the rest from `tools/convert_boost.sh`.
* replace boost::function, boost::bind with std::function and std::bind.
This required some manual fixes, notably std::placeholders,
some static_casts<>, and boost::function::clear -> = {}.
This removes the _io_lock in favor of a RCU.
The reason for this change is to ensure data structure
consistency, notably iterators. Previously adding/removing
ports invalidated iterators, which caused [rare] crashes,
since IO::ports() simply returned a PortSet reference.
(This breaks API)
IOPlugins pinout is not [yet] configurable. Trying to add ports
resuled in a segfault since the BufferSet was not resized
(nor the plugin reconfigured)
Since 62fc1d3c2e, Delivery buffers were flushed twice.
Once by copy_to_outputs() and again later by
Delivery::flush_buffers. This resulted in duplicate events
during export (see 576840c09e, MIDI buffers are not cleared
after flush to allow export processing to grab the data from
the port-buffers).
The workaround in 62fc1d3c2e is only relevant for ClickIO,
other Deliveries (Send is a Delivery) are explicitly flushed
by Route::flush_processor_buffers_locked.
I/O plugin Controls are destroyed with ~IOPlug, however
Session::destroy()'s call to drop_references() still
triggers AutomationControl::session_going_away() on the
binding proxy.
This is even properly documented in session_object.h:
> A named object associated with a Session. Objects derived
> from this class are expected to be destroyed before the
> session calls drop_references().
This is mostly a simple lexical search+replace but the absence of operator< for
std::weak_ptr<T> leads to some complications, particularly with Evoral::Sequence
and ExportPortChannel.
The idea is to run a plugin outside the process graph, and provide
its I/O as port (much like an external JACK app).
The intended use-case is NDI (provide additional I/O), but it could
also be useful for other cases.
