Stop using user agent to detect mobile devices. Use a media query and yepnope to load the appropriate css and customizations.

app/assets/javascripts/discourse/lib/mobile.js

@@ -5,30 +5,19 @@
   @module Mobile
 **/
 Discourse.Mobile = {
-  isMobileDevice: false,
+
   mobileView: false,
 
   init: function() {
     var $html = $('html');
-    this.isMobileDevice = $html.hasClass('mobile-device');
     this.mobileView = $html.hasClass('mobile-view');
-
-    if (localStorage && localStorage.mobileView) {
-      var savedValue = (localStorage.mobileView === 'true' ? true : false);
-      if (savedValue !== this.mobileView) {
-        this.reloadPage(savedValue);
-      }
-    }
   },
 
   toggleMobileView: function() {
     if (localStorage) {
       localStorage.mobileView = !this.mobileView;
     }
-    this.reloadPage(!this.mobileView);
-  },
-
-  reloadPage: function(mobile) {
-    window.location.assign(window.location.pathname + '?mobile_view=' + (mobile ? '1' : '0'));
+    window.location.reload();
   }
+
 };

app/controllers/application_controller.rb

@@ -26,7 +26,6 @@ class ApplicationController < ActionController::Base
   end
 
   before_filter :set_locale
-  before_filter :set_mobile_view
   before_filter :inject_preview_style
   before_filter :disable_customization
   before_filter :block_if_maintenance_mode
@@ -120,10 +119,6 @@ class ApplicationController < ActionController::Base
     end
   end
 
-  def set_mobile_view
-    session[:mobile_view] = params[:mobile_view] if params.has_key?(:mobile_view)
-  end
-
   def inject_preview_style
     style = request['preview-style']
     session[:preview_style] = style if style

app/helpers/application_helper.rb

@@ -19,10 +19,6 @@ module ApplicationHelper
     end
   end
 
-  def html_classes
-    "#{mobile_view? ? 'mobile-view' : 'desktop-view'} #{mobile_device? ? 'mobile-device' : 'not-mobile-device'}"
-  end
-
   def escape_unicode(javascript)
     if javascript
       javascript = javascript.dup.force_encoding("utf-8")
@@ -115,18 +111,8 @@ module ApplicationHelper
     "#{Discourse::base_uri}/login"
   end
 
-  def mobile_view?
-    return false unless SiteSetting.enable_mobile_theme
-    if session[:mobile_view]
-      session[:mobile_view] == '1'
-    else
-      mobile_device?
-    end
-  end
-
-  def mobile_device?
-    # TODO: this is dumb. user agent matching is a doomed approach. a better solution is coming.
-    request.user_agent =~ /Mobile|webOS|Nexus 7/ and !(request.user_agent =~ /iPad/)
+  def stylesheet_filenames(target=:desktop)
+    [asset_path("#{target}.css"), customization_disabled? ? nil : SiteCustomization.custom_stylesheet_path(session[:preview_style], target)].compact
   end
 
   def customization_disabled?

app/models/site_customization.rb

@@ -83,6 +83,12 @@ class SiteCustomization < ActiveRecord::Base
     style.stylesheet_link_tag(target).html_safe if style
   end
 
+  def self.custom_stylesheet_path(preview_style, target=:desktop)
+    preview_style ||= enabled_style_key
+    style = lookup_style(preview_style)
+    style.stylesheet_relative_path(target) if style
+  end
+
   def self.custom_header(preview_style, target=:desktop)
     preview_style ||= enabled_style_key
     style = lookup_style(preview_style)
@@ -175,14 +181,18 @@ class SiteCustomization < ActiveRecord::Base
     return "" unless stylesheet.present?
     return @stylesheet_link_tag if @stylesheet_link_tag
     ensure_stylesheets_on_disk!
-    @stylesheet_link_tag = "<link class=\"custom-css\" rel=\"stylesheet\" href=\"/#{CACHE_PATH}#{stylesheet_filename}?#{stylesheet_hash}\" type=\"text/css\" media=\"screen\">"
+    @stylesheet_link_tag = "<link class=\"custom-css\" rel=\"stylesheet\" href=\"#{stylesheet_relative_path(:desktop)}\" type=\"text/css\" media=\"screen\">"
   end
 
