Support for (non-facet) grid?

[katrinabrock]

Hello,
Thanks for this package!
I'm trying to make an animation that consists of multiple plots and I'm wondering if it's supported.

I found this doc, but it looks very outdated since it references magick rather than gifski. https://github.com/thomasp85/gganimate/wiki/Animation-Composition

I've tried using the girdExtra::arrangeGrob but it doesn't seem to work.

library(gridExtra)
library(ggpubr)
library(ggplot2)

# transition, then arrange
p1 <- ggplot(mtcars, aes(factor(cyl), mpg)) + 
  geom_boxplot() + 
  transition_states(
    gear
  )
p2 <- ggplot(mtcars, aes(qsec, mpg)) + 
  geom_line() + 
  transition_states(
    gear
  )
p_full <- arrangeGrob(p1, p2)

# arrange, then transition
p1 <- ggplot(mtcars, aes(factor(cyl), mpg)) + 
  geom_boxplot() 
p2 <- ggplot(mtcars, aes(qsec, mpg)) + 
  geom_line()
p_full <- arrangeGrob(p1, p2) + transition_states(gear)
str(p_full) # NULL

Trying to arrange together gganim objects, I get

Error in UseMethod("ggplot_gtable") : 
  no applicable method for 'ggplot_gtable' applied to an object of class "gganim_built"

Trying to add transition_states() to gtable object returns NULL

Is this functionality supported?