[Metalab] howto control windows position and size?

Hi people, I have a midi controller and I get the events from the controller easily, using for example, puredata on linux box. What I want is to be able to open windows of applications with a concrete size and in a concrete place on the desktop. For some time I'm looking for graphic environments to do that, but I'm not so lucky. Any one know or have an idea about how can I do that? (is it clear what I ask for?) thanks jaume