Recipe:

1. On any page, find/create a line of text with > 60 chars
2. Select roughly the middle 1/3 of the line of text
3. Change the width of brackets app

Results:
The painting of the selection highlighting briefly changes with the width of the window (seems to be a percentage of viewport width). It quickly snaps back to the correct size, but there is enough delay to make it very noticeable.

Expected:
Selection highlighting does not change with editor window width

This seems to be caused by recent CodeMirror changes.