perf: use fixed-size arrays for the font cache (#40898)
refactor: use fixed-size arrays for the font cache Since we know at compile time which [family x script] combos we want to cache, we can hold the cache in fixed std::arrays instead of in nested std::unordered_maps.
This commit is contained in:
Charles Kerr
GitHub
parent
37630a6128
commit
7b4d490bfe
1 changed files with 69 additions and 50 deletions
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@ -4,11 +4,12 @@
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#include "shell/browser/font_defaults.h"
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#include <array>
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#include <string>
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#include <unordered_map>
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#include <string_view>
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#include "base/stl_util.h"
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#include "base/strings/stringprintf.h"
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#include "base/strings/strcat.h"
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#include "base/strings/utf_string_conversions.h"
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#include "chrome/common/pref_names.h"
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#include "chrome/grit/platform_locale_settings.h"
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@ -106,70 +107,88 @@ const FontDefault kFontDefaults[] = {
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// ^^^^^ DO NOT EDIT ^^^^^
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std::string GetDefaultFontForPref(const char* pref_name) {
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for (auto pref : kFontDefaults) {
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if (strcmp(pref.pref_name, pref_name) == 0) {
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// Get `kFontDefault`'s default fontname for [font family, script].
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// e.g. ("webkit.webprefs.fonts.fixed", "Zyyy") -> "Monospace"
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std::string GetDefaultFont(const std::string_view family_name,
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const std::string_view script_name) {
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const std::string pref_name = base::StrCat({family_name, ".", script_name});
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for (const FontDefault& pref : kFontDefaults) {
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if (pref_name == pref.pref_name) {
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return l10n_util::GetStringUTF8(pref.resource_id);
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}
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}
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return std::string();
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return std::string{};
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}
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// Map from script to font.
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// Key comparison uses pointer equality.
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using ScriptFontMap = std::unordered_map<const char*, std::u16string>;
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// Each font family has kWebKitScriptsForFontFamilyMapsLength scripts.
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// This is a lookup array for script_index -> fontname
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using PerFamilyFonts =
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std::array<std::u16string, prefs::kWebKitScriptsForFontFamilyMapsLength>;
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// Map from font family to ScriptFontMap.
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// Key comparison uses pointer equality.
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using FontFamilyMap = std::unordered_map<const char*, ScriptFontMap>;
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// A lookup table mapping (font-family, script) -> font-name
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// e.g. ("sans-serif", "Zyyy") -> "Arial"
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FontFamilyMap g_font_cache;
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std::u16string FetchFont(const char* script, const char* map_name) {
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FontFamilyMap::const_iterator it = g_font_cache.find(map_name);
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if (it != g_font_cache.end()) {
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ScriptFontMap::const_iterator it2 = it->second.find(script);
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if (it2 != it->second.end())
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return it2->second;
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}
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std::string pref_name = base::StringPrintf("%s.%s", map_name, script);
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std::string font = GetDefaultFontForPref(pref_name.c_str());
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std::u16string font16 = base::UTF8ToUTF16(font);
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ScriptFontMap& map = g_font_cache[map_name];
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map[script] = font16;
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return font16;
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}
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void FillFontFamilyMap(const char* map_name,
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blink::web_pref::ScriptFontFamilyMap* map) {
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PerFamilyFonts MakeCacheForFamily(const std::string_view family_name) {
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PerFamilyFonts ret;
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for (size_t i = 0; i < prefs::kWebKitScriptsForFontFamilyMapsLength; ++i) {
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const char* script = prefs::kWebKitScriptsForFontFamilyMaps[i];
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std::u16string result = FetchFont(script, map_name);
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if (!result.empty()) {
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(*map)[script] = result;
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const char* script_name = prefs::kWebKitScriptsForFontFamilyMaps[i];
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ret[i] = base::UTF8ToUTF16(GetDefaultFont(family_name, script_name));
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}
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return ret;
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}
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void FillFontFamilyMap(const PerFamilyFonts& cache,
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blink::web_pref::ScriptFontFamilyMap& font_family_map) {
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for (size_t i = 0; i < prefs::kWebKitScriptsForFontFamilyMapsLength; ++i) {
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if (const std::u16string& fontname = cache[i]; !fontname.empty()) {
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char const* const script_name = prefs::kWebKitScriptsForFontFamilyMaps[i];
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font_family_map[script_name] = fontname;
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}
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}
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}
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struct FamilyCache {
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std::string_view family_name;
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// where to find the font_family_map in a WebPreferences instance
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blink::web_pref::ScriptFontFamilyMap blink::web_pref::WebPreferences::*
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map_offset;
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PerFamilyFonts fonts = {};
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};
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static auto MakeCache() {
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// the font families whose defaults we want to cache
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std::array<FamilyCache, 5> cache{{
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{prefs::kWebKitStandardFontFamilyMap,
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&blink::web_pref::WebPreferences::standard_font_family_map},
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{prefs::kWebKitFixedFontFamilyMap,
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&blink::web_pref::WebPreferences::fixed_font_family_map},
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{prefs::kWebKitSerifFontFamilyMap,
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&blink::web_pref::WebPreferences::serif_font_family_map},
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{prefs::kWebKitSansSerifFontFamilyMap,
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&blink::web_pref::WebPreferences::sans_serif_font_family_map},
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{prefs::kWebKitCursiveFontFamilyMap,
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&blink::web_pref::WebPreferences::cursive_font_family_map},
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}};
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// populate the cache
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for (FamilyCache& row : cache) {
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row.fonts = MakeCacheForFamily(row.family_name);
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}
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return cache;
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}
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} // namespace
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namespace electron {
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void SetFontDefaults(blink::web_pref::WebPreferences* prefs) {
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FillFontFamilyMap(prefs::kWebKitStandardFontFamilyMap,
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&prefs->standard_font_family_map);
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FillFontFamilyMap(prefs::kWebKitFixedFontFamilyMap,
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&prefs->fixed_font_family_map);
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FillFontFamilyMap(prefs::kWebKitSerifFontFamilyMap,
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&prefs->serif_font_family_map);
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FillFontFamilyMap(prefs::kWebKitSansSerifFontFamilyMap,
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&prefs->sans_serif_font_family_map);
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FillFontFamilyMap(prefs::kWebKitCursiveFontFamilyMap,
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&prefs->cursive_font_family_map);
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static auto const cache = MakeCache();
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for (FamilyCache const& row : cache) {
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FillFontFamilyMap(row.fonts, prefs->*row.map_offset);
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}
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}
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} // namespace electron
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