Populate the file panel using the event index if available.

[poljar]

As the title says, this pull request implements pulling events containing files out of the event index and populating the file panel with them.

This intends to fix element-hq/element-web#4959.

A demonstration of this can be found here.

The remaining issue for now is that live events aren't added to the file panel while the panel is open. If the panel is reopened the newly arrived events are added to the top instead of the bottom.

I suspect we want to fix both of those at the same time while we add the ability for riot-web, which doesn't have event indexing, to show at least events in the live timeline in the file panel.

The main issue with that seems to be that this filter isn't smart enough to understand decrypted events that contain URLs.

[turt2live]

seems generally sane - mostly comments about codestyle which our linter doesn't cover.

[poljar]

Updated now. Live events handling is still missing.

My plan is to add listeners for Room.timeline and Room.decrypted to add the live events to the loaded FilePanel.

If someone has a better idea, please shout.

[poljar]

This has been now updated to correctly handle the remaining problematic cases:

• New events that arrive while the panel is closed are correctly added when the panel is re-opened.
• New events that arrive while the panel is open.

[turt2live]

looks good to merge after the last 2 lint things. Thanks for working on this, and apologies for the delay in review.

ftr I have no idea how any of this is supposed to work, but it looks like its in the right places and does roughly the right thing. Very much assuming that bugs will show up over time and we can fix them as we see them.

[poljar]

ftr I have no idea how any of this is supposed to work, but it looks like its in the right places and does roughly the right thing. Very much assuming that bugs will show up over time and we can fix them as we see them.

Let me add a comment in that case to explain what it does.