These callbacks were named for the purpose of drawing (and that's probably
their main use case still), but nothing limits them to be used for that only.
They can be useful for non-drawing related things, essentially they act as
drop-box entering and exiting event handlers. Reflect that in the name, so also
more clear when they will be called, as opposed to what they are typically used
for. Drop-boxes already have such event handler callbacks, this makes their API
naming more consistent.
Also better differentiates between drawing and handling callbacks, the
difference matters (attempting to draw during handling won't work).
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