emHeightAscent property
      
      double
      get
      emHeightAscent
      
    
    
The read-only emHeightAscent property of the TextMetrics interface
returns the distance from the horizontal line indicated by the
CanvasRenderingContext2D.textBaseline property to the top of the em
square in the line box, in CSS pixels.
Implementation
external double get emHeightAscent;