I need quad4 elements otherwise the specific FEM is not working. Therefore I need a full quad mesh. My hope was - as it is for simple 2 D geometries - that someone has coded something in opencascade before. If not, then I have to code it myself or - depending on my time - look for another possibilities. I focus on fast FEM calculations and did not expect this troubles finding a 2D quad mesh generation code, but obviously it is not something very frequently needed.
Or if your model is more complicated, such as plane with interior holes, circular surface, you might use the gmsh library.
Although I have not used the gmsh library, I am sure that if you can control the number of boundary nodes, you can use it to generate a fully quadrilateral mesh