   def mobile_stylesheet_link_tag
     return "" unless mobile_stylesheet.present?
     return @mobile_stylesheet_link_tag if @mobile_stylesheet_link_tag
     ensure_stylesheets_on_disk!
-    @mobile_stylesheet_link_tag = "<link class=\"custom-css\" rel=\"stylesheet\" href=\"/#{CACHE_PATH}#{stylesheet_filename(:mobile)}?#{stylesheet_hash(:mobile)}\" type=\"text/css\" media=\"screen\">"
+    @mobile_stylesheet_link_tag = "<link class=\"custom-css\" rel=\"stylesheet\" href=\"#{stylesheet_relative_path(:mobile)}\" type=\"text/css\" media=\"screen\">"
+  end
+
+  def stylesheet_relative_path(target=:desktop)
+    "/#{CACHE_PATH}#{stylesheet_filename(target)}?#{stylesheet_hash(target)}"
   end
 end
 

app/views/common/_discourse_stylesheet.html.erb

@@ -1,15 +1,42 @@
 <%- unless SiteCustomization.override_default_style(session[:preview_style]) %>
-  <% if mobile_view? %>
-    <%= stylesheet_link_tag "mobile" %>
-  <% else %>
-    <%= stylesheet_link_tag "desktop" %>
-  <% end %>
+
+  <script type="text/javascript">
+    (function() {
+      var h = document.getElementsByTagName('html')[0],
+          isMobileView = (localStorage && localStorage.mobileView) ? (localStorage.mobileView === 'true') :
+              Modernizr.mq("only screen and (max-width: 480px), only screen and (max-device-width: 480px)");
+
+      h.className += (isMobileView ? ' mobile-view' : ' desktop-view');
+      Modernizr.load({
+        test: isMobileView,
+        yep:  <%= stylesheet_filenames(:mobile).inspect.html_safe  %>,
+        nope: <%= stylesheet_filenames(:desktop).inspect.html_safe %>,
+        complete: function() {
+          // CSS file(s) have loaded.
+          $(function() {
+            setTimeout(function() {
+              // Use setTimeout to make this happen in the next event loop.
+              // Trying to avoid a FOUC (flash of unstyled content).
+              if (isMobileView) {
+                $('#custom-mobile-header').show();
+              } else {
+                $('#custom-desktop-header').show();
+              }
+              $('#js-app').attr('style', ''); // Show everything.
+              $(window).trigger('scroll.discourse-dock'); // Calc header div positions now that they're visible.
+            }, 1);
+          });
+        }
+      });
+    })();
+  </script>
+
 <%- end %>
 
+<noscript>
+  <%= stylesheet_link_tag "desktop" %>
+</noscript>
+
 <%- if staff? %>
   <%= stylesheet_link_tag "admin"%>
 <%-end%>
-
-<%- unless customization_disabled? %>
-  <%= SiteCustomization.custom_stylesheet(session[:preview_style], mobile_view? ? :mobile : :desktop) %>
-<%- end %>

app/views/layouts/application.html.erb

@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="<%= SiteSetting.default_locale %>" class="<%= html_classes %>">
+<html lang="<%= SiteSetting.default_locale %>">
   <head>
     <meta charset="utf-8">
     <title><%= content_for?(:title) ? yield(:title) + ' - ' + SiteSetting.title : SiteSetting.title %></title>
@@ -20,19 +20,25 @@
       <%= javascript_include_tag "admin"%>
     <%- end %>
 
-    <%= render :partial => "common/special_font_face" %>
     <%= render :partial => "common/discourse_stylesheet" %>
+    <%= render :partial => "common/special_font_face" %>
 
     <%= discourse_csrf_tags %>
 
     <%= yield :head %>
   </head>
 
-  <body>
+  <body class="css-loading">
     <!--[if IE 9]><script type="text/javascript">ie = "new";</script><![endif]-->
 
+    <div id="js-app" style="display: none;">
       <%- unless customization_disabled? %>
-      <%= SiteCustomization.custom_header(session[:preview_style], mobile_view? ? :mobile : :desktop) %>
+        <div id='custom-desktop-header' style='display: none;'>
+          <%= SiteCustomization.custom_header(session[:preview_style], :desktop) %>
+        </div>
+        <div id='custom-mobile-header' style='display: none;'>
+          <%= SiteCustomization.custom_header(session[:preview_style], :mobile) %>
+        </div>
       <%- end %>
 
