gecko-dev/layout/style/nsStyleTransformMatrix.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* for the specific language governing rights and limitations under the
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*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Mozilla Corporation
*
* Contributor(s):
* Keith Schwarz <kschwarz@mozilla.com> (original author)
*
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* 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"),
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/*
* A class representing three matrices that can be used for style transforms.
*/
#ifndef nsStyleTransformMatrix_h_
#define nsStyleTransformMatrix_h_
#include "nsCSSValue.h"
#include "gfxMatrix.h"
#include "nsRect.h"
/**
* A class representing a style transformation matrix. The class actually
* wraps three different matrices, a constant matrix and two matrices
* whose values are scaled by the width and the height of the bounding
* rectangle for the object to transform. Thus, given a frame rectangle
* of dimensions (width, height) and a point (x, y) to transform, the matrix
* corresponds to the transform operation
*
* | a c e | |0 0 dX1| |0 0 dY1| | x |
*(| b d f | + |0 0 dX2| (width) + |0 0 dY2| (height)) | y |
* | 0 0 1 | |0 0 0| |0 0 0| | 1 |
*
* Note that unlike the Thebes gfxMatrix, vectors are column vectors and
* consequently the multiplication of a matrix A and a vector x is Ax, not xA.
*/
class nsStyleContext;
class nsPresContext;
class nsStyleTransformMatrix
{
public:
/**
* Constructor sets the matrix to the identity.
*/
nsStyleTransformMatrix();
/**
* Given a frame's bounding rectangle, returns a gfxMatrix
* corresponding to the transformation represented by this
* matrix. The transformation takes points in the frame's
* local space and converts them to points in the frame's
* transformed space.
*
* @param aBounds The frame's bounding rectangle.
* @param aFactor The number of app units per device pixel.
* @return A Thebes matrix corresponding to the transform.
*/
gfxMatrix GetThebesMatrix(const nsRect& aBounds, float aFactor) const;
/**
* Multiplies this matrix by another matrix, in that order. If A'
* is the value of A after A *= B, then for any vector x, the
* equivalence A'(x) == A(B(x)) holds.
*
* @param aOther The matrix to multiply this matrix by.
* @return A reference to this matrix.
*/
nsStyleTransformMatrix& operator *= (const nsStyleTransformMatrix &aOther);
/**
* Returns a new nsStyleTransformMatrix that is equal to one matrix
* multiplied by another matrix, in that order. If C is the result of
* A * B, then for any vector x, the equivalence C(x) = A(B(x)).
*
* @param aOther The matrix to multiply this matrix by.
* @return A new nsStyleTransformMatrix equal to this matrix multiplied
* by the other matrix.
*/
const nsStyleTransformMatrix
operator * (const nsStyleTransformMatrix &aOther) const;
/**
* Given an nsCSSValue::Array* containing a -moz-transform function,
* updates this matrix to hold the value of that function.
*
* @param aData The nsCSSValue::Array* containing the transform function.
* @param aContext The style context, used for unit conversion.
* @param aPresContext The presentation context, used for unit conversion.
* @param aCanStoreInRuleTree Set to false if the result cannot be cached
* in the rule tree, otherwise untouched.
*/
void SetToTransformFunction(const nsCSSValue::Array* aData,
nsStyleContext* aContext,
nsPresContext* aPresContext,
PRBool& aCanStoreInRuleTree);
/**
* Sets this matrix to be the identity matrix.
*/
void SetToIdentity();
/**
* Returns the value of the entry at the 2x2 submatrix of the
* transform matrix that defines the non-affine linear transform.
* The order is given as
* |elem[0] elem[2]|
* |elem[1] elem[3]|
*
* @param aIndex The element index.
* @return The value of the element at that index.
*/
float GetMainMatrixEntry(PRInt32 aIndex) const
{
NS_PRECONDITION(aIndex >= 0 && aIndex < 4, "Index out of bounds!");
return mMain[aIndex];
}
/**
* Returns the value of the X or Y translation component of the matrix,
* given the specified bounds.
*
* @param aBounds The bounds of the element.
* @return The value of the X or Ytranslation component.
*/
nscoord GetXTranslation(const nsRect& aBounds) const;
nscoord GetYTranslation(const nsRect& aBounds) const;
/**
* Returns whether the two matrices are equal or not.
*
* @param aOther The matrix to compare to.
* @return Whether the two matrices are equal.
*/
PRBool operator== (const nsStyleTransformMatrix& aOther) const;
PRBool operator!= (const nsStyleTransformMatrix& aOther) const
{
return !(*this == aOther);
}
private:
/* The three matrices look like this:
* |mMain[0] mMain[2] mDelta[0]|
* |mMain[1] mMain[3] mDelta[1]| <-- Constant matrix
* | 0 0 1|
*
* | 0 0 mX[0]|
* | 0 0 mX[1]| <-- Scaled by width of element
* | 0 0 0|
*
* | 0 0 mY[0]|
* | 0 0 mY[1]| <-- Scaled by height of element
* | 0 0 0|
*/
float mMain[4];
nscoord mDelta[2];
float mX[2];
float mY[2];
};
#endif