display lane count on sidebar

modules/ui/preset/index.js

@@ -5,6 +5,7 @@ export { combo, typeCombo, multiCombo } from './combo';
 export { cycleway } from './cycleway';
 export { text, url, number, email, tel } from './input';
 export { localized } from './localized';
+export { lanes } from './lanes';
 export { maxspeed } from './maxspeed';
 export { radio } from './radio';
 export { restrictions } from './restrictions';

modules/ui/preset/lanes.js

@@ -0,0 +1,44 @@
+export function lanes(field, context) {
+    var dispatch = d3.dispatch('change'),
+        wayID,
+        laneData;
+
+    function lanes(selection) {
+        // if form field is hidden or has detached from dom, clean up.
+        if (!d3.select('.inspector-wrap.inspector-hidden').empty() || !selection.node().parentNode) {
+            selection.call(lanes.off);
+            return;
+        }
+
+        laneData = context.entity(wayID).lanes();
+
+        var wrap = selection.selectAll('.preset-input-wrap')
+            .data([0]);
+
+        var enter = wrap.enter()
+            .append('div')
+            .attr('class', 'preset-input-wrap');
+
+        enter
+            .append('div')
+            .attr('class', 'lane-count')
+            .append('span');
+
+        selection.selectAll('.lane-count')
+          .text(laneData.tagged.lanes.count || laneData.defaults.lanes.count);
+
+    }
+
+
+    lanes.entity = function(_) {
+        if (!wayID || wayID !== _.id) {
+            wayID = _.id;
+        }
+    };
+
+    lanes.tags = function() {};
+    lanes.focus = function() {};
+    lanes.off = function() {};
+
+    return d3.rebind(lanes, dispatch, 'on');
+}