We were using a given tempo or meter point as part of the metric used when
recomputing its position. In fact, the metric should be only use the
tempo/meter immediately preceding the given point.
It is more useful to get the actual TempoPoint than just the Tempo
that we discover.
Aside: it would be awesome to understand how to use boost::intrusive to get the
next tempo point directly from the tempo hook.
This commit leaves two issues outstanding:
1. unclear/ugly semantics for drag operations that reset the GUI thread's tempo map to the writable copy
2. undo/redo for the tempo map
These will be addressed in future commits
std::upper_bound() was not the correct tool to find the existing point,
it should have been std::lower_bound(). For code consistency, this
change doesn't use either but like ::remove_tempo() and similar methods,
just iterates over the whole list
We do not want a value as large as the previous one, which limits the time
range that can be represented in 62 bits unnecessarily. The new value is
9 times smaller than the previous value, and loses only 384000 as a significant
factor.
This commit also switches to using an (inline) accessor for superclock_ticks_per_second,
making it possible in debug/testing phases to spot early/illegal uses of the value.
The old code used the instantaneous tempo at T0 to compute where the next
quarter note would be. This is incorrect, since the tempo is
changing (continuously, for now) during the time represented by that quarter
note. Instead, we need to add a quarter note (or technically, whatever the
tempo note type is) to get a new position in beats, then compute the superclock
time at that location (which will use our equations for tempo, including the
use of omega, the ramp factor).
These comments should correct an impression left in the commit message for
6e9e28343bc3695d that there may be some sort of problem with synchronization
of TempoMap changes. The actual problem is that TempoMap edits are done using
RCU, so the modifications are performaned using a copy of the map, but with
map elements taken from the pre-copy version.
The correct algorithm is to traverse the type-specific list of points,
find the point (if any) whose time matches that of the argument (because
we do not allow multiple points of the same type at the same time), and
then use that discovered point from the _points list.
This approach is required because the actual argument may no longer be
in the tempo map (due to a change made by another thread). The lack of
sync, however, needs investigation.
a negative beat position needs to be legal, so the assert was moved and modified. The only check
for a negative value is that the TempoPoint being used is at absolute zero.
This check might turn out to be wrong in the future, but for now we still require a tempo and
meter point at absolute zero
pbd/i18n.h MUST NEVER be included from header files and always be
the last include. This is because `_` is declared other headers
notably boost and some apple headers.
leading to issues like
../libs/pbd/gettext.h:58:27: error: expected unqualified-id before ‘const’
58 | # define gettext(Msgid) ((const char *) (Msgid))
