... 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.
... not member functions of AudacityProject.
AdornedRulerPanel is not (yet) made similarly independent of its overlay
code.
Two .cpp files implementing overlays escape dependency cycles to higher levels.
... instead, re-process the event, and let each handler bind to the one it
depends on.
This still leaves a critical ordering of construction of playback scroller and
play indicator overlay in AudacityProject::AudacityProject (reverse of the
previous), but that will be removed by other means.
... it's either the source of the connection that is being destroyed, or other
object (such as an ancestor window) transitively owning it and so causing it to
be destroyed too;
or, the sink is being destroyed, and that sink is a wxEvtHandler (which is
always so for Disconnect, though not for Unbind in case Bind was passed a
member function of a non-wxEvtHandler).
wxWidgets takes care of erasing the connection in such cases.
This removes most calls to Disconnect and Unbind. Many destructors shrank to
nothing.
Notably, in case of popup menu handling, the call to Disconnect is not removable
because the object being destroyed is neither the source nor the sink.
...no actions reimplemented to them yet.
Later commits will move special cases one at a time from TrackPanel, preserving
all click and drag capabilities at each step. With a few exceptions, but those
lost abilities are restored in yet later commits. (Ctrl+Click on the Label
track being one.)
