Backlight Change Notification?
Is there a decent (non-polling) way to get notified when a laptop panel’s backlight brightness changes? HAL exports methods to set and get the brightness level, as well as query the number of possible levels, but there doesn’t appear to be a way to get notified if the level changes. Calling org.freedesktop.Hal.LaptopPanel.GetBrightness() every five or ten seconds or so sounds like an awful idea, of course.
I’ve heard plans to use the XBACKLIGHT randr 1.2 property to do backlight setting, but I don’t think any drivers use this yet. Polling /sys is just as bad (why doesn’t sysfs or procfs support inotify, dammit!), and obviously isn’t portable anyway (not that HAL is particularly portable these days either).
Xfce Mailwach Plugin 1.1.0 Released
After a good two and a half years of being lazy, I’ve finally found some time to work on the Mailwatch plugin, and I have a new release ready too!
There’s lots of chewy goodness in this release. Here are some useful links:
As always, please report bugs over at the Xfce bug tracker.
Enjoy!
Signals
I meant to write about this a while ago, but I forgot, and it just popped into my head for some reason.
If you’re ever using POSIX signals as a means of primitive IPC, and SIGUSR1 and SIGUSR2 aren’t enough for you, never, ever, EVER make use of SIGRTMIN and/or SIGRTMIN plus some offset. Always use SIGRTMAX and SIGRTMAX minus some offset.
Why?
(Disclaimer: this might only be a problem on Linux, but if you want your app to be portable, blah blah blah…) Depending on what C library you’re using, and what pthreads implementation you’re using, the actual numerical value of SIGRTMIN may not be the same in different applications, depending on – get this – whether or not the app links with libpthread. In my case, the pthread impl makes use of the first 3 SIGRT slots, and so when you use the SIGRTMIN macro, you actually call __libc_current_sigrtmin(), and you get a number that’s 3 higher than what you get when you use SIGRTMIN in an app that doesn’t link against libpthread.
Fortunately, SIGRTMAX (which actually expands to a call to __libc_current_sigrtmax()) seems to be a bit more stable. That is, even if SIGRTMIN gets shifted up 3 slots, SIGRTMAX is still the same.
So, the moral of the story is: I never want to see the SIGRTMIN macro ever appear in your code, unless you really know what you’re doing. Instead, use things like SIGRTMAX, SIGRTMAX-4, etc. It may just save you 4 hours of debugging.