Pixel Offset

I have found myself needing a pixel offset (so that I can leave a space for my
system tray). While this is somewhat of an odd case, a pixel offset would also
be useful for drawing progress bars (given a middle-bar command) etc.

Feel free to call it something else. Additionally, I don't know if this is how
you would implement it but "it works for me" (I won't feel bad if you rewrite
the code entirely/refuse to accept the PR).