The new “on click” trigger of formula fields in v2.6

I've a lot of formula fields which make reference to image fields.

A click on the formula field opened the prevew of the image in normal size.

With the v2.6 it dosen't work more, nothing happens when we click on the formula field ;-(

I have noticed the new “on click” trigger of v2.6 but which script must we put in the formula field to get the same result : open an image as it's possible with an image field.