GetMonitorCapabilities returns false - qt

Question

I want to adjust the brightness of my monitor on Windows.
I follow this page:
How to use GetMonitorCapabilities and GetMonitorBrightness functions
but, the GetMonitorCapabilities function returns false.
I printed using qDebug, hPhysicalMonitor is NULL. Is this point wrong?
(The GetPhysicalMonitorsFromHMONITOR function returns true)
How can I fix this code?
HMONITOR hMonitor = NULL;
DWORD cPhysicalMonitors = 1;
LPPHYSICAL_MONITOR pPhysicalMonitors;
HWND hWnd = GetDesktopWindow();
// Get the monitor handle.
hMonitor = MonitorFromWindow(hWnd, MONITOR_DEFAULTTOPRIMARY);
// Get the number of physical monitors.
BOOL bSuccess = GetNumberOfPhysicalMonitorsFromHMONITOR(hMonitor, &cPhysicalMonitors);
if (bSuccess)
{
// Allocate the array of PHYSICAL_MONITOR structures.
pPhysicalMonitors = (LPPHYSICAL_MONITOR)malloc(cPhysicalMonitors* sizeof(PHYSICAL_MONITOR));
if (pPhysicalMonitors != NULL)
{
// Get the array.
bSuccess = GetPhysicalMonitorsFromHMONITOR( hMonitor, cPhysicalMonitors, pPhysicalMonitors);
if (bSuccess == FALSE)
{
qDebug("GetPhysicalMonitorsFromHMONITOR");
}
// Get physical monitor handle.
HANDLE hPhysicalMonitor = pPhysicalMonitors[0].hPhysicalMonitor;
DWORD pdwMonitorCapabilities = 0;
DWORD pdwSupportedColorTemperatures = 0;
bSuccess = GetMonitorCapabilities(hPhysicalMonitor, &pdwMonitorCapabilities, &pdwSupportedColorTemperatures);
if (bSuccess == FALSE)
{
qDebug("GetMonitorCapabilities");
}
DWORD pdwMinimumBrightness = 0;
DWORD pdwCurrentBrightness = 0;
DWORD pdwMaximumBrightness = 0;
bSuccess = GetMonitorBrightness(hPhysicalMonitor, &pdwMinimumBrightness, &pdwCurrentBrightness, &pdwMaximumBrightness);
if (bSuccess == FALSE)
{
qDebug("GetMonitorBrightness");
}
qDebug(QByteArray::number(bSuccess));
qDebug(QByteArray::number((WORD)pdwMinimumBrightness));
qDebug(QByteArray::number((WORD)pdwCurrentBrightness));
qDebug(QByteArray::number((WORD)pdwMaximumBrightness));
// Close the monitor handles.
bSuccess = DestroyPhysicalMonitors(cPhysicalMonitors, pPhysicalMonitors);
// Free the array.
free(pPhysicalMonitors);
}
}

Answer 1

If you want to adjust the brightness using WmiMonitorBrightnessMethods use the code below.
public static void SetWmiMonitorBrightness(byte targetBrightness)
{
ManagementScope scope = new ManagementScope("root\\WMI");
SelectQuery query = new SelectQuery("WmiMonitorBrightnessMethods");
using (ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, query))
{
using (ManagementObjectCollection objectCollection = searcher.Get())
{
foreach (ManagementObject mObj in objectCollection)
{
mObj.InvokeMethod("WmiSetBrightness",
new Object[] { UInt32.MaxValue, targetBrightness });
break;
}
}
}
}
Doing GetMonitorBrightness on the specific monitor I have causes ERROR_GRAPHICS_I2C_ERROR_TRANSMITTING_DATA.
So I used WmiSetBrightness instead. It works fine.
If you got a tip related to ERROR_GRAPHICS_I2C_ERROR_TRANSMITTING_DATA, please share it with me.