Re: Let \time in mid-measure work without warning in some cases (issue 143450043 by address@hidden)

[dak]

https://codereview.appspot.com/143450043/diff/20001/input/regression/time-signature-midmeasure.ly
File input/regression/time-signature-midmeasure.ly (right):

https://codereview.appspot.com/143450043/diff/20001/input/regression/time-signature-midmeasure.ly#newcode5
input/regression/time-signature-midmeasure.ly:5: \\partial except in an
anacrusis.
\partial is an anacrusis also in the middle of the piece, so this is a
bit weird as a description.  Also since \time does _not_ include an
implicit \partial 1*0, the change only needs to be _accompanied_ by
\partial, it does not make a difference whether the \partial is before
or after the \time.  So the start of the piece is no exception.

So it's rather "Time signature changes not followed by a complete
measure should be accompanied by a corresponding \partial".

In experimenting around, I found that the (warning case?)
{
  \set Timing.barNumberVisibility = #all-bar-numbers-visible
  \override Score.BarNumber.break-visibility = #all-visible
  \time 4/4 c'8 8 8 8 8 8 \bar "|" \time 3/4 8 8 8 8 8 8 |
}
produces ungainly output.  It happens that this is not actually related
to the \time change very much, so it can be fixed with a midmeasure
partial as either
{
  \set Timing.barNumberVisibility = #all-bar-numbers-visible
  \override Score.BarNumber.break-visibility = #all-visible
  \time 4/4 c'8 8 8 8 8 \partial 8 8 | 8 8 8 8 8 8 8 8
}
or
{
  \set Timing.barNumberVisibility = #all-bar-numbers-visible
  \override Score.BarNumber.break-visibility = #all-visible
  \time 4/4 c'8 8 \partial 2 8 8 8 8 | 8 8 8 8 8 8 8 8
}
with differences in autobeaming.

In summary, the only combination that appears tricky is when the _first_
bar is shorter than its time signature and should still be counted as
bar 1 rather than preceding it.

In that case, the \partial needs to be in mid-measure rather than at the
start.

I think that's more a feature of \partial than of \time.  Basically
\time starts at the beginning of a measure, and if you want to change
that, add \partial to it (after \time is likely prettier but not
required) to indicate how far the next bar is supposed to be.

Soooo.  I think this behaves as well as may be expected.  When writing
the documentation, some of it may be grouped better with \partial.
While \partial x \time a/b produces equal results to \time a/b \partial
x, I'd only show the latter form as it seems a bit more logical.

Nice.

https://codereview.appspot.com/143450043/