1// Copyright 2014 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_FONT_FAMILY_CACHE_H_
6#define CHROME_BROWSER_FONT_FAMILY_CACHE_H_
7
8#include "base/containers/hash_tables.h"
9#include "base/gtest_prod_util.h"
10#include "base/prefs/pref_change_registrar.h"
11#include "base/strings/string16.h"
12#include "base/supports_user_data.h"
13#include "content/public/browser/notification_observer.h"
14#include "content/public/browser/notification_registrar.h"
15#include "content/public/common/web_preferences.h"
16
17class PrefService;
18class Profile;
19
20FORWARD_DECLARE_TEST(FontFamilyCacheTest, Caching);
21
22// Caches font family preferences associated with a PrefService. This class
23// relies on the assumption that each concatenation of map_name + '.' + script
24// is a unique string. It also relies on the assumption that the (const char*)
25// keys used in both inner and outer hash_maps are compile time constants.
26class FontFamilyCache : public base::SupportsUserData::Data,
27                        public content::NotificationObserver {
28 public:
29  explicit FontFamilyCache(Profile* profile);
30  virtual ~FontFamilyCache();
31
32  // Gets or creates the relevant FontFamilyCache, and then fills |map|.
33  static void FillFontFamilyMap(Profile* profile,
34                                const char* map_name,
35                                content::ScriptFontFamilyMap* map);
36
37  // Fills |map| with font family preferences.
38  void FillFontFamilyMap(const char* map_name,
39                         content::ScriptFontFamilyMap* map);
40
41 protected:
42  // Exposed and virtual for testing.
43  // Fetches the font without checking the cache.
44  virtual base::string16 FetchFont(const char* script, const char* map_name);
45
46 private:
47  FRIEND_TEST_ALL_PREFIXES(::FontFamilyCacheTest, Caching);
48
49  // Map from script to font.
50  // Key comparison uses pointer equality.
51  typedef base::hash_map<const char*, base::string16> ScriptFontMap;
52
53  // Map from font family to ScriptFontMap.
54  // Key comparison uses pointer equality.
55  typedef base::hash_map<const char*, ScriptFontMap> FontFamilyMap;
56
57  // Checks the cache for the font. If not present, fetches the font and stores
58  // the result in the cache.
59  // This method needs to be very fast, because it's called ~20,000 times on a
60  // fresh launch with an empty profile. It's important to avoid unnecessary
61  // object construction, hence the heavy use of const char* and the minimal use
62  // of std::string.
63  // |script| and |map_name| must be compile time constants. Two behaviors rely
64  // on this: key comparison uses pointer equality, and keys must outlive the
65  // hash_maps.
66  base::string16 FetchAndCacheFont(const char* script, const char* map_name);
67
68  // Called when font family preferences changed.
69  // Invalidates the cached entry, and removes the relevant observer.
70  // Note: It is safe to remove the observer from the pref change callback.
71  void OnPrefsChanged(const std::string& pref_name);
72
73  // content::NotificationObserver override.
74  // Called when the profile is being destructed.
75  virtual void Observe(int type,
76                       const content::NotificationSource& source,
77                       const content::NotificationDetails& details) OVERRIDE;
78
79  // Cache of font family preferences.
80  FontFamilyMap font_family_map_;
81
82  // Weak reference.
83  // Note: The lifetime of this object is tied to the lifetime of the
84  // PrefService, so there is no worry about an invalid pointer.
85  const PrefService* prefs_;
86
87  // Reacts to profile changes.
88  PrefChangeRegistrar profile_pref_registrar_;
89
90  // Listens for profile destruction.
91  content::NotificationRegistrar notification_registrar_;
92
93  DISALLOW_COPY_AND_ASSIGN(FontFamilyCache);
94};
95
96#endif  // CHROME_BROWSER_FONT_FAMILY_CACHE_H_
97