There are classes of applications where it would be handy to have the cursor
be invisible for the entire application (e.g. games, and when the user wants
to draw only an object being rendered as the cursor moves).

One way to do this would be to define something like
Toolkit.setCursorVisibility(boolean visible)
boolean Toolkit.getCursorVisibility()

Another piece of functionality might be to have invisible cursors on a
per-component basis - somthing like Cursor.INVISIBLE_CURSOR.

One developer has tried the obvious workaround: implementing
Toolkit.createCustomCursor with a blank transparent image. He reports
that it performs badly in XOR mode because all the custom cursors flicker
(appear and disappear) as the mouse moves (another undesirable feature).