Re: Gets vertical skylines from grob stencils (issue 5626052)

[joeneeman]

On 2012/08/17 19:25:29, Keith wrote:
> On Fri, 17 Aug 2012 10:16:25 -0700, <mailto:address@hidden> wrote:

> >
> >

http://codereview.appspot.com/5626052/diff/106004/lily/axis-group-interface.cc#newcode780
> > lily/axis-group-interface.cc:780: while (dirty);
> > On 2012/08/17 08:12:56, Keith wrote:
> >> I am beginning to understand the new code. Would you consider again
using
> >> distance() instead of the repeated calls to intersects() in the
while(dirty)
> >> loop ?  It might look simpler now that you've been away from the
code
> >> for awhile.

> >> floors[j] = padding - forest[j][UP]~distance~pair[DOWN]
> >> ceilings[j] = forest[j][DOWN]~distance~pair[UP]

> >> You know the solution will be to move an amount equal to one of the
> floors[j],
> >> and you want to find the smallest that fits, so make
> >>    trials = sort (floors)
> >> and find the smallest among trials that satisfies
> >>     trials[n] > 0
> >> &&  for all j (trials[n] > floors[j]
> >>                 || trials[n] < ceilings[j] )

> > I am not adverse to using distance if possible - my trouble case is
the
> > following.
> >
> > AAAAAAAAA
> >
> >      BBBBBBBBBBBBB
> >
> > Image that object A above is placed first and LilyPond is now
> > considering whether it should leave B where it is or place it above
A.
> > The distance function would dictate that it needs to be shifted
above A
> > because its DOWN skyline is below A's UP.

> We need not let the distance function between A[UP] and B[DOWN]
dictate, because
> having positive distance between A[DOWN] and B[UP] is another
solution.

> Object AA, a member of the forest, sets two constraints
>          floor = padding  -  AA[UP] ~distance~ BB[DOWN]
>          ceiling = AA[DOWN] ~distance~ BB[UP]  - padding
> and we are checking that a trial location satisfies
>          (trial >= floor) OR (trial <= ceiling)

> I suppose you show BB having been placed just above the staff, and
that it still
> lies below the ceiling set by AA, so this trial position satisfies the
first
> test in the OR above, so we win.

> All these distances can be computed once, before raising the skylines
at all,
> because they tell you right away what trial values of raising BB will
clear AA.
> That would be much simpler for people like me to understand than
computing the
> four intersects() conditions, after having moved the skylines by zero
or more
> bump(s).


I've implemented this method in dev/jneem-skylines and it looks pretty
neat. Next, padding...

http://codereview.appspot.com/5626052/