PrefsPanel::Factory is a specialization of std::function...

... We don't need to define a class for it

src/AudacityApp.cpp

@@ -1829,9 +1829,8 @@ bool AudacityApp::InitTempDir()
       }
 
       // Only want one page of the preferences
-      DirectoriesPrefsFactory directoriesPrefsFactory;
       PrefsDialog::Factories factories;
-      factories.push_back(&directoriesPrefsFactory);
+      factories.push_back(DirectoriesPrefsFactory());
       GlobalPrefsDialog dialog(NULL, factories);
       dialog.ShowModal();
 

src/commands/CommandManager.cpp

@@ -1555,9 +1555,8 @@ bool CommandManager::HandleMenuID(int id, CommandFlag flags, CommandMask mask)
 #ifdef EXPERIMENTAL_EASY_CHANGE_KEY_BINDINGS
    if (::wxGetMouseState().ShiftDown()) {
       // Only want one page of the preferences
-      KeyConfigPrefsFactory keyConfigPrefsFactory{ entry->name };
       PrefsDialog::Factories factories;
-      factories.push_back(&keyConfigPrefsFactory);
+      factories.push_back(KeyConfigPrefsFactory( entry->name ));
       GlobalPrefsDialog dialog(GetActiveProject(), factories);
       dialog.ShowModal();
       MenuCreator::RebuildAllMenuBars();

src/prefs/BatchPrefs.cpp

@@ -95,8 +95,9 @@ BatchPrefs::~BatchPrefs()
 {
 }
 
-PrefsPanel *BatchPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+BatchPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew BatchPrefs(parent, winid);
-}
+};

src/prefs/BatchPrefs.h

@@ -39,10 +39,6 @@ private:
 };
 
 
-/// A PrefsPanelFactory that creates one BatchPrefs panel.
-class BatchPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one BatchPrefs panel.
+extern PrefsPanel::Factory BatchPrefsFactory;
 #endif

src/prefs/DevicePrefs.cpp

@@ -420,8 +420,10 @@ bool DevicePrefs::Commit()
    return true;
 }
 
-PrefsPanel *DevicePrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+DevicePrefsFactory = [](wxWindow *parent, wxWindowID winid)
+
 {
    wxASSERT(parent); // to justify safenew
    return safenew DevicePrefs(parent, winid);
-}
+};

src/prefs/DevicePrefs.h

@@ -57,11 +57,7 @@ class DevicePrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one DevicePrefs panel.
-class DevicePrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one DevicePrefs panel.
+extern PrefsPanel::Factory DevicePrefsFactory;
 
 #endif

src/prefs/DirectoriesPrefs.cpp

@@ -287,8 +287,11 @@ bool DirectoriesPrefs::Commit()
    return true;
 }
 
-PrefsPanel *DirectoriesPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
-{
-   wxASSERT(parent); // to justify safenew
-   return safenew DirectoriesPrefs(parent, winid);
+PrefsPanel::Factory
+DirectoriesPrefsFactory() {
+   return [](wxWindow *parent, wxWindowID winid)
+   {
+      wxASSERT(parent); // to justify safenew
+      return safenew DirectoriesPrefs(parent, winid);
+   };
 }

src/prefs/DirectoriesPrefs.h

@@ -44,10 +44,7 @@ class DirectoriesPrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one DirectoriesPrefs panel.
-class DirectoriesPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one DirectoriesPrefs panel.
+/// This one is used not only in the Preferences command.
+extern PrefsPanel::Factory DirectoriesPrefsFactory();
 #endif

src/prefs/EffectsPrefs.cpp

@@ -200,8 +200,9 @@ bool EffectsPrefs::Commit()
    return true;
 }
 
-PrefsPanel *EffectsPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+EffectsPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew EffectsPrefs(parent, winid);
-}
+};

src/prefs/EffectsPrefs.h

@@ -37,10 +37,6 @@ class EffectsPrefs final : public PrefsPanel
    void Populate();
 };
 
