theme: Add different ticks length for different axes (#2934)

* theme: Add different ticks length for different axes

* guides-axis: make assignment a bit more elegant

* styler changes to adhere to tidyverse style guide

* Fix 456e742 -- that commit was too aggressive

* NEWS: Update issue reference

* Remove unintended changes to Rd files

* theme: New example only uses one unit

* theme-default: Update theme_void

* Fix language and style according to Claus Wilke's recommendations

* NEWS.md: Fix typo.
* R/theme.r: Fix style and add comments for examples.

* An additional language improvement suggested by Claus Wilke

* Fix the NEWS.md entry

* Move the location of the NEWS.md entry.

Also use longer lines to somewhat better match other entries.

Author: pank

NEWS.md

@@ -121,6 +121,11 @@ core developer team.
 
 * `sec_axis()` now accepts functions as well as formulas (@yutannihilation, #3031).
 
+*   New theme elements allowing different ticks lengths for each axis. For instance,
+    this can be used to have inwards ticks on the x-axis (`axis.ticks.length.x`) and
+    outwards ticks on the y-axis (`axis.ticks.length.y`) (@pank, #2935).
+
+
 # ggplot2 3.1.0
 
 ## Breaking changes
@@ -230,7 +235,6 @@ This is a minor release and breaking changes have been kept to a minimum. End us
     `nlevel`, an alias for `scaled`, to better match the syntax of `stat_bin()`
     (@bjreisman, #2679).
 
-
 # ggplot2 3.0.0
 
 ## Breaking changes

R/guides-axis.r

@@ -14,6 +14,31 @@ guide_axis <- function(at, labels, position = "right", theme) {
   zero <- unit(0, "npc")
   one <- unit(1, "npc")
 
+  theme$axis.ticks.length.x.bottom <- with(
+    theme,
+    axis.ticks.length.x.bottom %||%
+      axis.ticks.length.x %||%
+      axis.ticks.length
+  )
+  theme$axis.ticks.length.x.top <- with(
+    theme,
+    axis.ticks.length.x.top %||%
+      axis.ticks.length.x %||%
+      axis.ticks.length
+  )
+  theme$axis.ticks.length.y.left <- with(
+    theme,
+    axis.ticks.length.y.left %||%
+      axis.ticks.length.y %||%
+      axis.ticks.length
+  )
+  theme$axis.ticks.length.y.right <- with(
+    theme,
+    axis.ticks.length.y.right %||%
+      axis.ticks.length.y %||%
+      axis.ticks.length
+  )
+
   label_render <- switch(position,
     top = "axis.text.x.top", bottom = "axis.text.x.bottom",
     left = "axis.text.y.left", right = "axis.text.y.right"
@@ -22,12 +47,12 @@ guide_axis <- function(at, labels, position = "right", theme) {
   label_x <- switch(position,
     top = ,
     bottom = at,
-    right = theme$axis.ticks.length,
-    left = one - theme$axis.ticks.length
+    right = theme$axis.ticks.length.y.right,
+    left = one - theme$axis.ticks.length.y.left
   )
   label_y <- switch(position,
-    top = theme$axis.ticks.length,
-    bottom = one - theme$axis.ticks.length,
+    top = theme$axis.ticks.length.x.top,
+    bottom = one - theme$axis.ticks.length.x.bottom,
     right = ,
     left = at
   )
@@ -58,18 +83,18 @@ guide_axis <- function(at, labels, position = "right", theme) {
   ticks <- switch(position,
     top = element_render(theme, "axis.ticks.x.top",
       x          = rep(at, each = 2),
-      y          = rep(unit.c(zero, theme$axis.ticks.length), nticks),
+      y          = rep(unit.c(zero, theme$axis.ticks.length.x.top), nticks),
       id.lengths = rep(2, nticks)),
     bottom = element_render(theme, "axis.ticks.x.bottom",
       x          = rep(at, each = 2),
-      y          = rep(unit.c(one - theme$axis.ticks.length, one), nticks),
+      y          = rep(unit.c(one - theme$axis.ticks.length.x.bottom, one), nticks),
       id.lengths = rep(2, nticks)),
     right = element_render(theme, "axis.ticks.y.right",
-      x          = rep(unit.c(zero, theme$axis.ticks.length), nticks),
+      x          = rep(unit.c(zero, theme$axis.ticks.length.y.right), nticks),
       y          = rep(at, each = 2),
       id.lengths = rep(2, nticks)),
     left = element_render(theme, "axis.ticks.y.left",
-      x          = rep(unit.c(one - theme$axis.ticks.length, one), nticks),
+      x          = rep(unit.c(one - theme$axis.ticks.length.y.left, one), nticks),
       y          = rep(at, each = 2),
       id.lengths = rep(2, nticks))
   )
@@ -79,21 +104,21 @@ guide_axis <- function(at, labels, position = "right", theme) {
     top    = gtable_col("axis",
       grobs   = list(labels, ticks),
       width   = one,
-      heights = unit.c(grobHeight(labels), theme$axis.ticks.length)
+      heights = unit.c(grobHeight(labels), theme$axis.ticks.length.x.top)
     ),
     bottom = gtable_col("axis",
       grobs   = list(ticks, labels),
       width   = one,
-      heights = unit.c(theme$axis.ticks.length, grobHeight(labels))
+      heights = unit.c(theme$axis.ticks.length.x.bottom, grobHeight(labels))
     ),
     right  = gtable_row("axis",
       grobs   = list(ticks, labels),
-      widths  = unit.c(theme$axis.ticks.length, grobWidth(labels)),
+      widths  = unit.c(theme$axis.ticks.length.y.right, grobWidth(labels)),
       height  = one
     ),
     left   = gtable_row("axis",
       grobs   = list(labels, ticks),
-      widths  = unit.c(grobWidth(labels), theme$axis.ticks.length),
+      widths  = unit.c(grobWidth(labels), theme$axis.ticks.length.y.left),
       height  = one
     )
   )

