Issue #3432 - Manage COM events with a resource class

src/plugin/PluginClass.h

Index: src/plugin/PluginClass.h
===================================================================
--- a/src/plugin/PluginClass.h
+++ b/src/plugin/PluginClass.h
@@ -41,6 +41,102 @@
 
 class CPluginMimeFilterClient;
 
+/**
+ * Resource class for COM events.
+ * If an instance exists, there's an active connection behind it.
+ *
+ * \tparam Sink
+ *   subclass of ATL::IDispEventImpl.
+ * \tparam Source
+ *   Type of event source. Implements IConnectionPoint
+ */
+template<class Sink, class Source>
+class AtlEventRegistration
+{
+  CComPtr<Sink> consumer;
+  CComPtr<Source> producer;
+public:
+  /**
+   * \throw std::runtime_error
+   *   If connection is not established
+   *
+   * \par Precondition
+   *   - consumer is not nullptr (not checked)
+   *   - producer is not nullptr (not checked)
+   */
+  AtlEventRegistration(Sink* consumer, Source* producer)
+    : consumer(consumer), producer(producer)
+  {
+    auto hr = consumer->DispEventAdvise(producer);
+    if (FAILED(hr))
+    {
+      DEBUG_ERROR_LOG(hr, PLUGIN_ERROR_SET_SITE, PLUGIN_ERROR_SET_SITE_ADVICE, "AtlEventRegistrationImpl::<constructor> - Advise");
+      throw std::runtime_error("DispEventAdvise() failed");
+    }
+  }
+
+  ~AtlEventRegistration() // noexcept
+  {
+    try
+    {
+      // Smart pointer members ensure that this statement does not fail because of life span
+      auto hr = consumer->DispEventUnadvise(producer);
+      if (FAILED(hr))
+      {
+        DEBUG_ERROR_LOG(hr, PLUGIN_ERROR_SET_SITE, PLUGIN_ERROR_SET_SITE_UNADVISE, "AtlEventRegistrationImpl::<destructor> - Unadvise");
+      }
+    }
+    catch (...)
+    {
+      // Suppress exceptions
+    }
+  }
+};
+
+/**
+ * Resource holder for COM events.
+ *
+ * Manages the life time of an 'AtlEventRegistration' instance.
+ * Allows events to be started and stopped at some time other than construction/destruction.
+ *
+ * \tparam Sink
+ *   subclass of ATL::IDispEventImpl.
+ * \tparam Source
+ *   Type of event source. Implements IConnectionPoint
+ */
+template<class Sink, class Source>
+class AtlEventRegistrationHolder
+{
+  typedef AtlEventRegistration<Sink, Source> ImplType;
+  std::unique_ptr<ImplType> impl;
+
+public:
+  AtlEventRegistrationHolder()
+    : impl(nullptr)
+  {}
+
+  ~AtlEventRegistrationHolder() // = default;
+  {}
+
+  bool Start(Sink* consumer, Source* producer) // noexcept
+  {
+    try
+    {
+      impl = new ImplType(consumer, producer);
+    }
+    catch (...)
+    {
+      impl = nullptr;
+      return false;
+    }
+    return true;
+  }
+
+  Stop() // noexcept
+  {
+    impl = nullptr;
+  }
+};
 
 class ATL_NO_VTABLE CPluginClass :
   public ATL::CComObjectRootEx<ATL::CComMultiThreadModel>,
@@ -73,7 +169,6 @@
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_DOCUMENTCOMPLETE, OnDocumentComplete)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_WINDOWSTATECHANGED, OnWindowStateChanged)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_COMMANDSTATECHANGE, OnCommandStateChange)
-    SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_ONQUIT, OnOnQuit)
   END_SINK_MAP()
 
   CPluginClass();
@@ -132,9 +227,7 @@
   void STDMETHODCALLTYPE OnDocumentComplete(IDispatch* frameBrowserDisp, VARIANT* /*urlOrPidl*/);
   void STDMETHODCALLTYPE OnWindowStateChanged(unsigned long flags, unsigned long validFlagsMask);
   void STDMETHODCALLTYPE OnCommandStateChange(long command, VARIANT_BOOL enable);
-  void STDMETHODCALLTYPE OnOnQuit();
-  void Unadvise();
-
+  
   void ShowStatusBar();
   bool IsStatusBarEnabled();
 
@@ -144,6 +237,12 @@
    * It's values are set and reset solely in SetSite().
    */
   CComPtr<IWebBrowser2> m_webBrowser2;
+  /**
+   * Event manager for events coming from our site object.
+   */
+  AtlEventRegistrationHolder<CPluginClass, IWebBrowser2> browserEvents;
+  bool detachedInitializationFailed;
+
   HWND m_hBrowserWnd;
   HWND m_hTabWnd;
   HWND m_hStatusBarWnd;
@@ -157,7 +256,6 @@
 
   NotificationMessage notificationMessage;
 
-  bool m_isAdvised;
   bool m_isInitializedOk;
 
   // Atom pane class