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36 :
37 : #ifndef MOZILLA_SVGLENGTHLISTSMILTYPE_H_
38 : #define MOZILLA_SVGLENGTHLISTSMILTYPE_H_
39 :
40 : #include "nsISMILType.h"
41 :
42 : class nsSMILValue;
43 :
44 : namespace mozilla {
45 :
46 : ////////////////////////////////////////////////////////////////////////
47 : // SVGLengthListSMILType
48 : //
49 : // Operations for animating an SVGLengthList.
50 : //
51 : class SVGLengthListSMILType : public nsISMILType
52 : {
53 : public:
54 : // Singleton for nsSMILValue objects to hold onto.
55 : static SVGLengthListSMILType sSingleton;
56 :
57 : protected:
58 : // nsISMILType Methods
59 : // -------------------
60 :
61 : /**
62 : * When this method initializes the SVGLengthListAndInfo for its nsSMILValue
63 : * argument, it has to blindly set its mCanZeroPadList to true despite
64 : * the fact that some attributes can't be zero-padded. (See the explaination
65 : * that follows.) SVGAnimatedLengthList::SMILAnimatedLengthList's
66 : * GetBaseValue() and ValueFromString() methods then override this for the
67 : * nsSMILValue objects that they create to set this flag to the appropriate
68 : * value for the attribute in question.
69 : *
70 : * The reason that we default to setting the mCanZeroPadList to true is
71 : * because the SMIL engine creates "zero" valued nsSMILValue objects for
72 : * intermediary calculations, and may pass such an nsSMILValue (along with an
73 : * nsSMILValue from an animation element - that is an nsSMILValue created by
74 : * SVGAnimatedLengthList::SMILAnimatedLengthList's GetBaseValue() or
75 : * ValueFromString() methods) into the Add(), ComputeDistance() or
76 : * Interpolate() methods below. Even in the case of animation of list
77 : * attributes that may *not* be padded with zeros (such as 'x' and 'y' on the
78 : * <text> element), we need to allow zero-padding of these "zero" valued
79 : * nsSMILValue's lists. One reason for this is illustrated by the following
80 : * example:
81 : *
82 : * <text x="2 4">foo
83 : * <animate by="2 2" .../>
84 : * </text>
85 : *
86 : * In this example there are two SMIL animation layers to be sandwiched: the
87 : * base layer, and the layer created for the <animate> element. The SMIL
88 : * engine calculates the result of each layer *independently*, before
89 : * compositing the results together. Thus for the <animate> sandwich layer
90 : * the SMIL engine interpolates between a "zero" nsSMILValue that it creates
91 : * (since there is no explicit "from") and the "2 2", before the result of
92 : * that interpolation is added to the "2 4" from the base layer. Clearly for
93 : * the interpolation between the "zero" nsSMILValue and "2 2" to work, the
94 : * "zero" nsSMILValue's SVGLengthListAndInfo must be zero paddable - hence
95 : * why this method always sets mCanZeroPadList to true.
96 : *
97 : * (Since the Add(), ComputeDistance() and Interpolate() methods may be
98 : * passed two input nsSMILValue objects for which CanZeroPadList() returns
99 : * opposite values, these methods must be careful what they set the flag to
100 : * on the nsSMILValue that they output. If *either* of the input nsSMILValues
101 : * has an SVGLengthListAndInfo for which CanZeroPadList() returns false,
102 : * then they must set the flag to false on the output nsSMILValue too. If
103 : * the methods failed to do that, then when the result nsSMILValue objects
104 : * from each sandwich layer are composited together, we could end up allowing
105 : * animation between lists of different length when we should not!)
106 : */
107 : virtual void Init(nsSMILValue& aValue) const;
108 :
109 : virtual void Destroy(nsSMILValue& aValue) const;
110 : virtual nsresult Assign(nsSMILValue& aDest, const nsSMILValue& aSrc) const;
111 : virtual bool IsEqual(const nsSMILValue& aLeft,
112 : const nsSMILValue& aRight) const;
113 : virtual nsresult Add(nsSMILValue& aDest, const nsSMILValue& aValueToAdd,
114 : PRUint32 aCount) const;
115 : virtual nsresult ComputeDistance(const nsSMILValue& aFrom,
116 : const nsSMILValue& aTo,
117 : double& aDistance) const;
118 : virtual nsresult Interpolate(const nsSMILValue& aStartVal,
119 : const nsSMILValue& aEndVal,
120 : double aUnitDistance,
121 : nsSMILValue& aResult) const;
122 :
123 : private:
124 : // Private constructor & destructor: prevent instances beyond my singleton,
125 : // and prevent others from deleting my singleton.
126 1464 : SVGLengthListSMILType() {}
127 1487 : ~SVGLengthListSMILType() {}
128 : };
129 :
130 : } // namespace mozilla
131 :
132 : #endif // MOZILLA_SVGLENGTHLISTSMILTYPE_H_
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