dom/smil/SMILType.h

   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_SMIL_SMILTYPE_H_
   8 #define DOM_SMIL_SMILTYPE_H_
   9
  10 #include "mozilla/Attributes.h"
  11 #include "nscore.h"
  12
  13 namespace mozilla {
  14
  15 class SMILValue;
  16
  17 //////////////////////////////////////////////////////////////////////////////
  18 // SMILType: Interface for defining the basic operations needed for animating
  19 // a particular kind of data (e.g. lengths, colors, transformation matrices).
  20 //
  21 // This interface is never used directly but always through a SMILValue that
  22 // bundles together a pointer to a concrete implementation of this interface and
  23 // the data upon which it should operate.
  24 //
  25 // We keep the data and type separate rather than just providing different
  26 // subclasses of SMILValue. This is so that sizeof(SMILValue) is the same
  27 // for all value types, allowing us to have a type-agnostic nsTArray of
  28 // SMILValue objects (actual objects, not pointers). It also allows most
  29 // SMILValues (except those that need to allocate extra memory for their
  30 // data) to be allocated on the stack and directly assigned to one another
  31 // provided performance benefits for the animation code.
  32 //
  33 // Note that different types have different capabilities. Roughly speaking there
  34 // are probably three main types:
  35 //
  36 // +---------------------+---------------+-------------+------------------+
  37 // | CATEGORY:           | DISCRETE      | LINEAR      | ADDITIVE         |
  38 // +---------------------+---------------+-------------+------------------+
  39 // | Example:            | strings,      | path data?  | lengths,         |
  40 // |                     | color k/words?|             | RGB color values |
  41 // |                     |               |             |                  |
  42 // | -- Assign?          |     X         |    X        |    X             |
  43 // | -- Add?             |     -         |    X?       |    X             |
  44 // | -- SandwichAdd?     |     -         |    -?       |    X             |
  45 // | -- ComputeDistance? |     -         |    -        |    X?            |
  46 // | -- Interpolate?     |     -         |    X        |    X             |
  47 // +---------------------+---------------+-------------+------------------+
  48 //
  49
  50 class SMILType {
  51   /**
  52    * Only give the SMILValue class access to this interface.
  53    */
  54   friend class SMILValue;
  55
  56  protected:
  57   /**
  58    * Initialises aValue and sets it to some identity value such that adding
  59    * aValue to another value of the same type has no effect.
  60    *
  61    * @pre  aValue.IsNull()
  62    * @post aValue.mType == this
  63    */
  64   virtual void Init(SMILValue& aValue) const = 0;
  65
  66   /**
  67    * Destroys any data associated with a value of this type.
  68    *
  69    * @pre  aValue.mType == this
  70    * @post aValue.IsNull()
  71    */
  72   virtual void Destroy(SMILValue& aValue) const = 0;
  73
  74   /**
  75    * Assign this object the value of another. Think of this as the assignment
  76    * operator.
  77    *
  78    * @param   aDest       The left-hand side of the assignment.
  79    * @param   aSrc        The right-hand side of the assignment.
  80    * @return  NS_OK on success, an error code on failure such as when the
  81    *          underlying type of the specified object differs.
  82    *
  83    * @pre aDest.mType == aSrc.mType == this
  84    */
  85   virtual nsresult Assign(SMILValue& aDest, const SMILValue& aSrc) const = 0;
  86
  87   /**
  88    * Test two SMILValue objects (of this SMILType) for equality.
  89    *
  90    * A return value of true represents a guarantee that aLeft and aRight are
  91    * equal. (That is, they would behave identically if passed to the methods
  92    * Add, SandwichAdd, ComputeDistance, and Interpolate).
  93    *
  94    * A return value of false simply indicates that we make no guarantee
  95    * about equality.
  96    *
  97    * NOTE: It's perfectly legal for implementations of this method to return
  98    * false in all cases.  However, smarter implementations will make this
  99    * method more useful for optimization.
 100    *
 101    * @param   aLeft       The left-hand side of the equality check.
 102    * @param   aRight      The right-hand side of the equality check.
 103    * @return  true if we're sure the values are equal, false otherwise.
 104    *
 105    * @pre aDest.mType == aSrc.mType == this
 106    */
 107   virtual bool IsEqual(const SMILValue& aLeft,
 108                        const SMILValue& aRight) const = 0;
 109
 110   /**
 111    * Adds two values.
