Issue #1652, #3456 - Replace 's_asyncWebBrowser2' with thread-safe facilities

src/plugin/PluginClass.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
- * Copyright (C) 2006-2015 Eyeo GmbH
+ * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
@@ skipping 10 matching lines @@
 #include "PluginMimeFilterClient.h"
 #include "AdblockPlusClient.h"
 #include "PluginClientBase.h"
 #include "PluginClientFactory.h"
 #include "PluginUtil.h"
 #include "../shared/Utils.h"
 #include "../shared/Dictionary.h"
 #include "IeVersion.h"
 #include "Instances.h"
 #include "../shared/Version.h"
+#include "Instances.h"
 #include <thread>
 #include <array>
 
 #ifdef DEBUG_HIDE_EL
 DWORD profileTime = 0;
 #endif
 
 extern CComModule _Module;
 
 typedef HANDLE (WINAPI *OPENTHEMEDATA)(HWND, LPCWSTR);
 typedef HRESULT (WINAPI *DRAWTHEMEBACKGROUND)(HANDLE, HDC, INT, INT, LPRECT, LPRECT);
 typedef HRESULT (WINAPI *CLOSETHEMEDATA)(HANDLE);
 
 HICON CPluginClass::s_hIcons[ICON_MAX] = { NULL, NULL, NULL };
 DWORD CPluginClass::s_hIconTypes[ICON_MAX] = { IDI_ICON_DISABLED, IDI_ICON_ENABLED, IDI_ICON_DEACTIVATED };
 uint32_t iconHeight = 32;
 uint32_t iconWidth = 32;
 
 CPluginMimeFilterClient* CPluginClass::s_mimeFilter = NULL;
 
 CLOSETHEMEDATA pfnClose = NULL;
 DRAWTHEMEBACKGROUND pfnDrawThemeBackground = NULL;
 OPENTHEMEDATA pfnOpenThemeData = NULL;
 
 ATOM CPluginClass::s_atomPaneClass = NULL;
 HINSTANCE CPluginClass::s_hUxtheme = NULL;
 SyncSet<CPluginClass*, nullptr> instanceSet;
-std::map<DWORD, CPluginClass*> CPluginClass::s_threadInstances;
 
 CComAutoCriticalSection CPluginClass::s_criticalSectionLocal;
 CComAutoCriticalSection CPluginClass::s_criticalSectionWindow;
+
+namespace
+{
+  /**
+   * A synchronized map whose key is always the current thread ID.
+   */
+  class CurrentThreadMap
+    : public SyncMap<DWORD, CPluginClass*, nullptr>
+  {
+    typedef SyncMap<DWORD, CPluginClass*, nullptr> Base;
+
+  public:
+    bool AddIfAbsent(CPluginClass* p)
+    {
+      return Base::AddIfAbsent(::GetCurrentThreadId(), p);
+    }
+
+    bool RemoveAndCheck()
+    {
+      return Base::RemoveIfPresent(::GetCurrentThreadId());
+    }
+
+    CPluginClass* Locate()
+    {
+      return Base::Locate(::GetCurrentThreadId());
+    }
+  };
+
+  /**
+   * Map from thread ID's to CPluginClass instances
+   */
+  CurrentThreadMap threadMap;
+}
 
 /*
  * Without namespace declaration, the identifier "Rectangle" is ambiguous
  * See http://msdn.microsoft.com/en-us/library/windows/desktop/dd162898(v=vs.85).aspx
  */
 namespace AdblockPlus
 {
   /**
     * Replacement for ATL type CRect.
     */
   class Rectangle
     : public RECT
   {
   public:
-    int Height() const
-    {
-      return bottom - top;
-    }
-
-    int Width() const
-    {
-      return right - left;
+    unsigned long Height() const
+    {
+      if (bottom < top)
+      {
+        throw std::runtime_error("invariant violation: rectangle bottom < top");
+      }
+      return static_cast<unsigned long>(bottom - top);
+    }
+
+    unsigned long Width() const
+    {
+      if (right < left)
+      {
+        throw std::runtime_error("invariant violation: rectangle right < left");
+      }
+      return static_cast<unsigned long>(right - left);
     }
   };
 }
 
 /**
  * Wrapper class for a browser site object that ensures proper site life cycle.
  *
  * The browser is guaranteed to be valid for the lifetime of the object.
  * What that means is that SetSite(0) on the containing BHO instance will not return before this object is destroyed.
  * This property avoids a race condition where one thread is using a browser site for services while IE is simultaneously shutting it down.
@@ skipping 80 matching lines @@
 
   operator bool() const
   {
     return browser != nullptr;
   }
 };
 
 CPluginClass::CPluginClass()
   : m_webBrowser2(nullptr)
 {
+  DEBUG_GENERAL([this]() -> std::wstring
+    {
+      std::wstring s = L"CPluginClass::<constructor>, this = ";
+      s += ToHexLiteral(this);
+      return s;
+    }());
+
   //Use this line to debug memory leaks
   //    _CrtDumpMemoryLeaks();
 
   m_isAdvised = false;
   m_hTabWnd = NULL;
   m_hStatusBarWnd = NULL;
   m_hPaneWnd = NULL;
   m_nPaneWidth = 0;
   m_pWndProcStatus = NULL;
   m_hTheme = NULL;
   m_isInitializedOk = false;
-
-
-  m_tab = new CPluginTab(this);
-
+  m_tab = new CPluginTab();
   Dictionary::Create(GetBrowserLanguage());
 }
 
 CPluginClass::~CPluginClass()
 {
+  DEBUG_GENERAL([this]() -> std::wstring
+    {
+      std::wstring s = L"CPluginClass::<destructor>, this = ";
+      s += ToHexLiteral(this);
+      return s;
+    }());
+
   delete m_tab;
 }
 
