Add recommends from review.

src/AudacityApp.cpp

@@ -1491,7 +1491,7 @@ bool AudacityApp::InitPart2()
    }
 
 #if defined(HAVE_UPDATES_CHECK)
-   mUpdateManager = std::make_unique<UpdateManager>();
+   UpdateManager::Start();
 #endif
 
    #ifdef USE_FFMPEG

src/AudacityApp.h

@@ -114,10 +114,6 @@ class AudacityApp final : public wxApp {
    std::unique_ptr<wxSocketServer> mIPCServ;
 #endif
 
-#if defined(HAVE_UPDATES_CHECK)
-   std::unique_ptr<UpdateManager> mUpdateManager;
-#endif
-
  public:
     DECLARE_EVENT_TABLE()
 };

src/update/UpdateManager.cpp

@@ -34,12 +34,34 @@ UpdateManager::UpdateManager()
         std::chrono::milliseconds(std::chrono::hours(12)).count())
 {
     mTimer.SetOwner(this, ID_TIMER);
-    mTimer.StartOnce();
 }
 
 UpdateManager::~UpdateManager()
 {
-    mTimer.Stop();
+    Stop();
+}
+
+UpdateManager& UpdateManager::GetInstance()
+{
+    static UpdateManager updateManager;
+
+    return updateManager;
+}
+
+void UpdateManager::Start()
+{
+    auto& instance = GetInstance();
+
+    if (!instance.mTimer.IsRunning())
+        instance.mTimer.StartOnce();
+}
+
+void UpdateManager::Stop()
+{
+    auto& instance = GetInstance();
+
+    if (instance.mTimer.IsRunning())
+        instance.mTimer.Stop();
 }
 
 void UpdateManager::enableUpdatesChecking(bool enable)
@@ -65,47 +87,42 @@ void UpdateManager::getUpdates()
 
     response->setRequestFinishedCallback([response, this](audacity::network_manager::IResponse*) {
 
-        wxFrame* parent = FindProjectFrame(GetActiveProject());
-        wxASSERT(parent);
-
-        if (!parent) return;
-
         if (response->getError() != audacity::network_manager::NetworkError::NoError)
         {
-            ShowExceptionDialog(parent,
-                XO("Error checking for update"),
-                XO("Unable to connect to Audacity update server."),
+            wxTheApp->CallAfter([] {ShowExceptionDialog(nullptr,
+                XC("Error checking for update", "update dialog"),
+                XC("Unable to connect to Audacity update server.", "update dialog"),
                 wxString());
+                });
 
             return;
         }
 
         if (!mUpdateDataParser.Parse(response->readAll<VersionPatch::UpdateDataFormat>(), &mVersionPatch))
         {
-            ShowExceptionDialog(parent,
-                XO("Error checking for update"),
-                XO("Update data was corrupted."),
+            wxTheApp->CallAfter([] {ShowExceptionDialog(nullptr,
+                XC("Error checking for update", "update dialog"),
+                XC("Update data was corrupted.", "update dialog"),
                 wxString());
+                });
 
             return;
         }
 
         if (mVersionPatch.version > CurrentBuildVersion())
         {
-            parent->CallAfter([this, parent] {
-                UpdatePopupDialog dlg(parent, this);
+            wxTheApp->CallAfter([this] {
+                UpdatePopupDialog dlg(nullptr, this);
                 const int code = dlg.ShowModal();
 
                 if (code == wxID_YES)
                 {
                     if (!wxLaunchDefaultBrowser(mVersionPatch.download))
                     {
-                        ShowExceptionDialog(parent,
-                            XO("Error downloading update"),
-                            XO("Can't open the Audacity download link."),
+                        ShowExceptionDialog(nullptr,
+                            XC("Error downloading update.", "update dialog"),
+                            XC("Can't open the Audacity download link.", "update dialog"),
                             wxString());
-
-                        return;
                     }
                 }
                 });

src/update/UpdateManager.h

@@ -30,6 +30,10 @@ public:
     UpdateManager();
     ~UpdateManager();
 
