Cursor position becomes inaccurate while typing in editor

[philrz]

tl;dr

When typing text interactively into the editor in Zui, the cursor placement can gradually become out-of-sync such that it creeps leftward of the characters being entered. The changes in #2881 likely caused the bug.

Details

The problem seems to repro starting with Zui Insiders 1.3.2-14, though I've also reproduced in the latest which is currently 1.4.2-7. Also, the community zync user that initially reported the problem was using Windows 11, but I've since reproduced the problem on Windows 11, Windows 10, and Windows 2019 Server.

The repro is shown in the attached video. I simply hit "+" to start a new tab and begin to type a long pool name from 012345678901234567890123456789. As I'm typing I can see the cursor start to move leftward of the new characters that I'm entering. After I'm done typing I can hit Home and End keys to move the cursor to the beginning/end of the line and it's clear that there's multiple characters now rendered to the right of where the cursor lands.

I'll note that I've sometimes managed to get the app into a state where the problem won't repro. The most reliable way I've found to always repro is to uninstall Zui Insiders completely, then clear out the app directories left behind and reinstall fresh. Then after first launch, immediately hit "+" and start typing.

Repro.mp4

In terms of narrowing down a likely root cause, the user that first reported the issue said:

The ZUI version 1.3.2-13 work fine, after this version, i have this problem.

I found this was indeed the case. I first used the same repro steps as in the video with Zui Insiders 1.3.2-13 and it did not repro. Then I used 1.3.2-14 as shown in the video and it did repro. The Actions run for building 1.3.2-13 was at https:/brimdata/zui/actions/runs/6789083410 and shows it to be based on Zui commit d29e674, and 1.3.2-14 was built at https:/brimdata/zui/actions/runs/6793346596 and shows it to be be based on Zui commit 2ffbdd8. The report d29e674...2ffbdd8 shows what changed between those Zui commits, so based on that, it seems almost certain that the changes in #2881 caused the bug.

[philrz]

Verified in Zui Insiders 1.4.2-11.

Repeating the original repro steps, the cursor now consistently stays just to the right of each typed character.

Verify.mp4

Thanks @jameskerr!