 HWND CPluginClass::GetBrowserHWND() const
 {
   if (!m_webBrowser2)
   {
     DEBUG_ERROR_LOG(0, 0, 0, "CPluginClass::GetBrowserHWND - Reached with m_webBrowser2 == nullptr");
     return nullptr;
   }
@@ skipping 11 matching lines @@
 {
   return m_webBrowser2.IsEqualObject(otherBrowser);
 }
 
 std::wstring CPluginClass::GetBrowserUrl() const
 {
   std::wstring url;
   if (m_webBrowser2)
   {
     CComBSTR bstrURL;
-    if (SUCCEEDED(m_webBrowser2->get_LocationURL(&bstrURL)) && bstrURL)
-    {
-      url = std::wstring(bstrURL, SysStringLen(bstrURL));
+    if (SUCCEEDED(m_webBrowser2->get_LocationURL(&bstrURL)))
+    {
+      url = ToWstring(bstrURL);
     }
   }
   else
   {
-    DEBUG_ERROR_LOG(0, 0, 0, "CPluginClass::GetBrowserUrl - Reached with m_webBrowser2 == nullptr");
+    DEBUG_GENERAL(L"CPluginClass::GetBrowserUrl - Reached with m_webBrowser2 == nullptr (probable invariant violation)");
+  }
+  if (url.empty())
+  {
     url = m_tab->GetDocumentUrl();
   }
   return url;
 }
 
 DWORD WINAPI CPluginClass::StartInitObject(LPVOID thisPtr)
 {
   if (thisPtr == NULL)
     return 0;
   if (!((CPluginClass*)thisPtr)->InitObject())
@@ skipping 15 matching lines @@
  * but it is not a proper substitute for one.
  */
 STDMETHODIMP CPluginClass::SetSite(IUnknown* unknownSite)
 {
   try
   {
     std::lock_guard<std::mutex> lock(siteGuard);
 
     if (unknownSite)
     {
-
-      DEBUG_GENERAL(L"================================================================================\nNEW TAB UI\n================================================================================")
+      DEBUG_GENERAL(L"================================================================================\nNEW TAB UI\n================================================================================");
 
       HRESULT hr = ::CoInitialize(NULL);
       if (FAILED(hr))
       {
         DEBUG_ERROR_LOG(hr, PLUGIN_ERROR_SET_SITE, PLUGIN_ERROR_SET_SITE_COINIT, "Class::SetSite - CoInitialize");
       }
 
       /*
        * We were instantiated as a BHO, so our site is always of type IWebBrowser2.
        */
       m_webBrowser2 = ATL::CComQIPtr<IWebBrowser2>(unknownSite);
       if (!m_webBrowser2)
       {
         throw std::logic_error("CPluginClass::SetSite - Unable to convert site pointer to IWebBrowser2*");
       }
+      DEBUG_GENERAL([this]() -> std::wstring
+        {
+          std::wstringstream ss;
+          ss << L"CPluginClass::SetSite, this = " << ToHexLiteral(this);
+          ss << L", browser = " << ToHexLiteral(m_webBrowser2);
+          return ss.str();
+        }());
+
+      /*
+       * Add ourselves to the thread map.
+       */
+      if (!threadMap.AddIfAbsent(this))
+      {
+        throw std::logic_error("CPluginClass::SetSite - May not overwrite existing entry in thread map");
+      }
       if (!instanceSet.InsertIfAbsent(this))
       {
         throw std::logic_error("CPluginClass::SetSite - May not overwrite existing entry in instance set");
       }
+
 
       //register the mimefilter
       //and only mimefilter
       //on some few computers the mimefilter does not get properly registered when it is done on another thread
       s_criticalSectionLocal.Lock();
       {
         s_mimeFilter = CPluginClientFactory::GetMimeFilterClientInstance();
       }
       s_criticalSectionLocal.Unlock();
 
       try
       {
-        DEBUG_GENERAL("Loaded as BHO");
         HRESULT hr = DispEventAdvise(m_webBrowser2);
         if (SUCCEEDED(hr))
         {
           m_isAdvised = true;
           try
           {
             std::thread startInitObjectThread(StartInitObject, this);
             startInitObjectThread.detach(); // TODO: but actually we should wait for the thread in the dtr.
           }
           catch (const std::system_error& ex)
           {
             DEBUG_SYSTEM_EXCEPTION(ex, PLUGIN_ERROR_THREAD, PLUGIN_ERROR_MAIN_THREAD_CREATE_PROCESS, 
               "Class::Thread - Failed to create StartInitObject thread");
           }
         }
         else
         {
           DEBUG_ERROR_LOG(hr, PLUGIN_ERROR_SET_SITE, PLUGIN_ERROR_SET_SITE_ADVICE, "Class::SetSite - Advise");
         }
       }
       catch (const std::runtime_error& ex)
       {
         DEBUG_EXCEPTION(ex);
         Unadvise();
       }
     }
     else
     {
+      DEBUG_GENERAL([this]() -> std::wstring
+      {
+        std::wstringstream ss;
+        ss << L"CPluginClass::SetSite, this = " << ToHexLiteral(this);
+        ss << L", browser = nullptr";
+        return ss.str();
+      }());
+
       Unadvise();
 
       // Destroy window
       if (m_pWndProcStatus)
       {
         ::SetWindowLongPtr(m_hStatusBarWnd, GWLP_WNDPROC, (LPARAM)(WNDPROC)m_pWndProcStatus);
 
         m_pWndProcStatus = NULL;
       }
 
       if (m_hPaneWnd)
       {
         DestroyWindow(m_hPaneWnd);
         m_hPaneWnd = NULL;
       }
 
       m_hTabWnd = NULL;
       m_hStatusBarWnd = NULL;
 
       // Remove instance from the list, shutdown threads
       HANDLE hMainThread = NULL;
       HANDLE hTabThread = NULL;
 
       if (!instanceSet.EraseWithCheck(this))
       {
         throw std::logic_error("CPluginClass::SetSite - Missing entry in instance set");
+      }
+      if (!threadMap.RemoveAndCheck())
+      {
+        throw std::logic_error("CPluginClass::SetSite - Missing entry in thread map");
       }
       s_criticalSectionLocal.Lock();
       {
         if (instanceSet.Empty())
         {
           // TODO: Explicitly releasing a resource when a container becomes empty looks like a job better suited for shared_ptr
           CPluginClientFactory::ReleaseMimeFilterClientInstance();
         }
       }
       s_criticalSectionLocal.Unlock();
       m_webBrowser2 = nullptr;
 
       DEBUG_GENERAL("================================================================================\nNEW TAB UI - END\n================================================================================")
 
       ::CoUninitialize();
     }
 
   }
   catch (...)
   {
   }
   IObjectWithSiteImpl<CPluginClass>::SetSite(unknownSite);
   return S_OK;
 }
 
 namespace
 {
   bool IsStatusBarDisabledInRegistry()

[Oleksandr, 2016/02/01 18:03:14]

I see no reason why IsStatusBarEnabled is refactored in this change set. It is
unrelated, IMO.

