layout/style/ServoUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* some utilities for Gecko to use for Servo initialization and assertions */
   8
   9 #ifndef mozilla_ServoUtils_h
  10 #define mozilla_ServoUtils_h
  11
  12 #include "mozilla/Assertions.h"
  13 #include "MainThreadUtils.h"
  14
  15 namespace mozilla {
  16
  17 // Defined in GeckoBindings.cpp.
  18 void InitializeServo();
  19 void ShutdownServo();
  20 void AssertIsMainThreadOrServoFontMetricsLocked();
  21
  22 class ServoStyleSet;
  23 extern ServoStyleSet* sInServoTraversal;
  24 inline bool IsInServoTraversal() {
  25   // The callers of this function are generally main-thread-only _except_
  26   // for potentially running during the Servo traversal, in which case they may
  27   // take special paths that avoid writing to caches and the like. In order
  28   // to allow those callers to branch efficiently without checking TLS, we
  29   // maintain this static boolean. However, the danger is that those callers
  30   // are generally unprepared to deal with non-Servo-but-also-non-main-thread
  31   // callers, and are likely to take the main-thread codepath if this function
  32   // returns false. So we assert against other non-main-thread callers here.
  33   MOZ_ASSERT(sInServoTraversal || NS_IsMainThread());
  34   return sInServoTraversal;
  35 }
  36 }  // namespace mozilla
  37
  38 #endif  // mozilla_ServoUtils_h