Add support for CSS based control of user specific components

Define some helper routines which can be used to make page elements
only display when the logged in user matches certain conditions and
add style rules to the layout to trigger those elements based on the
logged in user.

app/helpers/application_helper.rb

@@ -40,6 +40,45 @@ module ApplicationHelper
     return js
   end
 
+  def style_rules
+    css = ""
+
+    css << ".hidden { display: none }";
+    css << ".hide_unless_logged_in { display: none }" unless @user;
+    css << ".hide_if_logged_in { display: none }" if @user;
+    css << ".hide_if_user_#{@user.id} { display: none }" if @user;
+    css << ".show_if_user_#{@user.id} { display: inline }" if @user;
+    css << ".hide_unless_administrator { display: none }" unless @user and @user.administrator?;
+
+    return content_tag(:style, css)
+  end
+
+  def if_logged_in(tag = :div, &block)
+    concat(content_tag(tag, capture(&block), :class => "hide_unless_logged_in"))
+  end
+
+  def if_not_logged_in(tag = :div, &block)
+    concat(content_tag(tag, capture(&block), :class => "hide_if_logged_in"))
+  end
+
+  def if_user(user, tag = :div, &block)
+    if user
+      concat(content_tag(tag, capture(&block), :class => "hidden show_if_user_#{user.id}"))
+    end
+  end
+
+  def unless_user(user, tag = :div, &block)
+    if user
+      concat(content_tag(tag, capture(&block), :class => "hide_if_user_#{user.id}"))
+    else
+      concat(content_tag(tag, capture(&block)))
+    end
+  end
+
+  def if_administrator(tag = :div, &block)
+    concat(content_tag(tag, capture(&block), :class => "hide_unless_administrator"))
+  end
+
   def describe_location(lat, lon, zoom = nil, language = nil)
     zoom = zoom || 14
     language = language || request.user_preferred_languages.join(',')

app/views/layouts/site.html.erb

@@ -13,6 +13,7 @@
     <%= stylesheet_link_tag 'print', :media => "print" %>
     <%= tag("link", { :rel => "search", :type => "application/opensearchdescription+xml", :title => "OpenStreetMap Search", :href => "/opensearch/osm.xml" }) %>
     <%= tag("meta", { :name => "description", :content => "OpenStreetMap is the free wiki world map." }) %>
+    <%= style_rules %>
     <%= yield :head %>
     <title><%= t 'layouts.project_name.title' %><%= ' | '+ h(@title) if @title %></title>
   </head>