fix "inward" and "outward" hjust and vjust in geom_text() with angle > 45 (#4447)

Author: aphalo

NEWS.md

@@ -16,6 +16,9 @@
 * Fix a bug in `guide_bins()` where keys would disappear if the guide was 
   reversed (@thomasp85, #4210)
 
+* Fix bug in `geom_text()` where `"outward"` and `"inward"` justification for 
+  some `angle` values was reversed (@aphalo, #4169, #4447)
+
 * Fix a bug in legend justification where justification was lost of the legend
   dimensions exceeded the available size (@thomasp85, #3635)
 

R/geom-text.r

@@ -208,11 +208,12 @@ GeomText <- ggproto("GeomText", Geom,
     }
 
     data <- coord$transform(data, panel_params)
+
     if (is.character(data$vjust)) {
-      data$vjust <- compute_just(data$vjust, data$y)
+      data$vjust <- compute_just(data$vjust, data$y, data$x, data$angle)
     }
     if (is.character(data$hjust)) {
-      data$hjust <- compute_just(data$hjust, data$x)
+      data$hjust <- compute_just(data$hjust, data$x, data$y, data$angle)
     }
 
     textGrob(
@@ -234,11 +235,31 @@ GeomText <- ggproto("GeomText", Geom,
   draw_key = draw_key_text
 )
 
-compute_just <- function(just, x) {
-  inward <- just == "inward"
-  just[inward] <- c("left", "middle", "right")[just_dir(x[inward])]
-  outward <- just == "outward"
-  just[outward] <- c("right", "middle", "left")[just_dir(x[outward])]
+compute_just <- function(just, a, b = a, angle = 0) {
+  #  As justification direction is relative to the text, not the plotting area
+  #  we need to swap x and y if text direction is rotated so that hjust is
+  #  applied along y and vjust along x.
+  if (any(grepl("outward|inward", just))) {
+    # ensure all angles are in -360...+360
+    angle <- angle %% 360
+    # ensure correct behaviour for angles in -360...+360
+    angle <- ifelse(angle > 180, angle - 360, angle)
+    angle <- ifelse(angle < -180, angle + 360, angle)
+    rotated_forward <-
+      grepl("outward|inward", just) & (angle > 45 & angle < 135)
+    rotated_backwards <-
+      grepl("outward|inward", just) & (angle < -45 & angle > -135)
+
+    ab <- ifelse(rotated_forward | rotated_backwards, b, a)
+    just_swap <- rotated_backwards | abs(angle) > 135
+    inward <-
+      (just == "inward" & !just_swap | just == "outward" & just_swap)
+    just[inward] <- c("left", "middle", "right")[just_dir(ab[inward])]
+    outward <-
+      (just == "outward" & !just_swap) | (just == "inward" & just_swap)
+    just[outward] <- c("right", "middle", "left")[just_dir(ab[outward])]
+
+  }
 
   unname(c(left = 0, center = 0.5, right = 1,
     bottom = 0, middle = 0.5, top = 1)[just])

tests/testthat/test-geom-text.R

@@ -29,3 +29,63 @@ test_that("inward points close to center are centered", {
     c(0.5, 0.5, 0.5)
   )
 })
+
+test_that("inward moves text towards center at 90 degrees", {
+  expect_equal(
+    compute_just(c("inward", "inward", "inward"),
+                 c(0, 0.5, 1),
+                 c(0, 0.5, 1),
+                 c(90, 90, 90)),
+    c(0, 0.5, 1.0)
+  )
+})
+
+test_that("outward moves text away from center at 90 degrees", {
+  expect_equal(
+    compute_just(c("outward", "outward", "outward"),
+                 c(0, 0, 0),
+                 c(0, 0.5, 1),
+                 c(90, 90, 90)),
+    c(1.0, 0.5, 0)
+  )
+})
+
+test_that("only inward and outward respond to angle", {
+  expect_equal(
+    compute_just(c("inward", "left", "outward"),
+                 c(0, 0, 0),
+                 c(0, 0.5, 1),
+                 c(90, 90, 90)),
+    c(0.0, 0.0, 0.0)
+  )
+})
+
+test_that("inward moves text towards center at 150 degrees", {
+  expect_equal(
+    compute_just(c("inward", "inward", "inward"),
+                 c(0, 0.5, 1),
+                 c(0, 0.5, 1),
+                 c(150, 150, 150)),
+    c(1.0, 0.5, 0.0)
+  )
+})
+
+test_that("inward moves text towards center at -90 degrees", {
+  expect_equal(
+    compute_just(c("inward", "inward", "inward"),
+                 c(0, 0.5, 1),
+                 c(0, 0.5, 1),
+                 c(-90, -90, -90)),
+    c(1.0, 0.5, 0.0)
+  )
+})
+
+test_that("outward moves text away from center at 450 degrees", {
+  expect_equal(
+    compute_just(c("inward", "inward", "inward"),
+                 c(0, 0, 0),
+                 c(0, 0.5, 1),
+                 c(450, 450, 450)),
+    c(0.0, 0.5, 1.0)
+  )
+})