Previously the freewheel export thread directly called
Session::butler_transport_work(). The butler thread
may concurrently call the same function. This can lead
double free or memory corruption (see below)
Now export thread summons the butler and does nothing
until it completed its work.
```
Export Thread:
3 XMLNode::~XMLNode
4 ARDOUR::AutomationList::snapshot_history
5 ARDOUR::AutomationList::start_write_pass
6 ARDOUR::Automatable::non_realtime_locate
7 ARDOUR::Route::non_realtime_locate
8 ARDOUR::Session::non_realtime_locate
9 ARDOUR::Session::butler_transport_work
10 ARDOUR::Session::process_export_fw
Butler thread:
7 XMLNode::~XMLNode
8 ARDOUR::AutomationList::snapshot_history
9 ARDOUR::AutomationList::start_write_pass
10 ARDOUR::Automatable::non_realtime_locate
11 ARDOUR::Route::non_realtime_locate
12 ARDOUR::Session::non_realtime_locate
13 ARDOUR::Session::butler_transport_work
14 ARDOUR::Butler::thread_work
15 ARDOUR::Butler::_thread_work
```
Previously x-axis threshold was in samples. This is
useless unless zoomed in to the max. So in most cases
the first-move was always in x-direction, making constrained
y-axis drags near impossible.
Furthermore the threshold for copy-drags was increased
as per #8686
Region positions were updated in the GUI, before the playlist
was catching up.
The butler thread reads a region using the region's new position,
but the playlist's old range.
Thread 1 (GUI)
```
#22 ARDOUR::Playlist::notify_layering_changed()
#26 ARDOUR::AudioPlaylist::region_changed
#27 ARDOUR::Playlist::region_changed_proxy
#35 ARDOUR::Region::send_change
#36 ARDOUR::Region::set_position
#37 RegionRippleDrag::remove_unselected_from_views
#38 RegionRippleDrag::finished
```
LayeringChanged() also triggers DiskIOProcessor::playlist_modified
which schedules a pending-override and summons the butler.
Note that when moving only a few regions the butler starts after all
updates have been completed.
Butler thread:
```
#4 ARDOUR::AudioRegion::read_at
#5 ARDOUR::AudioPlaylist::read
#6 ARDOUR::DiskReader::audio_read
#7 ARDOUR::DiskReader::overwrite_existing_audio
#8 ARDOUR::DiskReader::overwrite_existing_buffers
#9 ARDOUR::Track::overwrite_existing_buffers
#10 ARDOUR::Session::non_realtime_overwrite
```
Region read fails:
```
libs/ardour/audioregion.cc:503 assert (position >= _position);
(gdb) p position
$1 = 1312000
(gdb) p _position
$2 = {<PBD::PropertyTemplate<long>> = {_have_old = true,
_current = 1336000, _old = 1312000} }
```
It is not needed in the relative case and causes issues when taking
sessions between platforms.
On windows, the default path would be "\export". When that is used
on linux the resulting fullpath would end up as
/your/session/path/\export
which is then not found on the file system.
This change is consistent with how relative paths are normally written and
does cure the default path when moved across platforms.
It does not solve the larger issue of mixed directory separators.
A relative path of "export\myMixV1" will still fail when moving between
platforms.
Previously the following were treated as equal
"MIDI_foo" == "MIDI bar"
So std::map<> PortManager::_ports and PortEngineSharedImpl:_ports
could only have either. This resulted in missing ports
and missing calls to existing ports in cycle_start().
This mainly affected MIDI tracks with imported files, since there
is "MIDI Clock in", and imported files result in tracks
"MIDI_file-name".
This issue was introduced in 6.6-200-g60ff3ef764
We do need to know that a reversal is intended before we do a locate, but we should
not enter Reversing before the declick is finished. So instead, we add a new
member, _reverse_after_declick to keep track, and enter Reversing just before
we start the locate
select(2) can only handle file descriptors up to 1024, and there are fairly easy to reproduce
cases where the file descriptor used here is larger than that.
Portmanager uses "ports" as local variable in various places
(usually vector<string>). While the compiler is fine with that,
it is confusing when debugging or reading code.
The DraggingView's time_axis_view (index) is set to the size of _time_axis_views
in ::motion() near line 1149. This makes it invalid as index into the vector.
