Feature request - use of expressions in animated labels

[tjebo]

background - stackoverflow https://stackoverflow.com/questions/67089930/not-getting-the-desired-title-in-gganimate-animated-labels-with-expression

The below is the original plot posted by the OP. No matter what combination I tried with paste, expression, parse, substitute, inside or outside of {...} (thinking this might do the trick kind because of the glue syntax), it either correctly parsed the expression (as in below) or the changing label, but never both.

library(gganimate)
#> Loading required package: ggplot2
ggplot(mtcars, aes(wt, mpg)) + 
  geom_point() + 
  transition_states(hp) +
  labs(title = expression('Hp = {closest_state}' ~ m^2 ~ m^-2))

^{Created on 2021-04-26 by the reprex package (v2.0.0)}

One workaround was suggested with the ggtext package which allows at least sub/supscript, but it fails with any more complex expression.

[tfjaeger]

Is this something under development? I'm running into the same limitation. Trying use plotmath functionality combined with reference to gganimate variables like {closest_state}. Thank you.