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// Copyright 2014 The Chromium Authors
// 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 <string>
#include <unordered_map>
#include "base/gtest_prod_util.h"
#include "base/memory/raw_ptr.h"
#include "base/supports_user_data.h"
#include "chrome/browser/font_pref_change_notifier.h"
#include "third_party/blink/public/common/web_preferences/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 maps are compile time constants.
// This class caches the strings necessary to update
// "blink::web_pref::ScriptFontFamilyMap". This is necessary since Chrome
// attempts to update blink::web_pref::ScriptFontFamilyMap 20000 times at
// startup. See https://crbug.com/308095.
class FontFamilyCache : public base::SupportsUserData::Data {
public:
explicit FontFamilyCache(Profile* profile);
FontFamilyCache(const FontFamilyCache&) = delete;
FontFamilyCache& operator=(const FontFamilyCache&) = delete;
~FontFamilyCache() override;
// Gets or creates the relevant FontFamilyCache, and then fills |map|.
static void FillFontFamilyMap(Profile* profile,
const char* map_name,
blink::web_pref::ScriptFontFamilyMap* map);
// Fills |map| with font family preferences.
void FillFontFamilyMap(const char* map_name,
blink::web_pref::ScriptFontFamilyMap* map);
protected:
// Exposed and virtual for testing.
// Fetches the font without checking the cache.
virtual std::u16string 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.
using ScriptFontMap = std::unordered_map<const char*, std::u16string>;
// Map from font family to ScriptFontMap.
// Key comparison uses pointer equality.
using FontFamilyMap = std::unordered_map<const char*, ScriptFontMap>;
// 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
// maps.
std::u16string 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);
// 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.
raw_ptr<const PrefService, AcrossTasksDanglingUntriaged> prefs_;
// Reacts to profile font changes. |font_change_registrar_| will be
// automatically unregistered when the FontPrefChangeNotifier is destroyed as
// part of Profile destruction, thus ensuring safe unregistration even though
// |this| is destroyed after the Profile destructor completes as part of
// Profile's super class destructor ~base::SupportsUserData.
FontPrefChangeNotifier::Registrar font_change_registrar_;
};
#endif // CHROME_BROWSER_FONT_FAMILY_CACHE_H_
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