Simplify (layer) axis alignment code

NEWS.md

@@ -46,7 +46,7 @@ where the formatting is also better._
 - Added layers, particularly from `tinyplot_add()`, should now respect the
   x-axis order of the original plot layer. This should ensure that we don't end
   up with misaligned layers. For example, when adding a ribbon on top of an
-  errorbar plot. (#517, #520 @grantmcdermott)
+  errorbar plot. (#517, #520, #523 @grantmcdermott)
 
 
 ### Documentation

R/align_layer.R

@@ -0,0 +1,36 @@
+# Ensure added layers respect the x-axis order of the original plot layer
+# (e.g., when adding lines or ribbons on top of errorbars)
+align_layer = function(settings) {
+
+  # Retrieve xlabs from current and original layers
+  xlabs_layer = settings[["xlabs"]]
+  xlabs_orig = get("xlabs", envir = get(".tinyplot_env", envir = parent.env(environment())))
+
+  # Only adjust if original layer has named xlabs
+  if (!is.null(names(xlabs_orig))) {
+    if (is.factor(settings$datapoints[["x"]])) {
+      # Case 1: relevel a factor (e.g., ribbon added to errorbars)
+      settings$datapoints[["x"]] = tryCatch(
+        factor(settings$datapoints[["x"]], levels = names(xlabs_orig)),
+        error = function(e) {
+          settings$datapoints[["x"]]
+        }
+      )
+      settings$datapoints = settings$datapoints[order(settings$datapoints[["x"]]), ]
+    } else if (!is.null(names(xlabs_layer))) {
+      # Case 2: match implicit integer -> label mapping (e.g., lines added to errorbars)
+      if (setequal(names(xlabs_layer), names(xlabs_orig))) {
+        orig_order = xlabs_orig[names(xlabs_layer)[settings$datapoints[["x"]]]]
+        x_layer = settings$datapoints[["x"]]
+        settings$datapoints[["x"]] = orig_order
+        # Adjust ancillary variables
+        for (v in c("rowid", "xmin", "xmax")) {
+          if (identical(settings$datapoints[[v]], x_layer)) {
+            settings$datapoints[[v]] = orig_order
+          }
+        }
+        settings$datapoints = settings$datapoints[order(settings$datapoints[["x"]]), ]
+      }
+    }
+  }
+}

R/tinyplot.R

@@ -868,13 +868,21 @@ tinyplot.default = function(
     settings$type_data(settings, ...)
   }
 
+  # ensure axis aligment of any added layers
+  if (!add) {
+    assign("xlabs", settings[["xlabs"]], envir = get(".tinyplot_env", envir = parent.env(environment())))
+  } else {
+    align_layer(settings)
+  }
+
   # flip -> swap x and y after type_data, except for boxplots (which has its own bespoke flip logic)
   flip_datapoints(settings)
 
 
   #
   ## bubble plot -----
   #
+
   # catch some simple aesthetics for bubble plots before the standard "by"
   # grouping sanitizers (actually: will only be used for dual_legend plots but
   # easiest to assign/determine now)
@@ -1181,60 +1189,6 @@ tinyplot.default = function(
   list2env(facet_window_args, environment())
 
 
-  #
-  ## layering axis alignment -----
-  #
-
-  # ensure added layers respect the x-axis order of the original plot layer
-  #   (e.g., when adding lines or ribbons on top of errorbars)
-  if (!add) {
-    # keep track of the x(y)labs from the original (1st) layer
-    assign("xlabs", xlabs, envir = get(".tinyplot_env", envir = parent.env(environment())))
-    assign("ylabs", ylabs, envir = get(".tinyplot_env", envir = parent.env(environment())))
-  } else {
-    # check whether we need to adjust any added layers
-    # aside: we need some extra accounting for flipped plots (x -> y)
-    if (!flip) {
-      labs_orig = "xlabs"
-      labs_layer = xlabs
-      dp_var = "x"  
-      dp_ovars = c("rowid", "xmin", "xmax")
-    } else {
-      labs_orig = "ylabs"
-      labs_layer = ylabs
-      dp_var = "y"
-      dp_ovars = c("rowid", "ymin", "ymax")
-    }
-    # retrieve the relevant axis labs from the original layer (and we only care
-    # if it's not null)
-    labs_orig = get(labs_orig, envir = get(".tinyplot_env", envir = parent.env(environment())))
-    if (!is.null(names(labs_orig))) {
-      if (is.factor(datapoints[[dp_var]])) {
-        # case 1: relevel a factor (e.g., ribbon added to errorbars)
-        datapoints[[dp_var]] = tryCatch(
-          factor(datapoints[[dp_var]], levels = names(labs_orig)),
-          error = function(e) {
-            datapoints[[dp_var]]
-          }
-        )
-        datapoints = datapoints[order(datapoints[[dp_var]]), ]
-      } else if (!is.null(names(labs_layer))) {
-        # case 2: match implicit integer -> label mapping (e.g., lines added to errorbars)
-        if (setequal(names(labs_layer), names(labs_orig))) {
-          orig_order = labs_orig[names(labs_layer)[datapoints[[dp_var]]]]
-          dp_var_layer = datapoints[[dp_var]]
-          datapoints[[dp_var]] = orig_order
-          # it's a bit of a pain, but we also have to adjust some ancillary vars
-          for (dov in dp_ovars) {
-            if (identical(datapoints[[dov]], dp_var_layer)) datapoints[[dov]] = orig_order
-          }
-          datapoints = datapoints[order(datapoints[[dp_var]]), ]
-        }
-      }
-    }
-  }
-
-
   #
   ## split and draw datapoints -----
   #