Re: Fixes note column skylines by adding stem tremolo to axis group. (issue4754054)

[address@hidden]

On Jul 19, 2011, at 6:11 PM, Neil Puttock wrote:

> On 19 July 2011 09:10, address@hidden <address@hidden> wrote:
> 
>> After making several round-trips around the source this morning, I can't put 
>> off composition any longer, but I fear that all I will compose today are 
>> songs about the Axis_group_interface if I don't understand how this works.
>> I believe that line 80 of note-spacing.cc is where the two skylines for the 
>> two note columns are calculated.  How, by adding a pure-height to the 
>> Stem_tremolo, does the Stem_tremolo make its way into this skyline?  And, if 
>> it doesn't make its way into this skyline, how is it taken into account 
>> during horizontal spacing?
> 
> I'm afraid I don't know why it works. I just suggested it based on
> seeing how similar collisions have been solved in the past (e.g., for
> ez-noteheads).

I figured out why it works - I figured I'd post this to the list in case anyone 
else ever wants to mess around with pure properties.

The StemTremolo is added to the paper column's element grob array via the 
axis-group-engraver because it does not have an axis-group-parent-Y.
Then, when horizontal spacing happens, its pure height function is passed 
through for its print function (separation-item.cc).

I may write a "pure" tutorial for the contributor's guide.  It has taken me a 
long time to figure out how "pure" works in lilypond, and if other people are 
as mystified as I was when I started trying to figure this stuff out, then I 
think an addition to the CG would help.

Cheers,
MS