Remove old code to remove duplicate engine state which was used to
work-around a bug since 3.x saved duplicates but broke with 4.x separate
i/o devices.
Add a new variant to purge old unused states per backend (after sorting).
* add an abstract StripableTimeAxisView (Route TAV + VCA TAV)
* move common strip-methods into STAV
* Add Automation Lanes to VCA TAV
* Allow ATAV without Automatable for VCA Controls
"Add and Close" is an odd one out and this button should really be
removed for consistency. Still it allows for a 2-click or
2-keyboard-shortcut very common action.
Double clicking on a file or pressing the Return key will now import it.
This means with autoplay enabled you can navigate a directory of audio files
using the up and down arrow keys and import the wanted files (with Return)
without having to touch the mouse.
Being able to use double click to import a file means you don't have to move
the mouse back and forth between the file browser and the import button.
You can still manually audition the file with space as before.
TempoMap::get_grid() supplies a list of beat positions, leaving the lines
to work out any subdivision positions.
This is fine, unless a tempo section falls in between beats.
Use a BeatsFramesConverter along with a quarter note position
(in the BBTPointsList) to make this easier.
Since 478f26b2ad, transport_rolling() is only true when actually rolling.
Count-in is a no-roll process (don't move playhead, no playhead UI
position interpolation 55b8b448).
But transport isn't exactly stopped either (preparing to roll), so
during count-in transport_stopped() == transport_rolling() == false.
The property names with underscores are "normalized" to replace the underscores
with hyphens in the XMLProperty constructor from within Meterbridge::get_state
and so have always been written with hyphens.
These property names have been "normalized"/changed to use a hyphen in the
XMLProperty ctor since 2008. That is before the Meterbridge existed so there
should be no files existing that contain these properties with underscores.
These are normalized in the PBD::XMLProperty ctor, which is why
Editor::get_transport_controllable_state() uses the hyphenated names to
retrieve the properties and will not result in any state format change.