[Eric, 2016/02/03 14:57:28]

It's not entirely unrelated. These changes tag along with the changes of type of
the various browser variables from 'IWebBrowser2' or 'CComPtr<IWebBrowser2' to
'AnyCurrentSiteBrowser'. Strictly speaking, they could go into a separate change
set, but it would be a "noissue" commit.

I don't see enough value in creating two change sets here to go through the
effort of splitting the change set up. It might be worth changing the commit
message to reflect that there are "noissue" changes tagging along here to
related parts of the code.

   {
     DEBUG_GENERAL("IsStatusBarDisabledInRegistry start");
     HKEY pHkey;
     HKEY pHkeySub;
     RegOpenCurrentUser(KEY_QUERY_VALUE, &pHkey);
     DWORD truth = 1;
     DWORD truthSize = sizeof(truth);
     RegOpenKey(pHkey, L"Software\\Microsoft\\Internet Explorer\\Main", &pHkeySub);
     LONG res = RegQueryValueEx(pHkeySub, L"StatusBarWeb", NULL, NULL, (BYTE*)&truth, &truthSize);
     RegCloseKey(pHkey);
@@ skipping 47 matching lines @@
     DEBUG_GENERAL("ShowStatusBar abort; no browser");
     return;
   }
   VARIANT_BOOL isVisible;
   HRESULT hr = browser->get_StatusBar(&isVisible);
   if (FAILED(hr))
   {
     DEBUG_ERROR_LOG(hr, PLUGIN_ERROR_UI, PLUGIN_ERROR_UI_GET_STATUSBAR, "CPluginClass::ShowStatusBar get_StatusBar");
     return;
   }
   if (!isVisible)

[Oleksandr, 2016/02/01 18:03:14]

Same here. Why is this done in the change set with the message "Replace
's_asyncWebBrowser2' with thread-safe facilities"? I don't think this is related
at all.

[Eric, 2016/02/03 14:57:28]

See above.

   {
     DEBUG_GENERAL("ShowStatusBar end early; browser told us status bar is visible");
     return;
   }
   Dictionary* dictionary = Dictionary::GetInstance();
   /*
    * Do we have enough rights to enable a status bar?
    */
   HKEY pHkey;
   LSTATUS regRes = RegOpenCurrentUser(KEY_WRITE, &pHkey);
@@ skipping 56 matching lines @@
   {
     ATL::CComQIPtr<IWebBrowser2> webBrowser = frameBrowserDisp;
     if (!webBrowser)
     {
       return;
     }
     if (!urlVariant || urlVariant->vt != VT_BSTR)
     {
       return;
     }
-    std::wstring url(urlVariant->bstrVal, SysStringLen(urlVariant->bstrVal));
+    std::wstring url = ToWstring(urlVariant->bstrVal);
 
     // If webbrowser2 is equal to top level browser (as set in SetSite), we are
     // navigating new page
     CPluginClient* client = CPluginClient::GetInstance();
     if (url.find(L"javascript") == 0)
     {
     }
     else if (IsRootBrowser(webBrowser))
     {
       m_tab->OnNavigate(url);
@@ skipping 58 matching lines @@
 // Entry point
 void STDMETHODCALLTYPE CPluginClass::OnWindowStateChanged(unsigned long flags, unsigned long validFlagsMask)
 {
   try
   {
     DEBUG_GENERAL(L"WindowStateChanged (check tab changed)");
     bool newtabshown = validFlagsMask == (OLECMDIDF_WINDOWSTATE_USERVISIBLE | OLECMDIDF_WINDOWSTATE_ENABLED)
       && flags == (OLECMDIDF_WINDOWSTATE_USERVISIBLE | OLECMDIDF_WINDOWSTATE_ENABLED);
     if (newtabshown)
     {
-      std::map<DWORD,CPluginClass*>::const_iterator it = s_threadInstances.find(GetCurrentThreadId());
-      if (it == s_threadInstances.end())
-      {
-        s_threadInstances[::GetCurrentThreadId()] = this;
-        if (!m_isInitializedOk)
-        {
-          m_isInitializedOk = true;
-          InitObject();
-          UpdateStatusBar();
-        }
+      if (!m_isInitializedOk)
+      {
+        m_isInitializedOk = true;
+        InitObject();
+        UpdateStatusBar();
       }
     }
     notificationMessage.Hide();
     DEBUG_GENERAL(L"WindowStateChanged (check tab changed) end");
   }
   catch (...)
   {
   }
 }
 
@@ skipping 325 matching lines @@
   {
     // Just return if the First Run Page should be suppressed
     if (CPluginClient::GetInstance()->GetPref(L"suppress_first_run_page", false))
       return;
 
     if (SUCCEEDED(CoInitialize(NULL)))
     {
       AnyCurrentSiteBrowser browser;
       if (browser)
       {
         NavigateNewTab(browser, FirstRunPageFileUrl());

[Oleksandr, 2016/02/01 18:03:14]

I agree this looks better with NavigateNewTab separated, but this is not
relevant to the present change at all. 

[Eric, 2016/02/03 14:57:28]

When I went through and changed types to use 'AnyCurrentSiteBrowser', I went
ahead and improved the code in its vicinity.

As I've said elsewhere, it could be split into a "noissue" commit, but I don't
see a lot of value in that at this point.

