Describe the bug
When selecting multiple characters with the mouse, or with shift+keyboard arrows, it highlight characters for the next line.

It seems the problem is coming from blizzard, and not from allindentandpurpose lib as i first though.
I can replicate the issue by pasting a big text in a simple editbox (tested with profiling editbox)

This does look similar to a problem that we had in 7.3, can you check whether cherry-picking 8305cd5 works? (That commit was later reverted when they fixed the bug.)

Nop it doesn't help, i tried with scaling enable and disable it's the same.

I also noted that clicking on a character to position cursor is off by a few lines and get worse the further down i do it.

Can you create a minimal example, so that we can report that to Blizzard?

https://i.imgur.com/FXe6132.gif
EditBoxBugTest.zip

I just told TSquare about it, so hopefully it won't release in that state.

And we reminded him again, no response though. Might want to try in a month or so again.

Tracked in Stanzilla/WoWUIBugs#1