Zooming, Panning & Selection

Covers user interaction features that let users explore chart data — zoom in/out, pan across the data range, and select individual points or series.

ZoomPanBehavior Setup

Initialize in initState to avoid recreation on each rebuild:

late ZoomPanBehavior _zoomPan;

@override
void initState() {
  _zoomPan = ZoomPanBehavior(
    enablePinching: true,           // Two-finger pinch zoom
    enableDoubleTapZooming: true,   // Double-tap to zoom in
    enableSelectionZooming: true,   // Drag to zoom to a rectangle
    enableMouseWheelZooming: true,  // Desktop/web mouse wheel
    enablePanning: true,            // Pan after zooming
    zoomMode: ZoomMode.x,           // x | y | xy
  );
  super.initState();
}

zoomPanBehavior: _zoomPan,

Zoom Mode

Control which axis can be zoomed:

ZoomPanBehavior(
  enablePinching: true,
  zoomMode: ZoomMode.x,
)

ZoomMode.x — zoom horizontally only (most common for time-series)
ZoomMode.y — zoom vertically only
ZoomMode.xy — zoom both axes

Directional Zooming

Detect the user's finger gesture direction and zoom accordingly:

ZoomPanBehavior(
  enablePinching: true,
  enableDirectionalZooming: true,
  zoomMode: ZoomMode.xy,
)

When the user pinches more horizontally, only the X axis zooms; more vertical pinch zooms the Y axis.

Selection Zooming

Allow the user to drag-select a rectangle on the chart to zoom into that region:

ZoomPanBehavior(
  enableSelectionZooming: true,
  selectionRectColor: Colors.blue.withOpacity(0.1),
  selectionRectBorderColor: Colors.blue,
  selectionRectBorderWidth: 1,
)

Zoom Reset

_zoomPan.reset();

Auto-Scrolling (Live / Real-Time Data)

Keep the latest N data points visible as new data arrives:

SfCartesianChart(
  primaryXAxis: DateTimeAxis(
    autoScrollingDelta: 10,                           
    autoScrollingDeltaType: DateTimeIntervalType.seconds,
    autoScrollingMode: AutoScrollingMode.end,         // end | start
  ),
  zoomPanBehavior: ZoomPanBehavior(enablePanning: true),
)

SelectionBehavior

Let users tap to select individual points or entire series. Use for highlighting, drilldown, or responding to user selection.

late SelectionBehavior _selection;

@override
void initState() {
  _selection = SelectionBehavior(enable: true);
  super.initState();
}

LineSeries<ChartData, String>(
  selectionBehavior: _selection,
)

Customize selected/unselected appearance:

SelectionBehavior(
  enable: true,
  selectedColor: Colors.blue,
  selectedBorderColor: Colors.blueAccent,
  selectedBorderWidth: 2,
  unselectedColor: Colors.grey.withOpacity(0.3),
  unselectedBorderColor: Colors.grey,
  unselectedOpacity: 0.4,
)

Selection type on the chart:

SfCartesianChart(
  selectionType: SelectionType.point,
  // point — selects individual data point
  // series — selects entire series
  // cluster — selects all points with the same x value across series
)

Multi-Point Selection

Allow selecting multiple points at once:

SfCartesianChart(
  enableMultiSelection: true,
  selectionType: SelectionType.point,
)

Responding to Selection Events

SfCartesianChart(
  onSelectionChanged: (SelectionArgs args) {
    final int seriesIndex = args.seriesIndex;
    final int pointIndex = args.pointIndex;
    // Use args.selectedColor, args.unselectedColor to adjust appearance
  },
)

Common Gotchas

Problem	Fix
Zoom resets on `setState`	Initialize `ZoomPanBehavior` in `initState`, not in `build`
Pan not working after zoom	Enable `enablePanning: true` in `ZoomPanBehavior`
Auto-scroll not updating	Call `_controller.updateDataSource(addedDataIndexes: [...])` instead of `setState`
Selection state lost on rebuild	Keep `SelectionBehavior` instance in `State`, not inline

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