translating ggproto from 3.5 to 4.0

[r2evans]

I've been using a UniquePanelCoords and coord_cartesian_panels from https://gist.github.com/burchill/d780d3e8663ad15bcbda7869394a348a for a few years, and it works great. The underlying need is to set clipping limits on different panels of a facet, where the limits vary by panel, akin to

ggplot() +
  coord_cartesian(ylim=..) +
  facet_grid(g ~ ., scales="free_y")

Unfortunately (and perhaps not surprisingly), ggplot2_4.0 has changed something enough where this no longer works. I've traced the problem into Geom$draw_layer, specifically in

    lapply(data_panels, function(data) {
      if (empty(data)) return(zeroGrob())

      panel_params <- layout$panel_params[[data$PANEL[1]]]
      inject(self$draw_panel(data, panel_params, coord, !!!params))
    })

where layout$panel_params is not set according to the needs of the Geom: layout$panel$params is just a list(), so that expression fails with

Error in geom_blank() (from file.R#117) : Problem while converting geom to grob.
ℹ Error occurred in the 1st layer.
Caused by error in `layout$panel_params[[data$PANEL[1]]]`:
! subscript out of bounds

I haven't been able to find something that documents the changes to the underlying ggproto and Geom and CoordCartesian specifically enough to provide insight and a means to translate UniquePanelCoords.

Do you have a suggestion on how to get past this bug, and/or if there is a better way to set clipping limits?

For the sake of reproducibility, here is the sample data and code in the gist.

UniquePanelCoords <- ggplot2::ggproto(
  "UniquePanelCoords", ggplot2::CoordCartesian,
  
  num_of_panels = 1,
  panel_counter = 1,
  panel_ranges = NULL,
  
  setup_layout = function(self, layout, params) {
    self$num_of_panels <- length(unique(layout$PANEL))
    self$panel_counter <- 1
    layout
  },
  
  setup_panel_params =  function(self, scale_x, scale_y, params = list()) {
    if (!is.null(self$panel_ranges) & length(self$panel_ranges) != self$num_of_panels)
      stop("Number of panel ranges does not equal the number supplied")
    
    train_cartesian <- function(scale, limits, name, given_range = NULL) {
      if (is.null(given_range))
        range <- ggplot2:::scale_range(scale, limits, self$expand)
      else
        range <- given_range
      
      out <- scale$break_info(range)
      out$arrange <- scale$axis_order()
      names(out) <- paste(name, names(out), sep = ".")
      out
    }
    
    cur_panel_ranges <- self$panel_ranges[[self$panel_counter]]
    if (self$panel_counter < self$num_of_panels)
      self$panel_counter <- self$panel_counter + 1
    else
      self$panel_counter <- 1
    
    c(train_cartesian(scale_x, self$limits$x, "x", cur_panel_ranges$x),
      train_cartesian(scale_y, self$limits$y, "y", cur_panel_ranges$y))
  }
)

coord_panel_ranges <- function(panel_ranges, expand = TRUE, default = FALSE, clip = "on") 
{
  ggplot2::ggproto(NULL, UniquePanelCoords, panel_ranges = panel_ranges, 
          expand = expand, default = default, clip = clip)
}


################### Examples ###########################################################################

