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painter_params.dart
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painter_params.dart
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import 'dart:ui';
import 'package:flutter/widgets.dart';
import 'chart_style.dart';
import 'candle_data.dart';
class PainterParams {
final List<CandleData> candles;
final ChartStyle style;
final Size size;
final double candleWidth;
final TextAlign horizontalLinesTextAlign;
final double startOffset;
final List<double> horizontalLines;
final double maxPrice;
final double minPrice;
final double maxVol;
final double minVol;
final double? horizontalLinesWidth;
final TextSpan horizontalLinesLabel;
final double xShift;
final Offset? tapPosition;
final List<double?>? leadingTrends;
final List<double?>? trailingTrends;
final Color? horizontalLinesColor;
PainterParams({
required this.candles,
required this.style,
required this.size,
this.horizontalLinesColor,
required this.candleWidth,
this.horizontalLinesWidth,
required this.horizontalLinesLabel,
required this.startOffset,
required this.maxPrice,
required this.horizontalLinesTextAlign,
required this.minPrice,
required this.maxVol,
required this.minVol,
this.horizontalLines = const [],
required this.xShift,
required this.tapPosition,
required this.leadingTrends,
required this.trailingTrends,
});
double get chartWidth => // width without price labels
size.width - style.priceLabelWidth;
double get chartHeight => // height without time labels
size.height - style.timeLabelHeight;
double get volumeHeight => chartHeight * style.volumeHeightFactor;
double get priceHeight => chartHeight - volumeHeight;
int getCandleIndexFromOffset(double x) {
final adjustedPos = x - xShift + candleWidth / 2;
final i = adjustedPos ~/ candleWidth;
return i;
}
double fitPrice(double y) =>
priceHeight * (maxPrice - y) / (maxPrice - minPrice);
double fitVolume(double y) {
final gap = 12; // the gap between price bars and volume bars
final baseAmount = 2; // display at least "something" for the lowest volume
if (maxVol == minVol) {
// Apparently max and min values (in the current visible range, at least)
// are the same. It's likely they passed in a bunch of zeroes, because
// they don't have real volume data or don't want to draw volumes.
assert(() {
if (style.volumeHeightFactor != 0) {
print('If you do not want to show volumes, '
'make sure to set `volumeHeightFactor` (ChartStyle) to zero.');
}
return true;
}());
// Since they are equal, we just draw all volume bars as half height.
return priceHeight + volumeHeight / 2;
}
final volGridSize = (volumeHeight - baseAmount - gap) / (maxVol - minVol);
final vol = (y - minVol) * volGridSize;
return volumeHeight - vol + priceHeight - baseAmount;
}
static PainterParams lerp(PainterParams a, PainterParams b, double t) {
double lerpField(double getField(PainterParams p)) =>
lerpDouble(getField(a), getField(b), t)!;
return PainterParams(
candles: b.candles,
horizontalLinesTextAlign: b.horizontalLinesTextAlign,
style: b.style,
horizontalLinesLabel: b.horizontalLinesLabel,
size: b.size,
candleWidth: b.candleWidth,
startOffset: b.startOffset,
maxPrice: lerpField((p) => p.maxPrice),
minPrice: lerpField((p) => p.minPrice),
maxVol: lerpField((p) => p.maxVol),
minVol: lerpField((p) => p.minVol),
xShift: b.xShift,
tapPosition: b.tapPosition,
leadingTrends: b.leadingTrends,
trailingTrends: b.trailingTrends,
);
}
bool shouldRepaint(PainterParams other) {
if (candles.length != other.candles.length) return true;
if (size != other.size ||
candleWidth != other.candleWidth ||
startOffset != other.startOffset ||
xShift != other.xShift) return true;
if (maxPrice != other.maxPrice ||
minPrice != other.minPrice ||
maxVol != other.maxVol ||
minVol != other.minVol) return true;
if (tapPosition != other.tapPosition) return true;
if (leadingTrends != other.leadingTrends ||
trailingTrends != other.trailingTrends) return true;
if (style != other.style) return true;
return false;
}
}
class PainterParamsTween extends Tween<PainterParams> {
PainterParamsTween({
PainterParams? begin,
required PainterParams end,
}) : super(begin: begin, end: end);
@override
PainterParams lerp(double t) => PainterParams.lerp(begin ?? end!, end!, t);
}