       <section id='main'>
@@ -62,6 +68,7 @@
       <%= render :partial => "common/discourse_javascript" %>
 
       <%= render_google_analytics_code %>
+    </div>
 
     <noscript data-path="<%= request.env['PATH_INFO'] %>">
       <header class="d-header">

spec/helpers/application_helper_spec.rb

@@ -11,78 +11,4 @@ describe ApplicationHelper do
     end
   end
 
-  describe "mobile_view?" do
-    context "enable_mobile_theme is true" do
-      before do
-        SiteSetting.stubs(:enable_mobile_theme).returns(true)
-      end
-
-      it "is true if mobile_view is '1' in the session" do
-        session[:mobile_view] = '1'
-        helper.mobile_view?.should be_true
-      end
-
-      it "is false if mobile_view is '0' in the session" do
-        session[:mobile_view] = '0'
-        helper.mobile_view?.should be_false
-      end
-
-      context "mobile_view is not set" do
-        it "is false if user agent is not mobile" do
-          controller.request.stubs(:user_agent).returns('Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.17 Safari/537.36')
-          helper.mobile_view?.should be_false
-        end
-
-        it "is true for iPhone" do
-          controller.request.stubs(:user_agent).returns('Mozilla/5.0 (iPhone; U; ru; CPU iPhone OS 4_2_1 like Mac OS X; ru) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148a Safari/6533.18.5')
-          helper.mobile_view?.should be_true
-        end
-
-        it "is false for iPad" do
-          controller.request.stubs(:user_agent).returns("Mozilla/5.0 (iPad; CPU OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B176 Safari/7534.48.3")
-          helper.mobile_view?.should be_false
-        end
-
-        it "is false for Nexus 10 tablet" do
-          controller.request.stubs(:user_agent).returns("Mozilla/5.0 (Linux; Android 4.2.1; Nexus 10 Build/JOP40D) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Safari/535.19")
-          helper.mobile_view?.should be_false
-        end
-
-        it "is true for Nexus 7 tablet" do
-          controller.request.stubs(:user_agent).returns("Mozilla/5.0 (Linux; Android 4.1.2; Nexus 7 Build/JZ054K) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Safari/535.19")
-          helper.mobile_view?.should be_true
-        end
-      end
-    end
-
-    context "enable_mobile_theme is false" do
-      before do
-        SiteSetting.stubs(:enable_mobile_theme).returns(false)
-      end
-
-      it "is false if mobile_view is '1' in the session" do
-        session[:mobile_view] = '1'
-        helper.mobile_view?.should be_false
-      end
-
-      it "is false if mobile_view is '0' in the session" do
-        session[:mobile_view] = '0'
-        helper.mobile_view?.should be_false
-      end
-
-      context "mobile_view is not set" do
-        it "is false if user agent is not mobile" do
-          controller.request.stubs(:user_agent).returns('Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.17 Safari/537.36')
-          helper.mobile_view?.should be_false
-        end
-
-        it "is false for iPhone" do
-          controller.request.stubs(:user_agent).returns('Mozilla/5.0 (iPhone; U; ru; CPU iPhone OS 4_2_1 like Mac OS X; ru) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148a Safari/6533.18.5')
-          helper.mobile_view?.should be_false
-        end
-      end
-    end
-  end
-
-
 end

vendor/assets/javascripts/browser-update.js.erb

@@ -5,7 +5,9 @@
 
 var $buo = function() {
 
-  var badAndroid = false, ua = null;
+  var badAndroid = false,
+      haveJquery = (typeof($) !== 'undefined'),
+      ua = null;
 
   // Sometimes we have to resort to parsing the user agent string. :(
   if (navigator && navigator.userAgent) {
@@ -53,6 +55,11 @@ var $buo = function() {
   // shift the body down to make room for our notification div
   document.body.style.marginTop = (div.clientHeight) + "px";
 
+  if (!haveJquery) {
+    var h = document.getElementsByTagName('html')[0];
+    h.className = h.className.replace(/(\s|^)css-loading(\s|$)/g, ' ');
+  }
+
 };
 
 $bu=$buo();