existence_check() calls prevent_deletion() -> mark_immutable()
which since a4d7b45fe0 calls close().
So the file needs to be open()ed after the existence check.
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 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.
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'
* use dummy-backend (don't expect engine to be running)
* add required TestUI / Receiver
Lots of regions: add scope to prevent SessionHandleRef
existing across session deletion
RunPC: take process-lock before processing, prevents various
assert() and concurrency issues.
Print a less cryptic error message in case the wrapper app
cannot be found. Also address a future race condition (once
we start parallel plugin scans and will exec-wrapper from a
helper thread).
If there are multiple connections, one might fail due to missing hardware,
but the rest could still be valid.
An easy way to reproduce this was to route "mackie control out" to a device
and to the Midi tracer port. When you opened the session again, connection
from the "mackie control out" to the device would not get restored because
the Midi tracer port does not exist at session start.
This most likely caused other issues with connections when changing backends.
Ardour MIDI tracks unconditionally remember any
MIDI CC/Patch changes that are received.
Patch changes are re-played after the session is loaded,
so that they can reach external synths after ports are
re-connected.
This can lead to issues with synth plugins. Their state
is set first. Receiving a patch-change may alter the synth's
state.
Particularly on macOS child process ReadStdout
may produce many partial lines unbuffered lines.
Since each log message appends a newline, the log
had entries like:
```
Thi
s is a
n examp
le
```
Even for a 32-bit build, MSVC expects 'time_t' to be 64-bit - whereas Glib (i.e. GStatBuf) seems to be using a 32-bit version. Since we're passing by address, this will cause problems in a Windows build.
We can kludge this by making sure we pass the expected type for 'time_t'. Ultimately though, it'd be safer to adapt 'localtime_r()' to accept its first parameter by value, rather than expecting a pointer.
