The first click to select a new stripable may actually un-select strip.
counting and ignoring this leads to strange behavior.
Also when the selection_counter hit zero, VCAs were not ignored.
whatever this workaround was good for, it's more trouble than it's worth.
As side-effect this also improves DnD + Gtk::Entry behavior with stock GTK.
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
Cloning a region retains the region-lock style.
Playlist partitioning set the region start-property only (audio-time).
If a MIDI region is locked to musical-time, Properties::start is ignored
and overwritten by Properties::start_beats.
* The UI and ctrl-surface controls use and display the combined value,
including control-masters.
* The Automation lane of a control is the raw value of the control
without masters.
When touching (or writing) automation, the control-master needs to be
factored out (or subtracted). e.g press+hold a control -> write inverse
master automation.
This went unnoticed because: VCA gain automation was always applied
(regardless of automation state) but when it was not playing
master_ratio() factored it out again (per block).
"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.
