To improve performance of graphics output, most graphics devices
provide some form of buffering. By default, Scheme's graphics
procedures flush this buffer after every drawing operation. The
procedures in this section allow the user to control the
flushing of the output buffer. Enables buffering for graphics-
device. In other words, after this procedure is called, graphics
operations are permitted to buffer their drawing requests. This
usually means that the drawing is delayed until the buffer is
flushed explicitly by the user, or until it fills up and is
flushed by the system. Disables buffering for graphics-device.
By default, all graphics devices are initialized with buffering
disabled. After this procedure is called, all drawing operations
perform their output immediately, before returning. graphics-
disable-bufferingflushes the output buffer if necessary.