The refX attribute for SVG specifies the x-coordinate of the reference point.
<length-percentage> | <number> | left | center | right
0
markerHeight
markerUnits
markerWIdth
orient
preserveAspectRatio
refY
viewBox
World Wide Web Consortium (W3C)
<length> | left | center | right
(none)
height
width
x
y