Indeed, you seem correct. The file is not included in the OpenOrbiter repository. It seems to have been replaced with DrawAPI, presumably because the D3D9 client is planned to be shipped by default. I can still see the sketchpad class in that file, but don't have the original code handy just now to do a diff. You might get away with just including DrawAPI.h instead of sketchpad2.h? Not sure at all. It seems kind of a bad move for backwards compatibility, but somebody that knows more about the current state of the source and the reasons for the decision than me will have to explain it...