       }
     }
     CoUninitialize();
   }
   catch (...)
   {
     // Suppress errors
   }
 }
 
@@ skipping 30 matching lines @@
     {
       return p->m_hStatusBarWnd == hStatusBarWnd;
     });
 }
 
 CPluginTab* CPluginClass::GetTab()
 {
   return m_tab;
 }
 
-CPluginTab* CPluginClass::GetTab(DWORD dwThreadId)
-{
-  CPluginTab* tab = NULL;
-
-  s_criticalSectionLocal.Lock();
-  {
-    std::map<DWORD,CPluginClass*>::const_iterator it = s_threadInstances.find(dwThreadId);
-    if (it != s_threadInstances.end())
-    {
-      tab = it->second->m_tab;
-    }
-  }
-  s_criticalSectionLocal.Unlock();
-
-  return tab;
-}
-
-
+CPluginTab* CPluginClass::GetTabForCurrentThread()
+{
+  auto p = threadMap.Locate();
+  return p ? p->m_tab : nullptr;
+}
+
+// Entry point
 STDMETHODIMP CPluginClass::QueryStatus(const GUID* pguidCmdGroup, ULONG cCmds, OLECMD prgCmds[], OLECMDTEXT* pCmdText)
 {
-  if (cCmds == 0) return E_INVALIDARG;
-  if (prgCmds == 0) return E_POINTER;
-
-  prgCmds[0].cmdf = OLECMDF_ENABLED;
-
+  try
+  {
+    if (cCmds == 0) return E_INVALIDARG;
+    if (prgCmds == 0) return E_POINTER;
+
+    prgCmds[0].cmdf = OLECMDF_ENABLED;
+  }
+  catch (...)
+  {
+    DEBUG_GENERAL(L"CPluginClass::QueryStatus - exception");
+    return E_FAIL;
+  }
   return S_OK;
 }
 
 HMENU CPluginClass::CreatePluginMenu(const std::wstring& url)
 {
   DEBUG_GENERAL("CreatePluginMenu");
   HINSTANCE hInstance = _AtlBaseModule.GetModuleInstance();
 
   HMENU hMenu = ::LoadMenu(hInstance, MAKEINTRESOURCE(IDR_MENU1));
 
@@ skipping 113 matching lines @@
 
   MENUITEMINFOW miiSep = {};
   miiSep.cbSize = sizeof(miiSep);
   miiSep.fMask = MIIM_TYPE | MIIM_FTYPE;
   miiSep.fType = MFT_SEPARATOR;
 
   CPluginClient* client = CPluginClient::GetInstance();
   CPluginSettings* settings = CPluginSettings::GetInstance();
   {
     ctext = dictionary->Lookup("menu", "menu-disable-on-site");
-    // Is domain in white list?
     ReplaceString(ctext, L"?1?", client->GetHostFromUrl(url));
-    if (client->IsWhitelistedUrl(GetTab()->GetDocumentUrl()))
-    {
+    /*
+     * The display state of the "disable on this site" menu item depends upon tab content
+     */
+    if (!GetTab()->IsPossibleToDisableOnSite())
+    {
+      // Since we can't disable the present content,
+      // it makes no sense to offer the user an option to block it.
+      fmii.fState = MFS_UNCHECKED | MFS_DISABLED;
+    }
+    else if (client->IsWhitelistedUrl(GetTab()->GetDocumentUrl()))
+    {
+      // Domain is in white list, indicated by a check mark
       fmii.fState = MFS_CHECKED | MFS_ENABLED;
     }
     else
     {
       fmii.fState = MFS_UNCHECKED | MFS_ENABLED;
     }
     fmii.fMask = MIIM_STRING | MIIM_STATE;
     fmii.dwTypeData = const_cast<LPWSTR>(ctext.c_str());
     fmii.cch = static_cast<UINT>(ctext.size());
 
@@ skipping 28 matching lines @@
   ctext = dictionary->Lookup("menu", "menu-settings");
   fmii.fMask  = MIIM_STATE | MIIM_STRING;
   fmii.fState = MFS_ENABLED;
   fmii.dwTypeData = const_cast<LPWSTR>(ctext.c_str());
   fmii.cch = static_cast<UINT>(ctext.size());
   ::SetMenuItemInfoW(hMenu, ID_MENU_SETTINGS, FALSE, &fmii);
 
