Quelle nsFontCache.cpp Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsFontCache.h"

#include "gfxTextRun.h"
#include "mozilla/Services.h"
#include "mozilla/ServoUtils.h"
#include "nsCRT.h"

#include "mozilla/dom/Document.h"
#include "nsPresContext.h"

using mozilla::services::GetObserverService;

NS_IMPL_ISUPPORTS(nsFontCache, nsIObserver)

// The Init and Destroy methods are necessary because it's not
// safe to call AddObserver from a constructor or RemoveObserver
// from a destructor.  That should be fixed.
void nsFontCache::Init(nsPresContext* aContext) {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  mContext = aContext;
  // register as a memory-pressure observer to free font resources
  // in low-memory situations.
  nsCOMPtr<nsIObserverService> obs = GetObserverService();
  if (obs) {
    obs->AddObserver(this, "memory-pressure", false);
  }

  mLocaleLanguage = nsLanguageAtomService::GetService()->GetLocaleLanguage();
  if (!mLocaleLanguage) {
    mLocaleLanguage = NS_Atomize("x-western");
  }
}

void nsFontCache::Destroy() {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  nsCOMPtr<nsIObserverService> obs = GetObserverService();
  if (obs) {
    obs->RemoveObserver(this, "memory-pressure");
  }
  Flush();
}

NS_IMETHODIMP
nsFontCache::Observe(nsISupports*, const char* aTopic, const char16_t*) {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  if (!nsCRT::strcmp(aTopic, "memory-pressure")) {
    Compact();
  }
  return NS_OK;
}

already_AddRefed<nsFontMetrics> nsFontCache::GetMetricsFor(
    const nsFont& aFont, const nsFontMetrics::Params& aParams) {
  // We may eventually want to put an nsFontCache on canvas2d workers, but for
  // now it is only used by the main-thread layout code and stylo.
  mozilla::AssertIsMainThreadOrServoFontMetricsLocked();

  nsAtom* language = aParams.language && !aParams.language->IsEmpty()
                         ? aParams.language
                         : mLocaleLanguage.get();

  // First check our cache
  // start from the end, which is where we put the most-recent-used element
  const int32_t n = mFontMetrics.Length() - 1;
  for (int32_t i = n; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics.Elements()[i];
    if (fm->Font().Equals(aFont) &&
        fm->GetUserFontSet() == aParams.userFontSet &&
        fm->Language() == language &&
        fm->Orientation() == aParams.orientation &&
#ifdef XP_WIN
        fm->AllowForceGDIClassic() == aParams.allowForceGDIClassic &&
#endif
        fm->ExplicitLanguage() == aParams.explicitLanguage) {
      if (i != n) {
        // promote it to the end of the cache
        mFontMetrics.RemoveElementAtUnsafe(i);
        mFontMetrics.AppendElement(fm);
      }
      fm->GetThebesFontGroup()->UpdateUserFonts();
      return do_AddRef(fm);
    }
  }

  if (!mReportedProbableFingerprinting) {
    // We try to detect font fingerprinting attempts by recognizing a large
    // number of cache misses in a short amount of time, which indicates the
    // usage of an unreasonable amount of different fonts by the web page.
    PRTime now = PR_Now();
    if (now - mLastCacheMiss > kFingerprintingTimeout) {
      mCacheMisses = 0;
    }
    mCacheMisses++;
    mLastCacheMiss = now;
    if (NS_IsMainThread() && mCacheMisses > kFingerprintingCacheMissThreshold) {
      mContext->Document()->RecordFontFingerprinting();
      mReportedProbableFingerprinting = true;
    }
  }

  // It's not in the cache. Get font metrics and then cache them.
  // If the cache has reached its size limit, drop the older half of the
  // entries; but if we're on a stylo thread (the usual case), we have
  // to post a task back to the main thread to do the flush.
  if (n >= kMaxCacheEntries - 1 && !mFlushPending) {
    if (NS_IsMainThread()) {
      Flush(mFontMetrics.Length() - kMaxCacheEntries / 2);
    } else {
      mFlushPending = true;
      nsCOMPtr<nsIRunnable> flushTask = new FlushFontMetricsTask(this);
      MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(flushTask));
    }
  }

  nsFontMetrics::Params params = aParams;
  params.language = language;
  RefPtr<nsFontMetrics> fm = new nsFontMetrics(aFont, params, mContext);
  // the mFontMetrics list has the "head" at the end, because append
  // is cheaper than insert
  mFontMetrics.AppendElement(do_AddRef(fm).take());
  return fm.forget();
}

void nsFontCache::UpdateUserFonts(gfxUserFontSet* aUserFontSet) {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  for (nsFontMetrics* fm : mFontMetrics) {
    gfxFontGroup* fg = fm->GetThebesFontGroup();
    if (fg->GetUserFontSet() == aUserFontSet) {
      fg->UpdateUserFonts();
    }
  }
}

void nsFontCache::FontMetricsDeleted(const nsFontMetrics* aFontMetrics) {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  mFontMetrics.RemoveElement(aFontMetrics);
}

void nsFontCache::Compact() {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  // Need to loop backward because the running element can be removed on
  // the way
  for (int32_t i = mFontMetrics.Length() - 1; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics[i];
    nsFontMetrics* oldfm = fm;
    // Destroy() isn't here because we want our device context to be
    // notified
    NS_RELEASE(fm);  // this will reset fm to nullptr
    // if the font is really gone, it would have called back in
    // FontMetricsDeleted() and would have removed itself
    if (mFontMetrics.IndexOf(oldfm) != mFontMetrics.NoIndex) {
      // nope, the font is still there, so let's hold onto it too
      NS_ADDREF(oldfm);
    }
  }
}

// Flush the aFlushCount oldest entries, or all if (aFlushCount < 0)
void nsFontCache::Flush(int32_t aFlushCount) {
  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
  int32_t n = aFlushCount < 0
                  ? mFontMetrics.Length()
                  : std::min<int32_t>(aFlushCount, mFontMetrics.Length());
  for (int32_t i = n - 1; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics[i];
    // Destroy() will unhook our device context from the fm so that we
    // won't waste time in triggering the notification of
    // FontMetricsDeleted() in the subsequent release
    fm->Destroy();
    NS_RELEASE(fm);
  }
  mFontMetrics.RemoveElementsAt(0, n);

  mLastCacheMiss = 0;
  mCacheMisses = 0;
}

quality82%

¤ Dauer der Verarbeitung: 0.14 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.