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/* -*- 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
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