First shot at way accuracy handles

css/map.css

@@ -24,6 +24,13 @@ image.handle {
     cursor: move;
 }
 
+circle.accuracy-handle {
+    fill:#DF2D2D;
+    stroke:#DF2D2D;
+    fill-opacity:0.2;
+    stroke-width:1;
+}
+
 circle.teaser-point {
     stroke-width: 2;
     stroke:#1DCAFF;

js/id/actions/modes.js

@@ -8,12 +8,8 @@ iD.modes._node = function(ll) {
     });
 };
 
-iD.modes.dist = function(a, b) {
-    return Math.sqrt(Math.pow(a[0] - b[0], 2) + Math.pow(a[1] - b[1], 2));
-};
-
 iD.modes.chooseIndex = function(way, point, map) {
-    var dist = iD.modes.dist;
+    var dist = iD.Util.dist;
     var projNodes = way.nodes.map(function(n) {
         return map.projection([n.lon, n.lat]);
     });

js/id/renderer/map.js

@@ -16,6 +16,13 @@ iD.Map = function() {
         dblclickEnabled = true,
         dragbehavior = d3.behavior.drag()
             .origin(function(entity) {
+                if (entity.accuracy) {
+                    var index = entity.index, wayid = entity.way;
+                    entity = iD.Node(entity);
+                    var connectedWay = map.history.graph().entity(wayid);
+                    connectedWay.nodes.splice(index, 0, entity.id);
+                    map.perform(iD.actions.addWayNode(connectedWay, entity));
+                }
                 var p = projection(ll2a(entity));
                 only = iD.Util.trueObj([entity.id].concat(
                     _.pluck(map.history.graph().parents(entity.id), 'id')));
@@ -143,13 +150,29 @@ iD.Map = function() {
                 waynodes.push(a);
             }
         }
+        var wayAccuracyHandles = ways.reduce(function(mem, w) {
+            return mem.concat(accuracyHandles(w));
+        }, []);
         drawHandles(waynodes, filter);
+        drawAccuracyHandles(wayAccuracyHandles, filter);
         drawCasings(ways, filter);
         drawFills(areas, filter);
         drawStrokes(ways, filter);
         drawMarkers(points, filter);
     }
 
+    function accuracyHandles(way) {
+        var handles = [];
+        for (var i = 0; i < way.nodes.length - 1; i++) {
+            handles[i] = iD.Node(iD.Util.interp(way.nodes[i], way.nodes[i + 1], 0.5));
+            handles[i].way = way.id;
+            handles[i].index = i + 1;
+            handles[i].accuracy = true;
+            handles[i].tags = { name: 'Improve way accuracy' };
+        }
+        return handles;
+    }
+
     function drawHandles(waynodes, filter) {
         var handles = g.hit.selectAll('image.handle')
             .filter(filter)
@@ -164,6 +187,20 @@ iD.Map = function() {
         }).classed('active', classActive);
     }
 
+    function drawAccuracyHandles(waynodes) {
+        var handles = g.hit.selectAll('circle.accuracy-handle')
+            .data(waynodes, key);
+        console.log(handles);
+        handles.exit().remove();
+        handles.enter().append('circle')
+            .attr({ r: 2, 'class': 'accuracy-handle' })
+            .call(dragbehavior);
+        handles.attr('transform', function(entity) {
+            var p = projection(ll2a(entity));
+            return 'translate(' + [~~p[0], ~~p[1]] + ')';
+        }).classed('active', classActive);
+    }
+
     function hideVector() {
         surface.selectAll('.layer-g *').remove();
     }

js/id/util.js

@@ -55,3 +55,14 @@ iD.Util.qsString = function(obj) {
         return encodeURIComponent(key) + '=' + encodeURIComponent(obj[key]);
     }).join('&');
 };
+
+iD.Util.interp = function(p1, p2, t) {
+    return {
+        lon: p1.lon + (p2.lon - p1.lon) * t,
+        lat: p1.lat + (p2.lat - p1.lat) * t
+    };
+};
+
+iD.Util.dist = function(a, b) {
+    return Math.sqrt(Math.pow(a[0] - b[0], 2) + Math.pow(a[1] - b[1], 2));
+};