XnView Software

Some image viewers will display a "pop-up" preview when hovering a thumbnail with the mouse.

This would be a great addition to XnView MP.

I have been hoping for more control "at the thumbnail"... sort of a "super thumbnail" approach similar to that used in Lightroom where there are a lot of controls (tag, rotate, rating, flag, copy, move etc) that fade into view directly inside the thumb cartouche when the mouse hovers over it. MP already has implemented a little of this by having colors and ratings icons on the thumb, which is great.

The problem with an "active" or "super" thumbnail approach is that it only works well for large thumbs. Sometimes it is better to interact with very small thumbs (in order to show more of them in the browser) that do not have enough "real estate" to clearly present the additional controls without hiding/overlaying portions of the thumbnail itself. A mouse-hover "pop-up" window would be an excellent substitute for icons on the thumb cartouches, especially when the thumbs are small.

If the popup preview could be user-customizable along the lines of my suggestion here, even better!

wouldn't that risk bloat and making it really slow?
There's a reason Lightroom is about 300MB!
I don't want XnView to go the way of ACDSee.

It's a common misconception that there is a one-to-one correspondence between the size of the exe and the scope of the functionality it delivers. Clever programming can pack quite a bit of useful stuff into a small executable. You might be surprised at a how little actual code would be required to implement many of my requests for XnView.