Qt/Caca Lighthouse Plugin


At the Qt Contributors Summit, Johannes‘ showed me his Qt/Caca Lighthouse plugin. Caca is a graphics library to output text instead of pixels. So this plugin lets you run Qt programs on the console :-)

His code needed some love, so I forked it and cleaned it up. Caca does not provide a event fd and so we have to keep polling caca for events. Since this wasn’t ideal, I moved the event handling to a separate thread and blocked for events. Unfortunately, I found that the caca library is not thread-safe and rendering and processing events in separate threads makes caca crash at randomly. So, I ended up moving the rendering to the event processing thread and having to resurrect the 20ms event timer again :-( The cool thing though is that now Qt renders to QImage in the main ui thread and hands it off to caca. Caca opens a X connection (or similar), converts the image into text, displays a window and handles events in another thread. With some refactoring and thanks to QMetaObject::invokeMethod, the threaded and non-threaded rendering are pretty much the same and can be switched using an environment variable (THREADED_CACA=1).

Animated tiles:


If you want to hack further, code is on gitorious. (Caca doesn’t seem to deliver gpm events with ncurses, so that would be a nice fix to have)

Update: Welcome slashdot readers