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