[TextEdit] Extra blank lines appear when pasting text with \r\n on Windows, and updating property inside callback fails to refresh UI

[pansy1110]

Summary

I am using Bun + TypeScript + Slint to build a curlconverter GUI. When pasting text containing Windows-style \r\n line endings into TextEdit, it renders double newlines (extra blank lines). Attempting to sanitize the text inside the callback does not refresh the UI.

Screenshots

• Actual (Buggy):

• Expected (Desired):

Minimal Reproducible Example

1. ui\window.slint

import { TextEdit } from "std-widgets.slint";

export component MainWindow inherits Window {
    title: "curlconverter";
    width: 800px;
    height: 600px;

    in-out property <string> left-text: "";
    callback left-text-changed(string);

    HorizontalLayout {
        padding: 0px;
        spacing: 0px;

        TextEdit {
            horizontal-stretch: 1;
            font-size: 14px;
            wrap: no-wrap;
            text: root.left-text;
            placeholder-text: "curl example.com";
        }

        TextEdit {
            horizontal-stretch: 1;
            font-size: 14px;
            wrap: no-wrap;
            placeholder-text: "import requests\n\nresponse = requests.get('http://example.com')";
        }
    }
}

2. index.ts

import * as slint from "slint-ui";
let ui = slint.loadFile(new URL("ui/window.slint", import.meta.url)) as any;
let mainWindow = new ui.MainWindow();

mainWindow.left_text_changed = (newText: string) => {
  // 1. Sanitize text by stripping \r
  let cleanedText = newText.replace(/\r\n/g, "\n");

  // 2. Programmatically assigning it back here has NO visual effect on UI
  if (cleanedText !== newText) {
    mainWindow.left_text = cleanedText;
  }
};

await mainWindow.run();

3.test_curl

url:https://fanqienovel.com/writer/zone/notice

curl 'https://fanqienovel.com/api/node/notice/list?page_index=1&page_count=10&location=16&aid=2503' \
  -H 'accept: application/json, text/plain, */*' \
  -H 'accept-language: zh-CN,zh;q=0.9,en;q=0.8' \
  -H 'priority: u=1, i' \
  -H 'referer: https://fanqienovel.com/writer/zone/notice' \
  -H 'sec-ch-ua: "Google Chrome";v="149", "Chromium";v="149", "Not)A;Brand";v="24"' \
  -H 'sec-ch-ua-mobile: ?0' \
  -H 'sec-ch-ua-platform: "Windows"' \
  -H 'sec-fetch-dest: empty' \
  -H 'sec-fetch-mode: cors' \
  -H 'sec-fetch-site: same-origin' \
  -H 'user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36'

Environment

• OS: Windows 10/11 x64
• Slint Version (slint-ui): 1.17.0
• Bun Version: 1.3.14
• TypeScript Version: 5.9.3

Questions

1. Why does TextEdit render \r\n as two separate line breaks on Windows?
2. How should I properly sanitize or format user input during a paste/edit event so that TextEdit successfully re-renders with the updated property value?

[ogoffart]

This is clearly a bug.
Made a fix in #12347