lightning_ggplot_internals.R

library(ggplot2)
library(ggdebug) # remotes::install_github("paleolimbot/ggdebug")

# the classic ggplot!
ggplot(mpg) +
  geom_point(aes(x = displ, y = hwy, colour = class)) 

# ...is really this:
p <- ggplot(mpg) +
  geom_point(
    aes(x = displ, y = hwy, colour = class), 
    stat = StatIdentity, 
    position = PositionIdentity
  ) +
  facet_null() +
  coord_cartesian() +
  scale_x_continuous() +
  scale_y_continuous() +
  scale_colour_hue()

# and is displayed in three steps
built <- ggplot_build(p)
drawn <- ggplot_gtable(built)
grid::grid.draw(drawn) # render

# Let's look under the hood!
ggdebug(
  # build
  FacetNull$compute_layout, FacetNull$map_data,
  Facet$init_scales, Facet$train_scales,
  StatIdentity$compute_layer,
  PositionIdentity$compute_layer,
  # Facet$init_scales, Facet$train_scales,
  CoordCartesian$setup_panel_params,
  
  # draw
  # Facet and Layout assemble all the parts
  CoordCartesian$render_bg,
  CoordCartesian$render_axis_h, CoordCartesian$render_axis_v, 
  GeomPoint$draw_panel
)

built <- ggplot_build(p)
drawn <- ggplot_gtable(built)
grid::grid.draw(drawn) # render

ggundebug()