26 replies to this topic

[dvda2k]

In Vista and Win 7, you can press Win + X to use Windows Mobility Center to adjust your LCD backlight. Windows Mobility Center talks to your graphics driver.

I searched MSDN and found some articles talking about "Backlight Control Interface". But I just don't know how to implement this code into Autohotkey.

Can anyone help? The MSDN link is here:
<!-- m -->http://msdn.microsof.../aa372656(VS.85<!-- m -->).aspx

[dvda2k]

BoBo³, thanks for your reply. Fortunately the MSDN website has some error-proof feature, the broken URL still gets you to the right place.

Do you have any comment on my question itself?

[..:: Free Radical ::..]

I humbly second that request for IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS

[..:: Free Radical ::..]

hLCD = CreateFile( "\\.\LCD" , #GENERIC_READ | #GENERIC_WRITE , #FILE_SHARE_READ | #FILE_SHARE_WRITE , #Null , #OPEN_EXISTING , #Null , #Null )

DeviceIoControl( hLCD , #IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS , #Null , #Null , MDB  , SizeOf ( MDB  ) , @ lReturnedBytes , #Null )

DeviceIoControl( hLCD , #IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS , SDB , SizeOf ( tDisplayBrightness ) , #Null , #Null , @ returnedBytes , #Null)

Can someone help me write the appropriate dllcall?

hLCD := DllCall("CreateFile", "str", "\\.\LCD", "Uint", 0, "Uint", 3, "Uint", 0, "Uint", 3, "Uint", 0, "Uint", 0)
SUPPORTED_BRIGHTNESS := DllCall("DeviceIoControl", "Uint", hLCD, "Uint", 0x125, "Uint", 0, "Uint", 0, "str", 0, "str", 256, "Uint", 0, "Uint", 0)

[temp01]

Does this work (I don't have an LCD monitor to test)? If not, what does the msgbox show?

hLCD := DllCall("CreateFile"
	, Str, "\\.\LCD"
	, UInt, 0x80000000 | 0x40000000  ; GENERIC_READ | GENERIC_WRITE
	, UInt, 0x1 | 0x2  ; FILE_SHARE_READ | FILE_SHARE_WRITE
	, UInt, 0
	, UInt, 0x3  ; OPEN_EXISTING
	, UInt, 0, UInt, 0)
if hLCD <> -1
{
	FILE_DEVICE_VIDEO := 0x00000023, METHOD_BUFFERED := 0, FILE_ANY_ACCESS := 0
	VarSetCapacity(DISPLAY_BRIGHTNESS, 3, 0)
		NumPut(0x03, DISPLAY_BRIGHTNESS, 0, "UChar")	; 0x01 = Set AC, 0x02 = Set DC, 0x03 = Set both
		NumPut(50, DISPLAY_BRIGHTNESS, 1, "UChar")		; The AC brightness level
		NumPut(50, DISPLAY_BRIGHTNESS, 2, "UChar")		; The DC brightness level
	Msgbox % ""
	. DllCall("DeviceIoControl"
		, UInt, hLCD
		, UInt, (FILE_DEVICE_VIDEO<<16 | 0x127<<2 | METHOD_BUFFERED<<14 | FILE_ANY_ACCESS) ; IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS
		, UInt, &DISPLAY_BRIGHTNESS, UInt, 3
		, UInt, 0, UInt, 0
		, UIntP, dwBytesReturned  ; Unused.
		, UInt, 0) "`nErrorLevel:`t`t" ErrorLevel "`nLastError:`t`t" A_LastError
	DllCall("CloseHandle", UInt, hLCD)
}

(based on this code (remarks))

[..:: Free Radical ::..]

Doesn't work
I am on a desktop LCD (AC power). Don't have a laptop.

Msgbox Output:

1
Errorlevel :  0
Last Error:  0

[temp01]

Try the code again (fixed NumPut offsets).

[..:: Free Radical ::..]

Same output and no effect. Perhaps my LCD doesn't support backlight control.

Can anyone else test this too?

[pajenn]

1
Errorlevel : 0
Last Error: 0

Same here. I can adjust my laptop LCD brightness with fn+f9/f10, but AHK cannot detect the 'fn' key (no sc/vk code) so I cannot remap it -- I'd prefer to use the mouse scroll wheel...

[temp01]

I think what you want is SetMonitorBrightness not IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS

[8]

Any ideas how to call DxgkDdiSetBrightness from AutoHotkey? (more info here)
IOCTL is deprecated in Vista/7 and mostly doesn't work anyway, but this method should be the same which is used in the mobility center.
Thanks.

[rcll]

Sorry to post in this old thread but I'm also looking for this solution.

The Fn keys on my laptop are signaled at BIOS level or something and seem impossible to remap using the HID DLL method to identify the keys.

Windows Mobility Center has a GUI brightness slider that corresponds to the same function, brightness up/brightness down. Can this be mapped to a hotkey?