Generate previews only for files that can have a preview

[labkode]

Only send previews for known mimetypes that can have them and app allows for that.

The logic should be:

1. Check what apps are installed
2. Get list of mimetypes handled by apps
3. Check if for each mime type the app can generate a preview
4. Send the preview (and cache in browser)

[kulmann]

Needs a product decision @tbsbdr
In my opinion the web ui should not assume which files can have previews. That's up to the backend. Especially when we implement a grid view (planned for Q2 or Q3 2021) and when we show file details in the right sidebar (planned for the current sprint, by end of May 2021) we will have a bigger version of previews without going into any extension. Would be a pity to hide previews just because we don't have an extension for that specific file type.

[labkode]

If the client does not have the knowledge that a particular mime type can have a preview means you will be sending N requests for N objects and most of the time (from experience) you won't get a preview, therefore you're waisting resources.

[pascalwengerter]

@labkode we discussed this internally and would suggest the following:

The admin provides a previewFileExtensions option in the config.json file. If it is present, previews only get fetched for the file types that are registered there. If the list is not present it falls back to the current behaviour and tries to fetch previews for every filetype.

What do you think of this approach?

Note: Handling the "Get list of mimetypes handled by apps" doesn't make sense for now since displaying previews for media files (as an example) is handled independently of the files-app-media-viewer communicating the ability to handle certain file extensions

[labkode]

@pascalwengerter I think is a good compromise.

[fschade]

@labkode, pr created. Happy to get your feedback #5159

[diocas]

@kulmann I'm re-opening this ticket because the option previewFileExtensions is no longer honoured and web tries to load previews for all file types.

[kulmann]

@diocas has been changed to mime types, see

web/config/config.json.sample-ocis

Line 28 in de72c25

"previewFileMimeTypes" : [

[kulmann]

Please close again if that works for you

[diocas]

Sorry! I saw that but didn't realise it was replacing the old config. Thanks

[kulmann]

Sorry! I saw that but didn't realise it was replacing the old config. Thanks

Well, we failed to announce it properly...