User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36

Steps to reproduce:

Dynamically add a textarea (on button click)

• Create it on click
• Set overflow: 'hidden'
• Add to body
• Set value to something that is more then one line, e.g. '1\n2\n3\n'

Reproduction https://codepen.io/tgknownasilya/pen/wvjboOo
Code from the pen:

// Test code
function show() {
  const hiddenTextarea = document.createElement('textarea');

  hiddenTextarea.style.overflow = 'hidden';

  document.body.appendChild(hiddenTextarea);

  hiddenTextarea.value = '1\n2\n3\n';
  console.log('3 lines', { scrollHeight: hiddenTextarea.scrollHeight });

  hiddenTextarea.value = '1\n2\n3\n';
  console.log('3 line',  { scrollHeight: hiddenTextarea.scrollHeight });
}

Actual results:

Initial value causes incorrect scrollHeight. Above code snippet logs:

3 lines
Object { scrollHeight: 36 }
3 line
Object { scrollHeight: 68 }

Expected results:

Expect it to log

3 lines
Object { scrollHeight: 68 }
3 line
Object { scrollHeight: 68 }

(note that this is correct in Chrome)

The Bugbug bot thinks this bug should belong to the 'Core::Layout: Scrolling and Overflow' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Note that on Firefox 103 on Linux this issue doesn't exist

Note its the "Remove useless ProcessPendingRestyles call" changeset that regressed this.

:emilio, since you are the author of the regressor, bug 1778983, could you take a look? Also, could you set the severity field?

For more information, please visit auto_nag documentation.

This is basically bug 1787062... It's an issue with editor initialization being async, see there. The good thing is that working around it is trivial (just add another layout-affecting getter call, like scrollHeight to flush the changes made by editor init.