-/// A PrefsPanelFactory that creates one EffectsPrefs panel.
-class EffectsPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one EffectsPrefs panel.
+extern PrefsPanel::Factory EffectsPrefsFactory;
 #endif

src/prefs/ExtImportPrefs.cpp

@@ -822,8 +822,9 @@ void ExtImportPrefsDropTarget::OnLeave()
 {
 }
 
-PrefsPanel *ExtImportPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+ExtImportPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew ExtImportPrefs(parent, winid);
-}
+};

src/prefs/ExtImportPrefs.h

@@ -114,10 +114,6 @@ class ExtImportPrefs final : public PrefsPanel
 };
 
 
-/// A PrefsPanelFactory that creates one ExtImportPrefs panel.
-class ExtImportPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one ExtImportPrefs panel.
+extern PrefsPanel::Factory ExtImportPrefsFactory;
 #endif

src/prefs/GUIPrefs.cpp

@@ -268,8 +268,9 @@ bool GUIPrefs::Commit()
    return true;
 }
 
-PrefsPanel *GUIPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+GUIPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew GUIPrefs(parent, winid);
-}
+};

src/prefs/GUIPrefs.h

@@ -53,10 +53,6 @@ class GUIPrefs final : public PrefsPanel
    wxArrayStringEx mRangeChoices;
 };
 
-/// A PrefsPanelFactory that creates one GUIPrefs panel.
-class GUIPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one GUIPrefs panel.
+extern PrefsPanel::Factory GUIPrefsFactory;
 #endif

src/prefs/ImportExportPrefs.cpp

@@ -128,8 +128,9 @@ bool ImportExportPrefs::Commit()
    return true;
 }
 
-PrefsPanel *ImportExportPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+ImportExportPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew ImportExportPrefs(parent, winid);
-}
+};

src/prefs/ImportExportPrefs.h

@@ -37,10 +37,6 @@ class ImportExportPrefs final : public PrefsPanel
    void Populate();
 };
 
-/// A PrefsPanelFactory that creates one ImportExportPrefs panel.
-class ImportExportPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one ImportExportPrefs panel.
+extern PrefsPanel::Factory ImportExportPrefsFactory;
 #endif

src/prefs/KeyConfigPrefs.cpp

@@ -688,9 +688,13 @@ void KeyConfigPrefs::Cancel()
    return;
 }
 
-PrefsPanel *KeyConfigPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+KeyConfigPrefsFactory( const CommandID &name )
 {
-   wxASSERT(parent); // to justify safenew
-   auto result = safenew KeyConfigPrefs{ parent, winid, mName };
-   return result;
+   return [=](wxWindow *parent, wxWindowID winid)
+   {
+      wxASSERT(parent); // to justify safenew
+      auto result = safenew KeyConfigPrefs{ parent, winid, name };
+      return result;
+   };
 }

src/prefs/KeyConfigPrefs.h

@@ -93,15 +93,9 @@ private:
 };
 
 
-/// A PrefsPanelFactory that creates one KeyConfigPrefs panel.
-class KeyConfigPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   KeyConfigPrefsFactory(const CommandID &name = {})
-      : mName{ name } {}
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-
-private:
-   CommandID mName;
-};
+/// A PrefsPanel::Factory that creates one KeyConfigPrefs panel.
+/// This factory can be parametrized by name, which specifies a command to be
+/// focused initially
+extern PrefsPanel::Factory KeyConfigPrefsFactory(
+   const CommandID &name = {} );
 #endif

src/prefs/LibraryPrefs.cpp

@@ -267,8 +267,9 @@ bool LibraryPrefs::Commit()
    return true;
 }
 
-PrefsPanel *LibraryPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+LibraryPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew LibraryPrefs(parent, winid);
-}
+};

src/prefs/LibraryPrefs.h

@@ -50,10 +50,6 @@ class LibraryPrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one LibraryPrefs panel.
-class LibraryPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one LibraryPrefs panel.
+extern PrefsPanel::Factory LibraryPrefsFactory;
 #endif

src/prefs/MidiIOPrefs.cpp

@@ -299,10 +299,11 @@ bool MidiIOPrefs::Validate()
    return true;
 }
 
-PrefsPanel *MidiIOPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+MidiIOPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew MidiIOPrefs(parent, winid);
-}
+};
 
