I switched a few weeks ago from unstable ("Sid") to testing ("Stretch") in the hope that my system, particularly X, would break less often. The very next day, I updated and discovered I couldn't use my system at night any more, because the program I use to reduce the screen brightness by tweaking X gamma no longer worked. Neither did other related programs, such as xgamma and xcalib.
The Dell monitor I use doesn't have reasonable hardware brightness controls: strangely, the brightness button works when the monitor is connected over VGA, but if I want to use the sharper HDMI connection, brightness adjustment no longer works. So I depend on software brightness adjustment in order to use my computer at night when the room is dim.
Fortunately, it turns out there's a workaround.
has options for both brightness and gamma:
xrandr --output HDMI1 --brightness .5 xrandr --output HDMI1 --gamma .5:.5:.5
I've always put xbrightness on a key, so I can use a function key to adjust brightness interactively up and down according to conditions. So a command that sets brightness to .5 or .8 isn't what I need; I need to get the current brightness and set it a little brighter or a little dimmer. xrandr doesn't offer that, so I needed to script it.
You can get the current brightness with
xrandr --verbose | grep -i brightness
But I was hoping there would be a more straightforward way to get
brightness from a program.
I looked into Python bindings for xrandr; there are some,
but with no documentation and no examples. After an hour
of fiddling around, I concluded that I could waste the rest of the day
poring through the source code and trying things hoping something would
work; or I could spend fifteen minutes
subprocess.call() to wrap the command-line xrandr.
So subprocesses it was. It made for a nice short script,
much simpler than the old xbrightness C program that used
[ 11:01 Mar 17, 2016 More linux | permalink to this entry | comments ]