 112    *
 113    * The count parameter facilitates repetition.
 114    *
 115    * By equation,
 116    *
 117    *   aDest += aValueToAdd * aCount
 118    *
 119    * Therefore, if aCount == 0, aDest will be unaltered.
 120    *
 121    * This method will fail if this data type is not additive or the value was
 122    * not specified using an additive syntax.
 123    *
 124    * See SVG 1.1, section 19.2.5. In particular,
 125    *
 126    *   "If a given attribute or property can take values of keywords (which are
 127    *   not additive) or numeric values (which are additive), then additive
 128    *   animations are possible if the subsequent animation uses a numeric value
 129    *   even if the base animation uses a keyword value; however, if the
 130    *   subsequent animation uses a keyword value, additive animation is not
 131    *   possible."
 132    *
 133    * If this method fails (e.g. because the data type is not additive), aDest
 134    * will be unaltered.
 135    *
 136    * @param   aDest       The value to add to.
 137    * @param   aValueToAdd The value to add.
 138    * @param   aCount      The number of times to add aValueToAdd.
 139    * @return  NS_OK on success, an error code on failure.
 140    *
 141    * @pre aValueToAdd.mType == aDest.mType == this
 142    */
 143   virtual nsresult Add(SMILValue& aDest, const SMILValue& aValueToAdd,
 144                        uint32_t aCount) const = 0;
 145
 146   /**
 147    * Adds aValueToAdd to the underlying value in the animation sandwich, aDest.
 148    *
 149    * For most types this operation is identical to a regular Add() but for some
 150    * types (notably <animateTransform>) the operation differs. For
 151    * <animateTransform> Add() corresponds to simply adding together the
 152    * transform parameters and is used when calculating cumulative values or
 153    * by-animation values. On the other hand SandwichAdd() is used when adding to
 154    * the underlying value and requires matrix post-multiplication. (This
 155    * distinction is most clearly indicated by the SVGT1.2 test suite. It is not
 156    * obvious within the SMIL specifications.)
 157    *
 158    * @param   aDest       The value to add to.
 159    * @param   aValueToAdd The value to add.
 160    * @return  NS_OK on success, an error code on failure.
 161    *
 162    * @pre aValueToAdd.mType == aDest.mType == this
 163    */
 164   virtual nsresult SandwichAdd(SMILValue& aDest,
 165                                const SMILValue& aValueToAdd) const {
 166     return Add(aDest, aValueToAdd, 1);
 167   }
 168
 169   /**
 170    * Calculates the 'distance' between two values. This is the distance used in
 171    * paced interpolation.
 172    *
 173    * @param   aFrom     The start of the interval for which the distance should
 174    *                    be calculated.
 175    * @param   aTo       The end of the interval for which the distance should be
 176    *                    calculated.
 177    * @param   aDistance The result of the calculation.
 178    * @return  NS_OK on success, or an appropriate error code if there is no
 179    *          notion of distance for the underlying data type or the distance
 180    *          could not be calculated.
 181    *
 182    * @pre aFrom.mType == aTo.mType == this
 183    */
 184   virtual nsresult ComputeDistance(const SMILValue& aFrom, const SMILValue& aTo,
 185                                    double& aDistance) const = 0;
 186
 187   /**
 188    * Calculates an interpolated value between two values using the specified
 189    * proportion.
 190    *
 191    * @param   aStartVal     The value defining the start of the interval of
 192    *                        interpolation.
 193    * @param   aEndVal       The value defining the end of the interval of
 194    *                        interpolation.
 195    * @param   aUnitDistance A number between 0.0 and 1.0 (inclusive) defining
 196    *                        the distance of the interpolated value in the
 197    *                        interval.
 198    * @param   aResult       The interpolated value.
 199    * @return  NS_OK on success, NS_ERROR_FAILURE if this data type cannot be
 200    *          interpolated or NS_ERROR_OUT_OF_MEMORY if insufficient memory was
 201    *          available for storing the result.
 202    *
 203    * @pre aStartVal.mType == aEndVal.mType == aResult.mType == this
 204    */
 205   virtual nsresult Interpolate(const SMILValue& aStartVal,
 206                                const SMILValue& aEndVal, double aUnitDistance,
 207                                SMILValue& aResult) const = 0;
 208 };
 209
 210 }  // namespace mozilla
 211
 212 #endif  // DOM_SMIL_SMILTYPE_H_