... handling the callbacks from the selection toolbars.
Next ProjectFileManager will be split out of ProjectManager, and
ProjectSelectionManager will be used by it during file opening, so separating
files for it avoids a cycle.
... that is, a factory function, open, close, import, undo/redo/rollback.
Also the callbacks from AudioIO, which need to invoke undo history push when
recording stops.
It is meant as a high-level class using several of the other things attached
to the project, while AudacityProject will be a low level class acting mostly
as just the container of the attached structures.
... as a preparation for splitting up class AudacityProject.
Use ProjectWindow as an alias for AudacityProject, and fetch it from the
project with a static member function, where certain of its services are used;
pretending they are not the same class.
Use global accessor functions to get wxFrame from the project where only
wxFrame's member functions are needed, so there will be less dependency on
ProjectWindow when it becomes a distinct class.
... Just one low-level function to simply set the variable, and one
high-level function that also pushes notifications. The danger of infinite
recursion in the toolbar code, as in the previous commit, doesn't exist here.
... Generalizing what was first done at 280e8d9 for certain menu command
handlers.
Allow core data structures to host data attached by other code, on which it
need have no compilation or link dependencies.
... so that USE_* macros will be seen first, and so
EXPERIMENTAL_AUTOMATED_INPUT_LEVEL_ADJUSTMENT, for one, is correctly defined.
I hesitated actually to include Audacity.h in Experimental.h. Maybe no
need for that hesitancy. But instead I use #error if Audacity.h has not been
seen yet.
... except Audacity.h; and in no others.
Do so even if Experimental.h gets multiply included, as in both the .h and
.cpp files.
This makes it easier to do a text scan to be sure there are no unintended quiet
changes of meaning because of omission of Experimental.h when the flag is
an enabled one.
Also move inclusions of Experimental.h earlier.
Also don't require Experimental.h to be preceded by Audacity.h to define
EXPERIMENTAL_MIDI_OUT correctly.
