point_line_dist
float dL = point_line_dist(fLeftTop, fLeftBottom, where, inset);
float dR = point_line_dist(fRightTop, fRightBottom, where, inset);
float dT = point_line_dist(fLeftTop, fRightTop, where, inset);
float dB = point_line_dist(fLeftBottom, fRightBottom, where, inset);