使用 C++ WinAPI 在 Windows 10 上设置亮度

问题描述

我正在尝试在 Windows 10 机器上设置亮度.显示器似乎不支持 setMonitorBrightness，并且 setDeviceGammaRamp 会改变伽玛、白点等，所以我尽量不使用它.

I am trying to set the brightness on a Windows 10 machine. The display doesn't seem to support setMonitorBrightness, and setDeviceGammaRamp alters the gamma, white point etc, so I would try not to use it.

我正在尝试使用 IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS 控件使其工作.当我使用 CreateFile() 获取监视器句柄时，我会检查句柄是否无效并且没有问题.但是当我使用 IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS 调用 DeviceIoControl() 时，我得到 ERROR_INVALID_HANDLE(错误 6).

I am trying to get this to work using IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS control. When I get the monitor handle using CreateFile(), I check if the handle is invalid and it is fine. But I get ERROR_INVALID_HANDLE (error 6) when I call 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() 来获取监视器句柄，还是我可以调用 MonitorFromWindow(nullptr, MONITOR_DEFAULTTOPRIMARY) 代替?

Also, should I be using CreateFile() to get the monitor handle, or can I call MonitorFromWindow(nullptr, MONITOR_DEFAULTTOPRIMARY) instead?

推荐答案

在通话中

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

&olp 指向一个未初始化的 OVERLAPPED 结构.这个结构有一个事件对象(hEvent)的句柄，它保存一个随机值.这是 DeviceIoControl 调用抱怨的无效句柄.

&olp points to an uninitialized OVERLAPPED structure. This structure has a handle to an event object (hEvent), that holds a random value. This is the invalid handle the DeviceIoControl call complains about.

由于您没有使用 FILE_FLAG_OVERLAPPED 标志调用 CreateFile(无论如何这对于显示设备来说确实没有意义)，您不需要传递OVERLAPPED 结构.只需传入NULL，调用就会成功:

Since you aren't calling CreateFile with a FILE_FLAG_OVERLAPPED flag (which really wouldn't make sense for a display device anyway) you don't need to pass an OVERLAPPED structure at all. Simply pass NULL, and the call will succeed:

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

这篇关于使用 C++ WinAPI 在 Windows 10 上设置亮度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！