#5541 setting direction of instrumentName makes lilypond crash

[Werner LEMBERG]

[git 49f41bf1c64ae1e2490571e73a85cbc4b2a9fb27]

This small example

\new Staff \with {
  \override InstrumentName.direction = 0
  instrumentName = "foo"
} { e'1 }

makes lilypond crash with

lilypond: ../flower/include/drul-array.hh:35:
 T& Drul_array<T>::at(Direction) [with T = Skyline]:
  Assertion `d == 1 || d == -1' failed.

[David Kastrup]

Rietveld issue: 556950043 (https://codereview.appspot.com/556950043)
Issue description:
Issue 5541: treat CENTER in Side_position_interface::aligned_side
Previously this led to an assertion failure (and obscure behavior
when assertions were disabled). This currently warns while doing a
reasonable replacement: it is conceivable that the replacement is
useful enough on its own, making it debatable whether a warning is
wanted.

[Werner LEMBERG]

Thanks for the fix. Regarding your question whether a warning should be emitted, I have no opinion. If your code provides a default without warning, we should probably document that, right?

[David Kastrup]

It does provide a warning, I thought that was quite obvious. I just stated that I am not sure that this is the best choice. We'll have to see how many reports of the "it does what I want but what's with the warning" we get. Problem is that people tend to ignore warnings anyway.

[Anonymous]

Passes make, make check and a full make doc.

[Anonymous]

Patch on countdown for August 12th

[Anonymous]

Patch counted down - please push.

[Anonymous]

Issue 5541: treat CENTER in Side_position_interface::aligned_side master staging
author  David Kastrup <dak@gnu.org> 
    Wed, 7 Aug 2019 11:51:54 +0100 (12:51 +0200)
committer   David Kastrup <dak@gnu.org> 
    Tue, 13 Aug 2019 11:17:44 +0100 (12:17 +0200)
commit  3f0b5c61a74aec1cd0054e4ecddcb2cbe41f01cc