Used by the routine at OBJECT_DONE.

Called at the end of every turn (OBJECT_DONE). The list at DRAW_LIST holds every record flagged to be drawn this turn (LIST_DRAWN). First, for each one that moved -- bit 5 of its flags -- the area covering both where it was drawn last turn (+1C to +1F) and where it is now (+18 to +1B) is cleared in the buffer and remembered on the stack. Then every listed object is drawn into the buffer in depth order (SORT_AND_DRAW), and the carried things on the panel if they changed (SHOW_CARRIED); and last the remembered areas -- and only those -- are copied to the screen.

Nothing is ever rubbed out on the screen itself, so nothing flickers; the scenery is made of objects too, so what stood behind a moving thing is simply drawn again. On the first turn in a room nothing is wiped at all: the buffer is freshly built and OBJECT_DONE copies all of it. The areas count towards the turn's drawing work (DRAW_WORK, CONTROL), which sets how long the main loop waits.