Add a check item to Tracks menu for the scrolling beyond zero preference

src/Menus.cpp

@@ -134,6 +134,7 @@ simplifies construction of menu items.
 #endif /* EXPERIMENTAL_SCOREALIGN */
 
 #include "tracks/ui/Scrubbing.h"
+#include "prefs/TracksPrefs.h"
 
 enum {
    kAlignStartZero = 0,
@@ -928,6 +929,16 @@ void AudacityProject::CreateMenusAndCommands()
 
       //////////////////////////////////////////////////////////////////////////
 
+      c->AddSeparator();
+      c->AddCheck(wxT("ScrollLeftOfZero"), _("Scroll left of zero"),
+                  FN(OnToggleScrollLeftOfZero),
+                  gPrefs->ReadBool(
+                     TracksPrefs::ScrollingPreferenceKey(),
+                     TracksPrefs::ScrollingPreferenceDefault()),
+                  AudioIONotBusyFlag, AudioIONotBusyFlag);
+
+      //////////////////////////////////////////////////////////////////////////
+
       c->EndMenu();
 
       // All of this is a bit hacky until we can get more things connected into
@@ -2511,6 +2522,15 @@ void AudacityProject::OnSortName()
    mTrackPanel->Refresh(false);
 }
 
+void AudacityProject::OnToggleScrollLeftOfZero()
+{
+   auto key = TracksPrefs::ScrollingPreferenceKey();
+   auto value = gPrefs->ReadBool(key, TracksPrefs::ScrollingPreferenceDefault());
+   gPrefs->Write(key, !value);
+   gPrefs->Flush();
+   UpdatePrefs();
+}
+
 void AudacityProject::OnSkipStart()
 {
    wxCommandEvent evt;

src/Menus.h

@@ -179,6 +179,8 @@ double GetTime(const Track *t);
 void OnSortTime();
 void OnSortName();
 
+void OnToggleScrollLeftOfZero();
+
 void OnSnapToOff();
 void OnSnapToNearest();
 void OnSnapToPrior();

src/ViewInfo.cpp

@@ -18,6 +18,7 @@ Paul Licameli
 #include "prefs/GUISettings.h"
 #include "Prefs.h"
 #include "xml/XMLWriter.h"
+#include "prefs/TracksPrefs.h"
 
 namespace {
 static const double gMaxZoom = 6000000;
@@ -133,7 +134,8 @@ void ViewInfo::UpdatePrefs()
 {
    ZoomInfo::UpdatePrefs();
 #ifdef EXPERIMENTAL_SCROLLING_LIMITS
-   gPrefs->Read(wxT("/GUI/ScrollBeyondZero"), &bScrollBeyondZero, false);
+   gPrefs->Read(TracksPrefs::ScrollingPreferenceKey(), &bScrollBeyondZero,
+                TracksPrefs::ScrollingPreferenceDefault());
 #endif
 
 }

src/prefs/TracksPrefs.cpp

@@ -45,6 +45,12 @@ TracksPrefs::~TracksPrefs()
 {
 }
 
+const wxChar *TracksPrefs::ScrollingPreferenceKey()
+{
+   static auto string = wxT("/GUI/ScrollBeyondZero");
+   return string;
+}
+
 void TracksPrefs::Populate()
 {
    mSoloCodes.Add(wxT("Simple"));
@@ -134,8 +140,8 @@ void TracksPrefs::PopulateOrExchange(ShuttleGui & S)
                     true);
 #ifdef EXPERIMENTAL_SCROLLING_LIMITS
       S.TieCheckBox(_("Enable scrolling left of &zero"),
-                    wxT("/GUI/ScrollBeyondZero"),
-                    false);
+                    ScrollingPreferenceKey(),
+                    ScrollingPreferenceDefault());
 #endif
 
       S.AddSpace(10);

src/prefs/TracksPrefs.h

@@ -29,6 +29,9 @@ class TracksPrefs final : public PrefsPanel
    ~TracksPrefs();
    bool Apply() override;
 
+   static const wxChar *ScrollingPreferenceKey();
+   static inline bool ScrollingPreferenceDefault() { return false; }
+
  private:
    void Populate();
    void PopulateOrExchange(ShuttleGui & S);

src/widgets/Ruler.cpp

@@ -82,6 +82,7 @@ array of Ruler::Label.
 #include "../Prefs.h"
 #include "../Snap.h"
 #include "../tracks/ui/Scrubbing.h"
+#include "../prefs/TracksPrefs.h"
 
 //#define SCRUB_ABOVE
 #define RULER_DOUBLE_CLICK
@@ -2044,7 +2045,8 @@ void AdornedRulerPanel::UpdatePrefs()
 #ifdef EXPERIMENTAL_TWO_TONE_TIME_RULER
    {
       bool scrollBeyondZero = false;
-      gPrefs->Read(wxT("/GUI/ScrollBeyondZero"), &scrollBeyondZero, false);
+      gPrefs->Read(TracksPrefs::ScrollingPreferenceKey(), &scrollBeyondZero,
+                   TracksPrefs::ScrollingPreferenceDefault());
       mRuler.SetTwoTone(scrollBeyondZero);
    }
 #endif