18. The machine-readable medium of claim 17 , wherein receiving the commands comprises receiving pass-through and preview commands, including the first and second commands, in any order, and the operations further comprise doing and undoing the preview commands in response to changes to the preview control.
18. The machine-readable medium of claim 17 , wherein receiving the commands comprises receiving pass-through and preview commands, including the first and second commands, in any order, and the operations further comprise doing and undoing the preview commands in response to changes to the preview control. 19. The machine-readable medium of claim 18 , wherein retaining commands in the command sequence comprises prioritizing pass-through commands over preview commands.