Making phrases in text invisible / visible on a display
I'm looking for a way to make text (phrases thereof) in a display
invisible / visible without changing the underlying string. Like for
example with an emphasis value #invisible similiar to the existing ones
#(normal bold italic narrow underlined struckOut). The effect should be
that #invisible emphasized portions of text are *automagically* collapsed
to zero width on the display (and/or perhaps an alternate / placeholder
symbol is shown instead of the collapsed).
Is there already something into that direction which can be reused.
If not and anyways: pointers, comments and suggestions all appreciated.