A flat terracotta tint on the object, plus chevrons on whichever edges of the view it runs past.
Two pieces: the clipped tint, and up to four glyphs chosen from which sides of the viewport the box crosses.
The most informative of the five. The tint answers which object is selected, the chevrons answer where the rest of it goes.
Four glyphs at most, so the cost is fixed. The tint has to stay light enough not to hide the drawing underneath it.