Define BackgoundCell, move some things into it

src/tracks/ui/BackgroundCell.cpp

@@ -0,0 +1,109 @@
+/**********************************************************************
+
+Audacity: A Digital Audio Editor
+
+BackgroundCell.cpp
+
+Paul Licameli split from TrackPanel.cpp
+
+**********************************************************************/
+
+#include "../../Audacity.h"
+#include "BackgroundCell.h"
+
+#include "../../HitTestResult.h"
+#include "../../Project.h"
+#include "../../RefreshCode.h"
+#include "../../TrackPanelMouseEvent.h"
+#include "../../UIHandle.h"
+
+#include <wx/cursor.h>
+#include <wx/event.h>
+
+namespace
+{
+   // Define this, just so the click to deselect can dispatch here
+   class BackgroundHandle : public UIHandle
+   {
+      BackgroundHandle() {}
+      BackgroundHandle(const BackgroundHandle&) = delete;
+      BackgroundHandle &operator=(const BackgroundHandle&) = delete;
+
+   public:
+
+      static BackgroundHandle& Instance()
+      {
+         static BackgroundHandle instance;
+         return instance;
+      }
+
+      static HitTestPreview HitPreview()
+      {
+         static wxCursor arrowCursor{ wxCURSOR_ARROW };
+         return { {}, &arrowCursor };
+      }
+
+      static HitTestResult HitAnywhere()
+      {
+         return {
+            HitPreview(),
+            &BackgroundHandle::Instance()
+         };
+      }
+
+      virtual ~BackgroundHandle()
+      {}
+
+      Result Click
+         (const TrackPanelMouseEvent &evt, AudacityProject *pProject) override
+      {
+         using namespace RefreshCode;
+         const wxMouseEvent &event = evt.event;
+         // Do not start a drag
+         Result result = Cancelled;
+
+         // AS: If the user clicked outside all tracks, make nothing
+         //  selected.
+         if ((event.ButtonDown() || event.ButtonDClick())) {
+            pProject->GetSelectionState().SelectNone
+               ( *pProject->GetTracks(), pProject->GetMixerBoard() );
+            result |= RefreshAll;
+         }
+
+         return result;
+      }
+
+      Result Drag
+         (const TrackPanelMouseEvent &, AudacityProject *) override
+      { return RefreshCode::RefreshNone; }
+
+      HitTestPreview Preview
+         (const TrackPanelMouseEvent &, const AudacityProject *) override
+      { return HitPreview(); }
+
+      Result Release
+         (const TrackPanelMouseEvent &, AudacityProject *,
+          wxWindow *) override
+      { return RefreshCode::RefreshNone; }
+
+      Result Cancel(AudacityProject *) override
+      { return RefreshCode::RefreshNone; }
+   };
+}
+
+BackgroundCell::~BackgroundCell()
+{
+}
+
+HitTestResult BackgroundCell::HitTest
+(const TrackPanelMouseEvent &,
+ const AudacityProject *)
+{
+   return BackgroundHandle::HitAnywhere();
+}
+
+Track *BackgroundCell::FindTrack()
+{
+   return nullptr;
+}
+

src/tracks/ui/BackgroundCell.h

@@ -0,0 +1,38 @@
+/**********************************************************************
+
+Audacity: A Digital Audio Editor
+
+BackgroundCell.h
+
+Paul Licameli split from TrackPanel.cpp
+
+**********************************************************************/
+
+#ifndef __AUDACITY_BACKGROUND_CELL__
+#define __AUDACITY_BACKGROUND_CELL__
+
+#include "CommonTrackPanelCell.h"
+
+class AudacityProject;
+
+class BackgroundCell final : public CommonTrackPanelCell
+{
+public:
+   BackgroundCell(AudacityProject *pProject)
+      : mpProject(pProject)
+   {}
+
+   virtual ~BackgroundCell();
+
+protected:
+   HitTestResult HitTest
+      (const TrackPanelMouseEvent &event,
+      const AudacityProject *) override;
+
+   Track *FindTrack() override;
+
+private:
+   AudacityProject *mpProject;
+};
+
+#endif