fix(ui): Sending read receipt in live timeline uses threaded event id instead

[jmartinesp]

Changes:

• In the live timeline, don't send read receipts for threaded events if hide_thread_events is enabled. EventMeta has now a thread_root_id field so we can know if the event is part of a thread, and TimelineController::latest_event_id filters those out if hide_thread_events is enabled.
  • Why do this instead of just filtering out non visible items? Because reactions, edits, replacements, etc. are also non-visible items that have to be taken into account for the read receipts. So it seems like we have 2 types of 'not visible' items in the timeline, those that aren't visible because we don't want to display them as separate items (aggregations), and those that aren't visible because they shouldn't be displayed at all.
  • Then why not avoid adding the items at all? Because some logic in the SDK depends on the threaded events being added to the remote events in the timeline, even if they aren't displayed because of hide_threaded_events, so some tests were broken.
• Fix test that was consistently failing locally on main - not really related to this PR, but it also made it fail in CI. It looks like a race condition of some kind.
• Modify ffi::Timeline::latest_event_id to use ui::Timeline::latest_event_id, which will return the value from TimelineController::latest_event_id.

Fixes element-hq/element-x-android#5639.

• Public API changes documented in changelogs (optional)

Signed-off-by:

[codspeed-hq]

CodSpeed Performance Report

Merging #5864 will not alter performance

_{Comparing fix/sending-read-receipts-in-threads (ee2eca3) with main (5d396e4)¹}

Summary

✅ 50 untouched

Footnotes

1. No successful run was found on main (ca43601) during the generation of this report, so 5d396e4 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.59%. Comparing base (9ab886f) to head (ee2eca3).
⚠️ Report is 13 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...rates/matrix-sdk-ui/src/timeline/controller/mod.rs	82.35%	3 Missing ⚠️
crates/matrix-sdk-ui/src/timeline/mod.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5864   +/-   ##
=======================================
  Coverage   88.59%   88.59%           
=======================================
  Files         363      363           
  Lines      102888   102926   +38     
  Branches   102888   102926   +38     
=======================================
+ Hits        91153    91188   +35     
- Misses       7496     7498    +2     
- Partials     4239     4240    +1     

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[Hywan]

Looks good to me, modulo the small feedback. Thank you for the new test and for the fix!

[Hywan]

Please add documentation for this field. Also —just a personal taste— I would put this field after event_id, not mandatory.

[Hywan]

Can you explain with an inline comment here why we want to filter out event with a thread root?

[Hywan]

You may want to precise that, contrary to latest_event, this method only returns the ID of the last remote event (which is obvious for us because a local event doesn't have an event ID, only a transaction ID, but it's better to make it clear.