LXCLIP(ix1.i2.r, iy1.i2.r, ix2.i2.r, iy2.i2.r)

	This routine will set the clipping rectangle for graphics output.
	A call to LXRST will clear the clipping rectangle, as will a call
	with coordinates (0, 0, 639, 511) while offering better graphics
	performance.  No LXERAS calls should be done while a clipping
	rectangle is in effect, as a the entire window will be cleared,
	but the 'repair' pixmap will not.