 #endif

src/prefs/MidiIOPrefs.h

@@ -68,12 +68,8 @@ class MidiIOPrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one MidiIOPrefs panel.
-class MidiIOPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one MidiIOPrefs panel.
+extern PrefsPanel::Factory MidiIOPrefsFactory;
 #endif
 
 #endif

src/prefs/ModulePrefs.cpp

@@ -180,8 +180,9 @@ void ModulePrefs::SetModuleStatus(const FilePath &fname, int iStatus){
    gPrefs->Flush();
 }
 
-PrefsPanel *ModulePrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+ModulePrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew ModulePrefs(parent, winid);
-}
+};

src/prefs/ModulePrefs.h

@@ -55,10 +55,6 @@ class ModulePrefs final : public PrefsPanel
    FilePaths mPaths;
 };
 
-/// A PrefsPanelFactory that creates one ModulePrefs panel.
-class ModulePrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one ModulePrefs panel.
+extern PrefsPanel::Factory ModulePrefsFactory;
 #endif

src/prefs/MousePrefs.cpp

@@ -218,8 +218,9 @@ bool MousePrefs::Commit()
    return true;
 }
 
-PrefsPanel *MousePrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+MousePrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew MousePrefs(parent, winid);
-}
+};

src/prefs/MousePrefs.h

@@ -41,10 +41,6 @@ class MousePrefs final : public PrefsPanel
    wxListCtrl * mList;
 };
 
-/// A PrefsPanelFactory that creates one MousePrefs panel.
-class MousePrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one MousePrefs panel.
+extern PrefsPanel::Factory MousePrefsFactory;
 #endif

src/prefs/PlaybackPrefs.cpp

@@ -183,9 +183,10 @@ bool PlaybackPrefs::Commit()
    return true;
 }
 
-PrefsPanel *PlaybackPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+PlaybackPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew PlaybackPrefs(parent, winid);
-}
+};
 

src/prefs/PlaybackPrefs.h

@@ -39,11 +39,7 @@ class PlaybackPrefs final : public PrefsPanel
 };
 
 
-/// A PrefsPanelFactory that creates one PlaybackPrefs panel.
-class PlaybackPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one PlaybackPrefs panel.
+extern PrefsPanel::Factory PlaybackPrefsFactory;
 
 #endif

src/prefs/PrefsDialog.cpp

@@ -487,72 +487,42 @@ PrefsDialog::Factories
 {
    // To do, perhaps:  create this table by registration, without including each PrefsPanel
    // class... and thus allowing a plug-in protocol
-   static DevicePrefsFactory devicePrefsFactory;
-   static PlaybackPrefsFactory playbackPrefsFactory;
-   static RecordingPrefsFactory recordingPrefsFactory;
-#ifdef EXPERIMENTAL_MIDI_OUT
-   static MidiIOPrefsFactory midiIOPrefsFactory;
-#endif
-   static QualityPrefsFactory qualityPrefsFactory;
-   static GUIPrefsFactory guiPrefsFactory;
-   static TracksPrefsFactory tracksPrefsFactory;
-   static ImportExportPrefsFactory importExportPrefsFactory;
-   static ExtImportPrefsFactory extImportPrefsFactory;
-   static ProjectsPrefsFactory projectsPrefsFactory;
-#if !defined(DISABLE_DYNAMIC_LOADING_FFMPEG) || !defined(DISABLE_DYNAMIC_LOADING_LAME)
-   static LibraryPrefsFactory libraryPrefsFactory;
-#endif
-   // static WaveformPrefsFactory waveformPrefsFactory;
-   static TracksBehaviorsPrefsFactory tracksBehaviorsPrefsFactory;
-   static SpectrumPrefsFactory spectrumPrefsFactory;
-   static DirectoriesPrefsFactory directoriesPrefsFactory;
-   static WarningsPrefsFactory warningsPrefsFactory;
-   static EffectsPrefsFactory effectsPrefsFactory;
-#ifdef EXPERIMENTAL_THEME_PREFS
-   static ThemePrefsFactory themePrefsFactory;
-#endif
-   // static BatchPrefsFactory batchPrefsFactory;
-   static KeyConfigPrefsFactory keyConfigPrefsFactory;
-   static MousePrefsFactory mousePrefsFactory;
-#ifdef EXPERIMENTAL_MODULE_PREFS
-   static ModulePrefsFactory modulePrefsFactory;
-#endif
 