   return true;
 }
 
-
+// Entry point
 STDMETHODIMP CPluginClass::Exec(const GUID*, DWORD nCmdID, DWORD, VARIANTARG*, VARIANTARG*)
 {
-  HWND hBrowserWnd = GetBrowserHWND();
-  if (!hBrowserWnd)
-  {
-    return E_FAIL;
-  }
-
-  // Create menu
-  HMENU hMenu = CreatePluginMenu(m_tab->GetDocumentUrl());
-  if (!hMenu)
-  {
-    return E_FAIL;
-  }
-
-  // Check if button in toolbar was pressed
-  int nIDCommand = -1;
-  BOOL bRightAlign = FALSE;
-
-  POINT pt;
-  GetCursorPos(&pt);
-
-  HWND hWndToolBar = ::WindowFromPoint(pt);
-
-  DWORD nProcessId;
-  ::GetWindowThreadProcessId(hWndToolBar, &nProcessId);
-
-  if (hWndToolBar && ::GetCurrentProcessId() == nProcessId)
-  {
-    ::ScreenToClient(hWndToolBar, &pt);
-    int nButton = (int)::SendMessage(hWndToolBar, TB_HITTEST, 0, (LPARAM)&pt);
-
-    if (nButton > 0)
-    {
-      TBBUTTON pTBBtn = {};
-
-      if (SendMessage(hWndToolBar, TB_GETBUTTON, nButton, (LPARAM)&pTBBtn))
-      {
-        RECT rcButton;
-        nIDCommand = pTBBtn.idCommand;
-
-        if (SendMessage(hWndToolBar, TB_GETRECT, nIDCommand, (LPARAM)&rcButton))
-        {
-          pt.x = rcButton.left;
-          pt.y = rcButton.bottom;
-          ClientToScreen(hWndToolBar, &pt);
-
-          RECT rcWorkArea;
-          SystemParametersInfo(SPI_GETWORKAREA, 0, (LPVOID)&rcWorkArea, 0);
-          if (rcWorkArea.right - pt.x < 150)
+  try
+  {
+    HWND hBrowserWnd = GetBrowserHWND();
+    if (!hBrowserWnd)
+    {
+      return E_FAIL;
+    }
+
+    // Create menu
+    HMENU hMenu = CreatePluginMenu(m_tab->GetDocumentUrl());
+    if (!hMenu)
+    {
+      return E_FAIL;
+    }
+
+    // Check if button in toolbar was pressed
+    int nIDCommand = -1;
+    BOOL bRightAlign = FALSE;
+
+    POINT pt;
+    GetCursorPos(&pt);
+
+    HWND hWndToolBar = ::WindowFromPoint(pt);
+
+    DWORD nProcessId;
+    ::GetWindowThreadProcessId(hWndToolBar, &nProcessId);
+
+    if (hWndToolBar && ::GetCurrentProcessId() == nProcessId)
+    {
+      ::ScreenToClient(hWndToolBar, &pt);
+      int nButton = (int)::SendMessage(hWndToolBar, TB_HITTEST, 0, (LPARAM)&pt);
+
+      if (nButton > 0)
+      {
+        TBBUTTON pTBBtn = {};
+
+        if (SendMessage(hWndToolBar, TB_GETBUTTON, nButton, (LPARAM)&pTBBtn))
+        {
+          RECT rcButton;
+          nIDCommand = pTBBtn.idCommand;
+
+          if (SendMessage(hWndToolBar, TB_GETRECT, nIDCommand, (LPARAM)&rcButton))
           {
-            bRightAlign = TRUE;
-            pt.x = rcButton.right;
+            pt.x = rcButton.left;
             pt.y = rcButton.bottom;
             ClientToScreen(hWndToolBar, &pt);
+
+            RECT rcWorkArea;
+            SystemParametersInfo(SPI_GETWORKAREA, 0, (LPVOID)&rcWorkArea, 0);
+            if (rcWorkArea.right - pt.x < 150)
+            {
+              bRightAlign = TRUE;
+              pt.x = rcButton.right;
+              pt.y = rcButton.bottom;
+              ClientToScreen(hWndToolBar, &pt);
+            }
           }
         }
       }
+      else
+      {
+        GetCursorPos(&pt);
+      }
+    }
+
+    // Display menu
+    UINT nFlags = 0;
+    if (bRightAlign)
+    {
+      nFlags |= TPM_RIGHTALIGN;
     }
     else
     {
-      GetCursorPos(&pt);
-    }
-  }
-
-  // Display menu
-  UINT nFlags = 0;
-  if (bRightAlign)
-  {
-    nFlags |= TPM_RIGHTALIGN;
-  }
-  else
-  {
-    nFlags |= TPM_LEFTALIGN;
-  }
-
-  DisplayPluginMenu(hMenu, nIDCommand, pt, nFlags);
+      nFlags |= TPM_LEFTALIGN;
+    }
+
+    DisplayPluginMenu(hMenu, nIDCommand, pt, nFlags);
+  }
+  catch (...)
+  {
+    // Suppress exception, log only
+    DEBUG_GENERAL(L"CPluginClass::Exec - exception");
+    return E_FAIL;
+  }
 
   return S_OK;
 }
 
-/////////////////////////////////////////////////////////////////////////////
-// Window procedures
-
+// Entry point
 LRESULT CALLBACK CPluginClass::NewStatusProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
-  // Find tab
-  CPluginClass *pClass = FindInstance(hWnd);
-  if (!pClass)
-  {
-    return DefWindowProc(hWnd, message, wParam, lParam);
-  }
-
-  // Process message
-  switch (message)
-  {
-  case SB_SIMPLE:
-    {
-      ShowWindow(pClass->m_hPaneWnd, !wParam);
+  CPluginClass *pClass;
+  try
+  {
+    // Find tab
+    pClass = FindInstance(hWnd);
+    if (!pClass)
+    {
+      /*
+       * Race condition if reached.
+       * We did not unhook the window procedure for the status bar when the last BHO instance using it terminated.
+       * The next best thing is to call the system default window function.
+       */
+      return DefWindowProc(hWnd, message, wParam, lParam);
+    }
+
+    // Process message
+    switch (message)
+    {
+    case SB_SIMPLE:
+      {
+        ShowWindow(pClass->m_hPaneWnd, !wParam);
+        break;
+      }
+
+    case WM_SYSCOLORCHANGE:
+      {
+        pClass->UpdateTheme();
+        break;
+      }
+
+    case SB_SETPARTS:
+      {
+        if (!lParam || !wParam || wParam > 30 || !IsWindow(pClass->m_hPaneWnd))
+        {
+          return CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
+        }
+
+        WPARAM nParts = wParam;
+        if (STATUSBAR_PANE_NUMBER >= nParts)
+        {
+          return CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
+        }
+
+        HLOCAL hLocal = LocalAlloc(LHND, sizeof(int) * (nParts + 1));
+        LPINT lpParts = (LPINT)LocalLock(hLocal);
+        memcpy(lpParts, (void*)lParam, wParam*sizeof(int));
+
+        for (unsigned i = 0; i < STATUSBAR_PANE_NUMBER; i++)
+        {
+          lpParts[i] -= pClass->m_nPaneWidth;
+        }
+        LRESULT hRet = CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, (LPARAM)lpParts);
+
+        AdblockPlus::Rectangle rcPane;
+        ::SendMessage(hWnd, SB_GETRECT, STATUSBAR_PANE_NUMBER, (LPARAM)&rcPane);
+
+        AdblockPlus::Rectangle rcClient;
+        ::GetClientRect(hWnd, &rcClient);
+
+        ::MoveWindow(
+          pClass->m_hPaneWnd,
+          lpParts[STATUSBAR_PANE_NUMBER] - pClass->m_nPaneWidth,
+          0,
+          pClass->m_nPaneWidth,
+          rcClient.Height(),
+          TRUE);
+
+        ::LocalFree(hLocal);
+        return hRet;
+      }
+
+    default:
       break;
     }
-
-  case WM_SYSCOLORCHANGE:
-    {
-      pClass->UpdateTheme();
-      break;
-    }
-
-  case SB_SETPARTS:
-    {
-      if (!lParam || !wParam || wParam > 30 || !IsWindow(pClass->m_hPaneWnd))
-      {
-        return CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
-      }
-
-      WPARAM nParts = wParam;
-      if (STATUSBAR_PANE_NUMBER >= nParts)
-      {
-        return CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
-      }
-
-      HLOCAL hLocal = LocalAlloc(LHND, sizeof(int) * (nParts+1));
-      LPINT lpParts = (LPINT)LocalLock(hLocal);
-      memcpy(lpParts, (void*)lParam, wParam*sizeof(int));
-
-      for (unsigned i = 0; i < STATUSBAR_PANE_NUMBER; i++)
-      {
-        lpParts[i] -= pClass->m_nPaneWidth;
-      }
-      LRESULT hRet = CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, (LPARAM)lpParts);
-
-      AdblockPlus::Rectangle rcPane;
-      ::SendMessage(hWnd, SB_GETRECT, STATUSBAR_PANE_NUMBER, (LPARAM)&rcPane);
-
-      AdblockPlus::Rectangle rcClient;
-      ::GetClientRect(hWnd, &rcClient);
-
-      ::MoveWindow(
-        pClass->m_hPaneWnd,
-        lpParts[STATUSBAR_PANE_NUMBER] - pClass->m_nPaneWidth,
-        0,
-        pClass->m_nPaneWidth,
-        rcClient.Height(),
-        TRUE);
-
-      ::LocalFree(hLocal);
-
-
-      return hRet;
-    }
-
-  default:
-    break;
-  }
-
-  LRESULT result = CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
-
-
-  return result;
-
+  }
+  catch (...)
+  {
+    // Suppress exception. Fall through to default handler.
+    DEBUG_GENERAL(L"CPluginClass::NewStatusProc - exception");
+  }
+  return ::CallWindowProc(pClass->m_pWndProcStatus, hWnd, message, wParam, lParam);
 }
 
