gecko/content/smil/nsISMILType.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is the Mozilla SMIL module.
*
* The Initial Developer of the Original Code is Brian Birtles.
* Portions created by the Initial Developer are Copyright (C) 2005
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Robert O'Callahan <roc+moz@cs.cmu.edu>
* Brian Birtles <birtles@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef NS_ISMILTYPE_H_
#define NS_ISMILTYPE_H_
#include "nscore.h"
class nsSMILValue;
//////////////////////////////////////////////////////////////////////////////
// nsISMILType: Interface for defining the basic operations needed for animating
// a particular kind of data (e.g. lengths, colors, transformation matrices).
//
// This interface is never used directly but always through an nsSMILValue that
// bundles together a pointer to a concrete implementation of this interface and
// the data upon which it should operate.
//
// We keep the data and type separate rather than just providing different
// subclasses of nsSMILValue. This is so that sizeof(nsSMILValue) is the same
// for all value types, allowing us to have a type-agnostic nsTArray of
// nsSMILValue objects (actual objects, not pointers). It also allows most
// nsSMILValues (except those that need to allocate extra memory for their
// data) to be allocated on the stack and directly assigned to one another
// provided performance benefits for the animation code.
//
// Note that different types have different capabilities. Roughly speaking there
// are probably three main types:
//
// +---------------------+---------------+-------------+------------------+
// | CATEGORY: | DISCRETE | LINEAR | ADDITIVE |
// +---------------------+---------------+-------------+------------------+
// | Example: | strings, | path data? | lengths, |
// | | color k/words?| | RGB color values |
// | | | | |
// | -- Assign? | X | X | X |
// | -- Add? | - | X? | X |
// | -- SandwichAdd? | - | -? | X |
// | -- ComputeDistance? | - | - | X? |
// | -- Interpolate? | - | X | X |
// +---------------------+---------------+-------------+------------------+
//
class nsISMILType
{
/**
* Only give the nsSMILValue class access to this interface.
*/
friend class nsSMILValue;
protected:
/**
* Initialises aValue and sets it to some identity value such that adding
* aValue to another value of the same type has no effect.
*
* @pre aValue.IsNull()
* @post aValue.mType == this
*/
virtual void Init(nsSMILValue& aValue) const = 0;
/**
* Destroys any data associated with a value of this type.
*
* @pre aValue.mType == this
* @post aValue.IsNull()
*/
virtual void Destroy(nsSMILValue& aValue) const = 0;
/**
* Assign this object the value of another. Think of this as the assignment
* operator.
*
* @param aDest The left-hand side of the assignment.
* @param aSrc The right-hand side of the assignment.
* @return NS_OK on success, an error code on failure such as when the
* underlying type of the specified object differs.
*
* @pre aDest.mType == aSrc.mType == this
*/
virtual nsresult Assign(nsSMILValue& aDest,
const nsSMILValue& aSrc) const = 0;
/**
* Test two nsSMILValue objects (of this nsISMILType) for equality.
*
* A return value of PR_TRUE represents a guarantee that aLeft and aRight are
* equal. (That is, they would behave identically if passed to the methods
* Add, SandwichAdd, ComputeDistance, and Interpolate).
*
* A return value of PR_FALSE simply indicates that we make no guarantee
* about equality.
*
* NOTE: It's perfectly legal for implementations of this method to return
* PR_FALSE in all cases. However, smarter implementations will make this
* method more useful for optimization.
*
* @param aLeft The left-hand side of the equality check.
* @param aRight The right-hand side of the equality check.
* @return PR_TRUE if we're sure the values are equal, PR_FALSE otherwise.
*
* @pre aDest.mType == aSrc.mType == this
*/
virtual PRBool IsEqual(const nsSMILValue& aLeft,
const nsSMILValue& aRight) const = 0;
/**
* Adds two values.
*
* The count parameter facilitates repetition.
*
* By equation,
*
* aDest += aValueToAdd * aCount
*
* Therefore, if aCount == 0, aDest will be unaltered.
*
* This method will fail if this data type is not additive or the value was
* not specified using an additive syntax.
*
* See SVG 1.1, section 19.2.5. In particular,
*
* "If a given attribute or property can take values of keywords (which are
* not additive) or numeric values (which are additive), then additive
* animations are possible if the subsequent animation uses a numeric value
* even if the base animation uses a keyword value; however, if the
* subsequent animation uses a keyword value, additive animation is not
* possible."
*
* If this method fails (e.g. because the data type is not additive), aDest
* will be unaltered.
*
* @param aDest The value to add to.
* @param aValueToAdd The value to add.
* @param aCount The number of times to add aValueToAdd.
* @return NS_OK on success, an error code on failure.
*
* @pre aValueToAdd.mType == aDest.mType == this
*/
virtual nsresult Add(nsSMILValue& aDest,
const nsSMILValue& aValueToAdd,
PRUint32 aCount) const = 0;
/**
* Adds aValueToAdd to the underlying value in the animation sandwich, aDest.
*
* For most types this operation is identical to a regular Add() but for some
* types (notably <animateTransform>) the operation differs. For
* <animateTransform> Add() corresponds to simply adding together the
* transform parameters and is used when calculating cumulative values or
* by-animation values. On the other hand SandwichAdd() is used when adding to
* the underlying value and requires matrix post-multiplication. (This
* distinction is most clearly indicated by the SVGT1.2 test suite. It is not
* obvious within the SMIL specifications.)
*
* @param aDest The value to add to.
* @param aValueToAdd The value to add.
* @return NS_OK on success, an error code on failure.
*
* @pre aValueToAdd.mType == aDest.mType == this
*/
virtual nsresult SandwichAdd(nsSMILValue& aDest,
const nsSMILValue& aValueToAdd) const
{
return Add(aDest, aValueToAdd, 1);
}
/**
* Calculates the 'distance' between two values. This is the distance used in
* paced interpolation.
*
* @param aFrom The start of the interval for which the distance should
* be calculated.
* @param aTo The end of the interval for which the distance should be
* calculated.
* @param aDistance The result of the calculation.
* @return NS_OK on success, or an appropriate error code if there is no
* notion of distance for the underlying data type or the distance
* could not be calculated.
*
* @pre aFrom.mType == aTo.mType == this
*/
virtual nsresult ComputeDistance(const nsSMILValue& aFrom,
const nsSMILValue& aTo,
double& aDistance) const = 0;
/**
* Calculates an interpolated value between two values using the specified
* proportion.
*
* @param aStartVal The value defining the start of the interval of
* interpolation.
* @param aEndVal The value defining the end of the interval of
* interpolation.
* @param aUnitDistance A number between 0.0 and 1.0 (inclusive) defining
* the distance of the interpolated value in the
* interval.
* @param aResult The interpolated value.
* @return NS_OK on success, NS_ERROR_FAILURE if this data type cannot be
* interpolated or NS_ERROR_OUT_OF_MEMORY if insufficient memory was
* available for storing the result.
*
* @pre aStartVal.mType == aEndVal.mType == aResult.mType == this
*/
virtual nsresult Interpolate(const nsSMILValue& aStartVal,
const nsSMILValue& aEndVal,
double aUnitDistance,
nsSMILValue& aResult) const = 0;
/**
* Protected destructor, to ensure that no one accidentally deletes an
* instance of this class.
* (The only instances in existence should be singletons - one per subclass.)
*/
~nsISMILType() {}
};
#endif // NS_ISMILTYPE_H_