I think the Xperts probably already know but, I just came across this.
Does it in XDP7 and XDPX. I'm not sure about other versions, but these two I have and I can check.

If you click to select an object, and you press the CTRL key, and then drag the object around the screen, you can move it in straight lines.
Left, right, up, down, in straight lines.
And at 45 degree angles as well.

You get a star shape that appears and guides you, to ensure that you are dragging the object on the line you want.

Try it!