Adds OnIdle handler

libraries/lib-utility/AppEvents.cpp

@@ -9,15 +9,23 @@
 #include <cassert>
 #include <vector>
 
+
+
 namespace AppEvents
 {
 namespace
 {
+struct IdleEvent
+{
+};
 
-struct EventHandlers final
+struct EventHandlers final : public Observer::Publisher<IdleEvent>
 {
    std::vector<std::function<void()>> appInitialized;
    bool AppInitializedCalled {};
+
+   using Observer::Publisher<IdleEvent>::Subscribe;
+   using Observer::Publisher<IdleEvent>::Publish;
 };
 
 EventHandlers& GetEventHandlers()
@@ -43,6 +51,12 @@ void OnAppInitialized(std::function<void()> callback)
       handlers.appInitialized.push_back(std::move(callback));
 }
 
+Observer::Subscription OnAppIdle(std::function<void()> callback)
+{
+   return GetEventHandlers().Subscribe([callback = std::move(callback)](auto&)
+                                       { callback(); });
+}
+
 void ProviderBase::HandleAppInitialized()
 {
    auto& handlers = GetEventHandlers();
@@ -56,4 +70,9 @@ void ProviderBase::HandleAppInitialized()
       callback();
 }
 
+void ProviderBase::HandleAppIdle()
+{
+   GetEventHandlers().Publish(IdleEvent{});
+}
+
 } // namespace AppEvents

libraries/lib-utility/AppEvents.h

@@ -8,6 +8,8 @@
 
 #include <functional>
 
+#include "Observer.h"
+
 namespace AppEvents
 {
 /*! Register callback to be called when application is initialized.
@@ -17,6 +19,13 @@ namespace AppEvents
  */
 UTILITY_API void OnAppInitialized(std::function<void()> callback);
 
+/*! Register callback to be called when application is idle.
+ *  @param callback Callback to be called when application is idle.
+ *  @pre `!!calback`
+ */
+
+UTILITY_API Observer::Subscription OnAppIdle(std::function<void()> callback);
+
 /*! Base class for application events providers.
  *  This class has no virtual methods and should not be publicly derived from.
  *  Derived classes should use the provided interface to fire events.
@@ -29,6 +38,7 @@ class UTILITY_API ProviderBase /* not final */
    virtual ~ProviderBase() = default;
 
    void HandleAppInitialized();
+   void HandleAppIdle();
 };
 
 } // namespace AppEvents

src/AudacityApp.cpp

@@ -1751,6 +1751,8 @@ void AudacityApp::OnIdle( wxIdleEvent &evt )
 {
    evt.Skip();
    try {
+      HandleAppIdle();
+
       if ( Journal::Dispatch() )
          evt.RequestMore();
    }