Whiteout / LyricHyphen

[Knut Petersen]

Hi everybody!

Whiteout for LyricHyphen grobs is not needed often, but it's essential if you 
engrave music that uses
mensuration lines.

Choosing a *box whiteout function is not an option as for  melismata spanning 
several bars also parts of
mensuration lines that do not collide with a hyphen would be destroyed.

Choosing the outline whiteout function is not a real option as it is broken if 
height / width of the object
to whiteout is small compared to the area that should be cleared (see first 
attachment).

Increasing the number of iterations (e.g. setting angle-increments to 32 and 
radial-increments to 3) is easy
and it helps (see 2nd attachment), but you'll end up with pdfs that contain 
mostly whiteout code ;-)

Therefore I propose that LyricHyphen grobs should implement their own whiteout 
routine. That would
give the desired result with a minimum of effort (see 3rd and 4th attachment).

The necessary changes are small, see 5th attachment ... obviously it's a redout 
instead of whiteout for
demonstration purposes ;-)

Obviously this code is not perfect:

It may whiteout only parts of a mensuration line if the vertical edge of the 
whiteout area is on top of only parts
of the mensuration line. Slightly increasing/decreasing the whiteout value 
would help in that situation.

It would be better to detect collision with mensuration lines and to insert 
whiteout code only if it is needed.
I don't know enough of the lilypond internals to implement that within 
reasonable time.

The code does not check whiteout-style ... don't know how to access that from 
within lyric-hyphen.cc.

Obviously a similar patch is needed for LyricExtender grobs if you agree that 
something like this patch should be
part of lilypond.

cu,
 Knut

WhiteoutOrig.jpg
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WhiteoutImproved.jpg
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WhiteoutEvenBetter-A.jpg
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WhiteoutEvenBetter-B.jpg
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0001-Experimental-Implement-special-whiteout-for-LyricHyp.patch
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