Ardour calls input_streams(), output_streams() to determine
if the plugin is about to be re-configured (old stream I/O count
!= new I/O count) and emit PluginIoReConfigure() if that’s true.
If the plugin has not been initialized (no format set), we can
safely assume that it will need to be reconfigured.
Forcing Audio=Midi=0 will do so.
The only time where the format is not yet set and hence the actual
channel count is still unknown) is during the first call to
PluginInsert::configure_io().
At the time of writing, this all is a NOOP anyway! The only user
of the PluginIoReConfigure() signal is the GUI to update connection
lines… and since the first PluginInsert::configure_io() happens
during insertion before the plugin is painted and subscribed to
PluginIoReConfigure(), this function could return any value.
Still 0,0 is just more appropriate than assuming mono audio in/out
and no midi.
e38eb0613e