 
 HICON CPluginClass::GetStatusBarIcon(const std::wstring& url)
 {
   // use the disable icon as defualt, if the client doesn't exists
   HICON hIcon = GetIcon(ICON_PLUGIN_DEACTIVATED);
 
-  CPluginTab* tab = GetTab(::GetCurrentThreadId());
+  CPluginTab* tab = GetTabForCurrentThread();
   if (tab)
   {
     CPluginClient* client = CPluginClient::GetInstance();
     if (CPluginSettings::GetInstance()->IsPluginEnabled())
     {
       if (client->IsWhitelistedUrl(url))
       {
         hIcon = GetIcon(ICON_PLUGIN_DISABLED);
       }
       else
       {
         CPluginSettings* settings = CPluginSettings::GetInstance();
         hIcon = GetIcon(ICON_PLUGIN_ENABLED);
       }
     }
   }
   return hIcon;
 }
 
-
+// Entry point
 LRESULT CALLBACK CPluginClass::PaneWindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
-  // Find tab
-  CPluginClass *pClass = FindInstance(GetParent(hWnd));
-  if (!pClass)
-  {
-    return ::DefWindowProc(hWnd, message, wParam, lParam);
-  }
-
-  // Process message
-  switch (message)
-  {
-
-  case WM_SETCURSOR:
-    {
-      ::SetCursor(::LoadCursor(NULL, IDC_ARROW));
-      return TRUE;
-    }
-  case WM_PAINT:
-    {
-      PAINTSTRUCT ps;
-      HDC hDC = ::BeginPaint(hWnd, &ps);
-
-      AdblockPlus::Rectangle rcClient;
-      ::GetClientRect(hWnd, &rcClient);
-
-      int nDrawEdge = 0;
-
-      // Old Windows background drawing
-      if (pClass->m_hTheme == NULL)
-      {
-        ::FillRect(hDC, &rcClient, (HBRUSH)(COLOR_BTNFACE + 1));
-        ::DrawEdge(hDC, &rcClient, BDR_RAISEDINNER, BF_LEFT);
-
-        nDrawEdge = 3;
-        rcClient.left += 3;
-
-        ::DrawEdge(hDC, &rcClient, BDR_SUNKENOUTER, BF_RECT);
-      }
-      // Themed background drawing
-      else
-      {
-        // Draw background
-        if (pfnDrawThemeBackground)
-        {
-          AdblockPlus::Rectangle rc = rcClient;
-          rc.right -= 2;
-          pfnDrawThemeBackground(pClass->m_hTheme, hDC, 0, 0, &rc, NULL);
-        }
-
-        // Copy separator picture to left side
-        int nHeight = rcClient.Height();
-        int nWidth = rcClient.Width() - 2;
-
-        for (int i = 0; i < 2; i++)
-        {
-          for (int j = 0; j < nHeight; j++)
+  try
+  {
+    // Find tab
+    CPluginClass *pClass = FindInstance(GetParent(hWnd));
+    if (!pClass)
+    {
+      return ::DefWindowProc(hWnd, message, wParam, lParam);
+    }
+
+    // Process message
+    switch (message)
+    {
+    case WM_SETCURSOR:
+      {
+        ::SetCursor(::LoadCursor(NULL, IDC_ARROW));
+        return TRUE;
+      }
+    case WM_PAINT:
+      {
+        PAINTSTRUCT ps;
+        HDC hDC = ::BeginPaint(hWnd, &ps);
+
+        AdblockPlus::Rectangle rcClient;
+        ::GetClientRect(hWnd, &rcClient);
+
+        int nDrawEdge = 0;
+
+        // Old Windows background drawing
+        if (pClass->m_hTheme == NULL)
+        {
+          ::FillRect(hDC, &rcClient, (HBRUSH)(COLOR_BTNFACE + 1));
+          ::DrawEdge(hDC, &rcClient, BDR_RAISEDINNER, BF_LEFT);
+
+          nDrawEdge = 3;
+          rcClient.left += 3;
+
+          ::DrawEdge(hDC, &rcClient, BDR_SUNKENOUTER, BF_RECT);
+        }
+        // Themed background drawing
+        else
+        {
+          // Draw background
+          if (pfnDrawThemeBackground)
           {
-            COLORREF clr = ::GetPixel(hDC, i + nWidth, j);
-
-            // Ignore black boxes (if source is obscured by other windows)
-            if (clr != -1 && (GetRValue(clr) > 8 || GetGValue(clr) > 8 || GetBValue(clr) > 8))
+            AdblockPlus::Rectangle rc = rcClient;
+            rc.right -= 2;
+            pfnDrawThemeBackground(pClass->m_hTheme, hDC, 0, 0, &rc, NULL);
+          }
+
+          // Copy separator picture to left side
+          int nHeight = rcClient.Height();
+          int nWidth = rcClient.Width() - 2;
+
+          for (int i = 0; i < 2; i++)
+          {
+            for (int j = 0; j < nHeight; j++)
             {
-              ::SetPixel(hDC, i, j, clr);
+              COLORREF clr = ::GetPixel(hDC, i + nWidth, j);
+
+              // Ignore black boxes (if source is obscured by other windows)
+              if (clr != -1 && (GetRValue(clr) > 8 || GetGValue(clr) > 8 || GetBValue(clr) > 8))
+              {
+                ::SetPixel(hDC, i, j, clr);
+              }
             }
           }
         }
-      }
-
-      // Draw icon
