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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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_SVGLENGTHLISTSMILTYPE_H_
#define MOZILLA_SVGLENGTHLISTSMILTYPE_H_
#include "mozilla/Attributes.h"
#include "nsISMILType.h"
class nsSMILValue;
namespace mozilla {
////////////////////////////////////////////////////////////////////////
// SVGLengthListSMILType
//
// Operations for animating an SVGLengthList.
//
class SVGLengthListSMILType : public nsISMILType
{
public:
// Singleton for nsSMILValue objects to hold onto.
static SVGLengthListSMILType sSingleton;
protected:
// nsISMILType Methods
// -------------------
/**
* When this method initializes the SVGLengthListAndInfo for its nsSMILValue
* argument, it has to blindly set its mCanZeroPadList to true despite
* the fact that some attributes can't be zero-padded. (See the explaination
* that follows.) SVGAnimatedLengthList::SMILAnimatedLengthList's
* GetBaseValue() and ValueFromString() methods then override this for the
* nsSMILValue objects that they create to set this flag to the appropriate
* value for the attribute in question.
*
* The reason that we default to setting the mCanZeroPadList to true is
* because the SMIL engine creates "zero" valued nsSMILValue objects for
* intermediary calculations, and may pass such an nsSMILValue (along with an
* nsSMILValue from an animation element - that is an nsSMILValue created by
* SVGAnimatedLengthList::SMILAnimatedLengthList's GetBaseValue() or
* ValueFromString() methods) into the Add(), ComputeDistance() or
* Interpolate() methods below. Even in the case of animation of list
* attributes that may *not* be padded with zeros (such as 'x' and 'y' on the
* <text> element), we need to allow zero-padding of these "zero" valued
* nsSMILValue's lists. One reason for this is illustrated by the following
* example:
*
* <text x="2 4">foo
* <animate by="2 2" .../>
* </text>
*
* In this example there are two SMIL animation layers to be sandwiched: the
* base layer, and the layer created for the <animate> element. The SMIL
* engine calculates the result of each layer *independently*, before
* compositing the results together. Thus for the <animate> sandwich layer
* the SMIL engine interpolates between a "zero" nsSMILValue that it creates
* (since there is no explicit "from") and the "2 2", before the result of
* that interpolation is added to the "2 4" from the base layer. Clearly for
* the interpolation between the "zero" nsSMILValue and "2 2" to work, the
* "zero" nsSMILValue's SVGLengthListAndInfo must be zero paddable - hence
* why this method always sets mCanZeroPadList to true.
*
* (Since the Add(), ComputeDistance() and Interpolate() methods may be
* passed two input nsSMILValue objects for which CanZeroPadList() returns
* opposite values, these methods must be careful what they set the flag to
* on the nsSMILValue that they output. If *either* of the input nsSMILValues
* has an SVGLengthListAndInfo for which CanZeroPadList() returns false,
* then they must set the flag to false on the output nsSMILValue too. If
* the methods failed to do that, then when the result nsSMILValue objects
* from each sandwich layer are composited together, we could end up allowing
* animation between lists of different length when we should not!)
*/
virtual void Init(nsSMILValue& aValue) const override;
virtual void Destroy(nsSMILValue& aValue) const override;
virtual nsresult Assign(nsSMILValue& aDest, const nsSMILValue& aSrc) const override;
virtual bool IsEqual(const nsSMILValue& aLeft,
const nsSMILValue& aRight) const override;
virtual nsresult Add(nsSMILValue& aDest, const nsSMILValue& aValueToAdd,
uint32_t aCount) const override;
virtual nsresult ComputeDistance(const nsSMILValue& aFrom,
const nsSMILValue& aTo,
double& aDistance) const override;
virtual nsresult Interpolate(const nsSMILValue& aStartVal,
const nsSMILValue& aEndVal,
double aUnitDistance,
nsSMILValue& aResult) const override;
private:
// Private constructor: prevent instances beyond my singleton.
constexpr SVGLengthListSMILType() {}
};
} // namespace mozilla
#endif // MOZILLA_SVGLENGTHLISTSMILTYPE_H_
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