code: function ( inSeg, inPt, inBetweenY ) {
  		var retVal;
  		var dXfrom = inSeg.vFrom.x - inPt.x;
  		var dXto = inSeg.vTo.x - inPt.x;
  		var dYfromZero = this.fpEqual( inSeg.vFrom.y, inPt.y );
  		if ( this.fpEqual( inSeg.vTo.y, inPt.y ) ) {
  			if ( dYfromZero )	return 0;		// all points on a horizontal line
  			retVal = dXto;
  		} else if ( dYfromZero ) {
  			retVal = dXfrom;
  /*		} else if ( inBetweenY && ( dXfrom * dXto > 0 ) ) {
  			// both x-coordinates of inSeg are on the same side of inPt
  			if ( Math.abs( dXto ) >= PNLTRI.Math.EPSILON_P )	return	dXto;
  			retVal = dXfrom;	*/
  		} else {
  			if ( inSeg.upward ) {
  				return	PNLTRI.Math.ptsCrossProd( inSeg.vFrom, inSeg.vTo, inPt );
  			} else {
  				return	PNLTRI.Math.ptsCrossProd( inSeg.vTo, inSeg.vFrom, inPt );
  			}
  		}
  		if ( Math.abs( retVal ) < PNLTRI.Math.EPSILON_P )		return	0;
  		return	retVal;
  	}
docs: Checks, whether the vertex inPt is to the left of line segment inSeg. Returns: >0: inPt is left of inSeg, <0: inPt is right of inSeg, =0: inPt is co-linear with inSeg  ATTENTION: always viewed from -y, not as if moving along the segment chain !!