1208412 - Text lines twitch up and down when I start typing in a new line in <textarea> with HWA on and off

Status: NEW

(Core :: Layout: Text and Fonts, defect)

Description

[arni2033]

Attachment: testpage - Text twitches Up and Down when I start typing in a new blank line in textarea.htm

STR:   (Win7_64, Nightly 44, 32bit, ID 20150923030230, new profile, safe mode)
1. Open attached HTML test page
2. Scroll the textarea to the bottom using mouse wheel
3. Click on the last line (that line is initially empty)
4. Type "s" in that line
5. Press BackSpace to delete symbol from Step 4

Result:       After Step 4 some lines moved 1px up. After Step 5 they restored their position
Expectations: Text lines should stay still

Comment 1

[arni2033]

Attachment: video - Text twitches Up and Down when I start typing in a new blank line in textarea.webm

Comment 2

[Kartikaya Gupta (email:[e-mail])]

The behaviour here seems to have changed between Aurora (49) and Nightly (50). On Aurora only some of the lines twitch but on Nightly they all twitch together. Tested on OS X, so maybe different from Windows. If the Aurora/Nightly difference is real, then it may be because of bug 1012752.