Rotate ruler on Fresco Desktop?

Space + r, try it! that's it

空格+r，试试吧！就是这样

For those trying to do this on a Windows desktop and having trouble, something I had to figure out was that the ruler has a pivot point. You can only rotate it at the pivot point. Hold down R and press down on the ruler with your drawing pen. You'll see a little blue box pop up with the current angle of the ruler. By letting go of R, you can can then use your pen to position the pivot point where you want it. Hold down R again, and press down on the ruler with your pen at the pivot point. This will let you rotate it. This works with a mouse as well, at least on Windows 10.

this doesn't work, at least on Windows. I found that I can move the ruler with the stylus, but I haven't found a way to rotate it.