From ba466fe474572c67b3c5fbfe2b2699ee2bea2fb1 Mon Sep 17 00:00:00 2001
From: Markus Koch <markus@notsyncing.net>
Date: Sun, 19 Apr 2020 22:00:35 +0200
Subject: [PATCH] leaflet-streets: Improve orientation detection for street
 names

---
 htdocs/leafletjs/Leaflet.streetlabels.js | 29 +++++++++++++-----------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/htdocs/leafletjs/Leaflet.streetlabels.js b/htdocs/leafletjs/Leaflet.streetlabels.js
index 8685ac9..1fb2754 100644
--- a/htdocs/leafletjs/Leaflet.streetlabels.js
+++ b/htdocs/leafletjs/Leaflet.streetlabels.js
@@ -126,8 +126,7 @@ L.StreetLabels = L.LabelTextCollision
                     var stopCoords = layer.getLatLngs()[layer.getLatLngs().length - 1];
 
                     //Flip lineString if bearing is negative
-                    if (this._getBearing(startCoords, stopCoords) < 0)
-                        layer = this._getLineStringReverse(layer);
+                    flip = (this._getBearing(startCoords, stopCoords) < 0);
 
                     if (layer._parts) {
                         ctx.textAlign = "center";
@@ -137,7 +136,7 @@ L.StreetLabels = L.LabelTextCollision
                             //Build the points list for the first part
                             var pathPoints = [];
                             for (var i = 0; i < part.length; i++) {
-                                var linePart = part[i];
+                                var linePart = (flip ? part[part.length - 1 - i] : part[i]);
                                 pathPoints.push(linePart.x);
                                 pathPoints.push(linePart.y);
                             }
@@ -158,16 +157,20 @@ L.StreetLabels = L.LabelTextCollision
             Source: https://makinacorpus.github.io/Leaflet.GeometryUtil/leaflet.geometryutil.js.html
          */
         _getBearing: function (startCoords, stopCoords) {
-            var rad = Math.PI / 180,
-                lat1 = startCoords.lat * rad,
-                lat2 = stopCoords.lat * rad,
-                lon1 = startCoords.lng * rad,
-                lon2 = stopCoords.lng * rad,
-                y = Math.sin(lon2 - lon1) * Math.cos(lat2),
-                x = Math.cos(lat1) * Math.sin(lat2) -
-                    Math.sin(lat1) * Math.cos(lat2) * Math.cos(lon2 - lon1);
-            var bearing = ((Math.atan2(y, x) * 180 / Math.PI) + 360) % 360;
-            return bearing >= 180 ? bearing - 360 : bearing;
+            if (startCoords.lat == stopCoords.lat) {
+                if (startCoords.lng > stopCoords.lng)
+                    return -180;
+                else
+                    return 180;
+            }
+            if (startCoords.lng == stopCoords.lng) {
+                if (startCoords.lat > stopCoords.lat)
+                    return -90;
+                else
+                    return 90;
+            }
+            var angle = Math.atan(stopCoords.lng - startCoords.lng, stopCoords.lat - startCoords.lat) * 180 / Math.Pi;
+            return angle;
         },
 
         /**