From 19082bcf2a2e4f50b9bbbe03afe398075875b940 Mon Sep 17 00:00:00 2001
From: Tom MacWright <tom@macwright.org>
Date: Sun, 9 Dec 2012 00:00:23 -0500
Subject: [PATCH] Make spliced nodes straight. Fixes #241

---
 js/id/modes/add_road.js |  6 +++---
 js/id/util.js           | 15 ++++++++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/js/id/modes/add_road.js b/js/id/modes/add_road.js
index 15b87ba59..bd37ed37e 100644
--- a/js/id/modes/add_road.js
+++ b/js/id/modes/add_road.js
@@ -38,13 +38,13 @@ iD.modes.AddRoad = function() {
 
             } else if (datum.type === 'way') {
                 // begin a new way starting from an existing way
-                node = iD.Node({loc: map.mouseCoordinates()}),
-                    index = iD.util.geo.chooseIndex(datum, d3.mouse(map.surface.node()), map);
+                choice = iD.util.geo.chooseIndex(datum, d3.mouse(map.surface.node()), map);
+                node = iD.Node({ loc: choice.loc }),
 
                 history.perform(
                     iD.actions.AddWay(way),
                     iD.actions.AddNode(node),
-                    iD.actions.AddWayNode(datum.id, node.id, index),
+                    iD.actions.AddWayNode(datum.id, node.id, choice.index),
                     iD.actions.AddWayNode(way.id, node.id),
                     'started a road');
 
diff --git a/js/id/util.js b/js/id/util.js
index bf5a2ef2d..7dc28a3ab 100644
--- a/js/id/util.js
+++ b/js/id/util.js
@@ -97,14 +97,23 @@ iD.util.geo.dist = function(a, b) {
 };
 
 iD.util.geo.chooseIndex = function(way, point, map) {
-    var dist = iD.util.geo.dist;
-    var projNodes = way.nodes.map(function(n) {
+    var dist = iD.util.geo.dist,
+        projNodes = way.nodes.map(function(n) {
         return map.projection(n.loc);
     });
+
     for (var i = 0, changes = []; i < projNodes.length - 1; i++) {
         changes[i] =
             (dist(projNodes[i], point) + dist(point, projNodes[i + 1])) /
             dist(projNodes[i], projNodes[i + 1]);
     }
-    return _.indexOf(changes, _.min(changes)) + 1;
+
+    var idx = _.indexOf(changes, _.min(changes)),
+        ratio = dist(projNodes[idx], point) / dist(projNodes[idx], projNodes[idx + 1]),
+        loc = iD.util.geo.interp(way.nodes[idx].loc, way.nodes[idx + 1].loc, ratio);
+
+    return {
+        index: idx + 1,
+        loc: loc
+    };
 };