A picture is easier to describe this issue than words. Basically, rich
text effects allowed for character visibility changes. While doing so
would work properly, the rich text label would render the next `word` in
an offset accounting for the hidden characters (leaving a huge space.)
This patch fixes this issue by keeping track of the amount of
`backtrack` necessary per line.
(cherry picked from commit b3fd4884d7)
0dedc0a1a3