From c9a20027ca673bd7e13a1f240b7b66a836201eef Mon Sep 17 00:00:00 2001
From: Thomas Lin Pedersen <thomasp85@gmail.com>
Date: Thu, 11 Jan 2024 10:56:16 +0100
Subject: [PATCH] Make sure node_angle results in legible text

---
 R/utils.R         | 13 ++++++++++---
 man/node_angle.Rd |  7 +++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/R/utils.R b/R/utils.R
index 9309049e..28ad8da4 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -13,6 +13,9 @@
 #' @param degrees Logical. Should the angle be returned in degree (`TRUE`)
 #' or radians (`FALSE`). Defaults to `TRUE`.
 #'
+#' @param avoid_flip Logical. Should the angle be adjusted so that text is
+#' always upside-down
+#'
 #' @return A vector with the angle of each node/edge
 #'
 #' @examples
@@ -27,9 +30,13 @@
 #'   expand_limits(x = c(-1.3, 1.3), y = c(-1.3, 1.3))
 #' @export
 #'
-node_angle <- function(x, y, degrees = TRUE) {
+node_angle <- function(x, y, degrees = TRUE, avoid_flip = TRUE) {
   angles <- atan2(y, x)
   angles[angles < 0] <- angles[angles < 0] + 2 * pi
+  if (avoid_flip) {
+    needs_flip <- angles > pi/2 & angles < 3*pi/2
+    angles[needs_flip] <- angles[needs_flip] + pi
+  }
   if (degrees) {
     angles * 360 / (2 * pi)
   } else {
@@ -39,10 +46,10 @@ node_angle <- function(x, y, degrees = TRUE) {
 #' @rdname node_angle
 #'
 #' @export
-edge_angle <- function(x, y, xend, yend, degrees = TRUE) {
+edge_angle <- function(x, y, xend, yend, degrees = TRUE, avoid_flip = TRUE) {
   x <- xend - x
   y <- yend - y
-  node_angle(x, y, degrees)
+  node_angle(x, y, degrees, avoid_flip = avoid_flip)
 }
 
 
diff --git a/man/node_angle.Rd b/man/node_angle.Rd
index a6b5c00f..4b25f68c 100644
--- a/man/node_angle.Rd
+++ b/man/node_angle.Rd
@@ -5,9 +5,9 @@
 \alias{edge_angle}
 \title{Get the angle of nodes and edges}
 \usage{
-node_angle(x, y, degrees = TRUE)
+node_angle(x, y, degrees = TRUE, avoid_flip = TRUE)
 
-edge_angle(x, y, xend, yend, degrees = TRUE)
+edge_angle(x, y, xend, yend, degrees = TRUE, avoid_flip = TRUE)
 }
 \arguments{
 \item{x, y}{A vector of positions}
@@ -15,6 +15,9 @@ edge_angle(x, y, xend, yend, degrees = TRUE)
 \item{degrees}{Logical. Should the angle be returned in degree (\code{TRUE})
 or radians (\code{FALSE}). Defaults to \code{TRUE}.}
 
+\item{avoid_flip}{Logical. Should the angle be adjusted so that text is
+always upside-down}
+
 \item{xend, yend}{The end position of the edge}
 }
 \value{