1. Consolidate linking enable/disable logic b/w Edit Toolbar and Menu

2. Save user's preference for enabling linking

3. fix a bug by which changes to global prefs like SWPlaythrough were not
visually reflected in other open projects.

src/Menus.cpp

@@ -1479,6 +1479,13 @@ void AudacityProject::SelectAllIfNone()
       OnSelectAll();
 }
 
+void AudacityProject::ModifyAllProjectToolbarMenus()
+{
+   AProjectArray::iterator i;
+   for (i = gAudacityProjects.begin(); i != gAudacityProjects.end(); ++i) {
+      (*i)->ModifyToolbarMenus();
+   }
+}
 
 void AudacityProject::ModifyToolbarMenus()
 {
@@ -1523,6 +1530,8 @@ void AudacityProject::ModifyToolbarMenus()
    mCommandManager.Check(wxT("Duplex"), active);
    gPrefs->Read(wxT("/AudioIO/SWPlaythrough"),&active, false);
    mCommandManager.Check(wxT("SWPlaythrough"), active);
+   gPrefs->Read(wxT("/GUI/LinkTracks"), &active, true);
+   SetStickyFlag(active);
    mCommandManager.Check(wxT("StickyLabels"), mStickyFlag);
 }
 
@@ -1900,7 +1909,7 @@ void AudacityProject::OnToggleSoundActivated()
    bool pause;
    gPrefs->Read(wxT("/AudioIO/SoundActivatedRecord"), &pause, false);
    gPrefs->Write(wxT("/AudioIO/SoundActivatedRecord"), !pause);
-   ModifyToolbarMenus();
+   ModifyAllProjectToolbarMenus();
 }
 
 void AudacityProject::OnTogglePlayRecording()
@@ -1908,7 +1917,7 @@ void AudacityProject::OnTogglePlayRecording()
    bool Duplex;
    gPrefs->Read(wxT("/AudioIO/Duplex"), &Duplex, false);
    gPrefs->Write(wxT("/AudioIO/Duplex"), !Duplex);
-   ModifyToolbarMenus();
+   ModifyAllProjectToolbarMenus();
 }
 
 void AudacityProject::OnToggleSWPlaythrough()
@@ -1916,7 +1925,7 @@ void AudacityProject::OnToggleSWPlaythrough()
    bool SWPlaythrough;
    gPrefs->Read(wxT("/AudioIO/SWPlaythrough"), &SWPlaythrough, false);
    gPrefs->Write(wxT("/AudioIO/SWPlaythrough"), !SWPlaythrough);
-   ModifyToolbarMenus();
+   ModifyAllProjectToolbarMenus();
 }
 
 #ifdef AUTOMATED_INPUT_LEVEL_ADJUSTMENT
@@ -1925,7 +1934,7 @@ void AudacityProject::OnToogleAutomatedInputLevelAdjustment()
    bool AVEnabled;
    gPrefs->Read(wxT("/AudioIO/AutomatedInputLevelAdjustment"), &AVEnabled, false);
    gPrefs->Write(wxT("/AudioIO/AutomatedInputLevelAdjustment"), !AVEnabled);
-   ModifyToolbarMenus();
+   ModifyAllProjectToolbarMenus();
 }
 #endif
 
@@ -5091,10 +5100,12 @@ int AudacityProject::DoAddLabel(double left, double right)
 
 void AudacityProject::OnStickyLabel()
 {
-   SetStickyFlag(!GetStickyFlag());
-   EditToolBar *toolbar = GetEditToolBar();
-   toolbar->EnableDisableButtons();
-   GetTrackPanel()->Refresh(false);
+   bool linkTracks;
+   gPrefs->Read(wxT("/GUI/LinkTracks"), &linkTracks, true);
+   gPrefs->Write(wxT("/GUI/LinkTracks"), !linkTracks);
+
+   // Toolbar, project "sticky flag" handled within
+   ModifyAllProjectToolbarMenus();
 }
 
 void AudacityProject::OnAddLabel()

src/Menus.h

@@ -37,6 +37,8 @@ void AddEffectsToMenu(CommandManager* c, const EffectSet& effects);
 void CreateRecentFilesMenu(CommandManager *c);
 void ModifyUndoMenus();
 void ModifyToolbarMenus();
+// Calls ModifyToolbarMenus() on all projects
+void ModifyAllProjectToolbarMenus();
 
 int GetFocusedFrame();
 wxUint32 GetUpdateFlags();

src/Project.cpp

@@ -813,7 +813,9 @@ AudacityProject::AudacityProject(wxWindow * parent, wxWindowID id,
    mViewInfo.bRedrawWaveform = false;
 
    mLockPlayRegion = false;
-   SetStickyFlag(true);
+   bool linkTracks;
+   gPrefs->Read(wxT("/GUI/LinkTracks"), &linkTracks, true);
+   SetStickyFlag(linkTracks);
 
    CreateMenusAndCommands();
 
@@ -4440,6 +4442,15 @@ bool AudacityProject::IsSticky()
 #endif
 }
 
+void AudacityProject::SetStickyFlag(bool flag)
+{
+   if (flag != mStickyFlag) {
+      mStickyFlag = flag;
+      if (GetTrackPanel())
+         GetTrackPanel()->Refresh(false);
+   }
+}
+
 void AudacityProject::HandleTrackMute(Track *t, const bool exclusive)
 {
    // "exclusive" mute means mute the chosen track and unmute all others.

src/Project.h

@@ -284,7 +284,7 @@ class AUDACITY_DLL_API AudacityProject:  public wxFrame,
    void EditClipboardByLabel( WaveTrack::EditDestFunction action );
    bool IsSticky();
    bool GetStickyFlag() { return mStickyFlag; };
-   void SetStickyFlag(bool flag) { mStickyFlag = flag; };
+   void SetStickyFlag(bool flag);
 
    // "exclusive" mute means mute the chosen track and unmute all others.
    void HandleTrackMute(Track *t, const bool exclusive); 

src/toolbars/EditToolBar.cpp

@@ -50,6 +50,7 @@
 #include "../AudioIO.h"
 #include "../ImageManipulation.h"
 #include "../Internat.h"
+#include "../Prefs.h"
 #include "../Project.h"
 #include "../Theme.h"
 #include "../UndoManager.h"
@@ -240,15 +241,7 @@ void EditToolBar::OnButton(wxCommandEvent &event)
          break;
 #ifdef EXPERIMENTAL_LINKING
       case ETBLinkID:
-         if (!busy){
-            p->OnStickyLabel();
-            if (p->GetStickyFlag())
-               mButtons[ETBLinkID]->PushDown();
-            else
-               mButtons[ETBLinkID]->PopUp();
-            p->ModifyToolbarMenus();
-            p->GetTrackPanel()->Refresh(false);
-         }
+         if (!busy) p->OnStickyLabel();
          return;//avoiding the call to SetButton()
 #endif
       case ETBZoomInID:
@@ -313,7 +306,10 @@ void EditToolBar::EnableDisableButtons()
    mButtons[ETBPasteID]->SetEnabled(p->Clipboard());
    
 #ifdef EXPERIMENTAL_LINKING
-   if (p->GetStickyFlag())
+   bool linkTracks;
+   gPrefs->Read(wxT("/GUI/LinkTracks"), &linkTracks, true);
+
+   if (linkTracks)
       mButtons[ETBLinkID]->PushDown();
    else
       mButtons[ETBLinkID]->PopUp();