+    static UpdateManager& GetInstance();
+    static void Start();
+    static void Stop();
+
     void getUpdates();
 
     void enableUpdatesChecking(bool enable);

src/update/UpdatePopupDialog.cpp

@@ -27,7 +27,7 @@ END_EVENT_TABLE()
 IMPLEMENT_CLASS (UpdatePopupDialog, wxDialogWrapper)
 
 UpdatePopupDialog::UpdatePopupDialog (wxWindow* parent, UpdateManager* updateManager)
-    : wxDialogWrapper (parent, -1, XO ("Update Audacity"),
+    : wxDialogWrapper (parent, -1, XC("Update Audacity", "update dialog"),
         wxDefaultPosition, wxDefaultSize,
         wxCAPTION),
       mUpdateManager (updateManager)
@@ -49,8 +49,8 @@ UpdatePopupDialog::UpdatePopupDialog (wxWindow* parent, UpdateManager* updateMan
 
             S.Prop(1).AddSpace(1, 0, 1);
 
-            S.Id (wxID_NO).AddButton (XO ("Skip"));
-            S.Id (wxID_YES).AddButton (XO ("Install update"));
+            S.Id (wxID_NO).AddButton (XC ("&Skip", "update dialog"));
+            S.Id (wxID_YES).AddButton (XC("&Install update", "update dialog"));
 
             S.SetBorder (5);
         }
@@ -88,14 +88,15 @@ HtmlWindow* UpdatePopupDialog::AddHtmlContent (wxWindow* parent)
     wxStringOutputStream o;
     wxTextOutputStream informationStr (o);
 
-    static const auto title = XO("Audacity %s is available!")
+    // i18n-hint Substitution of version number for %s.
+    static const auto title = XC("Audacity %s is available!", "update dialog")
         .Format(mUpdateManager->getVersionPatch().version.getString());
 
     informationStr
         << wxT("<html><body><h3>")
         << title.Translation()
         << wxT("</h3><h5>")
-        << XO("Changelog")
+        << XC("Changelog", "update dialog")
         << wxT("</h5><p>");
 
     informationStr << wxT("<ul>");
@@ -109,7 +110,9 @@ HtmlWindow* UpdatePopupDialog::AddHtmlContent (wxWindow* parent)
     informationStr << wxT("</ul></p>");
 
     informationStr << wxT("<p>");
-    informationStr << XO("<a href = \"https://github.com/audacity/audacity/releases\">Read more on GitHub</a>");
+    informationStr << wxT("<a href = \"https://github.com/audacity/audacity/releases\">");
+    informationStr << XC("Read more on GitHub", "update dialog");
+    informationStr << wxT("</a>");
     informationStr << wxT("</p>");
 
     informationStr << wxT("</body></html>");

src/update/VersionId.cpp

@@ -50,9 +50,8 @@ wxString VersionId::getString() const
 
 bool VersionId::operator== (const VersionId& other)
 {
-    return mVersion == other.mVersion &&
-           mRelease == other.mRelease &&
-           mRevision == other.mRevision;
+    return std::tie(mVersion, mRelease, mRevision) ==
+           std::tie(other.mVersion, other.mRelease, other.mRevision);
 }
 
 bool VersionId::operator!= (const VersionId& other)
@@ -62,19 +61,8 @@ bool VersionId::operator!= (const VersionId& other)
 
 bool VersionId::operator< (const VersionId& other)
 {
-    if (mVersion < other.mVersion)
-        return true;
-
-    if (mRelease < other.mRelease &&
-        mVersion == other.mVersion)
-        return true;
-
-    if (mRevision < other.mRevision &&
-        mVersion == other.mVersion &&
-        mRelease == other.mRelease)
-        return true;
-
-    return false;
+    return std::tie(mVersion, mRelease, mRevision) <
+           std::tie(other.mVersion, other.mRelease, other.mRevision);
 }
 
 bool VersionId::operator> (const VersionId& other)