ShuttleGui lets you specify whether a button is default. Use that.

src/AboutDialog.cpp

@@ -238,9 +238,10 @@ AboutDialog::AboutDialog(wxWindow * parent)
       PopulateLicensePage( S );
    }
    S.EndNotebook();
-   wxButton *ok = safenew wxButton(S.GetParent(), wxID_OK, _("OK"));
-   ok->SetDefault();
-   S.Prop(0).AddWindow( ok );
+
+   S.Id(wxID_OK)
+      .Prop(0)
+      .AddButton(_("OK"), wxALIGN_CENTER, true);
 
    Fit();
    this->Centre();

src/Benchmark.cpp

@@ -225,7 +225,7 @@ void BenchmarkDialog::MakeBenchmarkDialog()
       {
          S.StartHorizontalLay(wxALIGN_LEFT, false);
          {
-            S.Id(RunID).AddButton(_("Run"))->SetDefault();
+            S.Id(RunID).AddButton(_("Run"), wxALIGN_CENTRE, true);
             S.Id(BSaveID).AddButton(_("Save"));
             /* i18n-hint verb; to empty or erase */
             S.Id(ClearID).AddButton(_("Clear"));

src/Dependencies.cpp

@@ -364,12 +364,12 @@ void DependencyDialog::PopulateOrExchange(ShuttleGui& S)
          PopulateList();
 
          mCopySelectedFilesButton =
-            S.Id(CopySelectedFilesButtonID).AddButton(
-               _("Copy Selected Files"),
-               wxALIGN_LEFT);
+            S.Id(CopySelectedFilesButtonID)
+               .AddButton(
+                  _("Copy Selected Files"),
+                  wxALIGN_LEFT, true);
          mCopySelectedFilesButton->Enable(
             mFileListCtrl->GetSelectedItemCount() > 0);
-         mCopySelectedFilesButton->SetDefault();
          mCopySelectedFilesButton->SetFocus();
       }
       S.EndStatic();

src/HistoryWindow.cpp

@@ -135,7 +135,7 @@ HistoryWindow::HistoryWindow(AudacityProject *parent, UndoManager *manager):
       S.StartHorizontalLay(wxALIGN_RIGHT, false);
       {
          S.SetBorder(10);
-         S.Id(wxID_OK).AddButton(_("&OK"))->SetDefault();
+         S.Id(wxID_OK).AddButton(_("&OK"), wxALIGN_CENTER, true);
       }
       S.EndHorizontalLay();
    }

src/ShuttleGui.cpp

@@ -348,7 +348,8 @@ wxCheckBox * ShuttleGuiBase::AddCheckBoxOnRight( const wxString &Prompt, bool Se
    return pCheckBox;
 }
 
-wxButton * ShuttleGuiBase::AddButton(const wxString &Text, int PositionFlags)
+wxButton * ShuttleGuiBase::AddButton(
+   const wxString &Text, int PositionFlags, bool setDefault)
 {
    UseUpId();
    if( mShuttleMode != eIsCreating )
@@ -359,10 +360,13 @@ wxButton * ShuttleGuiBase::AddButton(const wxString &Text, int PositionFlags)
    mpWind->SetName(wxStripMenuCodes(Text));
    miProp=0;
    UpdateSizersCore(false, PositionFlags | wxALL);
+   if (setDefault)
+      pBtn->SetDefault();
    return pBtn;
 }
 
-wxBitmapButton * ShuttleGuiBase::AddBitmapButton(const wxBitmap &Bitmap, int PositionFlags)
+wxBitmapButton * ShuttleGuiBase::AddBitmapButton(
+   const wxBitmap &Bitmap, int PositionFlags, bool setDefault)
 {
    UseUpId();
    if( mShuttleMode != eIsCreating )
@@ -375,6 +379,8 @@ wxBitmapButton * ShuttleGuiBase::AddBitmapButton(const wxBitmap &Bitmap, int Pos
 //      wxSystemSettings::GetColour(wxSYS_COLOUR_BTNFACE));
    miProp=0;
    UpdateSizersCore(false, PositionFlags | wxALL);
+   if (setDefault)
+      pBtn->SetDefault();
    return pBtn;
 }
 

src/ShuttleGui.h

@@ -139,10 +139,16 @@ public:
    wxTreeCtrl * AddTree();
    wxRadioButton * AddRadioButton( const wxString & Prompt );
    wxRadioButton * AddRadioButtonToGroup( const wxString & Prompt);
+   // Only the last button specified as default (if more than one) will be
    // Always ORs the flags with wxALL (which affects borders):
-   wxButton * AddButton( const wxString & Text, int PositionFlags = wxALIGN_CENTRE );
+   wxButton * AddButton(
+      const wxString & Text, int PositionFlags = wxALIGN_CENTRE,
+      bool setDefault = false );
+   // Only the last button specified as default (if more than one) will be
    // Always ORs the flags with wxALL (which affects borders):
-   wxBitmapButton * AddBitmapButton(const wxBitmap &Bitmap, int PositionFlags = wxALIGN_CENTRE);
+   wxBitmapButton * AddBitmapButton(
+      const wxBitmap &Bitmap, int PositionFlags = wxALIGN_CENTRE,
+      bool setDefault = false );
    // When PositionFlags is 0, applies wxALL (which affects borders),
    // and either wxALIGN_CENTER (if bCenter) or else wxEXPAND
    wxStaticText * AddVariableText(const wxString &Str, bool bCenter = false, int PositionFlags = 0);

src/SplashDialog.cpp

@@ -140,10 +140,11 @@ void SplashDialog::Populate( ShuttleGui & S )
    {
       S.SetBorder( 5 );
       S.Id( DontShowID).AddCheckBox( _("Don't show this again at start up"), !bShow );
-      wxButton *ok = safenew wxButton(S.GetParent(), wxID_OK);
-      ok->SetDefault();
       S.SetBorder( 5 );
-      S.Prop(0).AddWindow( ok, wxALIGN_RIGHT| wxALL );
+
+      S.Id(wxID_OK)
+         .Prop(0)
+         .AddButton(_("OK"), wxALIGN_RIGHT| wxALL, true);
    }
    S.EndVerticalLay();
 }

src/export/ExportCL.cpp

@@ -533,7 +533,7 @@ ProgressResult ExportCL::Export(AudacityProject *project,
       S.AddTextWindow(cmd + wxT("\n\n") + output);
       S.StartHorizontalLay(wxALIGN_CENTER, false);
       {
-         S.Id(wxID_OK).AddButton(_("&OK"))->SetDefault();
+         S.Id(wxID_OK).AddButton(_("&OK"), wxALIGN_CENTER, true);
       }
       dlg.GetSizer()->AddSpacer(5);
       dlg.Layout();

src/widgets/HelpSystem.cpp

@@ -189,7 +189,7 @@ void HelpSystem::ShowHtmlText(wxWindow *pParent,
 
       S.Prop(1).AddWindow( html, wxEXPAND );
 
-      S.Id( wxID_CANCEL ).AddButton( _("Close") )->SetDefault();
+      S.Id( wxID_CANCEL ).AddButton( _("Close"), wxALIGN_CENTER, true );
    }
    S.EndPanel();