Load only visible previews

[rnveach]

I am on 6.0.0a (stable).
I was going ask to allow users the option to enable/disable previews, but I saw it already brought up in closed #5171, but it was discussed going with Filters instead of an enable/disable option. The only thing similar with what I am requesting, was with issue #3817, but it was never marked as going anywhere. I wasn't sure to add onto that issue, so I decided to start a new one.

One problem I have with the previews is that it displays an image for every file in the directory. If you are viewing a folder with 10 images, this is fine. But when you get to a folder with 100+ images, this can be a considerable download time and wasted bandwidth. The user may not even scroll through the entire listing, they could want to go to a deeper folder or be in the wrong folder, so there isn't a need to download most of the previews. And if the user is on a slow or limited connection, the previews could take a while to download. A filter probably wouldn't help with this issue as the entire folder is still loaded on the first pass before the user has a chance to apply the filter.

To help with the page load time, I think owncloud should implement "lazy load" of the preview images. Basically, the images are only loaded when the user scrolls them into view. The text file list is still loaded like normal, so the scroll bar wouldn't change in size.
I would still also like an option for enabling/disabling preview images for the user. The main case against this was having 2 different views, but I think this be done within 1 view. The lazy image load would just load a blank white image instead of the actual preview. This allows you to keep virtually the same code and page layout while giving users a bandwidth saving feature.

[PVince81]

Good point, the lazy loading of non-visible previews makes sense.

CC @owncloud/designers

[jancborchardt]

This ties in with the original lazy loading issue at #251 because not only the previews are the cause for load.

[PVince81]

Since we have infinite scrolling now, only the previews of the currently visible page/section are loaded. When you scroll down the next batch of previews is loaded when the next batch of rows is appended.
Closing.