Configurable minimum editable zoom

API.md

@@ -141,4 +141,17 @@ var iD = iD()
   .taginfo(iD.taginfo().endpoint('url'))
   .imagery(customImagery);
 
-```    
+```
+
+### Minimum Editable Zoom
+
+The minimum zoom at which iD enters the edit mode is configured using the `iD().minEditableZoom()` accessor. The default value is 16. To change this initialise iD as 
+
+```js
+
+var iD = iD().
+  .minEditableZoom(zoom_level)
+
+```
+
+This should be set with caution for performance reasons. The OpenStreetMap API has a limitation of 50000 nodes per request.

js/id/behavior/edit.js

@@ -1,7 +1,7 @@
 iD.behavior.Edit = function(context) {
     function edit() {
         context.map()
-            .minzoom(16);
+            .minzoom(context.minEditableZoom());
     }
 
     edit.off = function() {

js/id/id.js

@@ -30,6 +30,16 @@ window.iD = function () {
         }
     };
 
+    /* Accessor for setting minimum zoom for editing features. */
+
+    var minEditableZoom = 16;
+    context.minEditableZoom = function(_) {
+        if (!arguments.length) return minEditableZoom;
+        minEditableZoom = _;
+        connection.tileZoom(_);
+        return context;
+    };
+
     var history = iD.History(context),
         dispatch = d3.dispatch('enter', 'exit'),
         mode,

js/id/renderer/map.js

@@ -162,7 +162,7 @@ iD.Map = function(context) {
             iD.ui.flash(context.container())
                 .select('.content')
                 .text(t('cannot_zoom'));
-            return setZoom(16, true);
+            return setZoom(context.minEditableZoom(), true);
         }
 
         projection
@@ -342,7 +342,7 @@ iD.Map = function(context) {
     map.zoomTo = function(entity, zoomLimits) {
         var extent = entity.extent(context.graph()),
             zoom = map.extentZoom(extent);
-        zoomLimits = zoomLimits || [16, 20];
+        zoomLimits = zoomLimits || [context.minEditableZoom(), 20];
         map.centerZoom(extent.center(), Math.min(Math.max(zoom, zoomLimits[0]), zoomLimits[1]));
     };
 
@@ -406,7 +406,7 @@ iD.Map = function(context) {
     };
 
     map.editable = function() {
-        return map.zoom() >= 16;
+        return map.zoom() >= context.minEditableZoom();
     };
 
     map.minzoom = function(_) {

js/id/ui/notice.js

@@ -5,7 +5,7 @@ iD.ui.Notice = function(context) {
 
         var button = div.append('button')
             .attr('class', 'zoom-to notice')
-            .on('click', function() { context.map().zoom(16); });
+            .on('click', function() { context.map().zoom(context.minEditableZoom()); });
 
         button.append('span')
             .attr('class', 'icon zoom-in-invert');