viewportScalingFactor property
      
      double
      get
      viewportScalingFactor
      
    
    
Returns the current viewport scale.
A scale of 1.0 would map the data directly to the output range, while a value of 2.0 would map the data to an output of double the range so you only see half the data in the viewport. This is the equivalent to zooming. Its value is likely >= 1.0.
Implementation
double get viewportScalingFactor => scale!.viewportScalingFactor;