From d35e55f1f0943b6cb3df049a84e6f715982a255e Mon Sep 17 00:00:00 2001
From: Dmitry Vedenko <dmitry@crsib.me>
Date: Thu, 7 Dec 2023 15:37:22 +0300
Subject: [PATCH] Adds ability to run code after the app initialization

---
 libraries/lib-utility/AppEvents.cpp  | 59 ++++++++++++++++++++++++++++
 libraries/lib-utility/AppEvents.h    | 28 +++++++++++++
 libraries/lib-utility/CMakeLists.txt |  2 +
 src/AudacityApp.cpp                  |  2 +
 src/AudacityApp.h                    |  6 ++-
 5 files changed, 96 insertions(+), 1 deletion(-)
 create mode 100644 libraries/lib-utility/AppEvents.cpp
 create mode 100644 libraries/lib-utility/AppEvents.h

diff --git a/libraries/lib-utility/AppEvents.cpp b/libraries/lib-utility/AppEvents.cpp
new file mode 100644
index 000000000000..d41e14540ab1
--- /dev/null
+++ b/libraries/lib-utility/AppEvents.cpp
@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * SPDX-FileName: AppEvents.cpp
+ * SPDX-FileContributor: Dmitry Vedenko
+ */
+
+#include "AppEvents.h"
+
+#include <cassert>
+#include <vector>
+
+namespace AppEvents
+{
+namespace
+{
+
+struct EventHandlers final
+{
+   std::vector<std::function<void()>> appInitialized;
+   bool AppInitializedCalled {};
+};
+
+EventHandlers& GetEventHandlers()
+{
+   static EventHandlers handlers;
+   return handlers;
+}
+
+} // namespace
+
+void OnAppInitialized(std::function<void()> callback)
+{
+   assert(callback);
+
+   if (!callback)
+      return;
+
+   auto& handlers = GetEventHandlers();
+
+   if (handlers.AppInitializedCalled)
+      callback();
+   else
+      handlers.appInitialized.push_back(std::move(callback));
+}
+
+void AppEventsProvider::HandleAppInitialized()
+{
+   auto& handlers = GetEventHandlers();
+
+   handlers.AppInitializedCalled = true;
+
+   std::vector<std::function<void()>> callbacks;
+   std::swap(callbacks, handlers.appInitialized);
+
+   for (auto& callback : handlers.appInitialized)
+      callback();
+}
+
+} // namespace AppEvents
diff --git a/libraries/lib-utility/AppEvents.h b/libraries/lib-utility/AppEvents.h
new file mode 100644
index 000000000000..2677f58d0bc3
--- /dev/null
+++ b/libraries/lib-utility/AppEvents.h
@@ -0,0 +1,28 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * SPDX-FileName: AppEvents.h
+ * SPDX-FileContributor: Dmitry Vedenko
+ */
+
+#pragma once
+
+#include <functional>
+
+namespace AppEvents
+{
+/*! Register callback to be called when application is initialized.
+ *  If application is already initialized, callback will be called immediately.
+ *  @param callback Callback to be called when application is initialized.
+ *  @pre `!!calback`
+ */
+UTILITY_API void OnAppInitialized(std::function<void()> callback);
+
+class UTILITY_API AppEventsProvider /* not final */
+{
+protected:
+   virtual ~AppEventsProvider() = default;
+
+   void HandleAppInitialized();
+};
+
+} // namespace AppEvents
diff --git a/libraries/lib-utility/CMakeLists.txt b/libraries/lib-utility/CMakeLists.txt
index 8332a693141e..5610c4f290c3 100644
--- a/libraries/lib-utility/CMakeLists.txt
+++ b/libraries/lib-utility/CMakeLists.txt
@@ -16,6 +16,8 @@ correspond to things in the standard.
 ]]#
 
 set( SOURCES
+   AppEvents.cpp
+   AppEvents.h
    BufferedStreamReader.cpp
    BufferedStreamReader.h
    CFResources.cpp
diff --git a/src/AudacityApp.cpp b/src/AudacityApp.cpp
index fb84d6ce2196..0ce6e6fd2147 100644
--- a/src/AudacityApp.cpp
+++ b/src/AudacityApp.cpp
@@ -1731,6 +1731,8 @@ bool AudacityApp::InitPart2()
    }
 #endif
 
+   HandleAppInitialized();
+
    return TRUE;
 }
 
diff --git a/src/AudacityApp.h b/src/AudacityApp.h
index 2764cae2fe69..9ecea52a7c63 100644
--- a/src/AudacityApp.h
+++ b/src/AudacityApp.h
@@ -18,6 +18,7 @@
 #include "Identifier.h"
 #include "Observer.h"
 #include "Theme.h"
+#include "AppEvents.h"
 
 #include <wx/app.h> // to inherit
 #include <wx/timer.h> // member variable
@@ -34,7 +35,10 @@ class CommandHandler;
 class AppCommandEvent;
 class AudacityProject;
 
-class AudacityApp final : public wxApp {
+class AudacityApp final
+   : public wxApp
+   , private AppEvents::AppEventsProvider
+{
  public:
    AudacityApp();
    ~AudacityApp();