ProjectAudioManager doesn't use ProjectWindow, which doesn't use...

ControlToolBar, after we make a system to register functions that calculate
necessary minimum widths for status bar fields.

Also let Scrubbing.cpp register its own strings.

Also be sure to size the status field sufficiently for "Playing at Speed".

src/ProjectStatus.h

@@ -12,10 +12,13 @@ Paul Licameli
 #define __AUDACITY_PROJECT_STATUS__
 #endif
 
+#include <utility>
+#include <vector>
 #include <wx/event.h> // to declare custom event type
 #include "ClientData.h" // to inherit
 
 class AudacityProject;
+class wxString;
 class wxWindow;
 
 enum StatusBarField : int {
@@ -43,6 +46,24 @@ public:
    ProjectStatus &operator= ( const ProjectStatus & ) = delete;
    ~ProjectStatus() override;
 
+   // Type of a function to report translated strings, and also report an extra
+   // margin, to request that the corresponding field of the status bar should
+   // be wide enough to contain any of those strings plus the margin.
+   using StatusWidthResult = std::pair< std::vector<wxString>, unsigned >;
+   using StatusWidthFunction = std::function<
+      StatusWidthResult( const AudacityProject &, StatusBarField )
+   >;
+   using StatusWidthFunctions = std::vector< StatusWidthFunction >;
+
+   // Typically a static instance of this struct is used.
+   struct RegisteredStatusWidthFunction
+   {
+      explicit
+      RegisteredStatusWidthFunction( const StatusWidthFunction &function );
+   };
+
+   static const StatusWidthFunctions &GetStatusWidthFunctions();
+
    const wxString &Get( StatusBarField field = mainStatusBarField ) const;
    void Set(const wxString &msg,
       StatusBarField field = mainStatusBarField);