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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_UI_WEBUI_SHOWN_SECTIONS_HANDLER_H_
      6 #define CHROME_BROWSER_UI_WEBUI_SHOWN_SECTIONS_HANDLER_H_
      7 #pragma once
      8 
      9 #include "chrome/browser/prefs/pref_change_registrar.h"
     10 #include "content/browser/webui/web_ui.h"
     11 #include "content/common/notification_observer.h"
     12 
     13 class Extension;
     14 class Value;
     15 class PrefService;
     16 
     17 // Use for the shown sections bitmask.
     18 // Currently, only the THUMB and APPS sections can be toggled by the user. Other
     19 // sections are shown automatically if they have data, and hidden otherwise.
     20 enum Section {
     21   // If one of these is set, the corresponding section shows large thumbnails,
     22   // else it shows only a small overview list.
     23   THUMB = 1 << 0,
     24   APPS = 1 << 6,
     25 
     26   // We use the low 16 bits for sections, the high 16 bits for menu mode.
     27   ALL_SECTIONS_MASK = 0x0000FFFF,
     28 
     29   // If one of these is set, then the corresponding section is shown in a menu
     30   // at the bottom of the NTP and no data is directly visible on the NTP.
     31   MENU_THUMB = 1 << (0 + 16),
     32   MENU_RECENT = 1 << (2 + 16),
     33   MENU_APPS = 1 << (6 + 16),
     34 };
     35 
     36 class ShownSectionsHandler : public WebUIMessageHandler,
     37                              public NotificationObserver {
     38  public:
     39   explicit ShownSectionsHandler(PrefService* pref_service);
     40   virtual ~ShownSectionsHandler() {}
     41 
     42   // Helper to get the current shown sections.
     43   static int GetShownSections(PrefService* pref_service);
     44 
     45   // Expands |section|, collapsing any previously expanded section. This is the
     46   // same thing that happens if a user clicks on |section|.
     47   static void SetShownSection(PrefService* prefs, Section section);
     48 
     49   // WebUIMessageHandler implementation.
     50   virtual void RegisterMessages();
     51 
     52   // NotificationObserver implementation.
     53   virtual void Observe(NotificationType type,
     54                        const NotificationSource& source,
     55                        const NotificationDetails& details);
     56 
     57   // Callback for "getShownSections" message.
     58   void HandleGetShownSections(const ListValue* args);
     59 
     60   // Callback for "setShownSections" message.
     61   void HandleSetShownSections(const ListValue* args);
     62 
     63   static void RegisterUserPrefs(PrefService* pref_service);
     64 
     65   static void MigrateUserPrefs(PrefService* pref_service,
     66                                int old_pref_version,
     67                                int new_pref_version);
     68 
     69   static void OnExtensionInstalled(PrefService* prefs,
     70                                    const Extension* extension);
     71 
     72  private:
     73   PrefService* pref_service_;
     74   PrefChangeRegistrar pref_registrar_;
     75 
     76   DISALLOW_COPY_AND_ASSIGN(ShownSectionsHandler);
     77 };
     78 
     79 #endif  // CHROME_BROWSER_UI_WEBUI_SHOWN_SECTIONS_HANDLER_H_
     80