transition: more accurate preview
transition: more accurate preview

now it goes from 0 -> 1, swaps and next 0 -> 1 again instead of 0 -> 1 -> 0.

ext/slideshow,ext/slideshow-frontend,ext/slideshow,ext/slideshow-frontend,ext/slideshow,ext/slideshow,ext/slideshow-frontend,ext/slideshow,ext/slideshow