Autocomplete view wrongly laid out for a frame when opening

[chrisbobbe]

When opening the autocomplete, e.g. for an @-mention, the list of options is wrongly laid out for a frame before moving to the intended layout.

Relevant frames from video (below)

Notice it's covering the text input and doesn't include all the results we have calculated:

Actual	Should be

Video

image_picker_4C820BC6-0163-4923-B1CD-81253D2D0E9D-16537-00000899A82D171BScreenRecording_01-27-2025.14-25-57_1.mp4

Diagnosis

My video was taken at the current revision for

• autocomplete: Support @-wildcard in user-mention autocomplete #889

but the bug exists on main, just with a user-mention option shown instead of a wildcard mention. (Greg tested this in the office on Friday.)

It reproduces with Flutter at flutter/flutter@329745473 but not its parent, so in fact this seems to be the extra frame delay that was introduced upstream and caught by our tests; see PR #1190. Probably the right fix is to file an issue upstream for not painting the autocomplete options during the extra frame, when it's not ready to be laid out correctly.