third_party/WebKit/Source/core/css/CSSFontFaceSource.cpp

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#include "core/css/CSSFontFaceSource.h"

#include "core/css/CSSFontFace.h"
#include "platform/fonts/FontCacheKey.h"
#include "platform/fonts/FontDescription.h"
#include "platform/fonts/FontFaceCreationParams.h"
#include "platform/fonts/SimpleFontData.h"

namespace {
// An excessive amount of SimpleFontData objects is generated from
// CSSFontFaceSource if a lot of varying FontDescriptions point to a web
// font. These FontDescriptions can vary in size, font-feature-settings or
// font-variation settings. Well known cases are animations of font-variation
// settings, compare crbug.com/778352. For a start, let's reduce this number to
// 1024, which is still a large number and should have enough steps for font
// animations from the same font face source, but avoids unbounded growth.
const size_t kMaxCachedFontData = 1024;
}  // namespace

namespace blink {

CSSFontFaceSource::~CSSFontFaceSource() = default;

scoped_refptr<SimpleFontData> CSSFontFaceSource::GetFontData(
    const FontDescription& font_description,
    const FontSelectionCapabilities& font_selection_capabilities) {
  // If the font hasn't loaded or an error occurred, then we've got nothing.
  if (!IsValid())
    return nullptr;

  if (IsLocal()) {
    // We're local. Just return a SimpleFontData from the normal cache.
    return CreateFontData(font_description, font_selection_capabilities);
  }

  FontCacheKey key = font_description.CacheKey(FontFaceCreationParams());

  scoped_refptr<SimpleFontData>& font_data =
      font_data_table_.insert(key, nullptr).stored_value->value;
  if (!font_data)
    font_data = CreateFontData(font_description, font_selection_capabilities);

  font_cache_key_age.PrependOrMoveToFirst(key);
  PruneOldestIfNeeded();

  DCHECK_LE(font_data_table_.size(), kMaxCachedFontData);
  // No release, because fontData is a reference to a RefPtr that is held in the
  // font_data_table_.
  return font_data;
}

void CSSFontFaceSource::PruneOldestIfNeeded() {
  if (font_cache_key_age.size() > kMaxCachedFontData) {
    DCHECK_EQ(font_cache_key_age.size() - 1, kMaxCachedFontData);
    FontCacheKey& key = font_cache_key_age.back();
    auto font_data_entry = font_data_table_.Take(key);
    font_cache_key_age.pop_back();
    DCHECK_EQ(font_cache_key_age.size(), kMaxCachedFontData);
    if (font_data_entry && font_data_entry->GetCustomFontData())
      font_data_entry->GetCustomFontData()->ClearFontFaceSource();
  }
}

void CSSFontFaceSource::PruneTable() {
  if (font_data_table_.IsEmpty())
    return;

  for (const auto& item : font_data_table_) {
    SimpleFontData* font_data = item.value.get();
    if (font_data && font_data->GetCustomFontData())
      font_data->GetCustomFontData()->ClearFontFaceSource();
  }
  font_cache_key_age.clear();
  font_data_table_.clear();
}

}  // namespace blink