You can see here five applications launched in the one time, four of them are rolled up and one active is chrome browser. Somehow icon of the current active application are shifted down for the few pixels from original state, you can see it on the picture.
How to turn off this feature? I want to leave all buttons straight in one line, no matter launched they are or not. (Same effect if you just move mouse cursor over the icon without clicking on it)
I'm using xubuntu 14.04 LTS with xfce 4.12. I would be very grateful for the help. Thanks you.