We cannot call TempoMetric::superclock_at (BBT_Time) if the BBT time is beyond
the range of the current TempoMetric. We must discover that *before* we make
that call, not as part of the test to see if we've exceeded the range.
There were many logical errors in the previous implementation. This one is
simpler to read, and appears to work much better.
It also allows the caller to specify the quarter-note subdivision to use when
generating the grid, rather than choosing only between some bar modulo or
quarter notes.
introducing a new time signature that uses non-quarter notes as the denominator
will move the beat position a given BBT time (since the middle "B" of BBT
refers to "beats" given by the denominator, not quarters).
This is never for inline references to parameters, only for starting parameter
documentation blocks. The "@p" command is for this, although unfortunately
Doxygen doesn't actually do anything with it and it's just an alias for code
text.
MIDI clock start at the next beat (round_up_to_beat), so
here we have to round the current tick, rather than fall
back to a tick that is not yet complete, as 14da117bc8 does.
Reproduced with the Session from #9027
Start loop at bar 40 with MClk generator enabled.
```
#3 in __GI___assert_fail (assertion=0x7fedd86c4fd5 "clk_pos >= pos", file=0x7fedd86c38b7 "../libs/temporal/tempo.cc", line=3336, function=0x7fedd86c4f60 "void Temporal::TempoMap::midi_clock_beat_at_or_after(Temporal::samplepos_t, Temporal::samplepos_t&, uint32_t&) const") at assert.c:101
#4 in Temporal::TempoMap::midi_clock_beat_at_or_after(long, long&, unsigned int&) const (this= 0x560187e92c00, pos=20691033, clk_pos=@0x7fedc02178b8: 20691032, clk_beat=@0x7fedc02178c4: 11472) at ../libs/temporal/tempo.cc:3336
#5 in ARDOUR::MidiClockTicker::tick(long, long, unsigned int, long) (this=0x56018eed6db0, start_sample=20691033, end_sample=20692057, n_samples=1024, pre_roll=0) at ../libs/ardour/ticker.cc:170
#6 in ARDOUR::Session::send_mclk_for_cycle(long, long, unsigned int, long) (this=0x56018a216340, start_sample=20691033, end_sample=20692057, n_samples=1024, pre_roll=0) at ../libs/ardour/session.cc:7495
#7 in ARDOUR::AudioEngine::process_callback(unsigned int) (this=0x5601881a4f20, nframes=1024) at ../libs/ardour/audioengine.cc:563
```
This fixes various rounding issues. Notably superclock to sample
conversion must always round down when playing forward.
`::process (start, end, speed = 1)` uses exclusive end.
Processing begins at `start` and end ends just before `end`.
Next cycle will begin with the current end.
One example where this failed:
- New session at 48kHz
- Change tempo to 130 BPM
- Enable snap to 1/8 note
- Snap playhead to 1|3|0
- Enable Metronome
- Play
`assert (superclock_to_samples ((*i).sclock(), sample_rate()) < end);`
end = 177231 samples == superclock 1042118280
A grid point is found at superclock 1042116920 (that is < 1042118280).
However converting it back to samples rounded it to sample 177231 == end,
while actual location is 1360 super-clock ticks before end.
The metronome click has to be started this cycle, since the same
position will not be found at the beginning of the next cycle, with
start = 177232.
Similarly a samplecnt_t t, converted to music-time and back must not be
later than the given sample.
```
timepos_t tsc (t);
assert (timepos_t::from_ticks (tsc.ticks ()).samples () <= t);
```
IOW. When playing forward, all super-clock time between 1|1|0 and 1|1|1
should round down to 1|1|0. "We have not yet reached the first tick".
This addressee a bug where ardour 6 was able to write negative
duration `length="-1"` `length-beats="-3.3650500597559585e-05"`
Ideally timecnt_t::string_to should check for invalid,
negative, duration. But this also catches a more generic case.
```
exception at str.substr (1)
#3 Temporal::timepos_t::string_to (this=0x7fffffff7bb0, str="") at libs/temporal/timeline.cc:904
#4 Temporal::timecnt_t::string_to (this=0x7fffffff7ba0, str="-2") at libs/temporal/timeline.cc:294
#5 PBD::string_to<Temporal::timecnt_t> (str="-2") at libs/ardour/ardour/types_convert.h:131
```
The default clock-limit is 99:59:59:00, just under 360000 seconds
(see ARDOUR_UI::parameter_changed, clock-display-limit).
AudioClock calculates this limit pos as
`timepos_t (limit_sec * _session->sample_rate())`
This caused an overflow leading to a negative value:
```
timepos_t (359999 * 96000)
samples_to_superclock (359999 * 96000, 96000)
int_div_round (359999 * 96000 * 282240000, 96000)
```
Ideally this will be optimized, here the sample-rate cancels out,
so we could use a c'tor usin seconds.
In other cases we could cache the pre-calculated sc_per_sample:
`superclock_ticks_per_second() / superclock_t (sr)` which is an
integer for all commonly used sample-rates.
audio time nominally uses superclocks as its canonical unit. However
many things at a higher level only understand samples. If we
increment or decrement a superclock value by 1, the vast majority of
the time we will still get the same sample value after
conversion. Thus to correctly alter an audio time by an amount
that will manifest as 1 sample's difference, we have to use
samples_to_superclock(1)
Usually C++ class instance has the same mem address as its first parent.
LuaBridge uses this to for derived classes. A TemopPoint instance has
the same address as its parent Tempo. However due to virtual inheritance
this was not the case due to a lack of virtual d'tor.
Now the following Lua code works correctly
```
tm = Temporal.TempoMap.read()
tp = Temporal.timepos_t (0)
print (tm:tempo_at(tp):note_type())
```
Previously the last line failed calling Tempo::note_type()
on a TempoPoint instance, due to memory offset e.g.
TempoPoint: 0x600000ff90e0 Tempo: 0x600000ff90e8
