sf aspect ratio is flipped, which is why conversions have always been a bit off

Author: cpsievert

R/ggplotly.R

@@ -711,20 +711,28 @@ gg2list <- function(p, width = NULL, height = NULL,
       )
 
       # set scaleanchor/scaleratio if these are fixed coordinates
+      # the logic here is similar to what p$coordinates$aspect() does,
+      # but the ratio is scaled to the data range by plotly.js 
       fixed_coords <- c("CoordSf", "CoordFixed", "CoordMap", "CoordQuickmap")
       if (inherits(p$coordinates, fixed_coords)) {
         axisObj$scaleanchor <- anchor
         ratio <- p$coordinates$ratio %||% 1
-        # a la CoordSf$aspect
+        axisObj$scaleratio <- if (xy == "y") ratio else 1 / ratio
+        
         if (inherits(p$coordinates, "CoordSf")) {
           if (isTRUE(sf::st_is_longlat(rng$crs))) {
             ratio <- cos(mean(rng$y_range) * pi/180)
           }
+          # note how ratio is flipped in CoordSf$aspect() vs CoordFixed$aspect()
+          axisObj$scaleratio <- if (xy == "y") 1 / ratio else ratio
         }
-        axisObj$scaleratio <- if (xy == "y") ratio else 1 / ratio
       }
 
-      # TODO: should we implement aspect ratios?
+      # TODO: seems like we _could_ support this with scaleanchors, 
+      # but inverse transform by the panel ranges?
+      # also, note how aspect.ratio overwrites fixed coordinates:
+      # ggplot(mtcars, aes(wt, mpg)) + geom_point() + coord_fixed(0.5)
+      # ggplot(mtcars, aes(wt, mpg)) + geom_point() + coord_fixed(0.5) + theme(aspect.ratio = 1)
       if (!is.null(theme$aspect.ratio)) {
         warning(
           "Aspect ratios aren't yet implemented, but you can manually set", 

tests/testthat/test-ggplot-sf.R

@@ -54,3 +54,14 @@ test_that("geom_sf() with basic polygons and points.", {
   expect_equivalent(l$data[[2]]$mode, "lines")
   expect_equivalent(l$data[[3]]$mode, "markers")
 })
+
+test_that("sf aspect ratio is correct", {
+  skip_if_not_installed("sf")
+  
+  p <- ggplot(nc) + geom_sf() 
+  
+  l <- save_outputs(p, "sf-aspect")
+  
+  expect_equivalent(l$layout$xaxis$scaleanchor, "y")
+  expect_equal(l$layout$xaxis$scaleratio, 0.81678435872298)
+})