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−/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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− *
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− * This Source Code Form is subject to the terms of the Mozilla Public
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− * License, v. 2.0. If a copy of the MPL was not distributed with this
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− * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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−
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−#ifndef mozilla_image_FrameTimeout_h
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−#define mozilla_image_FrameTimeout_h
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−
+
−#include <stdint.h>
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−#include "mozilla/Assertions.h"
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−
+
−namespace mozilla {
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−namespace image {
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−
+
−/**
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− * FrameTimeout wraps a frame timeout value (measured in milliseconds) after
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− * first normalizing it. This normalization is necessary because some tools
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− * generate incorrect frame timeout values which we nevertheless have to
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− * support. For this reason, code that deals with frame timeouts should always
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− * use a FrameTimeout value rather than the raw value from the image header.
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− */
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−struct FrameTimeout
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−{
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−  /**
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−   * @return a FrameTimeout of zero. This should be used only for math
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−   * involving FrameTimeout values. You can't obtain a zero FrameTimeout from
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−   * FromRawMilliseconds().
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−   */
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−  static FrameTimeout Zero() { return FrameTimeout(0); }
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−
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−  /// @return an infinite FrameTimeout.
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−  static FrameTimeout Forever() { return FrameTimeout(-1); }
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−
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−  /// @return a FrameTimeout obtained by normalizing a raw timeout value.
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−  static FrameTimeout FromRawMilliseconds(int32_t aRawMilliseconds)
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−  {
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−    // Normalize all infinite timeouts to the same value.
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−    if (aRawMilliseconds < 0) {
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−      return FrameTimeout::Forever();
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−    }
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−
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−    // Very small timeout values are problematic for two reasons: we don't want
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−    // to burn energy redrawing animated images extremely fast, and broken tools
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−    // generate these values when they actually want a "default" value, so such
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−    // images won't play back right without normalization. For some context,
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−    // see bug 890743, bug 125137, bug 139677, and bug 207059. The historical
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−    // behavior of IE and Opera was:
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−    //   IE 6/Win:
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−    //     10 - 50ms is normalized to 100ms.
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−    //     >50ms is used unnormalized.
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−    //   Opera 7 final/Win:
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−    //     10ms is normalized to 100ms.
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−    //     >10ms is used unnormalized.
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−    if (aRawMilliseconds >= 0 && aRawMilliseconds <= 10 ) {
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−      return FrameTimeout(100);
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−    }
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−
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−    // The provided timeout value is OK as-is.
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−    return FrameTimeout(aRawMilliseconds);
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−  }
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−
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−  bool operator==(const FrameTimeout& aOther) const
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−  {
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−    return mTimeout == aOther.mTimeout;
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−  }
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−
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−  bool operator!=(const FrameTimeout& aOther) const { return !(*this == aOther); }
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−
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−  FrameTimeout operator+(const FrameTimeout& aOther)
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−  {
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−    if (*this == Forever() || aOther == Forever()) {
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−      return Forever();
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−    }
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−
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−    return FrameTimeout(mTimeout + aOther.mTimeout);
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−  }
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−
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−  FrameTimeout& operator+=(const FrameTimeout& aOther)
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−  {
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−    *this = *this + aOther;
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−    return *this;
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−  }
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−
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−  /**
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−   * @return this FrameTimeout's value in milliseconds. Illegal to call on a
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−   * an infinite FrameTimeout value.
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−   */
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−  uint32_t AsMilliseconds() const
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−  {
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−    if (*this == Forever()) {
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−      MOZ_ASSERT_UNREACHABLE("Calling AsMilliseconds() on an infinite FrameTimeout");
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−      return 100;  // Fail to something sane.
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−    }
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−
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−    return uint32_t(mTimeout);
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−  }
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−
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−  /**
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−   * @return this FrameTimeout value encoded so that non-negative values
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−   * represent a timeout in milliseconds, and -1 represents an infinite
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−   * timeout.
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−   *
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−   * XXX(seth): This is a backwards compatibility hack that should be removed.
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−   */
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−  int32_t AsEncodedValueDeprecated() const { return mTimeout; }
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−
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−private:
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−  explicit FrameTimeout(int32_t aTimeout)
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−    : mTimeout(aTimeout)
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−  { }
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−
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−  int32_t mTimeout;
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−};
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−
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−} // namespace image
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−} // namespace mozilla
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−
+
−#endif // mozilla_image_FrameTimeout_h