Re: Tied accidentals in chords still taking up space (was: Issue 415 in lilypond: Hidden accidental of tied note still takes space)

[Joe Neeman]

On Sun, 2009-03-29 at 02:34 -0300, Han-Wen Nienhuys wrote:
> On Sat, Mar 28, 2009 at 11:31 PM, Joe Neeman <address@hidden> wrote:
> 
> 
> > The problem is that the current support for conditional accidentals is
> > insufficient if there are multiple accidentals, not all of which are
> > tied (see bug 612). The reason is that the positions of all the
> > accidentals can change completely when an accidental is added or
> > removed. So I think we need to run the whole layout algorithm twice,
> > once with the conditional accidentals and once without, and I suggested
> > that copying all of the accidentals is the simplest way to do it. I
> > realize that this goes against the convention of only cloning items in
> > the breakable columns, but I don't see another way to do it; the
> 
> I am worried that this will lead to all kinds of other problems, when
> other callbacks try to follow head -> accidental links, and screw up
> because they end up at the wrong accidental object.
Requesting note_head->accidental_grob before line-breaking is likely to
be fragile anyway, because the accidental could always suicide...

> Is it not possible
> to have accidental place calculate two sets of offsets, and add some
> logic to make sure that the actual stencil and placement calculation
> does not get triggered during line breaking?  Then after the
> linebreaking, one set of placements is used for positioning the
> accidentals.  Of course there will be some ugly hacks needed (similar
> to the conditional skyline support) to extract the correct outline of
> the accidentals during spacing/linebreaking.

I'm not sure it would be easier, but it's worth checking out anyway.
Chris, could you try adding

Skyline Accidental_placement::conditional_skyline(Grob* me, Grob* left)

?
This function would run the accidental layout algorithm on the correct
(with respect to "left") set of accidentals but without actually calling
translate_axis on the accidentals. Instead, it would just return the
left_skyline that results from the accidental placement (ie, the value
of left_skyline_ at accidental-placement.cc:391). Then add

Skyline Accidental_placement::conditional_skyline(vector<Grob*> const&
elts, Grob* left)

which merges the results of conditional_skyline(me, left) for each me in
elts. Finally, modify Separation_item::conditional_skyline to return
this skyline. This should prevent any of the accidentals from being
translated until after line-breaking.

Sorry to ask you to re-implement what you've already done, but it could
end up significantly cleaner if there are no complications.

Joe