    static PrefsNode nodes[] = {
-      &devicePrefsFactory,
-      &playbackPrefsFactory,
-      &recordingPrefsFactory,
+      DevicePrefsFactory,
+      PlaybackPrefsFactory,
+      RecordingPrefsFactory,
 #ifdef EXPERIMENTAL_MIDI_OUT
-      &midiIOPrefsFactory,
+      MidiIOPrefsFactory,
 #endif
-      &qualityPrefsFactory,
-      &guiPrefsFactory,
+      QualityPrefsFactory,
+      GUIPrefsFactory,
 
       // Group other page(s)
-      PrefsNode(&tracksPrefsFactory, 2),
-      // &waveformPrefsFactory,
-      &tracksBehaviorsPrefsFactory,
-      &spectrumPrefsFactory,
+      PrefsNode(TracksPrefsFactory, 2),
+      // WaveformPrefsFactory(),
+      TracksBehaviorsPrefsFactory,
+      SpectrumPrefsFactory(),
 
       // Group one other page
-      PrefsNode(&importExportPrefsFactory, 1),
-      &extImportPrefsFactory,
+      PrefsNode(ImportExportPrefsFactory, 1),
+      ExtImportPrefsFactory,
 
-      &projectsPrefsFactory,
+      ProjectsPrefsFactory,
 #if !defined(DISABLE_DYNAMIC_LOADING_FFMPEG) || !defined(DISABLE_DYNAMIC_LOADING_LAME)
-      &libraryPrefsFactory,
+      LibraryPrefsFactory,
 #endif
-      &directoriesPrefsFactory,
-      &warningsPrefsFactory,
-      &effectsPrefsFactory,
+      DirectoriesPrefsFactory(),
+      WarningsPrefsFactory,
+      EffectsPrefsFactory,
 #ifdef EXPERIMENTAL_THEME_PREFS
-      &themePrefsFactory,
+      ThemePrefsFactory,
 #endif
       // &batchPrefsFactory,
-      &keyConfigPrefsFactory,
-      &mousePrefsFactory,
+      KeyConfigPrefsFactory(),
+      MousePrefsFactory,
 #ifdef EXPERIMENTAL_MODULE_PREFS
-      &modulePrefsFactory,
+      ModulePrefsFactory,
 #endif
    };
 
@@ -601,7 +571,7 @@ PrefsDialog::PrefsDialog
                   it != end; ++it, ++iPage)
                {
                   const PrefsNode &node = *it;
-                  PrefsPanelFactory &factory = *node.pFactory;
+                  const PrefsPanel::Factory &factory = node.factory;
                   wxWindow *const w = factory(mCategories, wxID_ANY);
                   if (stack.empty())
                      // Parameters are: AddPage(page, name, IsSelected, imageId).
@@ -629,7 +599,7 @@ PrefsDialog::PrefsDialog
 
          // Unique page, don't show the factory
          const PrefsNode &node = factories[0];
-         PrefsPanelFactory &factory = *node.pFactory;
+         const PrefsPanel::Factory &factory = node.factory;
          mUniquePage = factory(this, wxID_ANY);
          wxWindow * uniquePageWindow = S.Prop(1).AddWindow(mUniquePage, wxEXPAND);
          // We're not in the wxTreebook, so add the accelerator here

src/prefs/PrefsDialog.h

@@ -12,6 +12,7 @@
 #ifndef __AUDACITY_PREFS_DIALOG__
 #define __AUDACITY_PREFS_DIALOG__
 