-      if (CPluginClient::GetInstance())
-      {
-        HICON hIcon = GetStatusBarIcon(pClass->GetTab()->GetDocumentUrl());
-
-        int offx = nDrawEdge;
-        if (hIcon)
-        {
-          //Get the RECT for the leftmost pane (the status text pane)
+
+        // Draw icon
+        if (CPluginClient::GetInstance())
+        {
+          HICON hIcon = GetStatusBarIcon(pClass->GetTab()->GetDocumentUrl());
+
+          int offx = nDrawEdge;
+          if (hIcon)
+          {
+            //Get the RECT for the leftmost pane (the status text pane)
+            RECT rect;
+            BOOL rectRes = ::SendMessage(pClass->m_hStatusBarWnd, SB_GETRECT, 0, (LPARAM)&rect);
+            ::DrawIconEx(hDC, 0, rect.bottom - rect.top - iconHeight, hIcon, iconWidth, iconHeight, NULL, NULL, DI_NORMAL);
+            offx += iconWidth;
+          }
+#ifdef _DEBUG
+          // Display version
+          HFONT hFont = (HFONT)::SendMessage(pClass->m_hStatusBarWnd, WM_GETFONT, 0, 0);
+          HGDIOBJ hOldFont = ::SelectObject(hDC, hFont);
+
+          AdblockPlus::Rectangle rcText = rcClient;
+          rcText.left += offx;
+          ::SetBkMode(hDC, TRANSPARENT);
+          ::DrawTextW(hDC, IEPLUGIN_VERSION, -1, &rcText, DT_WORD_ELLIPSIS | DT_LEFT | DT_SINGLELINE | DT_VCENTER);
+
+          ::SelectObject(hDC, hOldFont);
+#endif // _DEBUG
+        }
+
+        // Done!
+        EndPaint(hWnd, &ps);
+
+        return 0;
+      }
+
+    case WM_LBUTTONUP:
+    case WM_RBUTTONUP:
+      {
+        std::wstring url = pClass->GetBrowserUrl();
+        if (url != pClass->GetTab()->GetDocumentUrl())
+        {
+          pClass->GetTab()->SetDocumentUrl(url);
+        }
+
+        // Create menu
+        HMENU hMenu = pClass->CreatePluginMenu(url);
+        if (!hMenu)
+        {
+          return 0;
+        }
+
+        // Display menu
+        POINT pt;
+        ::GetCursorPos(&pt);
+
+        RECT rc;
+        ::GetWindowRect(hWnd, &rc);
+
+        if (rc.left >= 0 && rc.top >= 0)
+        {
+          pt.x = rc.left;
+          pt.y = rc.top;
+        }
+
+        pClass->DisplayPluginMenu(hMenu, -1, pt, TPM_LEFTALIGN | TPM_BOTTOMALIGN);
+        break;
+      }
+    case WM_DESTROY:
+      break;
+    case SC_CLOSE:
+      break;
+
+    case WM_UPDATEUISTATE:
+      {
+        CPluginTab* tab = GetTabForCurrentThread();
+        if (tab)
+        {
+          tab->OnActivate();
           RECT rect;
-          BOOL rectRes = ::SendMessage(pClass->m_hStatusBarWnd, SB_GETRECT, 0, (LPARAM)&rect);
-          ::DrawIconEx(hDC, 0, rect.bottom - rect.top - iconHeight, hIcon, iconWidth, iconHeight, NULL, NULL, DI_NORMAL);
-          offx += iconWidth;
-        }
-#ifdef _DEBUG
-        // Display version
-        HFONT hFont = (HFONT)::SendMessage(pClass->m_hStatusBarWnd, WM_GETFONT, 0, 0);
-        HGDIOBJ hOldFont = ::SelectObject(hDC,hFont);
-
-        AdblockPlus::Rectangle rcText = rcClient;
-        rcText.left += offx;
-        ::SetBkMode(hDC, TRANSPARENT);
-        ::DrawTextW(hDC, IEPLUGIN_VERSION, -1, &rcText, DT_WORD_ELLIPSIS|DT_LEFT|DT_SINGLELINE|DT_VCENTER);
-
-        ::SelectObject(hDC, hOldFont);
-#endif // _DEBUG
-      }
-
-      // Done!
-      EndPaint(hWnd, &ps);
-
-      return 0;
-    }
-
-  case WM_LBUTTONUP:
-  case WM_RBUTTONUP:
-    {
-      std::wstring url = pClass->GetBrowserUrl();
-      if (url != pClass->GetTab()->GetDocumentUrl())
-      {
-        pClass->GetTab()->SetDocumentUrl(url);
-      }
-
-      // Create menu
-      HMENU hMenu = pClass->CreatePluginMenu(url);
-      if (!hMenu)
-      {
-        return 0;
-      }
-
-      // Display menu
-      POINT pt;
-      ::GetCursorPos(&pt);
-
-      RECT rc;
-      ::GetWindowRect(hWnd, &rc);
-
-      if (rc.left >= 0 && rc.top >= 0)
-      {
-        pt.x = rc.left;
-        pt.y = rc.top;
-      }
-
-      pClass->DisplayPluginMenu(hMenu, -1, pt, TPM_LEFTALIGN|TPM_BOTTOMALIGN);
-    }
-    break;
-  case WM_DESTROY:
-    break;
-  case SC_CLOSE:
-    break;
-
-  case WM_UPDATEUISTATE:
-    {
-      CPluginTab* tab = GetTab(::GetCurrentThreadId());
-      if (tab)
-      {
-        tab->OnActivate();
+          GetWindowRect(pClass->m_hPaneWnd, &rect);
+          pClass->notificationMessage.MoveToCenter(rect);
+        }
+        if (LOWORD(wParam) == UIS_CLEAR)
+        {
+          pClass->notificationMessage.Hide();
