BaseChartPainter class abstract

Base painter for all chart types with common utilities.

This abstract class provides shared functionality for rendering charts, including grid lines, axes, labels, and coordinate transformations. All chart painters should extend this class to inherit these features.

Features

Automatic grid and axis rendering
Optimized coordinate transformations
Efficient repaint detection
Batched drawing operations

Example

class MyChartPainter extends BaseChartPainter {
  MyChartPainter({
    required super.theme,
    required super.dataSets,
  });

  @override
  void paint(Canvas canvas, Size size) {
    // Draw grid and axes
    drawGrid(canvas, size, minX, maxX, minY, maxY);
    drawAxes(canvas, size, minX, maxX, minY, maxY);

    // Draw your chart content
    // ...

    // Draw labels
    drawAxisLabels(canvas, size, minX, maxX, minY, maxY);
  }
}

Constructors

BaseChartPainter({required ChartTheme theme, required List<ChartDataSet> dataSets, bool showGrid = true, bool showAxis = true, bool showLabel = true}): Creates a base chart painter.
const

Properties

dataSets → List<ChartDataSet>: The data sets to render in the chart.
final
hashCode → int: The hash code for this object.
no setterinherited
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
semanticsBuilder → SemanticsBuilderCallback?: Returns a function that builds semantic information for the picture drawn by this painter.
no setterinherited
showAxis → bool: Whether to show axis lines.
final
showGrid → bool: Whether to show grid lines.
final
showLabel → bool: Whether to show axis labels.
final
theme → ChartTheme: The theme to use for styling the chart.
final

Methods

addListener(VoidCallback listener) → void: Register a closure to be notified when it is time to repaint.
inherited
drawAxes(Canvas canvas, Size size, double minX, double maxX, double minY, double maxY) → void: Draw axis lines.
drawAxisLabels(Canvas canvas, Size size, double minX, double maxX, double minY, double maxY, {List<ChartDataSet>? dataSets}) → void: Draw axis labels (optimized with text style caching).
drawGrid(Canvas canvas, Size size, double minX, double maxX, double minY, double maxY) → void: Draw grid lines (optimized with batched operations).
getDataBounds(double getValue(ChartDataPoint), double combine(double, double)) → void: Get data bounds (to be overridden by subclasses).
getNiceMaxY(double maxY, {int targetIntervals = 5}) → double: Helper to calculate a "nice" maximum Y value for axis scaling.
hitTest(Offset position) → bool?: Called whenever a hit test is being performed on an object that is using this custom paint delegate.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
paint(Canvas canvas, Size size) → void: Called whenever the object needs to paint. The given Canvas has its coordinate space configured such that the origin is at the top left of the box. The area of the box is the size of the size argument.
inherited
pointToCanvas(ChartDataPoint point, Size size, double minX, double maxX, double minY, double maxY) → Offset: Convert data point to canvas coordinates (optimized).
removeListener(VoidCallback listener) → void: Remove a previously registered closure from the list of closures that the object notifies when it is time to repaint.
inherited
shouldRebuildSemantics(covariant CustomPainter oldDelegate) → bool: Called whenever a new instance of the custom painter delegate class is provided to the RenderCustomPaint object, or any time that a new CustomPaint object is created with a new instance of the custom painter delegate class (which amounts to the same thing, because the latter is implemented in terms of the former).
inherited
shouldRepaint(covariant BaseChartPainter oldDelegate) → bool: Called whenever a new instance of the custom painter delegate class is provided to the RenderCustomPaint object, or any time that a new CustomPaint object is created with a new instance of the custom painter delegate class (which amounts to the same thing, because the latter is implemented in terms of the former).
override
toString() → String: A string representation of this object.
inherited

Operators

operator ==(Object other) → bool: The equality operator.
inherited