Unread tracker is reset before image are loaded

[erdnaxeli]

Description

When you open a room with images in the last messages the unread tracker position and behavior is computed before image are loaded.

Steps to reproduce

See the attached screen capture t.zip. We see the unread tracker, then images are loaded and:

1. I'm still at the end of the messages
2. The unread tracker is lost
3. The "go to unread message" is not also not here.

It should either load images and put them beside my scroll position, or keep the unread tracker.

Version information

• Platform: web (in-browser)?

• Browser: Firefox 54.0

• OS: Ubuntu
  URL: private riot, version 0.11.4

[lampholder]

In the video, at 00:07 we see the horizontal green line read marker and the end of the timeline - then all the images are loaded in causing problems.

@lukebarnard1 suggested this problem could be fixed by having correctly-sized placeholders in place of the images before the images have loaded - he suggested that we might already have something similar in place for E2E encrypted rooms that could be retrofitted on to this.

[lukebarnard1]

It's worth noting that in the video the timeline is scrolled down to the bottom, so when the images resize, the timeline pins itself to the most recent message instead of a third of the way down the screen, which is the normal behaviour.

[erdnaxeli]

It's the normal behaviour, but if the images where already resized the unread tracked would have been outside of the current view and not removed.

[lukebarnard1]

@erdnaxeli yep, I'd put money on that.