Skip to content

feat: Add the gauge marker painter #2096

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
imaNNeo merged 1 commit into from
Apr 29, 2026
Merged

feat: Add the gauge marker painter #2096

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
143 changes: 41 additions & 102 deletions example/lib/presentation/samples/gauge/gauge_chart_sample1.dart
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,3 @@
import 'dart:math';
import 'dart:ui';

import 'package:fl_chart/fl_chart.dart';
import 'package:fl_chart_app/presentation/resources/app_resources.dart';
import 'package:flutter/material.dart';
Expand All @@ -15,6 +12,12 @@ class GaugeChartSample1 extends StatefulWidget {
class GaugeChartSample1State extends State<GaugeChartSample1> {
double _value = 0.5;

// Continuous min/max thresholds — deliberately off the 11-tick grid
// (0.0, 0.1, ..., 1.0) to show GaugeMarker carries an arbitrary
// value, not a discrete tick index.
static const _minValue = 0.23;
static const _maxValue = 0.77;

@override
Widget build(BuildContext context) {
return Padding(
Expand All @@ -40,16 +43,46 @@ class GaugeChartSample1State extends State<GaugeChartSample1> {
position: GaugeTickPosition.center,
count: 11,
offset: 0,
painter: _MyCustomGaugeMinMaxTickPainter(
painter: GaugeTickCirclePainter(
color: AppColors.contentColorWhite,
radius: 5,
minIndex: 2,
maxIndex: 8,
minMaxLineLength: 40,
minMaxLineStrokeWidth: 4,
),
checkToShowTick: GaugeTicks.hideEndpoints,
),
markers: const [
GaugeMarker(
value: _minValue,
position: GaugeTickPosition.center,
painter: GaugeMarkerLinePainter(
length: 40,
thickness: 4,
color: Colors.green,
label: 'Min',
labelStyle: TextStyle(
color: Colors.green,
fontSize: 12,
fontWeight: FontWeight.bold,
),
labelSide: GaugeMarkerLabelSide.inward,
),
),
GaugeMarker(
value: _maxValue,
position: GaugeTickPosition.center,
painter: GaugeMarkerLinePainter(
length: 40,
thickness: 4,
color: Colors.red,
label: 'Max',
labelStyle: TextStyle(
color: Colors.red,
fontSize: 12,
fontWeight: FontWeight.bold,
),
labelSide: GaugeMarkerLabelSide.inward,
),
),
],
pointers: [
// Needle extending from center toward the current value.
GaugePointer(
Expand Down Expand Up @@ -95,97 +128,3 @@ class GaugeChartSample1State extends State<GaugeChartSample1> {
);
}
}

class _MyCustomGaugeMinMaxTickPainter extends GaugeTickCirclePainter {
_MyCustomGaugeMinMaxTickPainter({
super.color,
super.radius,
required this.minIndex,
required this.maxIndex,
required this.minMaxLineLength,
required this.minMaxLineStrokeWidth,
this.textOffset = 6,
this.minTextStyle = const TextStyle(
color: Colors.green,
fontSize: 12,
fontWeight: FontWeight.bold,
),
this.maxTextStyle = const TextStyle(
color: Colors.red,
fontSize: 12,
fontWeight: FontWeight.bold,
),
}) : super();

final int minIndex;
final int maxIndex;
final double minMaxLineLength;
final double minMaxLineStrokeWidth;
final double textOffset;
final TextStyle minTextStyle;
final TextStyle maxTextStyle;

final _paint = Paint();

@override
void draw(Canvas canvas, GaugeTickInfo tickInfo) {
super.draw(canvas, tickInfo);

if (tickInfo.index != minIndex && tickInfo.index != maxIndex) {
return;
}
final isMin = tickInfo.index == minIndex;
final text = isMin ? "Min" : "Max";
final textStyle = isMin ? minTextStyle : maxTextStyle;
final rotation = isMin ? pi : 0.0;
final textPainter = TextPainter(
text: TextSpan(text: text, style: textStyle),
textDirection: TextDirection.ltr,
)..layout();
// 180 degrees
canvas.rotate(rotation);
final offsetX = isMin
? 0 + textPainter.width + textOffset
: 0 - textPainter.width - minMaxLineLength / 2 - textOffset;
textPainter.paint(canvas, Offset(offsetX, 0 - textPainter.height / 2));
_paint.color = textStyle.color!;
_paint.strokeWidth = minMaxLineStrokeWidth;
canvas.drawLine(
Offset(0 - minMaxLineLength / 2, 0),
Offset(0 + minMaxLineLength / 2, 0),
_paint,
);
}

@override
GaugeTickPainter lerp(GaugeTickPainter b, double t) {
if (b is! _MyCustomGaugeMinMaxTickPainter) {
return b;
}
return _MyCustomGaugeMinMaxTickPainter(
color: Color.lerp(color, b.color, t)!,
radius: lerpDouble(radius, b.radius, t)!,
minIndex: minIndex,
maxIndex: maxIndex,
minMaxLineLength: lerpDouble(minMaxLineLength, b.minMaxLineLength, t)!,
minMaxLineStrokeWidth:
lerpDouble(minMaxLineStrokeWidth, b.minMaxLineStrokeWidth, t)!,
textOffset: lerpDouble(textOffset, b.textOffset, t)!,
minTextStyle: TextStyle.lerp(minTextStyle, b.minTextStyle, t)!,
maxTextStyle: TextStyle.lerp(maxTextStyle, b.maxTextStyle, t)!,
);
}

@override
List<Object?> get props =>
[
super.props,
minIndex,
maxIndex,
minMaxLineLength,
minMaxLineStrokeWidth,
textOffset,
minTextStyle,
maxTextStyle,
];
}
Loading
Loading