The read-only bounds var returns the map coordinates, in pixels, covered by the client’s viewport when accounting for pixel offsets, eye, step, etc. (The coordinates are only relevant to the default client.dir value of NORTH, and the TOPDOWN_MAP or SIDE_MAP map formats.)
If the viewport is not currently on the map (for instance, when the eye is at a null location), the var reads as null. Otherwise, it is a list with five values (x, y, width, height, z) in the same form used by the bounds proc.
The alias vars bound_x, bound_y, bound_width, and bound_height can also be used to retrieve the individual values from the list. They too will be null if the viewport is not on the map.