Re: grace notes break preceding ties in MIDI

[Adam Spiers]

On Sun, Jan 13, 2013 at 4:40 PM, Adam Spiers
<address@hidden> wrote:
> On Sat, Jan 12, 2013 at 12:52 PM, Adam Spiers <address@hidden> wrote:
>> On Tue, Jan 8, 2013 at 5:59 PM, Adam Spiers <address@hidden> wrote:
>>> On Tue, Jan 8, 2013 at 5:41 PM, Eluze <address@hidden> wrote:
>>>> I've added an issue to the tracker:
>>>> https://code.google.com/p/lilypond/issues/detail?id=3091&thanks=3091&ts=1357666391

[snipped]

> I have finally pinned this down!  And I'm close to a fix.  The culprit
> is in Midi_walker::process():
>
>           if (note->audio_->length_mom_.to_bool ())
>             do_start_note (note);
>
> This to_bool () check is too simplistic.  Here is the explanation ...

[snipped]

> I believe a reasonable approach would be to use a different check:
>
>           if (note->audio_->length_mom_.main_part_ ||
>               note->audio_->length_mom_.grace_part_.sign () == 1)
>             do_start_note (note);
>
> It may even warrant a new Audio_note::is_positive_duration() method
> which could be used here.
>
> Thoughts?
>
> However, this suggested workaround is not sufficient by itself - there
> is a related issue with the ordering of NoteOff events which I'm
> working on now.

Addressing the related issue led me to a better, single fix for both.
The real problem is that \grace causes the immediately preceding
Audio_note (or Audio_notes if the \grace follows a chord) to be
shortened, but it fails to check whether the Audio_note is part of a
tie.

I have published my fix here and will submit to Rietveld soon:

https://github.com/aspiers/lilypond/commits/tie-grace-fix