Quelle FrameTimeout.h Sprache: C

/* -*- Mode: C++; tab-width: 2; 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/. */

#ifndef mozilla_image_FrameTimeout_h
#define mozilla_image_FrameTimeout_h

#include <stdint.h>
#include "mozilla/Assertions.h"

namespace mozilla {
namespace image {

/**
* FrameTimeout wraps a frame timeout value (measured in milliseconds) after
* first normalizing it. This normalization is necessary because some tools
* generate incorrect frame timeout values which we nevertheless have to
* support. For this reason, code that deals with frame timeouts should always
* use a FrameTimeout value rather than the raw value from the image header.
*/
struct FrameTimeout {
  /**
   * @return a FrameTimeout of zero. This should be used only for math
   * involving FrameTimeout values. You can't obtain a zero FrameTimeout from
   * FromRawMilliseconds().
   */
  static FrameTimeout Zero() { return FrameTimeout(0); }

  /// @return an infinite FrameTimeout.
  static FrameTimeout Forever() { return FrameTimeout(-1); }

  /// @return a FrameTimeout obtained by normalizing a raw timeout value.
  static FrameTimeout FromRawMilliseconds(int32_t aRawMilliseconds) {
    // Normalize all infinite timeouts to the same value.
    if (aRawMilliseconds < 0) {
      return FrameTimeout::Forever();
    }

    // Very small timeout values are problematic for two reasons: we don't want
    // to burn energy redrawing animated images extremely fast, and broken tools
    // generate these values when they actually want a "default" value, so such
    // images won't play back right without normalization. For some context,
    // see bug 890743, bug 125137, bug 139677, and bug 207059. The historical
    // behavior of IE and Opera was:
    //   IE 6/Win:
    //     10 - 50ms is normalized to 100ms.
    //     >50ms is used unnormalized.
    //   Opera 7 final/Win:
    //     10ms is normalized to 100ms.
    //     >10ms is used unnormalized.
    if (aRawMilliseconds >= 0 && aRawMilliseconds <= 10) {
      return FrameTimeout(100);
    }

    // The provided timeout value is OK as-is.
    return FrameTimeout(aRawMilliseconds);
  }

  bool operator==(const FrameTimeout& aOther) const {
    return mTimeout == aOther.mTimeout;
  }

  bool operator!=(const FrameTimeout& aOther) const {
    return !(*this == aOther);
  }

  FrameTimeout operator+(const FrameTimeout& aOther) {
    if (*this == Forever() || aOther == Forever()) {
      return Forever();
    }

    return FrameTimeout(mTimeout + aOther.mTimeout);
  }

  FrameTimeout& operator+=(const FrameTimeout& aOther) {
    *this = *this + aOther;
    return *this;
  }

  /**
   * @return this FrameTimeout's value in milliseconds. Illegal to call on a
   * an infinite FrameTimeout value.
   */
  uint32_t AsMilliseconds() const {
    if (*this == Forever()) {
      MOZ_ASSERT_UNREACHABLE(
          "Calling AsMilliseconds() on an infinite FrameTimeout");
      return 100;  // Fail to something sane.
    }

    return uint32_t(mTimeout);
  }

  /**
   * @return this FrameTimeout value encoded so that non-negative values
   * represent a timeout in milliseconds, and -1 represents an infinite
   * timeout.
   *
   * XXX(seth): This is a backwards compatibility hack that should be removed.
   */
  int32_t AsEncodedValueDeprecated() const { return mTimeout; }

private:
  explicit FrameTimeout(int32_t aTimeout) : mTimeout(aTimeout) {}

  int32_t mTimeout;
};

}  // namespace image
}  // namespace mozilla

#endif  // mozilla_image_FrameTimeout_h

quality100%

¤ Dauer der Verarbeitung: 0.13 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.