onVerticalScale method

void onVerticalScale(
  1. double deltaY
)

Vertical scale drag on price scale (Y-axis zoom).

Implementation

void onVerticalScale(double deltaY) {
  // deltaY > 0 -> dragged down -> zoom out (expand span)
  // deltaY < 0 -> dragged up -> zoom in (compress span)
  final factor = 1.0 + (deltaY / 120.0);
  _verticalScale = (_verticalScale * factor).clamp(0.05, 30.0);
  notifyListeners();
}