Contribution Heatmap

A high-performance, GitHub-like contribution heatmap widget for Flutter. This widget provides a visual representation of contribution data over time, similar to GitHub's contribution graph.

✨ Features

• 🚀 Ultra-High Performance: Custom RenderBox implementation with optimized rendering pipeline
• 👆 Interactive: Full tap support with proper hit testing and gesture handling
• 🎨 Fully Customizable: Colors, sizing, labels, and layout options
• ♿ Accessibility Ready: Supports text scaling and high contrast modes
• 🌍 Internationalized: Locale-aware text rendering with customizable start weekdays
• 💾 Memory Efficient: Optimized data structures minimize memory usage and GC pressure
• 🔧 Smart Invalidation: Only recomputes what's needed, not on every frame

🚀 Quick Start

Basic Usage

import 'package:flutter/material.dart';
import 'package:contribution_heatmap/contribution_heatmap.dart';

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ContributionHeatmap(
      entries: [
        ContributionEntry(DateTime(2025, 8, 15), 5),
        ContributionEntry(DateTime(2025, 8, 16), 3),
        ContributionEntry(DateTime(2025, 8, 17), 8),
        // Add more entries...
      ],
      onCellTap: (date, value) {
        print('Tapped: $date with $value contributions');
      },
    );
  }
}

Advanced Usage

ContributionHeatmap(
  entries: myContributionData,
  
  // Custom date range
  minDate: DateTime(2025, 1, 1),
  maxDate: DateTime.now(),
  
  // Visual customization
  cellSize: 14.0,
  cellSpacing: 4.0,
  cellRadius: 3.0,
  padding: EdgeInsets.all(20),
  
  // Custom color scale
  colorScale: (value) {
    if (value == 0) return Colors.grey[100]!;
    if (value <= 2) return Colors.green[200]!;
    if (value <= 5) return Colors.green[400]!;
    return Colors.green[600]!;
  },
  
  // Custom text styles
  monthTextStyle: TextStyle(
    color: Colors.grey[600],
    fontSize: 12,
    fontWeight: FontWeight.w500,
  ),
  weekdayTextStyle: TextStyle(
    color: Colors.grey[500],
    fontSize: 11,
  ),
  
  // Week starts on Sunday (US style)
  startWeekday: DateTime.sunday,
  
  // Handle cell interactions
  onCellTap: (date, value) {
    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: Text('${date.toIso8601String().split('T')[0]}'),
        content: Text('$value contributions on this date'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: Text('Close'),
          ),
        ],
      ),
    );
  },
)

📊 Data Model

ContributionEntry

The Data structure for contribution data:

class ContributionEntry {
  final DateTime date;  // Day-level precision
  final int count;      // Number of contributions (>= 0)
  const ContributionEntry(this.date, this.count);
}

🎨 Customization Options

Visual Properties

Property	Type	Default	Description
cellSize	double	12.0	Size of each contribution cell
cellSpacing	double	3.0	Spacing between cells
cellRadius	double	2.0	Corner radius for rounded cells
padding	EdgeInsets	EdgeInsets.all(16)	Outer padding around widget

Labels & Text

Property	Type	Default	Description
showMonthLabels	bool	true	Show month names above the heatmap
showWeekdayLabels	bool	true	Show day names on the left
monthTextStyle	TextStyle?	null	Custom style for month labels
weekdayTextStyle	TextStyle?	null	Custom style for weekday labels

Date & Layout

Property	Type	Default	Description
minDate	DateTime?	null	Override minimum date (auto-calculated if null)
maxDate	DateTime?	null	Override maximum date (auto-calculated if null)
startWeekday	int	DateTime.monday	First day of week (1=Mon, 7=Sun)

Colors & Interaction

Property	Type	Default	Description
colorScale	Color Function(int)?	null	Custom color mapping function
onCellTap	void Function(DateTime, int)?	null	Callback for cell tap events

⚡ Performance Characteristics

Rendering Performance

• O(1) cell value lookups during painting
• Custom RenderBox implementation bypasses widget rebuilds
• Smart invalidation - only recomputes when properties actually change
• Efficient hit testing with proper bounds checking

Memory Efficiency

• HashMap-based data structure for fast lookups
• Minimal object allocation during painting
• Proper gesture recognizer cleanup prevents memory leaks
• Optimized text rendering with cached TextPainter objects

Scalability

• Handles thousands of data points efficiently
• Constant time complexity for cell rendering
• Responsive layout adapts to available space
• Smooth interactions even with large datasets

📝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

📄 License

This project is licensed under the BSD 3-Clause License - see the LICENSE file for details.