+        }
+        break;
+      }
+    case WM_WINDOWPOSCHANGING:
+      {
         RECT rect;
         GetWindowRect(pClass->m_hPaneWnd, &rect);
-        pClass->notificationMessage.Move(rect.left + (rect.right - rect.left) / 2, rect.top + (rect.bottom - rect.top) / 2); 
-      }
-      if (LOWORD(wParam) == UIS_CLEAR)
-      {
-        pClass->notificationMessage.Hide();
-      }
-    }
-    break;
-  case WM_WINDOWPOSCHANGING:
-    {
-      RECT rect;
-      GetWindowRect(pClass->m_hPaneWnd, &rect);
-      if (pClass->notificationMessage.IsVisible())
-      {
-        pClass->notificationMessage.Move(rect.left + (rect.right - rect.left) / 2, rect.top + (rect.bottom - rect.top) / 2); 
-      }
-    }
-    break;
-  case WM_WINDOWPOSCHANGED:
-    {
-      WINDOWPOS* wndPos = reinterpret_cast<WINDOWPOS*>(lParam);
-      if (wndPos->flags & SWP_HIDEWINDOW)
-      {
-        pClass->notificationMessage.Hide();
-      }
-    }
-    break;
-  case WM_ALREADY_UP_TO_DATE:
-    {
-      Dictionary* dictionary = Dictionary::GetInstance();
-      std::wstring upToDateText = dictionary->Lookup("updater", "update-already-up-to-date-text");
-      std::wstring upToDateTitle = dictionary->Lookup("updater", "update-already-up-to-date-title");
-      pClass->notificationMessage.SetTextAndIcon(upToDateText, upToDateTitle, TTI_INFO);
-    }
-    break;
-  case WM_UPDATE_CHECK_ERROR:
-    {
-      Dictionary* dictionary = Dictionary::GetInstance();
-      std::wstring errorText = dictionary->Lookup("updater", "update-error-text");
-      std::wstring errorTitle = dictionary->Lookup("updater", "update-error-title");
-      pClass->notificationMessage.SetTextAndIcon(errorText, errorText, TTI_ERROR);
-    }
-    break;
-  case WM_DOWNLOADING_UPDATE:
-    {
-      Dictionary* dictionary = Dictionary::GetInstance();
-      std::wstring downloadingText = dictionary->Lookup("updater", "downloading-update-text");
-      std::wstring downloadingTitle = dictionary->Lookup("updater", "downloading-update-title");
-      pClass->notificationMessage.SetTextAndIcon(downloadingText, downloadingTitle, TTI_INFO);
-    }
-    break;
-  }
-
-  return DefWindowProc(hWnd, message, wParam, lParam);
+        if (pClass->notificationMessage.IsVisible())
+        {
+          pClass->notificationMessage.MoveToCenter(rect);
+        }
+        break;
+      }
+    case WM_WINDOWPOSCHANGED:
+      {
+        WINDOWPOS* wndPos = reinterpret_cast<WINDOWPOS*>(lParam);
+        if (wndPos->flags & SWP_HIDEWINDOW)
+        {
+          pClass->notificationMessage.Hide();
+        }
+        break;
+      }
+    case WM_ALREADY_UP_TO_DATE:
+      {
+        Dictionary* dictionary = Dictionary::GetInstance();
+        std::wstring upToDateText = dictionary->Lookup("updater", "update-already-up-to-date-text");
+        std::wstring upToDateTitle = dictionary->Lookup("updater", "update-already-up-to-date-title");
+        pClass->notificationMessage.SetTextAndIcon(upToDateText, upToDateTitle, TTI_INFO);
+        break;
+      }
+    case WM_UPDATE_CHECK_ERROR:
+      {
+        Dictionary* dictionary = Dictionary::GetInstance();
+        std::wstring errorText = dictionary->Lookup("updater", "update-error-text");
+        std::wstring errorTitle = dictionary->Lookup("updater", "update-error-title");
+        pClass->notificationMessage.SetTextAndIcon(errorText, errorTitle, TTI_ERROR);
+        break;
+      }
+    case WM_DOWNLOADING_UPDATE:
+      {
+        Dictionary* dictionary = Dictionary::GetInstance();
+        std::wstring downloadingText = dictionary->Lookup("updater", "downloading-update-text");
+        std::wstring downloadingTitle = dictionary->Lookup("updater", "downloading-update-title");
+        pClass->notificationMessage.SetTextAndIcon(downloadingText, downloadingTitle, TTI_INFO);
+        break;
+      }
+    }
+  }
+  catch (...)
+  {
+    // Suppress exception. Fall through to default handler.
+    DEBUG_GENERAL(L"CPluginClass::PaneWindowProc - exception");
+  }
+  return ::DefWindowProc(hWnd, message, wParam, lParam);
 }
 
 
 void CPluginClass::UpdateStatusBar()
 {
   DEBUG_GENERAL("*** Updating statusbar")
   if (m_hPaneWnd == NULL)
   {
     CreateStatusBarPane();
   }
@@ skipping 48 matching lines @@
   s_criticalSectionLocal.Unlock();
 
   return icon;
 }
 
 ATOM CPluginClass::GetAtomPaneClass()
 {
   return s_atomPaneClass;
 }