How to identify the current display configuration from registry?

Question

I wanted to read the current configuration of display from registry. Suppose, a dual output system is configured with "Extended these displays" settings then i want to know where in registry this information will be stored?
I tried to get the info from 
1. HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\VIDEO which gives only the display devices being registered in the system.
2. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video which has multiple guid tags and then multiple subkeys.
3. HKEY_CURRENT_CONFIG\System\CurrentControlSet\Control\VIDEO which has multiple subkeys.
Unable to get the right registry for this case. when multiple displays connected, then i want to know whether it is configured as extended/duplicate. 
Please guide me if it is possible.

Answer 1

There is no direct way for getting the monitor count. we need to code for each graphic card separately. 
i found a way like below, for those of you interested in getting the exact monitor count:
int ComputerInfo::GetRegistryValue( CSString regPath, CSString valueName, int cntIndex )
int monCount = 0;
BYTE pBuffer[1024];
DWORD nMaxLength;
CSString szSubKey = regPath;
szSubKey = szSubKey.substr(18);
CSString szValueName = valueName;
DWORD rc;
DWORD dwType;
HKEY hOpenedKey;
LOG_INFO ( "Registry key " << szSubKey << "\\" << szValueName );
if( ERROR_SUCCESS == RegOpenKeyEx (
HKEY_LOCAL_MACHINE, // handle of open key
szSubKey, // address of name of subkey to open
0, // reserved
KEY_READ, // security access mask
&hOpenedKey // address of handle of open key
rc = RegQueryValueEx(
hOpenedKey,
(const char*)szValueName,
0,
&dwType,
(LPBYTE)pBuffer,
&nMaxLength );
if( rc != ERROR_SUCCESS )
LOG_INFO ( "Registry key " << valueName << " not found." );
monCount = 0;
else
LOG_INFO ( "Monitor Count: " << CSString(pBuffer[cntIndex]) );
monCount = pBuffer[cntIndex];
RegCloseKey( hOpenedKey );
else
monCount = 0;
return monCount;
int ComputerInfo::GetMonitorCount()
int fResult;
fResult = GetSystemMetrics(SM_CMONITORS);
LOG_INFO( "Video Output Count from System: " << fResult );
if ( fResult == 1 )
// I need to get the address of a few multi-monitor functions
HMODULE user32 = GetModuleHandle ("User32.DLL");
typedef BOOL WINAPI tEnumDisplayDevices (void*, DWORD, DISPLAY_DEVICE*, DWORD);
tEnumDisplayDevices* fEnumDisplayDevices = (tEnumDisplayDevices*) GetProcAddress (user32, "EnumDisplayDevicesA");
if (fEnumDisplayDevices == NULL) return false;
// count the number of monitors attached to the system
DISPLAY_DEVICE dd; dd.cb = sizeof(dd);
for (DWORD dev=0; fEnumDisplayDevices (NULL, dev, &dd, 0); ++dev)
LOG_INFO ("Device: " << dd.cb << ", " << dd.DeviceID << ", " << dd.DeviceKey << ", " << dd.DeviceName << ", " << dd.DeviceString << ", " << dd.StateFlags );
CSString devName = dd.DeviceName;
DISPLAY_DEVICE dd1; dd1.cb = sizeof(dd1);
// after second call DispDev.DeviceString contains monitor's name
EnumDisplayDevices(devName, 0, &dd1, 0);
LOG_INFO ("Device: " << dd1.cb << ", " << dd1.DeviceID << ", " << dd1.DeviceKey << ", " << dd1.DeviceName << ", " << dd1.DeviceString << ", " << dd1.StateFlags );
if (dd.StateFlags & DISPLAY_DEVICE_MIRRORING_DRIVER)
LOG_INFO ("Device: " << dd.DeviceName << " is a mirroring driver device. " );
continue;
if (dd.StateFlags & DISPLAY_DEVICE_ATTACHED_TO_DESKTOP)
LOG_INFO ("Device: " << dd.DeviceName << " is attached to the desktop. " );
if ( StringUtils::StartsWith( dd.DeviceString, "Matrox", false ) )
return GetRegistryValue(dd.DeviceKey, "ContextItem.Config", 40);
else if ( StringUtils::StartsWith( dd.DeviceString, "NVIDIA", false ) )
if ( !StringUtils::StartsWith( dd.DeviceString, "NVIDIA ION", false ) )
return GetRegistryValue(dd.DeviceKey, "NV_TargetData", 0);
else
return GetSystemMetrics(SM_CMONITORS);
else if ( StringUtils::StartsWith( dd.DeviceString, "Intel", false ) )
return GetRegistryValue(dd.DeviceKey, "CurrentState", 0);
else
return GetSystemMetrics(SM_CMONITORS);
else
LOG_INFO ("Device: " << dd.DeviceName << " is not attached. " );
LOG_INFO ( "No Devices found." );
return 0;
else
LOG_INFO( "Considered Video Output Count from System. " << fResult );
return fResult;