onScrollWheel method

void onScrollWheel(
  1. double deltaY,
  2. double focalX,
  3. double canvasWidth
)

Implementation

void onScrollWheel(double deltaY, double focalX, double canvasWidth) {
  if (_disposed) return;
  if (!constraints.enableScrollZoom) return;
  if (canvasWidth <= 0 ||
      !canvasWidth.isFinite ||
      !focalX.isFinite ||
      !deltaY.isFinite) {
    return;
  }
  final scaleDelta = deltaY < 0 ? 1.15 : 0.87;
  final frac = value.canvasToFraction(focalX, canvasWidth);
  value = value.zoomAroundFraction(frac, scaleDelta);
  _applyConstraints();
}