accidental spacing (multiple signs): X-extent and ly:accidental-interface::width

[Torsten Anders]

Hello Lilyponders,

I am still looking for a way to avoid collisions of accidentals  
consisting of multiple signs. I searched various sources including the  
Internals Reference and finally came across the accidental slot/ 
property X-extent (the extent of accidentals in the X direction).

  http://lilypond.org/doc/v2.12/Documentation/user/lilypond-internals/Accidental

Firstly, I would like to know whether changing this slot/property is  
actually a good idea for avoiding collisions of accidentals.

Anyway, the documentation says it is hard coded, but I could actually  
change it: it indeed allows for an increased accidental spacing  
between accidentals and graphical objects such as bar lines.

I attached two examples that only differ in one line. In  
closeSpacing.ly X-extent is explicitly set to its default, and there  
is much collision of accidentals and other graphical objects.

    \override Accidental #'X-extent = #ly:accidental-interface::width

By contrast, widerSpacing.ly sets X-extent to the following value  
resulting in a much better though still not good result (instead of  
globally changing this value it should later be set for individual  
accidentals).

    \override Accidental #'X-extent = #'(0.5 . 3.0)

The improvement is that accidentals do not overlap each other in the  
chord anymore, and the space between the bar line and the chord is  
increased to give way for the accidentals (something that a simple  
horizontal shift of the accidental would not do). However, accidentals  
still overlap with the preceeding note.

I tried to understand X-extent and ly:accidental-interface::width, but  
I could not find any further documentation. I even tried searching the  
source, using the nice grep interface of gitweb. However, I had no  
success.

  
http://git.savannah.gnu.org/gitweb/?p=lilypond.git&a=search&h=HEAD&st=grep&s=accidental-interface

So, I have a few questions.

  - What exactly does this pair of numbers mean? Why are there two  
values to specify the width of a graphical object?
  - What is the definition of ly:accidental-interface::width?

Also, I would appreciate suggestions how to avoid collisions between  
accidentals and preceding notes.

Thank you very much!

Best,
Torsten

--
Torsten Anders
Interdisciplinary Centre for Computer Music Research
University of Plymouth
Office: +44-1752-586219
Private: +44-1752-558917
http://strasheela.sourceforge.net
http://www.torsten-anders.de

closeSpacing.ly
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closeSpacing.pdf
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widerSpacing.ly
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widerSpacing.pdf
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