[3].dx, segment.corners[3].dy)
..close();
canvas.drawPath(path, Paint()..color = segment.fillColor);
canvas.drawPath(
path,
Paint()
..color = segment.strokeColor
..style = PaintingStyle.stroke,
);
}
}
@override
bool shouldRepaint(Painter oldDelegate) =>
segments.isNotEmpty && !listEquals(segments, oldDelegate.segments);
}
Also see: Tab Triggers