[UX][D8] Make the "Manage files" page have a file manager look and feel.

[klonos]

I would like to propose the following:

• add thumbnails for images
• add file icons for the rest of the file types
• improve the table responsiveness on narrower screens

I would expect this page to have a file manager look and feel, and having thumbnails is key to achieving that. Here's what's in D8 core (Media module):

The view that generates this admin page is also not specifying any priorities for the rendered table columns, so it scrolls off the screen on mobile. If it turns out that we have a hard time deciding which columns should be low priority, then we should have the mobile version of that page be like the views listing table on mobile (tablesaw-style table rows stacked on top of each other):

[oadaeh]

While I like the idea of a thumbnail in the list, it will require going to the file system for each item in the list. And for sites with lots of files, that will make the page load slow and potentially have the side-effect of impacting general site performance while the page is being loaded. Granted, "lots of files" might be over 1,000 or 5,000 or 10,000, depending on the hosting structure, but that's not that far fetched.

[klonos]

I see your point @oadaeh, but that page only shows a few 10s of files each time. If thumbnails are stored once generated, we won't have to be generating them over and over. We could perhaps generate those on file upload.

I wonder how/if we have addressed this in the Image Browser (#3134), and if we can reuse the thumbnails generated for the images loaded in it.

[oadaeh]

Where and how would the thumbnails be stored?

The problem is not in displaying or generating the thumbnails. It is in accessing a directory that is overloaded with files, even & especially the thumbnail directory itself. Per every thumbnail displayed on the page. It doesn't only matter the size of the files, but also that they exist.

And maybe this isn't really a problem that needs to be considered here, since a site owner in this situation probably has other issues to take care of.