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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_BROWSER_FONT_FAMILY_CACHE_H_
#define CHROME_BROWSER_FONT_FAMILY_CACHE_H_
#include "base/containers/hash_tables.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/strings/string16.h"
#include "base/supports_user_data.h"
#include "components/prefs/pref_change_registrar.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"
#include "content/public/common/web_preferences.h"
class PrefService;
class Profile;
FORWARD_DECLARE_TEST(FontFamilyCacheTest, Caching);
// Caches font family preferences associated with a PrefService. This class
// relies on the assumption that each concatenation of map_name + '.' + script
// is a unique string. It also relies on the assumption that the (const char*)
// keys used in both inner and outer hash_maps are compile time constants.
class FontFamilyCache : public base::SupportsUserData::Data,
public content::NotificationObserver {
public:
explicit FontFamilyCache(Profile* profile);
~FontFamilyCache() override;
// Gets or creates the relevant FontFamilyCache, and then fills |map|.
static void FillFontFamilyMap(Profile* profile,
const char* map_name,
content::ScriptFontFamilyMap* map);
// Fills |map| with font family preferences.
void FillFontFamilyMap(const char* map_name,
content::ScriptFontFamilyMap* map);
protected:
// Exposed and virtual for testing.
// Fetches the font without checking the cache.
virtual base::string16 FetchFont(const char* script, const char* map_name);
private:
FRIEND_TEST_ALL_PREFIXES(::FontFamilyCacheTest, Caching);
// Map from script to font.
// Key comparison uses pointer equality.
typedef base::hash_map<const char*, base::string16> ScriptFontMap;
// Map from font family to ScriptFontMap.
// Key comparison uses pointer equality.
typedef base::hash_map<const char*, ScriptFontMap> FontFamilyMap;
// Checks the cache for the font. If not present, fetches the font and stores
// the result in the cache.
// This method needs to be very fast, because it's called ~20,000 times on a
// fresh launch with an empty profile. It's important to avoid unnecessary
// object construction, hence the heavy use of const char* and the minimal use
// of std::string.
// |script| and |map_name| must be compile time constants. Two behaviors rely
// on this: key comparison uses pointer equality, and keys must outlive the
// hash_maps.
base::string16 FetchAndCacheFont(const char* script, const char* map_name);
// Called when font family preferences changed.
// Invalidates the cached entry, and removes the relevant observer.
// Note: It is safe to remove the observer from the pref change callback.
void OnPrefsChanged(const std::string& pref_name);
// content::NotificationObserver override.
// Called when the profile is being destructed.
void Observe(int type,
const content::NotificationSource& source,
const content::NotificationDetails& details) override;
// Cache of font family preferences.
FontFamilyMap font_family_map_;
// Weak reference.
// Note: The lifetime of this object is tied to the lifetime of the
// PrefService, so there is no worry about an invalid pointer.
const PrefService* prefs_;
// Reacts to profile changes.
PrefChangeRegistrar profile_pref_registrar_;
// Listens for profile destruction.
content::NotificationRegistrar notification_registrar_;
DISALLOW_COPY_AND_ASSIGN(FontFamilyCache);
};
#endif // CHROME_BROWSER_FONT_FAMILY_CACHE_H_
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