I actually use the SAME exact code, so I am not sure how it could work in one addon and not the other. For what its worth, I have several animated thumbs in showcase on my site. Can you show me on your site where you upload the SAME gif in both addons and one works and the other doesn't?
for me this function mean that -> when i place my mouse over a xfmg album with more than one media i can see a random preview of these medias.
So i thought it´s here the same when i´m with my mouse over a showcase item with more than one media.
Here in your showcase and on my site i´ve never seen an animated thumbnail somewhere, what does it mean otherwise?
Ah, no... that isn't what that option is for. That option is for creating an animated thumbnail of a single animated image. Normal thumb creation is a .jpg, but choosing that will allow the thumbnail generation to create a .gif. GIF are a single image with multiple frames that make the image appear to be "animated".
as you can see, the Cover Image is an animated image for all the various thumbnail sizes.
What you are referring to is specific Album functionality built into XFMG. You'd need to suggest similar functionality be added to showcase for the Grid View and Modular View (wouldn't work for List View).