This also requires a change in the type of reference held by
a MidiAutomationListBinder.
Both the MidiSource and MidiModel have a reference to each other, and it is
important that we avoid circular references to avoid problems with object
destruction. We had been accomplishing this by having the Model hold a
weak_ptr<MidiSource>. However, the lifetime of a MidiSource and its MidiModel
are coincident and there's really no need to use a smart ptr at all. A normal
reference is just fine. However, due to constructors that accept a serialized
state, we cannot use an actual reference (we cannot set the constructor in the
initializer list), so we use a bare ptr instead.
This forces a similar change in MidiAutomationListBinder, which also maintains
a reference to the Source. However, the only purpose of this object is to
ensure that if the Source is destroyed, relevant commands will be removed from
the undo/redo history, and so all that matters here is that the binder connects
to the Destroyed signal of the source, and arranges for its own destruction
when received.
Note that the previous construction of the binder, actually holding a
shared_ptr<MidiSource> would appear have prevented the Destroyed signal from
ever being emitted (from ~Destructible), and so this may also be a bug fix that
allows MidiSources to actually be deleted (the memory object, not the file).
Paul Davis
1686db8b0c