Repurpose coord expansion (#6027)

* `default_expansion()` handles longer `expand` arg

* Parser for expand argument

* insert parser at relevant places

* Use Coord$setup_params() to setup expand

* fix plot helper not including params

* Redocument parameter

* fix `coord_flip()` case

* add test

* add news bullet

Author: teunbrand

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* `coord_*(expand)` can now take a logical vector to control expansion at any
+  side of the panel (top, right, bottom, left) (@teunbrand, #6020)
 * (Breaking) The defaults for all geoms can be set at one in the theme. 
   (@teunbrand based on pioneering work by @dpseidel, #2239)
     * A new `theme(geom)` argument is used to track these defaults.

R/coord-.R

@@ -184,10 +184,11 @@ Coord <- ggproto("Coord",
   # Will generally have to return FALSE for coordinate systems that enforce a fixed aspect ratio.
   is_free = function() FALSE,
 
-  setup_params = function(data) {
+  setup_params = function(self, data) {
     list(
       guide_default = guide_axis(),
-      guide_missing = guide_none()
+      guide_missing = guide_none(),
+      expand = parse_coord_expand(self$expand %||% TRUE)
     )
   },
 
@@ -243,6 +244,26 @@ render_axis <- function(panel_params, axis, scale, position, theme) {
   }
 }
 
+# Elaborates an 'expand' argument for every side (top, right, bottom or left)
+parse_coord_expand <- function(expand) {
+  check_logical(expand)
+  if (anyNA(expand)) {
+    cli::cli_abort("{.arg expand} cannot contain missing values.")
+  }
+
+  if (!is_named(expand)) {
+    return(rep_len(expand, 4))
+  }
+
+  # Match by top/right/bottom/left
+  out <- rep(TRUE, 4)
+  i <- match(names(expand), .trbl)
+  if (sum(!is.na(i)) > 0) {
+    out[i] <- unname(expand)[!is.na(i)]
+  }
+  out
+}
+
 # Utility function to check coord limits
 check_coord_limits <- function(
     limits, arg = caller_arg(limits), call = caller_env()

R/coord-cartesian-.R

@@ -9,6 +9,10 @@
 #' @param expand If `TRUE`, the default, adds a small expansion factor to
 #'   the limits to ensure that data and axes don't overlap. If `FALSE`,
 #'   limits are taken exactly from the data or `xlim`/`ylim`.
+#'   Giving a logical vector will separately control the expansion for the four
+#'   directions (top, left, bottom and right). The `expand` argument will be
+#'   recycled to length 4 if necessary. Alternatively, can be a named logical
+#'   vector to control a single direction, e.g. `expand = c(bottom = FALSE)`.
 #' @param default Is this the default coordinate system? If `FALSE` (the default),
 #'   then replacing this coordinate system with another one creates a message alerting
 #'   the user that the coordinate system is being replaced. If `TRUE`, that warning
@@ -100,8 +104,8 @@ CoordCartesian <- ggproto("CoordCartesian", Coord,
 
   setup_panel_params = function(self, scale_x, scale_y, params = list()) {
     c(
-      view_scales_from_scale(scale_x, self$limits$x, self$expand),
-      view_scales_from_scale(scale_y, self$limits$y, self$expand)
+      view_scales_from_scale(scale_x, self$limits$x, params$expand[c(4, 2)]),
+      view_scales_from_scale(scale_y, self$limits$y, params$expand[c(3, 1)])
     )
   },
 

R/coord-flip.R

@@ -89,6 +89,7 @@ CoordFlip <- ggproto("CoordFlip", CoordCartesian,
   },
 
   setup_panel_params = function(self, scale_x, scale_y, params = list()) {
+    params$expand <- params$expand[c(2, 1, 4, 3)]
     parent <- ggproto_parent(CoordCartesian, self)
     panel_params <- parent$setup_panel_params(scale_x, scale_y, params)
     flip_axis_labels(panel_params)

R/coord-radial.R

@@ -66,7 +66,6 @@ coord_radial <- function(theta = "x",
     check_bool(r.axis.inside, allow_null = TRUE)
   }
 
-  check_bool(expand)
   check_bool(rotate.angle)
   check_number_decimal(start, allow_infinite = FALSE)
   check_number_decimal(end, allow_infinite = FALSE, allow_null = TRUE)
@@ -139,8 +138,8 @@ CoordRadial <- ggproto("CoordRadial", Coord,
   setup_panel_params = function(self, scale_x, scale_y, params = list()) {
 
     params <- c(
-      view_scales_polar(scale_x, self$theta, expand = self$expand),
-      view_scales_polar(scale_y, self$theta, expand = self$expand),
+      view_scales_polar(scale_x, self$theta, expand = params$expand[c(4, 2)]),
+      view_scales_polar(scale_y, self$theta, expand = params$expand[c(3, 1)]),
       list(bbox = polar_bbox(self$arc, inner_radius = self$inner_radius),
            arc = self$arc, inner_radius = self$inner_radius)
     )
@@ -469,27 +468,27 @@ CoordRadial <- ggproto("CoordRadial", Coord,
   },
 
