SVGLengthListSMILType.h (4478B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 /* This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 7 #ifndef DOM_SVG_SVGLENGTHLISTSMILTYPE_H_ 8 #define DOM_SVG_SVGLENGTHLISTSMILTYPE_H_ 9 10 #include "mozilla/SMILType.h" 11 12 namespace mozilla { 13 14 class SMILValue; 15 16 //////////////////////////////////////////////////////////////////////// 17 // SVGLengthListSMILType 18 // 19 // Operations for animating an SVGLengthList. 20 // 21 class SVGLengthListSMILType : public SMILType { 22 public: 23 // Singleton for SMILValue objects to hold onto. 24 static SVGLengthListSMILType sSingleton; 25 26 protected: 27 // SMILType Methods 28 // ------------------- 29 30 /** 31 * When this method initializes the SVGLengthListAndInfo for its SMILValue 32 * argument, it has to blindly set its mCanZeroPadList to true despite 33 * the fact that some attributes can't be zero-padded. (See the explaination 34 * that follows.) SVGAnimatedLengthList::SMILAnimatedLengthList's 35 * GetBaseValue() and ValueFromString() methods then override this for the 36 * SMILValue objects that they create to set this flag to the appropriate 37 * value for the attribute in question. 38 * 39 * The reason that we default to setting the mCanZeroPadList to true is 40 * because the SMIL engine creates "zero" valued SMILValue objects for 41 * intermediary calculations, and may pass such a SMILValue (along with a 42 * SMILValue from an animation element - that is a SMILValue created by 43 * SVGAnimatedLengthList::SMILAnimatedLengthList's GetBaseValue() or 44 * ValueFromString() methods) into the Add(), ComputeDistance() or 45 * Interpolate() methods below. Even in the case of animation of list 46 * attributes that may *not* be padded with zeros (such as 'x' and 'y' on the 47 * <text> element), we need to allow zero-padding of these "zero" valued 48 * SMILValue's lists. One reason for this is illustrated by the following 49 * example: 50 * 51 * <text x="2 4">foo 52 * <animate by="2 2" .../> 53 * </text> 54 * 55 * In this example there are two SMIL animation layers to be sandwiched: the 56 * base layer, and the layer created for the <animate> element. The SMIL 57 * engine calculates the result of each layer *independently*, before 58 * compositing the results together. Thus for the <animate> sandwich layer 59 * the SMIL engine interpolates between a "zero" SMILValue that it creates 60 * (since there is no explicit "from") and the "2 2", before the result of 61 * that interpolation is added to the "2 4" from the base layer. Clearly for 62 * the interpolation between the "zero" SMILValue and "2 2" to work, the 63 * "zero" SMILValue's SVGLengthListAndInfo must be zero paddable - hence 64 * why this method always sets mCanZeroPadList to true. 65 * 66 * (Since the Add(), ComputeDistance() and Interpolate() methods may be 67 * passed two input SMILValue objects for which CanZeroPadList() returns 68 * opposite values, these methods must be careful what they set the flag to 69 * on the SMILValue that they output. If *either* of the input SMILValues 70 * has an SVGLengthListAndInfo for which CanZeroPadList() returns false, 71 * then they must set the flag to false on the output SMILValue too. If 72 * the methods failed to do that, then when the result SMILValue objects 73 * from each sandwich layer are composited together, we could end up allowing 74 * animation between lists of different length when we should not!) 75 */ 76 void InitValue(SMILValue& aValue) const override; 77 78 void DestroyValue(SMILValue& aValue) const override; 79 nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const override; 80 bool IsEqual(const SMILValue& aLeft, const SMILValue& aRight) const override; 81 nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd, 82 uint32_t aCount) const override; 83 nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo, 84 double& aDistance) const override; 85 nsresult Interpolate(const SMILValue& aStartVal, const SMILValue& aEndVal, 86 double aUnitDistance, SMILValue& aResult) const override; 87 88 private: 89 // Private constructor: prevent instances beyond my singleton. 90 constexpr SVGLengthListSMILType() = default; 91 }; 92 93 } // namespace mozilla 94 95 #endif // DOM_SVG_SVGLENGTHLISTSMILTYPE_H_