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// Copyright 2015 The Chromium 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:math' as math;
import 'package:flutter/material.dart';
class StockArrowPainter extends CustomPainter {
StockArrowPainter({ this.color, this.percentChange });
final Color color;
final double percentChange;
@override
void paint(Canvas canvas, Size size) {
final Paint paint = new Paint()..color = color;
paint.strokeWidth = 1.0;
const double padding = 2.0;
assert(padding > paint.strokeWidth / 2.0); // make sure the circle remains inside the box
final double r = (size.shortestSide - padding) / 2.0; // radius of the circle
final double centerX = padding + r;
final double centerY = padding + r;
// Draw the arrow.
final double w = 8.0;
double h = 5.0;
double arrowY;
if (percentChange < 0.0) {
h = -h;
arrowY = centerX + 1.0;
} else {
arrowY = centerX - 1.0;
}
final Path path = new Path();
path.moveTo(centerX, arrowY - h); // top of the arrow
path.lineTo(centerX + w, arrowY + h);
path.lineTo(centerX - w, arrowY + h);
path.close();
paint.style = PaintingStyle.fill;
canvas.drawPath(path, paint);
// Draw a circle that circumscribes the arrow.
paint.style = PaintingStyle.stroke;
canvas.drawCircle(new Point(centerX, centerY), r, paint);
}
@override
bool shouldRepaint(StockArrowPainter oldPainter) {
return oldPainter.color != color
|| oldPainter.percentChange != percentChange;
}
}
class StockArrow extends StatelessWidget {
StockArrow({ Key key, this.percentChange }) : super(key: key);
final double percentChange;
int _colorIndexForPercentChange(double percentChange) {
final double maxPercent = 10.0;
final double normalizedPercentChange = math.min(percentChange.abs(), maxPercent) / maxPercent;
return 100 + (normalizedPercentChange * 8.0).floor() * 100;
}
Color _colorForPercentChange(double percentChange) {
if (percentChange > 0)
return Colors.green[_colorIndexForPercentChange(percentChange)];
return Colors.red[_colorIndexForPercentChange(percentChange)];
}
@override
Widget build(BuildContext context) {
return new Container(
width: 40.0,
height: 40.0,
margin: const EdgeInsets.symmetric(horizontal: 5.0),
child: new CustomPaint(
painter: new StockArrowPainter(
// TODO(jackson): This should change colors with the theme
color: _colorForPercentChange(percentChange),
percentChange: percentChange
)
)
);
}
}