Reorganising my projects home, I copied in the old documentation for my hbeat program. The docs needed some updating, so I decided to check it all still works ok. Fearing bitrot, I was pleased and a little suprised to see that on my recently rebuilt ubuntu machine, all I needed was

sudo apt-get install libsdl1.2-dev
sudo apt-get install libsdl-mixer1.2-dev
cabal-dev install hbeat

Or at least that's what I first thought. The program fired up ok, but failed to respond to mouse clicks as expected. It turns out that this was a pre-existing bug - if the screen redraws don't happen fast enough, hbeat gets further and further behind in it's event processing eventually ignoring everything. A small code fix (now published to hackage) causes out-of-date redraw requests to be dropped. But why was I seeing this problem now? It seems that since I wrote the software, openGL via SDL seems to have got alot slower. The compositing window manager (compiz) seems to be the culprit - it's consuming significant cpu time whilst hbeat is running. Some references to this can be found here. I guess there's a downside to all those fancy compositing effects. It's a shame hbeat is now a fair bit glitchier than it was before. Maybe sometime I'll look at this, but for now at least it still works.