function modeAdjust(a, b, c, d, mode) {
            if (mode === constants.CORNER) {
              return { x: a, y: b, w: c, h: d };
            } else if (mode === constants.CORNERS) {
              return { x: a, y: b, w: c - a, h: d - b };
            } else if (mode === constants.RADIUS) {
              return { x: a - c, y: b - d, w: 2 * c, h: 2 * d };
            } else if (mode === constants.CENTER) {
              return { x: a - c * 0.5, y: b - d * 0.5, w: c, h: d };
            }
          }
_globalInit

TODO: ???
if sketch is on window
assume "global" mode
and instantiate p5 automatically
otherwise do nothing

@private
@return {Undefined}