R/theme-defaults.r

@@ -139,6 +139,12 @@ theme_grey <- function(base_size = 11, base_family = "",
     axis.text.y.right =  element_text(margin = margin(l = 0.8 * half_line / 2), hjust = 0),
     axis.ticks =         element_line(colour = "grey20"),
     axis.ticks.length =  unit(half_line / 2, "pt"),
+    axis.ticks.length.x = NULL,
+    axis.ticks.length.x.top = NULL,
+    axis.ticks.length.x.bottom = NULL,
+    axis.ticks.length.y = NULL,
+    axis.ticks.length.y.left = NULL,
+    axis.ticks.length.y.right = NULL,
     axis.title.x =       element_text(
                            margin = margin(t = half_line / 2),
                            vjust = 1
@@ -459,6 +465,12 @@ theme_void <- function(base_size = 11, base_family = "",
     axis.text =          element_blank(),
     axis.title =         element_blank(),
     axis.ticks.length =  unit(0, "pt"),
+    axis.ticks.length.x = NULL,
+    axis.ticks.length.x.top = NULL,
+    axis.ticks.length.x.bottom = NULL,
+    axis.ticks.length.y = NULL,
+    axis.ticks.length.y.left = NULL,
+    axis.ticks.length.y.right = NULL,
     legend.box =         NULL,
     legend.key.size =    unit(1.2, "lines"),
     legend.position =    "right",
@@ -528,6 +540,12 @@ theme_test <- function(base_size = 11, base_family = "",
     axis.text.y.right =  element_text(margin = margin(l = 0.8 * half_line / 2), hjust = 0),
     axis.ticks =         element_line(colour = "grey20"),
     axis.ticks.length =  unit(half_line / 2, "pt"),
+    axis.ticks.length.x = NULL,
+    axis.ticks.length.x.top = NULL,
+    axis.ticks.length.x.bottom = NULL,
+    axis.ticks.length.y = NULL,
+    axis.ticks.length.y.left = NULL,
+    axis.ticks.length.y.right = NULL,
     axis.title.x =       element_text(
                            margin = margin(t = half_line / 2),
                            vjust = 1

