Double application launch prevention lock added

(fixes #24)

ZRCola/zrcolaapp.cpp

@@ -32,6 +32,9 @@ wxIMPLEMENT_APP(ZRColaApp);
 
 ZRColaApp::ZRColaApp() :
     m_mainWnd(NULL),
+#ifdef __WXMSW__
+    m_running(NULL),
+#endif
     wxApp()
 {
 }
@@ -66,6 +69,25 @@ bool ZRColaApp::OnInit()
         wxVERIFY(m_locale.AddCatalog(wxT("ZRCola-zrcdb")));
     }
 
+#ifdef __WXMSW__
+    // Create global event.
+    m_running = ::CreateEvent(NULL, FALSE, FALSE, _T(ZRCOLA_CFG_APPLICATION) _T("{BBDE7AAD-29B6-4B83-ADA1-92AFA81A0883}"));
+    wxASSERT(m_running);
+    if (::GetLastError() == ERROR_ALREADY_EXISTS) {
+        // ZRCola is already running. Find its window.
+        HWND okno = ::FindWindow(_T("wxWindowNR"), _("ZRCola"));
+        if (okno) {
+            if (::IsIconic(okno))
+                ::SendMessage(okno, WM_SYSCOMMAND, SC_RESTORE, 0);
+            ::SetActiveWindow(okno);
+            ::SetForegroundWindow(okno);
+
+            // Not an error condition actually; Just nothing else to do...
+            return false;
+        }
+    }
+#endif
+
     std::fstream dat((LPCTSTR)GetDatabasePath(), std::ios_base::in | std::ios_base::binary);
     if (dat.good()) {
         if (stdex::idrec::find<ZRCola::recordid_t, ZRCola::recordsize_t, ZRCOLA_RECORD_ALIGN>(dat, ZRCOLA_DB_ID, sizeof(ZRCola::recordid_t))) {
@@ -145,3 +167,18 @@ bool ZRColaApp::OnInit()
 
     return true;
 }
+
+
+int ZRColaApp::OnExit()
+{
+    int res = wxApp::OnExit();
+
+#ifdef __WXMSW__
+    if (m_running) {
+        wxVERIFY(::CloseHandle(m_running));
+        m_running = NULL;
+    }
+#endif
+
+    return res;
+}

ZRCola/zrcolaapp.h

@@ -52,6 +52,12 @@ public:
     ///
     virtual bool OnInit();
 
+    ///
+    /// Called when application uninitializes.
+    ///
+    /// \returns Result code to return to OS
+    ///
+    virtual int OnExit();
 
     ///
     /// \returns Path to ZRCola.zrcdb file
@@ -70,6 +76,9 @@ public:
 
 protected:
     wxLocale m_locale;              ///< Current locale
+#ifdef __WXMSW__
+    HANDLE m_running;               ///< Global Win32 event to determine if another instance of ZRCola is already running
+#endif
 };