When display thumbnail for folders is enabled, if a folder has child folders that have a folder.jpg, the parent thumbnail will display up to 4 images to show what is in that folders child folders.
I would like this to do the same for child zips. So the parent would display the 4 thumbnails of the child zip files.
I accept that this would be more expensive to grab the images. To alleviate this could perhaps only display in the parent if there is already a thumbnail in the thumbnail cache for that zip (to save opening the zip).
Thinking along those lines, it might make sense to have a script or tool which pre-calculates the folder.jpg thumbnails for such folders. Then the caching/generation is in your control, and as a bonus the thumbnails work everywhere.
I think the built-in scripting in Opus should be able to get the images from the zips, but wouldn't be able to combine the images into a 4x4 grid. It could call a tool like ImageMagick to do that part.
Maybe there's scope for a script like that to do other things for generating custom folder.jpgs as well.
I almost added to the post a request for having scripting ability to hook in to the thumbnail display generation. So that would be awesome.
To save needing to use an external tool for the 2x2, the api could allow setting a single image, or up to 4 images. Then dopus could use the internal code to do what its already doing when getting 4 images.
To make it efficient we would need to be able to hook in to the thumbnail generating and caching.