Re: Keep a staff alive with multiple layers (issue 308910043 by address@hidden)

[mark . opus11]

On 2016/08/12 14:52:42, mark_opus11.net wrote:
> Use key? (integer or symbol)

I looked at doing this, as David suggested, by introducing two new
properties (removal-friends and removal-foes) but found the
resultant logical permutations too confusing to either document
clearly or be useful to a user.

So I have returned to a cleaner implementation of Patch Set 1, in
which remove-layer will accept a key with the following
behaviours:

- integer: layer removed when larger than smallest retained
- 'any: layer kept alive by any other layer
- #f: layer independent of the Keep_alive_together_engraver
- '(): layer does not participate in the layering decisions

Using a single polymorphic property avoids any possibility of
setting contradictory values for any single layer. The use of the
key type allows the potential for other behaviours to be added in
the future.

https://codereview.appspot.com/308910043/