Programmer grid format - %gd
%gd is for program development only. It overlays a grid over the window and any
items within it. This enables controls to be positioned using the %ap format.
The grid is marked in small intervals corresponding to the average character
size of the default font, with major divisions every 10 such units. The grid
starts at the left and top margins, but extends over the right and bottom
margins, since this may help in the placement of further controls.