test_data <- structure(list(DataType = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("A", "B"), class = "factor"), 
    ExpType = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 
    2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
    2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("X", "Y"), class = "factor"), 
    EffectSize = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 
    1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 
    2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L), .Label = c("15", "35"
    ), class = "factor"), Nsubjects = c(8, 16, 32, 64, 8, 16, 
    32, 64, 8, 16, 32, 64, 8, 16, 32, 64, 8, 16, 32, 64, 8, 16, 
    32, 64, 8, 16, 32, 64, 8, 16, 32, 64), Odds = c(1.06248116259846, 
    1.09482076720863, 1.23086993413208, 1.76749340505612, 1.06641831731573, 
    1.12616954196688, 1.48351814320987, 3.50755080416964, 1.11601399761081, 
    1.18352602009495, 1.45705466646283, 2.53384744810515, 1.13847061762186, 
    1.24983742407086, 1.97075900741022, 6.01497152563726, 1.02798821372378, 
    1.06297006279249, 1.19432835697453, 1.7320754674107, 1.02813271730924, 
    1.09355953747203, 1.44830680332583, 3.4732692664923, 1.06295915758305, 
    1.12008443626365, 1.3887632112682, 2.46321037334, 1.06722652223114, 
    1.1874936754725, 1.89870184372054, 5.943747409114), Upper = c(1.72895843644471, 
    2.09878774769559, 2.59771794965346, 5.08513435549015, 1.72999898901071, 
    1.8702196882561, 3.85385388850167, 5.92564404180303, 1.99113042576373, 
    2.61074135841984, 3.45852331828636, 4.83900142207583, 1.57897154221764, 
    1.8957409107653, 10, 75, 2.3763918424135, 2.50181951057562, 
    3.45037180395673, 3.99515276392065, 2.04584535265976, 2.39317394040066, 
    2.832526733659, 5.38414183471915, 1.40569501856836, 2.6778044191832, 
    2.98023068052396, 4.75934650422069, 1.54116883311054, 2.50647989271592, 
    3.48517589981551, 100), Lower = c(0.396003888752214, 0.0908537867216577, 
    -0.135978081389309, -1.55014754537791, 0.40283764562075, 
    0.382119395677663, -0.88681760208193, 1.08945756653624, 0.240897569457892, 
    -0.243689318229938, -0.544413985360706, 0.228693474134466, 
    0.69796969302609, 0.603933937376415, 0.183548809738402, 3.57236968943798, 
    -0.320415414965949, -0.375879384990643, -1.06171509000767, 
    -0.531001829099242, 0.010420081958713, -0.206054865456611, 
    0.0640868729926525, 1.56239669826544, 0.720223296597732, 
    -0.437635546655903, -0.202704257987574, 0.167074242459314, 
    0.593284211351745, -0.131492541770921, 0.312227787625573, 
    3.76692741957876)), .Names = c("DataType", "ExpType", "EffectSize", 
"Nsubjects", "Odds", "Upper", "Lower"), class = c("tbl_df", "tbl", 
"data.frame"), row.names = c(NA, -32L))

# Bad plot:
test_data %>%
  ggplot(aes(x=Nsubjects, y = Odds, color=EffectSize)) +
  facet_wrap(DataType ~ ExpType, labeller = label_both, scales="free") +
  geom_line(size=2) +
  geom_ribbon(aes(ymax=Upper, ymin=Lower, fill=EffectSize, color=NULL), alpha=0.2)

# Better plot
test_data %>%
  ggplot(aes(x=Nsubjects, y = Odds, color=EffectSize)) +
  facet_wrap(DataType ~ ExpType, labeller = label_both, scales="free") +
  geom_line(size=2) +
  geom_ribbon(aes(ymax=Upper, ymin=Lower, fill=EffectSize, color=NULL), alpha=0.2) +
  coord_panel_ranges(panel_ranges = list(
    list(x=c(8,64), y=c(1,4)), # Panel 1
    list(x=c(8,64), y=c(1,6)), # Panel 2
    list(NULL),                # Panel 3, an empty list falls back on the default values
    list(x=c(8,64), y=c(1,7))  # Panel 4
  ))

# Error in `geom_line()`:
# ! Problem while converting geom to grob.
# ℹ Error occurred in the 1st layer.
# Caused by error in `layout$panel_params[[data$PANEL[1]]]`:
# ! subscript out of bounds
# Run `rlang::last_trace()` to see where the error occurred.

[teunbrand]

From a quick glance, I spot that UniquePanelCoords$setup_layout() does not implement the parental method, which appends a COORD variable to the layout. This was added in 4.0.0 to avoid some overhead.

Also there is no ggplot2:::scale_range() functions AFAICT.

I'd recommend trying out the following method, and trying to adjust from there.

  setup_layout = function(self, layout, params) {
    layout$COORD <- seq_len(nrow(layout))
    self$num_of_panels <- length(unique(layout$PANEL))
    self$panel_counter <- 1
    layout
  }

[r2evans]

ahh, that gets me further, now I need to see where ggplot2:::scale_range migrated to ... (7f317d4)

I had an internal mod (I didn't remember it was different) that fixes that and was instead

    train_cartesian <- function(scale, limits, name, given_range = c(NA, NA)) {
      if (anyNA(given_range)) {
        expansion <- ggplot2:::default_expansion(scale, expand = self$expand)
        range <- ggplot2:::expand_limits_scale(scale, expansion, coord_limits = limits)
        isna <- is.na(given_range)
        given_range[isna] <- range[isna]
      }
      ...
    }

Now I'm running into some self$panel_limits vs self$panel_ranges, not sure if they are equivalent.

[r2evans]

Your mention of layout$COORD seems an important change. I've been reading through ?Coord and https://ggplot2-book.org/extensions#sec-new-coords, but I don't see mention of it or other things custom Coords need to make sure of. Is there a more details discussion of changes that extensions need to be aware of?

Notably, https://tidyverse.org/blog/2025/09/ggplot2-4-0-0/#goodies-for-extensions and https://tidyverse.org/blog/2025/10/ggplot2-styling/ are good but don't mention that requirement.