initPathFunc method
      
void
initPathFunc()
      
     
    
    
Implementation
void initPathFunc() {
  if (pathFunc != null) {
    return;
  }
  if (pathArc == 0) {
    pathFunc = straightPath;
  } else {
    pathFunc = pathAlongArc(pathArc, axis: pathArcAxis);
  }
}