Improve zoom level selection when invoking Potlatch on an object

When invoking Potlatch on a node/way/relation object we should
normally have valid location information in the map parameters, so
use any zoom which is there if possible, otherwise fall back to an
object type specific default value.

Fixes #605.

app/controllers/site_controller.rb

@@ -50,18 +50,22 @@ class SiteController < ApplicationController
       bbox = Node.find(params[:node]).bbox.to_unscaled
       @lat = bbox.centre_lat
       @lon = bbox.centre_lon
+      @zoom = 18
     elsif params[:way]
       bbox = Way.find(params[:way]).bbox.to_unscaled
       @lat = bbox.centre_lat
       @lon = bbox.centre_lon
+      @zoom = 17
     elsif params[:note]
       note = Note.find(params[:note])
       @lat = note.lat
       @lon = note.lon
+      @zoom = 17
     elsif params[:gpx]
       trace = Trace.visible_to(@user).find(params[:gpx])
       @lat = trace.latitude
       @lon = trace.longitude
+      @zoom = 16
     end
   end
 

app/views/site/_potlatch.html.erb

@@ -51,11 +51,11 @@
     // 700,600 for fixed size, 100%,100% for resizable
   }
 
+  var mapParams = OSM.mapParams();
   <% if @lat && @lon -%>
-  doSWF(<%= @lat %>,<%= @lon %>,16);
+    doSWF(<%= @lat %>, <%= @lon %>, mapParams.zoom || <%= @zoom %>);
   <% else -%>
-  var params = OSM.mapParams();
-  doSWF(params.lat, params.lon, params.zoom || 17);
+    doSWF(mapParams.lat, mapParams.lon, mapParams.zoom || 17);
   <% end -%>
 
   $(document).ready(function () {

app/views/site/_potlatch2.html.erb

@@ -70,11 +70,11 @@
     }
   }
 
+  var mapParams = OSM.mapParams();
   <% if @lat && @lon -%>
-  doSWF(<%= @lat %>,<%= @lon %>,16);
+    doSWF(<%= @lat %>, <%= @lon %>, mapParams.zoom || <%= @zoom %>);
   <% else -%>
-  var params = OSM.mapParams();
-  doSWF(params.lat, params.lon, params.zoom || 17);
+    doSWF(mapParams.lat, mapParams.lon, mapParams.zoom || 17);
   <% end -%>
 
   $("body").on("click", "a.set_position", function (e) {