fix everything

windows-snapshot-tool/src/LimitSingleInstance.h

@@ -0,0 +1,38 @@
+#ifndef LimitSingleInstance_H
+#define LimitSingleInstance_H
+
+#include <windows.h> 
+
+//This code is from Q243953 in case you lose the article and wonder
+//where this code came from.
+class CLimitSingleInstance
+{
+protected:
+  DWORD  m_dwLastError;
+  HANDLE m_hMutex;
+
+public:
+  CLimitSingleInstance(TCHAR *strMutexName)
+  {
+    //Make sure that you use a name that is unique for this application otherwise
+    //two apps may think they are the same if they are using same name for
+    //3rd parm to CreateMutex
+    m_hMutex = CreateMutex(NULL, FALSE, strMutexName); //do early
+    m_dwLastError = GetLastError(); //save for use later...
+  }
+   
+  ~CLimitSingleInstance() 
+  {
+    if (m_hMutex)  //Do not forget to close handles.
+    {
+       CloseHandle(m_hMutex); //Do as late as possible.
+       m_hMutex = NULL; //Good habit to be in.
+    }
+  }
+
+  BOOL IsAnotherInstanceRunning() 
+  {
+    return (ERROR_ALREADY_EXISTS == m_dwLastError);
+  }
+};
+#endif

windows-snapshot-tool/src/main.cpp

@@ -1,4 +1,8 @@
 #include "resource.h"
+#include "LimitSingleInstance.h"
+
+
+CLimitSingleInstance g_SingleInstanceObj(TEXT("Global\\{38593226-AABB-1234-7592-D335AAB6F22A}"));
 
 /*variables*/
 UINT WM_TASKBAR = 0;
@@ -26,6 +30,13 @@ int WINAPI WinMain (HINSTANCE hThisInstance,
                     LPSTR lpszArgument,
                     int nCmdShow)
 {
+    if (g_SingleInstanceObj.IsAnotherInstanceRunning())
+    {
+        HWND existingApp = FindWindow(0, szClassName);
+        SendMessage(existingApp, WM_DESTROY, 0, 0);
+        //return FALSE;
+    }
+
     /* This is the handle for our window */
     MSG messages;            /* Here messages to the application are saved */
     WNDCLASSEX wincl;        /* Data structure for the windowclass */
@@ -181,6 +192,7 @@ LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM
     break;
 
     case WM_HOTKEY_FREEZE:
+    case WM_HOTKEY:
     {
         doScreenshot();
     }