+#include <functional>
 #include <vector>
 #include "../widgets/wxPanelWrapper.h" // to inherit
 #include "../Internat.h"
@@ -19,7 +20,6 @@
 class wxTreebook;
 class wxTreeEvent;
 class PrefsPanel;
-class PrefsPanelFactory;
 class ShuttleGui;
 
 #ifdef __GNUC__
@@ -33,14 +33,16 @@ class PrefsDialog /* not final */ : public wxDialogWrapper
  public:
     // An array of PrefsNode specifies the tree of pages in pre-order traversal.
     struct PrefsNode {
-       PrefsPanelFactory * CONST pFactory;
+       using Factory =
+         std::function< PrefsPanel * (wxWindow *parent, wxWindowID winid) >;
+       Factory factory;
        CONST int nChildren;
        bool expanded;
 
-       PrefsNode(PrefsPanelFactory *pFactory_,
+       PrefsNode(const Factory &factory_,
           int nChildren_ = 0,
           bool expanded_ = true)
-          : pFactory(pFactory_), nChildren(nChildren_), expanded(expanded_)
+          : factory(factory_), nChildren(nChildren_), expanded(expanded_)
        {}
     };
    typedef std::vector<PrefsNode> Factories;

src/prefs/PrefsPanel.h

@@ -22,17 +22,12 @@ MousePrefs, QualityPrefs, SpectrumPrefs and ThemePrefs.
   To actually add the new panel, edit the PrefsDialog constructor
   to append the panel to its list of panels.
 
-*******************************************************************//**
-
-\class PrefsPanelFactory
-\brief Base class for factories such as GUIPrefsFactory that produce a
-PrefsPanel.
-
 *//*******************************************************************/
 
 #ifndef __AUDACITY_PREFS_PANEL__
 #define __AUDACITY_PREFS_PANEL__
 
+#include <functional>
 #include "../widgets/wxPanelWrapper.h" // to inherit
 #include "../include/audacity/ComponentInterface.h"
 
@@ -52,6 +47,11 @@ class ShuttleGui;
 class PrefsPanel /* not final */ : public wxPanelWrapper, ComponentInterface
 {
  public:
+   // \brief Type alias for factories such as GUIPrefsFactory that produce a
+   // PrefsPanel.
+   using Factory =
+      std::function< PrefsPanel * (wxWindow *parent, wxWindowID winid) >;
+
    PrefsPanel(wxWindow * parent, wxWindowID winid, const wxString &title)
    :  wxPanelWrapper(parent, winid)
    {
@@ -86,11 +86,4 @@ class PrefsPanel /* not final */ : public wxPanelWrapper, ComponentInterface
    virtual void Cancel();
 };
 
-class PrefsPanelFactory /* not final */
-{
-public:
-   // Precondition: parent != NULL
-   virtual PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) = 0;
-};
-
 #endif

src/prefs/ProjectsPrefs.cpp

@@ -99,8 +99,9 @@ bool ProjectsPrefs::Commit()
    return true;
 }
 
-PrefsPanel *ProjectsPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+ProjectsPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew ProjectsPrefs(parent, winid);
-}
+};

src/prefs/ProjectsPrefs.h

@@ -37,10 +37,6 @@ class ProjectsPrefs final : public PrefsPanel
    void Populate();
 };
 
-/// A PrefsPanelFactory that creates one ProjectPrefs panel.
-class ProjectsPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one ProjectPrefs panel.
+extern PrefsPanel::Factory ProjectsPrefsFactory;
 #endif

src/prefs/QualityPrefs.cpp

@@ -277,11 +277,12 @@ bool QualityPrefs::Commit()
    return true;
 }
 
-PrefsPanel *QualityPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+QualityPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew QualityPrefs(parent, winid);
-}
+};
 
 sampleFormat QualityPrefs::SampleFormatChoice()
 {

src/prefs/QualityPrefs.h

@@ -59,10 +59,6 @@ class QualityPrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one QualityPrefs panel.
-class QualityPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one QualityPrefs panel.
+extern PrefsPanel::Factory QualityPrefsFactory;
 #endif

src/prefs/RecordingPrefs.cpp

@@ -305,8 +305,9 @@ void RecordingPrefs::OnToggleCustomName(wxCommandEvent & /* Evt */)
    mToggleCustomName->Enable(mUseCustomTrackName);
 }
 
