Tuesday, 20 June 2006

Setting display brightness: updated tool

Here is my cleaned-up brightness tool, which now uses the IOKit APIs instead of the weird O3Engine SPIs that the old version did.

Quick example: 

% ./brightness
usage: ./brightness [-m|-d display] [-v] <brightness>
   or: ./brightness -l [-v]
% ./brightness -l
display 0: main display, ID 0x4270a80
display 0: brightness 0.734375
% ./brightness -v 0.3
display 0: brightness 0.296875

-m changes the brightness of the main display; -d changes brightness of whatever display number/ID you provide. -l -v dumps display attributes—sorry for the ugly XML output, but CoreFoundation claims to be unable to output an OpenStep-format property list even though Cocoa has no problem doing the same.

* 11:07 AM | Computing, Mac OS X

7 comments on “Setting display brightness: updated tool”

  1. matt
    7 July 2006 | 11:28 PM

    hi,

    i had to move the “const CFString…” (line 9) to inside of the main function to get this to compile on os x 10.4.7, xcode 2.3 (using your 1st line comment in the terminal to compile).

    thanks,
    -matt

  2. Peter Hosey
    15 August 2006 | 4:57 AM

    When you say “Cocoa has no problem”, are you referring to -description or NSPropertyListSerialization? AFAIK, the latter simply maps to the CF functions, and will fail in the same way.

  3. Nicholas Riley
    15 August 2006 | 11:11 AM

    I’m just referring to -description. I don’t care about serialization, just making something human-readable.

  4. blog.seriot.ch » Blog Archive » Brightness
    13 November 2006 | 12:03 PM

    […] http://njr.sabi.net/2006/06/20/setting-display-brightness-updated-tool/ […]

  5. dirk schelfhout
    5 January 2007 | 4:30 AM

    I run this code on an intel imac with external 23 inch display. It doesn’t work for the external display :
    [Session started at 2007-01-05 11:26:18 +0100.]
    display 0: main display, ID 0×424a6d5
    /Users/schelfd/dev/testB/bright/build/Debug/bright: failed to get brightness of display 0×424a6d5 (error -536870201)display 1: ID 0×4271600
    display 1: brightness 0.000000

    bright has exited with status 0.

    I believe the error is : // device read locked
    I tried running as root as well and changing the main display
    I run 40.4.8

  6. Nicholas Riley
    8 January 2007 | 11:26 AM

    Yeah, I’ve had this report from someone else too. I don’t have a dual-display machine to test with unfortunately - when I first wrote it, I had access to a Power Mac G5 with two displays and it did work fine on both.

    You are using an external Apple Cinema display (aluminum bezel, DVI)?

  7. Grant
    12 October 2007 | 4:10 PM

    Confirmed that the IOKit-based methods do not work with Intel-based desktop systems with externally-attached Apple Cinema displays.

    In my specific case, IODisplayGetFloatParameter(…, CFSTR(kIODisplayBrightnessKey), …) returns ‘kIOReturnUnsupported’ on a Mac Pro with twin 20″ Apple Cinema displays whereas it works just fine on my MacBook Pro C2D.

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