existence_check() calls prevent_deletion() -> mark_immutable()
which since a4d7b45fe0 calls close().
So the file needs to be open()ed after the existence check.
This allows to fit complete text "> 100.1%",
which is useful when chasing external transport, and yet
still have a reasonable shuttle width when using semi-tones.
TransportStateChange() triggers various updates.
However at the time the signal is handled
`transport_rolling()` and/or `transport_state_rolling()`
may still return false.
This fixes incorrect In/Disk display on tracks (RouteUI)
and incorrect automation write-pass handling,
when toggling stop/play.
This reverts most of 50c555f1a1
* Never render from `map_transport_state()` callback
* re-instantiate deadzone, only update when last_speed_displayed
differs by 0.5%
* Fix Pool OOM due to mapping state doing direct UI changes
instead of delegating this to lower priority render()
This is for at least two reasons: transport will effectively
move with 32 samples * 6.25% = 2 samples per cycle and the
resampler cannot up/downsample a factor of > 16 with
reasonable quality.
* localize speed changes into varispeed dialog
* make speed-changes idempotent
* remember window position (do not overlap with button)
ideally the window would show up below the "Vari" button
This happens with e.g. the IEM suite when a user has both
/usr/lib/vst and /usr/lib/lxvst in the search path.
The same plugin was found twice due to symlinks:
```
/usr/lib/lxvst/iem.at -> ../x86_64-linux-gnu/iem-plugin-suite/vst
/usr/lib/vst/iem.at -> ../x86_64-linux-gnu/iem-plugin-suite/vst
```
And then blacklisted itself:
> "Ignoring plugin 'MultiBandCompressor'.
> VST-ID conflicts with other plugin 'MultiBandCompressor' files:
> '/usr/lib/x86_64-linux-gnu/iem-plugin-suite/vst/MultiBandCompressor.so' vs
> '/usr/lib/x86_64-linux-gnu/iem-plugin-suite/vst/MultiBandCompressor.so'
Since 80c11a763a the GUI is notified when the xrun counter
is reset (previously the rec-ui xrun counter never returned
to zero).
However when create-xrun-marker is enabled ARDOUR_UI::xrun_handler
tried to create a marker at -1 which causes various issues.
