previously, _chunksize =
```
minimum_disk_read_bytes / sizeof (Sample)
```
can become larger then actual allocated ringbuffer:
```
audio_playback_buffer_seconds * sample-rate
```
In which case the buffer was never filled.
The disk writer has similar issues
This fixes an issue when undoing region fades.
Particularly but not limited to the following:
1. select a region and split it in the middle
2. switch to range tool. make a range selection across the split
3. Edit > Fade > Fade range seection (or press `/`)
4. Undo
Previously the fade-out of the earlier region was not undone.
When some other transport related session event (anything that
requires non_realtime_work_pending, e.g. PostTransportOverWrite)
coincides with SessionEvent::AutoLoop, the auto-loop event
was removed from the main event queue and executed as one-shot
immediate event.
While looping the AutoLoop event needs to remain on the main
event queue.
`butler_transport_work()` may be called for various reasons,
notably PostTransportOverWrite. At that point in time the
transport may still be rolling or stopping with rtloc already
set.
This can cause DR::Underruns since seek clear the entire
disk reader buffer.
This is needed to properly decrement "should_do_transport_work".
After a seek the DR:_pending_overwrite flag will have been
cleared, so not much extra work happens here.
The left edge of a region on the the editor is rounded to be
on a pixel. When zoomed out, the position corresponding to that
pixel is not usually identical to the region's position().
We need to correct for this as best as possible, while keeping
peaks aligned to pixels.
Previously loop-wrap around asked the butler to perform
a unnecessary seek operation next time it is summoned.
If the butler is then summoned for a PostTransportOverWrite
event, the seek causes a DR::Underrun.
