Pasting 2+ emojis shows cursor before last emoji

[joshtriplett]

Using a supported version?

• I have searched open and closed issues for duplicates.
• I am using Signal-Desktop as provided by the Signal team, not a 3rd-party package.

Overall summary

If you paste in a series of 2+ emojis, Signal shows the cursor being before the last emoji, rather than at the end of the paste. The cursor appears exactly where it would if positioned before the last emoji, but this seems to be a visual artifact and it doesn't actually seem to be there, as subsequent typing or pastes go to the end and pressing left moves the cursor one to the left of the end rather than two to the left of the end.

Steps to reproduce

Go to a chat.
Enter several emoji. I used: 🐝🐝🐝
Select all, and cut.
Paste.
Observe the apparent cursor position. Then type or move the cursor.

Expected result

Cursor at end of pasted text.

Actual result

Cursor appears to be before the last emoji.

Screenshots

Signal version

8.5.0-beta.2

Operating system

Debian sid

Version of Signal on your phone

No response

Link to debug log

No response

[apurv3170]

Hey, I looked into this and traced the bug to ts/quill/signal-clipboard/index.dom.ts file.

Inside the onCapturePaste method, setSelection is called before Quill has flushed its DOM update from updateContents, causing the cursor to land at the wrong position. The fix is to wrap setSelection,scrollSelectionIntoViewandfocus in a requestAnimationFrame so they run after Quill reconciles the DOM.

I've tested this locally and it resolves the issue with emoji sequences like:

I'd open a PR if moderators would assign me this.