-PrefsPanel *RecordingPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+RecordingPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew RecordingPrefs(parent, winid);
-}
+};

src/prefs/RecordingPrefs.h

@@ -44,10 +44,6 @@ class RecordingPrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one RecordingPrefs panel.
-class RecordingPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one RecordingPrefs panel.
+extern PrefsPanel::Factory RecordingPrefsFactory;
 #endif

src/prefs/SpectrumPrefs.cpp

@@ -575,13 +575,12 @@ BEGIN_EVENT_TABLE(SpectrumPrefs, PrefsPanel)
 
 END_EVENT_TABLE()
 
-SpectrumPrefsFactory::SpectrumPrefsFactory(WaveTrack *wt)
-: mWt(wt)
+PrefsPanel::Factory
+SpectrumPrefsFactory( WaveTrack *wt )
 {
-}
-
-PrefsPanel *SpectrumPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
-{
-   wxASSERT(parent); // to justify safenew
-   return safenew SpectrumPrefs(parent, winid, mWt);
+   return [=](wxWindow *parent, wxWindowID winid)
+   {
+      wxASSERT(parent); // to justify safenew
+      return safenew SpectrumPrefs(parent, winid, wt);
+   };
 }

src/prefs/SpectrumPrefs.h

@@ -105,14 +105,8 @@ class SpectrumPrefs final : public PrefsPanel
    bool mCommitted{};
 };
 
-/// A PrefsPanelFactory that creates one SpectrumPrefs panel.
-class SpectrumPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   explicit SpectrumPrefsFactory(WaveTrack *wt = 0);
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-
-private:
-   WaveTrack *const mWt;
-};
+/// A PrefsPanel::Factory that creates one SpectrumPrefs panel.
+/// This factory can be parametrized by a single track, to change settings
+/// non-globally
+extern PrefsPanel::Factory SpectrumPrefsFactory( WaveTrack *wt = 0 );
 #endif

src/prefs/ThemePrefs.cpp

@@ -216,8 +216,9 @@ bool ThemePrefs::Commit()
    return true;
 }
 
-PrefsPanel *ThemePrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+ThemePrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew ThemePrefs(parent, winid);
-}
+};

src/prefs/ThemePrefs.h

@@ -46,10 +46,6 @@ class ThemePrefs final : public PrefsPanel
    DECLARE_EVENT_TABLE()
 };
 
-/// A PrefsPanelFactory that creates one ThemePrefs panel.
-class ThemePrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one ThemePrefs panel.
+extern PrefsPanel::Factory ThemePrefsFactory;
 #endif

src/prefs/TracksBehaviorsPrefs.cpp

@@ -134,12 +134,9 @@ bool TracksBehaviorsPrefs::Commit()
    return true;
 }
 
-TracksBehaviorsPrefsFactory::TracksBehaviorsPrefsFactory()
-{
-}
-
-PrefsPanel *TracksBehaviorsPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+TracksBehaviorsPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew TracksBehaviorsPrefs(parent, winid);
-}
+};

src/prefs/TracksBehaviorsPrefs.h

@@ -43,12 +43,6 @@ class TracksBehaviorsPrefs final : public PrefsPanel
    wxArrayStringEx mSoloChoices;
 };
 
-/// A PrefsPanelFactory that creates one TracksBehaviorsPrefs panel.
-class TracksBehaviorsPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   explicit TracksBehaviorsPrefsFactory();
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-
-};
+/// A PrefsPanel::Factory that creates one TracksBehaviorsPrefs panel.
+extern PrefsPanel::Factory TracksBehaviorsPrefsFactory;
 #endif

src/prefs/TracksPrefs.cpp

@@ -406,8 +406,9 @@ bool TracksPrefs::Commit()
    return true;
 }
 
-PrefsPanel *TracksPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+TracksPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew TracksPrefs(parent, winid);
-}
+};

src/prefs/TracksPrefs.h

@@ -54,10 +54,6 @@ class TracksPrefs final : public PrefsPanel
    static int iPreferencePinned;
 };
 
