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120 lines
3.6 KiB
C++
120 lines
3.6 KiB
C++
/* -*- 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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#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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/// @return an infinite FrameTimeout.
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static FrameTimeout Forever() { return FrameTimeout(-1); }
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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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// 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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// The provided timeout value is OK as-is.
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return FrameTimeout(aRawMilliseconds);
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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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bool operator!=(const FrameTimeout& aOther) const { return !(*this == aOther); }
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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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return FrameTimeout(mTimeout + aOther.mTimeout);
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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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* @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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return uint32_t(mTimeout);
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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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private:
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explicit FrameTimeout(int32_t aTimeout)
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: mTimeout(aTimeout)
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{ }
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int32_t mTimeout;
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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
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