recent_view: Fix no topic found at center of recent view.

[amanagr]

The bug is hard to reproduce, but I was able to reproduce with #30134 and used the same strategy to fix it here.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: web/src/recent_view_ui.ts

Function	Unhandled Issue
recenter_focus_if_off_screen	Error: Assertion failed recenter_focus_if_off_scr... Event Count: 20 Affected Users: 18

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[timabbott]

Can you spell out a bit more what this means / why it is correct? I'm missing some detail here.

[amanagr]

So, there are 2 possibilities of topic_element being null here.

• One is if we haven't rendered the list yet, which is fixed by is_waiting_for_revive_current_focus which fixes the sentry error.
• Other is if there is no row at the vertical center of the recent view but slightly above it. In that case, we focus on the last element. This is just something that I noticed is possible but not entierly sure if it is possible to get into this state.

[timabbott]

OK I wrote a comment trying to explain this and will merge ... but I'm not sure it's entirely correct.

Also, $topic_rows.index($(topic_element).closest("tr")[0]); seems like it's not limited to just conversation rows, but it could fire on a header row : I wonder if we shouldn't be using table_wrapper_element.getBoundingClientRect();, but instead table_wrapper_element.find("tbody").getBoundingClientRect();... I guess find is bad because of nested tables, but you get the idea.

[timabbott]

OK, pushed a revision that I think is a good merge point, even if I'm not entirely certain that we're doing the right thing in some unlikely/theoretical cases there.

[timabbott]

Test failure looks like an unrelated infrastructure failure affecting the realm_playground puppeteer test.