::model_changed() is used when the model has changed (eg. new notes or some
notes deleted); ::view_changed() is used when only some view parameter (e.g.
zoom, scroll, track height etc) has been altered.
Not fully functional yet (::view_chanted() ignores scroll)
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).
Program Changes are stored as an offset from the 'source' start, and must be translated to/from region time.
Better locating of patches wrt the grid:
You can't assume time_to_pixel is steady across the timeline
* calculate position of the patch-change flag
* calculate region start position, and set flag's x offset from there
also: consolidate patch-location code into display_patch_changes()
When adding a note, use these criteria to choose the channel number:
* if the user has explicitly specified a note in the pulldown, use that
* if the user has AUTO selected and we are in a region, choose the nearest note's channel (consistent with velocity behavior)
* as a fallback, query the track for its channel-filter (old behavior)
update_ghost_note() can only be called with a valid, non-null
_ghost_note. Explicit checks trigger clang static analyzer to
report false positives, since _ghost_note is unconditionally
used in this method as well.
