Ristretto does not scroll large images when mouse/trackpad scrolls:  the current image instead moves through the list of all images in the directory.

This makes is difficult to move around in a large/zoomed in image, as neither keys nor mouse-scrolling (or 2-finger trackpad scrolling/etc) move the image.  The only option left is the scroll bars, which are much less easy to use in many themes.

Default trackpad scroll speeds move through directory images very very quickly, so the current behavior is not very useful.  Intuitive behavior would be scrolling the image.