IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS control code

Sets the current AC and DC backlight levels.

To perform this operation, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,            // handle to device
  IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, // dwIoControlCode
  (LPVOID) lpInBuffer,         // input buffer
  (DWORD) nInBufferSize,       // size of the input buffer
  NULL,                        // lpOutBuffer
  0,                           // nOutBufferSize 
  (LPDWORD) lpBytesReturned,   // number of bytes returned
  (LPOVERLAPPED) lpOverlapped  // OVERLAPPED structure
);

Parameters

hDevice

A handle to the \\.\LCD device. To retrieve a device handle, call the CreateFile function.

dwIoControlCode

The control code for the operation. This value identifies the specific operation to be performed and the type of device on which to perform it. Use IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS for this operation.

lpInBuffer

A pointer to a DISPLAY_BRIGHTNESS structure.

nInBufferSize

The size of the buffer pointed to by lpOutBuffer, in bytes.

lpOutBuffer

Not used with this operation; set to NULL.

nOutBufferSize

Not used with this operation; set to zero.

lpBytesReturned

A pointer to a variable that receives the actual count of bytes returned by the function in the output buffer.

If lpOverlapped is NULL (nonoverlapped I/O), lpBytesReturned is used internally and cannot be NULL.

If lpOverlapped is not NULL (overlapped I/O), lpBytesReturned can be NULL.

lpOverlapped

A pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, lpOverlapped must point to a valid OVERLAPPED structure. In this case, the operation is performed as an overlapped (asynchronous) operation. If the device was opened with the FILE_FLAG_OVERLAPPED flag and lpOverlapped is NULL, the function fails in unpredictable ways.

If hDevice was opened without specifying the FILE_FLAG_OVERLAPPED flag, lpOverlapped is ignored and DeviceIoControl does not return until the operation has been completed, or until an error occurs.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value.

If the operation fails or is pending, DeviceIoControl returns zero. To get extended error information, call GetLastError.

Remarks

The values specified in the ucACBrightness and ucDCBrightness members of the DISPLAY_BRIGHTNESS structure must have been previously returned by IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS. For example, if the supported values are 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100, then using a value of 33 would be an error.

The header file used to build applications that include this functionality, Ntddvdeo.h, is included in the Microsoft Windows Driver Development Kit (DDK). For information on obtaining the DDK, see https://www.microsoft.com/whdc/devtools/ddk/default.mspx.

Alternatively, you can define this control code as follows:

#define IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS \
  CTL_CODE(FILE_DEVICE_VIDEO, 0x127, METHOD_BUFFERED, FILE_ANY_ACCESS)

Requirements

See also

Backlight Control Interface

DeviceIoControl

DISPLAY_BRIGHTNESS

IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS

IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS