geom_raster() fallback for non-Cartesian coords (#5627)

* fallback mechanism

* add tests

* add news bullet

* put bullet in appropriate place

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* `geom_raster()` now falls back to rendering as `geom_rect()` when coordinates
+ are not Cartesian (#5503).
 * `stat_ecdf()` now has an optional `weight` aesthetic (@teunbrand, #5058).
 * Position scales combined with `coord_sf()` can now use functions in the 
  `breaks` argument. In addition, `n.breaks` works as intended and 

R/geom-raster.R

@@ -88,9 +88,14 @@ GeomRaster <- ggproto("GeomRaster", Geom,
  draw_panel = function(self, data, panel_params, coord, interpolate = FALSE,
  hjust = 0.5, vjust = 0.5) {
  if (!inherits(coord, "CoordCartesian")) {
- cli::cli_abort(c(
- "{.fn {snake_class(self)}} only works with {.fn coord_cartesian}."
+ cli::cli_inform(c(
+ "{.fn {snake_class(self)}} only works with {.fn coord_cartesian}.",
+ i = "Falling back to drawing as {.fn {snake_class(GeomRect)}}."
  ))
+ data$linewidth <- 0.3 # preventing anti-aliasing artefacts
+ data$colour <- data$fill
+ grob <- GeomRect$draw_panel(data, panel_params, coord)
+ return(grob)
  }
 
  # Convert vector of data to raster

tests/testthat/_snaps/geom-raster.md

@@ -14,13 +14,6 @@
 
  `vjust` must be a number, not the string "a".
 
----
-
- Problem while converting geom to grob.
- i Error occurred in the 1st layer.
- Caused by error in `draw_panel()`:
- ! `geom_raster()` only works with `coord_cartesian()`.
-
 # geom_raster() fails with pattern fills
 
  Problem while converting geom to grob.

tests/testthat/test-geom-raster.R

@@ -6,7 +6,7 @@ test_that("geom_raster() checks input and coordinate system", {
 
  df <- data_frame(x = rep(c(-1, 1), each = 3), y = rep(-1:1, 2), z = 1:6)
  p <- ggplot(df, aes(x, y, fill = z)) + geom_raster() + coord_polar()
- expect_snapshot_error(ggplotGrob(p))
+ expect_message(ggplotGrob(p), "only works with")
 })
 
 test_that("geom_raster() fails with pattern fills", {
@@ -66,6 +66,14 @@ test_that("geom_raster draws correctly", {
  geom_point(colour = "red")
  )
 
+ # In non-linear coordinates
+ df <- data.frame(x = c(1, 2, 1, 2), y = c(1, 1, 2, 2), fill = LETTERS[1:4])
+ suppressMessages(
+ expect_doppelganger("rectangle fallback",
+ ggplot(df, aes(x, y, fill = fill)) + geom_raster() + coord_polar()
+ )
+ )
+
  # Categorical fill, irregular swatches ---------------------------------------
 
  df <- expand.grid(x = 1:10, y = 1:10)