También tuve problemas similares en Windows 7 y probar diferentes enfoques, pero no pudo encontrar la respuesta correcta hasta que encontré esto: http://ofekshilon.com/2011/11/13/reading-monitor-physical-dimensions-or-getting-the-edid-the-right-way/
Funciona para mí para diferentes tamaños de pantalla!
#include <atlstr.h>
#include <SetupApi.h>
#pragma comment(lib, "setupapi.lib")
#define NAME_SIZE 128
const GUID GUID_CLASS_MONITOR = {0x4d36e96e, 0xe325, 0x11ce, 0xbf, 0xc1, 0x08, 0x00, 0x2b, 0xe1, 0x03, 0x18};
// Assumes hDevRegKey is valid
bool GetMonitorSizeFromEDID(const HKEY hDevRegKey, short& WidthMm, short& HeightMm)
{
DWORD dwType, AcutalValueNameLength = NAME_SIZE;
TCHAR valueName[NAME_SIZE];
BYTE EDIDdata[1024];
DWORD edidsize=sizeof(EDIDdata);
for (LONG i = 0, retValue = ERROR_SUCCESS; retValue != ERROR_NO_MORE_ITEMS; ++i)
{
retValue = RegEnumValue (hDevRegKey, i, &valueName[0],
&AcutalValueNameLength, NULL, &dwType,
EDIDdata, // buffer
&edidsize); // buffer size
if (retValue != ERROR_SUCCESS || 0 != _tcscmp(valueName,_T("EDID")))
continue;
WidthMm = ((EDIDdata[68] & 0xF0) << 4) + EDIDdata[66];
HeightMm = ((EDIDdata[68] & 0x0F) << 8) + EDIDdata[67];
return true; // valid EDID found
}
return false; // EDID not found
}
bool GetSizeForDevID(const CString& TargetDevID, short& WidthMm, short& HeightMm)
{
HDEVINFO devInfo = SetupDiGetClassDevsEx(
&GUID_CLASS_MONITOR, //class GUID
NULL, //enumerator
NULL, //HWND
DIGCF_PRESENT, // Flags //DIGCF_ALLCLASSES|
NULL, // device info, create a new one.
NULL, // machine name, local machine
NULL);// reserved
if (NULL == devInfo)
return false;
bool bRes = false;
for (ULONG i=0; ERROR_NO_MORE_ITEMS != GetLastError(); ++i)
{
SP_DEVINFO_DATA devInfoData;
memset(&devInfoData,0,sizeof(devInfoData));
devInfoData.cbSize = sizeof(devInfoData);
if (SetupDiEnumDeviceInfo(devInfo,i,&devInfoData))
{
HKEY hDevRegKey = SetupDiOpenDevRegKey(devInfo,&devInfoData,
DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_READ);
if(!hDevRegKey || (hDevRegKey == INVALID_HANDLE_VALUE))
continue;
bRes = GetMonitorSizeFromEDID(hDevRegKey, WidthMm, HeightMm);
RegCloseKey(hDevRegKey);
}
}
SetupDiDestroyDeviceInfoList(devInfo);
return bRes;
}
int _tmain(int argc, _TCHAR* argv[])
{
short WidthMm, HeightMm;
DISPLAY_DEVICE dd;
dd.cb = sizeof(dd);
DWORD dev = 0; // device index
int id = 1; // monitor number, as used by Display Properties > Settings
CString DeviceID;
bool bFoundDevice = false;
while (EnumDisplayDevices(0, dev, &dd, 0) && !bFoundDevice)
{
DISPLAY_DEVICE ddMon;
ZeroMemory(&ddMon, sizeof(ddMon));
ddMon.cb = sizeof(ddMon);
DWORD devMon = 0;
while (EnumDisplayDevices(dd.DeviceName, devMon, &ddMon, 0) && !bFoundDevice)
{
if (ddMon.StateFlags & DISPLAY_DEVICE_ACTIVE &&
!(ddMon.StateFlags & DISPLAY_DEVICE_MIRRORING_DRIVER))
{
DeviceID.Format (L"%s", ddMon.DeviceID);
DeviceID = DeviceID.Mid (8, DeviceID.Find (L"\\", 9) - 8);
bFoundDevice = GetSizeForDevID(DeviceID, WidthMm, HeightMm);
}
devMon++;
ZeroMemory(&ddMon, sizeof(ddMon));
ddMon.cb = sizeof(ddMon);
}
ZeroMemory(&dd, sizeof(dd));
dd.cb = sizeof(dd);
dev++;
}
return 0;
}
25/72 = 0.347222. No tengo idea de dónde sacaste 25. –