-/// A PrefsPanelFactory that creates one TracksPrefs panel.
-class TracksPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one TracksPrefs panel.
+extern PrefsPanel::Factory TracksPrefsFactory;
 #endif

src/prefs/WarningsPrefs.cpp

@@ -106,8 +106,9 @@ bool WarningsPrefs::Commit()
    return true;
 }
 
-PrefsPanel *WarningsPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
+PrefsPanel::Factory
+WarningsPrefsFactory = [](wxWindow *parent, wxWindowID winid)
 {
    wxASSERT(parent); // to justify safenew
    return safenew WarningsPrefs(parent, winid);
-}
+};

src/prefs/WarningsPrefs.h

@@ -37,10 +37,6 @@ class WarningsPrefs final : public PrefsPanel
    void PopulateOrExchange(ShuttleGui & S) override;
 };
 
-/// A PrefsPanelFactory that creates one WarningPrefs panel.
-class WarningsPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-};
+/// A PrefsPanel::Factory that creates one WarningPrefs panel.
+extern PrefsPanel::Factory WarningsPrefsFactory;
 #endif

src/prefs/WaveformPrefs.cpp

@@ -247,13 +247,12 @@ EVT_CHOICE(ID_RANGE, WaveformPrefs::OnControl)
 EVT_CHECKBOX(ID_DEFAULTS, WaveformPrefs::OnDefaults)
 END_EVENT_TABLE()
 
-WaveformPrefsFactory::WaveformPrefsFactory(WaveTrack *wt)
-: mWt(wt)
+PrefsPanel::Factory
+WaveformPrefsFactory(WaveTrack *wt)
 {
-}
-
-PrefsPanel *WaveformPrefsFactory::operator () (wxWindow *parent, wxWindowID winid)
-{
-   wxASSERT(parent); // to justify safenew
-   return safenew WaveformPrefs(parent, winid, mWt);
+   return [=](wxWindow *parent, wxWindowID winid)
+   {
+      wxASSERT(parent); // to justify safenew
+      return safenew WaveformPrefs(parent, winid, wt);
+   };
 }

src/prefs/WaveformPrefs.h

@@ -63,14 +63,8 @@ private:
    bool mPopulating;
 };
 
-/// A PrefsPanelFactory that creates one WaveformPrefs panel.
-class WaveformPrefsFactory final : public PrefsPanelFactory
-{
-public:
-   explicit WaveformPrefsFactory(WaveTrack *wt = 0);
-   PrefsPanel *operator () (wxWindow *parent, wxWindowID winid) override;
-
-private:
-   WaveTrack *const mWt;
-};
+/// A PrefsPanel::Factory that creates one WaveformPrefs panel.
+/// This factory can be parametrized by a single track, to change settings
+/// non-globally
+extern PrefsPanel::Factory WaveformPrefsFactory(WaveTrack *wt);
 #endif

src/tracks/playabletrack/wavetrack/ui/WaveTrackControls.cpp

@@ -781,13 +781,10 @@ void WaveTrackMenuTable::OnSpectrogramSettings(wxCommandEvent &)
    }
 
    WaveTrack *const pTrack = static_cast<WaveTrack*>(mpData->pTrack);
-   // WaveformPrefsFactory waveformFactory(pTrack);
-   // TracksBehaviorsPrefsFactory tracksBehaviorsFactory();
-   SpectrumPrefsFactory spectrumFactory(pTrack);
 
    PrefsDialog::Factories factories;
-   // factories.push_back(&waveformFactory);
-   factories.push_back(&spectrumFactory);
+   // factories.push_back(WaveformPrefsFactory( pTrack ));
+   factories.push_back(SpectrumPrefsFactory( pTrack ));
    const int page =
       // (pTrack->GetDisplay() == WaveTrack::Spectrum) ? 1 :
       0;