base/prefs/pref_registry.h

   1 // Copyright (c) 2012 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 BASE_PREFS_PREF_REGISTRY_H_
   6 #define BASE_PREFS_PREF_REGISTRY_H_
   7
   8 #include "base/containers/hash_tables.h"
   9 #include "base/memory/ref_counted.h"
  10 #include "base/prefs/base_prefs_export.h"
  11 #include "base/prefs/pref_value_map.h"
  12
  13 namespace base {
  14 class Value;
  15 }
  16
  17 class DefaultPrefStore;
  18 class PrefStore;
  19
  20 // Preferences need to be registered with a type and default value
  21 // before they are used.
  22 //
  23 // The way you use a PrefRegistry is that you register all required
  24 // preferences on it (via one of its subclasses), then pass it as a
  25 // construction parameter to PrefService.
  26 //
  27 // Currently, registrations after constructing the PrefService will
  28 // also work, but this is being deprecated.
  29 class BASE_PREFS_EXPORT PrefRegistry : public base::RefCounted<PrefRegistry> {
  30  public:
  31   // Registration flags that can be specified which impact how the pref will
  32   // behave or be stored. This will be passed in a bitmask when the pref is
  33   // registered. Subclasses of PrefRegistry can specify their own flags. Care
  34   // must be taken to ensure none of these overlap with the flags below.
  35   enum PrefRegistrationFlags {
  36     // No flags are specified.
  37     NO_REGISTRATION_FLAGS = 0,
  38
  39     // The first 8 bits are reserved for subclasses of PrefRegistry to use.
  40   };
  41
  42   typedef PrefValueMap::const_iterator const_iterator;
  43   typedef base::hash_map<std::string, uint32> PrefRegistrationFlagsMap;
  44
  45   PrefRegistry();
  46
  47   // Retrieve the set of registration flags for the given preference. The return
  48   // value is a bitmask of PrefRegistrationFlags.
  49   uint32 GetRegistrationFlags(const std::string& pref_name) const;
  50
  51   // Gets the registered defaults.
  52   scoped_refptr<PrefStore> defaults();
  53
  54   // Allows iteration over defaults.
  55   const_iterator begin() const;
  56   const_iterator end() const;
  57
  58   // Changes the default value for a preference. Takes ownership of |value|.
  59   //
  60   // |pref_name| must be a previously registered preference.
  61   void SetDefaultPrefValue(const std::string& pref_name, base::Value* value);
  62
  63  protected:
  64   friend class base::RefCounted<PrefRegistry>;
  65   virtual ~PrefRegistry();
  66
  67   // Used by subclasses to register a default value and registration flags for
  68   // a preference. |flags| is a bitmask of |PrefRegistrationFlags|.
  69   void RegisterPreference(const std::string& path,
  70                           base::Value* default_value,
  71                           uint32 flags);
  72
  73   scoped_refptr<DefaultPrefStore> defaults_;
  74
  75   // A map of pref name to a bitmask of PrefRegistrationFlags.
  76   PrefRegistrationFlagsMap registration_flags_;
  77
  78  private:
  79   DISALLOW_COPY_AND_ASSIGN(PrefRegistry);
  80 };
  81
  82 #endif  // BASE_PREFS_PREF_REGISTRY_H_