Re: Slur collision detection and resolution works for sharp symbol but fails for flat symbol

[Carl Sorensen]

On 5/27/18, 9:52 AM, "Aaron Hill" <address@hidden> wrote:

    On 2018-05-27 06:29, Jürgen Reuter wrote:
    > Looks like slur collision detection and resolution (the slur is moved
    > upwards) works fine for sharp accidentals, but is ignored for flat
    > accidentals.

Slur collision is not ignored.  There are a number of different parameters 
governing the goodness of slurs.  The goodness of each factor is calculated and 
summed to give the overall goodness (actually, badness) of the slur.  A number 
of slurs are tried, and the slur with the lowest badness is used.

The parameters that can be adjusted to get a particular outcome are found in 
the Slur.details property, and are listed, along with their default values, in 
the Notation reference:
http://lilypond.org/doc/v2.19/Documentation/internals/slur

In this particular case, increasing the accidental-collision penalty will cause 
the slur to avoid the accidental.

   \version "2.18.2"
   {
     \override Slur.direction = #UP
    \override Slur.details.accidental-collision = #20 % the default is 3; a 
higher value will make it more likely the accidental is avoided
     \override Slur.height-limit = #10
     a'( ges'') a'( gis'') % Collision with both accidentals.
     \override Stem.direction = #UP
     a'( ges'') a'( gis'') % Collision with flat only.
   }


This is not a bug, but just a hard slur to engrave, so the default values of 
the details may not be optimal.

HTH,

Carl