   setup_params = function(self, data) {
-    if (isFALSE(self$r_axis_inside)) {
-      place <- in_arc(c(0, 0.5, 1, 1.5) * pi, self$arc)
-      if (place[1]) {
-        return(list(r_axis = "left", fake_arc = c(0, 2) * pi))
-      }
-      if (place[3]) {
-        return(list(r_axis = "left", fake_arc = c(1, 3)* pi))
-      }
-      if (place[2]) {
-        return(list(r_axis = "bottom", fake_arc = c(0.5, 2.5) * pi))
-      }
-      if (place[4]) {
-        return(list(r_axis = "bottom", fake_arc = c(1.5, 3.5) * pi))
-      }
+    params <- ggproto_parent(Coord, self)$setup_params(data)
+    if (!isFALSE(self$r_axis_inside)) {
+      return(params)
+    }
+
+    place <- in_arc(c(0, 0.5, 1, 1.5) * pi, self$arc)
+    if (!any(place)) {
       cli::cli_warn(c(
         "No appropriate placement found for {.arg r_axis_inside}.",
         i = "Axis will be placed at panel edge."
       ))
-      self$r_axis_inside <- TRUE
+      params$r_axis_inside <- TRUE
+      return(params)
     }
-    return(NULL)
+
+    params$r_axis   <- if (any(place[c(1, 3)])) "left" else "bottom"
+    params$fake_arc <- switch(
+      which(place[c(1, 3, 2, 4)])[1],
+      c(0, 2), c(1, 3), c(0.5, 2.5), c(1.5, 3.5)
+    ) * pi
+    params
   }
 )
 

R/coord-sf.R

@@ -18,12 +18,10 @@ CoordSf <- ggproto("CoordSf", CoordCartesian,
   },
 
   setup_params = function(self, data) {
-    crs <- self$determine_crs(data)
+    params <- ggproto_parent(Coord, self)$setup_params(data)
 
-    params <- list(
-      crs = crs,
-      default_crs = self$default_crs
-    )
+    params$crs <- self$determine_crs(data)
+    params$default_crs <- self$default_crs
     self$params <- params
 
     params
@@ -170,8 +168,8 @@ CoordSf <- ggproto("CoordSf", CoordCartesian,
 
   setup_panel_params = function(self, scale_x, scale_y, params = list()) {
     # expansion factors for scale limits
-    expansion_x <- default_expansion(scale_x, expand = self$expand)
-    expansion_y <- default_expansion(scale_y, expand = self$expand)
+    expansion_x <- default_expansion(scale_x, expand = params$expand[c(4, 2)])
+    expansion_y <- default_expansion(scale_y, expand = params$expand[c(3, 1)])
 
     # get scale limits and coord limits and merge together
     # coord limits take precedence over scale limits

R/coord-transform.R

@@ -153,8 +153,8 @@ CoordTrans <- ggproto("CoordTrans", Coord,
 
   setup_panel_params = function(self, scale_x, scale_y, params = list()) {
     c(
-      view_scales_from_scale_with_coord_trans(scale_x, self$limits$x, self$trans$x, self$expand),
-      view_scales_from_scale_with_coord_trans(scale_y, self$limits$y, self$trans$y, self$expand)
+      view_scales_from_scale_with_coord_trans(scale_x, self$limits$x, self$trans$x, params$expand[c(4, 2)]),
+      view_scales_from_scale_with_coord_trans(scale_y, self$limits$y, self$trans$y, params$expand[c(3, 1)])
     )
   },
 

R/scale-expansion.R

@@ -98,11 +98,24 @@ expand_range4 <- function(limits, expand) {
 #'
 default_expansion <- function(scale, discrete = expansion(add = 0.6),
                               continuous = expansion(mult = 0.05), expand = TRUE) {
-  if (!expand) {
-    return(expansion(0, 0))
+  out <- expansion()
+  if (!any(expand)) {
+    return(out)
   }
+  scale_expand <- scale$expand %|W|%
+    if (scale$is_discrete()) discrete else continuous
 
-  scale$expand %|W|% if (scale$is_discrete()) discrete else continuous
+  # for backward compatibility, we ensure expansions have expected length
+  expand <- rep_len(expand, 2L)
+  scale_expand <- rep_len(scale_expand, 4)
+
+  if (expand[1]) {
+    out[1:2] <- scale_expand[1:2]
+  }
+  if (expand[2]) {
+    out[3:4] <- scale_expand[3:4]
+  }
+  out
 }
 
 #' Expand limits in (possibly) transformed space