new bar-lines / issue 1320

[Thomas Morley]

Hi,

together with Marc Hohl I was working on Issue 1320 for a couple of weeks.
Now we have a first working version using a new approach to design BarLines:
Only simple BarLines are predefined e.g "|"  "."  ":"  etc (plus some
exceptions).
Some defaults for the line-break and the SpanBars are predefined, too.
All is stacked together on-the-fly.

It is now possible to define a plethora of BarLines:
Using all glyphs from '("|"  ":"  "*" "." ";" "'" "S" "k" "" "||" "-"
"|:" ".|:" ":|" ":|." ":|:" ":..:" "x") combining them as you want.
The behaviour at line-break and of SpanBars can be changed quite
easily. Also, you can define different behaviour for the same
BarLine-glyph. And it is possible to integrate user-defined
print-procedures, too.

Please note, there was need to change some glyphs:
"*" - dotted-bar-line
";"  - dashed-bar-line
"-"  - used to print a double-line-span-bar, while using \bar "S"
"x" – is a placeholder getting his extent from the substring of the
BarLine-glyph, only used in SpanBars.

As a repeat-sign you have to use e.g. ".|:"
The former repeat-signs e.g. "|:" will now print a single line and a
colon, only.

Of course the present code has to be improved a lot before we can
think of a patch.
But now we have to make a decision about further development:
We played around with the idea to replace all relevant parts of
bar-line.cc and span-bar.cc with scheme-code.
Would this be suitable?
Or should we limit it to solve Issue 1320 and create a snippet?

All other observations, hints and suggestions are highly apreciated!

-Harm

custom-bars-22.ly
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