This is an initial work-around for signal emission with
Playlist:region_lock held:
Playlist::duplicate() takes RegionWriteLock() and then calls
RegionFactory::create(). The newly created region does NOT have
property-changes suspended, and the RegionFactory can change
region-properties which results in signal-emission.
This in turn can lead to a call Editor::session_gui_extents()
-> ARDOUR::Playlist::get_extent() -> Playlist::RegionReadLock
which deadlocks: https://pastebin.com/84rSbsA3
Eventually we need a mechanism to create regions with
->suspend_property_changes() and add it to the playlist's
thawlist (pass a thawlist to the region-factory).
When there are no input ports at the time the engine starts
running, MonitorInputChanged signal was not subscribed to.
This breaks AFL solo. This happens e.g. when re-starting the
engine with ALSA slave devices.
This GTK button style is out of place in both contexts.
Furthermore it is inconsistent to not have the same button
in the editor (there is a dropzone).
The calculation to round the distance to seconds has to be performed
using floating point maths, not just the result being cast to double.
The time-granularity must not be zero.
