msglist: On event-queue refresh, re-fetch the position you were reading; control scroll position

[chrisbobbe]

When we learn that our connection to the server ("event queue") has expired, after we get a new one, we re-fetch messages in any open message lists because the old data may be out-of-date.

When possible, after the re-fetch, we want to show the user the same messages, in their same positions onscreen, as before. This issue is for doing that.

Currently, after the re-fetch, we always put the user at the latest messages in the view, regardless of what messages they were looking at before.

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First, the code should choose a message to anchor to; see #1008: "But a simple algorithm would be […]".

The re-fetch should be done at that anchor; this requires

• Open a message list in the middle of history, when requested #82

We should also try to put the fetched "anchor" message in the same position onscreen as it was before the re-fetch.

Related issues

• msglist: Control scroll position on renarrowing for bulk message moves #1009

[E-m-i-n-e-n-c-e]

Can't we take a different approach to solve this issue. Instead of anchoring and re fetching. Can't we just preserve the state of the messageList so that it only loads once when you open the app for the first time

@chrisbobbe

[chrisbobbe]

No:

we re-fetch messages […] because the old data may be out-of-date.

[E-m-i-n-e-n-c-e]

No:

we re-fetch messages […] because the old data may be out-of-date.

I see . I thought we could try preserving the state of just the scroll controller but that wouldn't work if there are new messages. So we need a message to anchor to (preferably bottom most) and then set scroll position so that the anchored msg is just visible.

Can i take this issue?