1 means that your cursor will snap to the grid lines,
0.5 will also snap halfway between them,
Off will not snap to the grid lines.
On will snap to the ends of previously drawn lines or arcs,
Off will not.
Whether the line and arc tools should snap to particular angles in increments of
Off to disable.
This is so that angled lines can snap to particular lengths.
1 corresponds to the size of one grid cell. Can also be