使用 C++ WinAPI 在 Windows 10 上设置亮度

我正在尝试在 Windows 10 计算机上设置亮度。显示器好像不支持setMonitorBrightness, and setDeviceGammaRamp改变伽玛、白点等，所以我尽量不使用它。

我正在尝试使用它来使其工作IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS控制。当我使用监视器句柄时CreateFile()，我检查句柄是否无效，没有问题。但我得到ERROR_INVALID_HANDLE（错误6）当我打电话时DeviceIoControl() with IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS.

typedef struct _DISPLAY_BRIGHTNESS {  
   UCHAR ucDisplayPolicy;  
   UCHAR ucACBrightness;  
   UCHAR ucDCBrightness;  
} DISPLAY_BRIGHTNESS, *PDISPLAY_BRIGHTNESS; 

DISPLAY_BRIGHTNESS _displayBrightness;

_displayBrightness.ucDisplayPolicy = 0;
_displayBrightness.ucACBrightness = 0;  //for testing purposes
_displayBrightness.ucDCBrightness = 0;

DWORD ret = NULL;
OVERLAPPED olp;

DWORD nOutBufferSize = sizeof(_displayBrightness);
HANDLE h = CreateFile(L"\\\\.\\LCD",
    GENERIC_READ | GENERIC_WRITE,
    0,
    NULL,
    OPEN_EXISTING,
    0, NULL);

if (h == INVALID_HANDLE_VALUE) {
    //Does not reach here
    return false;
}  

if (!DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, (DISPLAY_BRIGHTNESS *)&_displayBrightness, nOutBufferSize, NULL, 0, &ret, &olp))
{
    // GetLastError() returns error code 6 - Invalid handle 
    return false;
} 

另外，我应该使用CreateFile()获取监视器句柄，或者我可以调用MonitorFromWindow(nullptr, MONITOR_DEFAULTTOPRIMARY)反而？

在通话中

DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS,
                (DISPLAY_BRIGHTNESS*)&_displayBrightness, nOutBufferSize, NULL, 0, &ret,
                &olp)

&olp指向未初始化的重叠 https://msdn.microsoft.com/en-us/library/windows/desktop/ms684342.aspx结构。该结构有一个事件对象的句柄（hEvent），它保存一个随机值。这是无效句柄DeviceIoControl打电话投诉。

既然你没有打电话CreateFile with a FILE_FLAG_OVERLAPPED标志（无论如何这对于显示设备来说确实没有意义）你不需要传递OVERLAPPED结构完全。简单地通过NULL，调用将会成功：

DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS,
                (DISPLAY_BRIGHTNESS*)&_displayBrightness, nOutBufferSize, NULL, 0, &ret,
                NULL)