Timeline class

A high-performance Flutter timeline/Gantt chart widget for displaying project schedules.

The Timeline widget provides a scrollable view of project stages, milestones, and activities across a date range. It uses lazy rendering and direct scroll calculations to efficiently handle large datasets (500+ days with 100+ stages).

Features

• Native Scrolling: Uses Flutter's native ScrollController for all scroll management
• Direct Calculations: Calculates scroll state directly using pure functions
• Lazy Rendering: Only renders visible items plus a configurable buffer
• Data Caching: Caches formatted data to avoid redundant calculations
• External Configuration: Performance tuning via JSON configuration file

Scroll Architecture

The Timeline uses a simplified scroll architecture that relies entirely on native Flutter ScrollControllers without custom abstraction layers:

1. Native Controllers: Uses _controllerHorizontal for horizontal and vertical scrolling respectively
2. Direct State Management: Maintains scroll state in local variables (_centerItemIndex, _visibleStart, _visibleEnd)
3. Pure Calculation Functions: Calls pure functions from scroll_calculations.dart to calculate center index and visible range

Example

Timeline(
  colors: myColors,
  infos: {'startDate': '2024-01-01', 'endDate': '2024-12-31'},
  elements: myElements,
  elementsDone: [],
  capacities: [],
  stages: myStages,
  openDayDetail: (day) => print('Clicked: ${day['date']}'),
)

See also:

• TimelineConfiguration for performance tuning options
• calculateCenterDateIndex for center item calculation