R/theme-elements.r

@@ -292,6 +292,12 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   axis.text.y.left    = el_def("element_text", "axis.text.y"),
   axis.text.y.right   = el_def("element_text", "axis.text.y"),
   axis.ticks.length   = el_def("unit"),
+  axis.ticks.length.x = el_def("unit", "axis.ticks.length"),
+  axis.ticks.length.x.top = el_def("unit", "axis.ticks.length.x"),
+  axis.ticks.length.x.bottom = el_def("unit", "axis.ticks.length.x"),
+  axis.ticks.length.y  = el_def("unit", "axis.ticks.length"),
+  axis.ticks.length.y.left = el_def("unit", "axis.ticks.length.y"),
+  axis.ticks.length.y.right = el_def("unit", "axis.ticks.length.y"),
   axis.ticks.x        = el_def("element_line", "axis.ticks"),
   axis.ticks.x.top    = el_def("element_line", "axis.ticks.x"),
   axis.ticks.x.bottom = el_def("element_line", "axis.ticks.x"),

R/theme.r

@@ -47,7 +47,8 @@
 #'   `axis.ticks.y.left`, `axis.ticks.y.right`). `axis.ticks.*.*` inherits from
 #'   `axis.ticks.*` which inherits from `axis.ticks`, which in turn inherits
 #'   from `line`
-#' @param axis.ticks.length length of tick marks (`unit`)
+#' @param axis.ticks.length,axis.ticks.length.x,axis.ticks.length.x.top,axis.ticks.length.x.bottom,axis.ticks.length.y,axis.ticks.length.y.left,axis.ticks.length.y.right
+#' length of tick marks (`unit`)
 #' @param axis.line,axis.line.x,axis.line.x.top,axis.line.x.bottom,axis.line.y,axis.line.y.left,axis.line.y.right
 #'   lines along axes ([element_line()]). Specify lines along all axes (`axis.line`),
 #'   lines for each plane (using `axis.line.x` or `axis.line.y`), or individually
@@ -192,12 +193,21 @@
 #' )
 #'
 #' # Axes ----------------------------------------------------------------------
+#' # Change styles of axes texts and lines
 #' p1 + theme(axis.line = element_line(size = 3, colour = "grey80"))
 #' p1 + theme(axis.text = element_text(colour = "blue"))
 #' p1 + theme(axis.ticks = element_line(size = 2))
-#' p1 + theme(axis.ticks.length = unit(.25, "cm"))
+#'
+#' # Change the appearance of the y-axis title
 #' p1 + theme(axis.title.y = element_text(size = rel(1.5), angle = 90))
 #'
+#' # Make ticks point outwards on y-axis and inwards on x-axis
+#' p1 + theme(
+#'   axis.ticks.length.y = unit(.25, "cm"),
+#'   axis.ticks.length.x = unit(-.25, "cm"),
+#'   axis.text.x = element_text(margin = margin(t = .3, unit = "cm"))
+#' )
+#'
 #' \donttest{
 #' # Legend --------------------------------------------------------------------
 #' p2 <- ggplot(mtcars, aes(wt, mpg)) +
@@ -275,6 +285,12 @@ theme <- function(line,
                   axis.ticks.y.left,
                   axis.ticks.y.right,
                   axis.ticks.length,
+                  axis.ticks.length.x,
+                  axis.ticks.length.x.top,
+                  axis.ticks.length.x.bottom,
+                  axis.ticks.length.y,
+                  axis.ticks.length.y.left,
+                  axis.ticks.length.y.right,
                   axis.line,
                   axis.line.x,
                   axis.line.x.top,