onDragUpdate method

@protected bool onDragUpdate(Point<double> localPosition, double scale)

Implementation

@protected
bool onDragUpdate(Point<double> localPosition, double scale) {
  if (!_isPanning || _lastPosition == null || _chart == null) {
    return false;
  }

  // Pinch gestures should be handled by the [PanAndZoomBehavior].
  if (scale != 1.0) {
    _isPanning = false;
    return false;
  }

  // Update the domain axis's viewport translate to pan the chart.
  final domainAxis = _chart!.domainAxis;

  if (domainAxis == null) {
    return false;
  }

  // This is set during onDragUpdate and NOT onDragStart because we don't yet
  // know during onDragStart whether pan/zoom behavior is panning or zooming.
  // During panning, domain tick provider set to generate ticks with locked
  // steps.
  _domainAxisTickProvider.mode = PanningTickProviderMode.stepSizeLocked;

  final domainScalingFactor = domainAxis.viewportScalingFactor;

  var domainChange = 0.0;
  if (domainAxis.isVertical) {
    domainChange =
        domainAxis.viewportTranslatePx + localPosition.y - _lastPosition!.y;
  } else {
    domainChange =
        domainAxis.viewportTranslatePx + localPosition.x - _lastPosition!.x;
  }

  final chart = this.chart!;
  domainAxis.setViewportSettings(domainScalingFactor, domainChange,
      drawAreaWidth: chart.drawAreaBounds.width,
      drawAreaHeight: chart.drawAreaBounds.height);

  _lastPosition = localPosition;

  chart.redraw(skipAnimation: true, skipLayout: true);
  return true;
}