code: protected double getKnobPercent() {
  		// If we have no range
  		if (maxValue <= minValue) {
  			return 0;
  		}
  
  		// Calculate the relative progress
  		double percent = (curValue - minValue) / (maxValue - minValue);
  		return Math.max(0.0, Math.min(1.0, percent));
  	}
docs: Get the percentage of the knob's position relative to the size of the line. The return value will be between 0.0
  and 1.0.
  
  @return the current percent complete