layout/style/nsStyleTransformMatrix.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is mozilla.org code.
  16  *
  17  * The Initial Developer of the Original Code is
  18  *   Mozilla Corporation
  19  *
  20  * Contributor(s):
  21  *   Keith Schwarz <kschwarz@mozilla.com> (original author)
  22  *
  23  * Alternatively, the contents of this file may be used under the terms of
  24  * either of the GNU General Public License Version 2 or later (the "GPL"),
  25  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  26  * in which case the provisions of the GPL or the LGPL are applicable instead
  27  * of those above. If you wish to allow use of your version of this file only
  28  * under the terms of either the GPL or the LGPL, and not to allow others to
  29  * use your version of this file under the terms of the MPL, indicate your
  30  * decision by deleting the provisions above and replace them with the notice
  31  * and other provisions required by the GPL or the LGPL. If you do not delete
  32  * the provisions above, a recipient may use your version of this file under
  33  * the terms of any one of the MPL, the GPL or the LGPL.
  34  *
  35  * ***** END LICENSE BLOCK ***** */
  36
  37 /*
  38  * A class representing three matrices that can be used for style transforms.
  39  */
  40
  41 #ifndef nsStyleTransformMatrix_h_
  42 #define nsStyleTransformMatrix_h_
  43
  44 #include "nsCSSValue.h"
  45 #include "gfxMatrix.h"
  46 #include "nsRect.h"
  47
  48 struct nsCSSValueList;
  49
  50 /**
  51  * A class representing a style transformation matrix.  The class actually
  52  * wraps three different matrices, a constant matrix and two matrices
  53  * whose values are scaled by the width and the height of the bounding
  54  * rectangle for the object to transform.  Thus, given a frame rectangle
  55  * of dimensions (width, height) and a point (x, y) to transform, the matrix
  56  * corresponds to the transform operation
  57  *
  58  * | a c e |   |0 0 dX1|           |0 0 dY1|           | x |
  59  *(| b d f | + |0 0 dX2| (width) + |0 0 dY2| (height)) | y |
  60  * | 0 0 1 |   |0 0   0|           |0 0   0|           | 1 |
  61  *
  62  * Note that unlike the Thebes gfxMatrix, vectors are column vectors and
  63  * consequently the multiplication of a matrix A and a vector x is Ax, not xA.
  64  */
  65 class nsStyleContext;
  66 class nsPresContext;
  67 class nsStyleTransformMatrix
  68 {
  69  public:
  70   /**
  71    * Constructor sets the matrix to the identity.
  72    */
  73   nsStyleTransformMatrix();
  74
  75   /**
  76    * Given a frame's bounding rectangle, returns a gfxMatrix
  77    * corresponding to the transformation represented by this
  78    * matrix.  The transformation takes points in the frame's
  79    * local space and converts them to points in the frame's
  80    * transformed space.
  81    *
  82    * @param aBounds The frame's bounding rectangle.
  83    * @param aFactor The number of app units per device pixel.
  84    * @return A Thebes matrix corresponding to the transform.
  85    */
  86   gfxMatrix GetThebesMatrix(const nsRect& aBounds, float aFactor) const;
  87
  88   /**
  89    * Multiplies this matrix by another matrix, in that order.  If A'
  90    * is the value of A after A *= B, then for any vector x, the
  91    * equivalence A'(x) == A(B(x)) holds.
  92    *
  93    * @param aOther The matrix to multiply this matrix by.
  94    * @return A reference to this matrix.
  95    */
  96   nsStyleTransformMatrix& operator *= (const nsStyleTransformMatrix &aOther);
  97
  98   /**
  99    * Returns a new nsStyleTransformMatrix that is equal to one matrix
 100    * multiplied by another matrix, in that order.  If C is the result of
 101    * A * B, then for any vector x, the equivalence C(x) = A(B(x)).
 102    *
 103    * @param aOther The matrix to multiply this matrix by.
 104    * @return A new nsStyleTransformMatrix equal to this matrix multiplied
 105    *         by the other matrix.
 106    */
 107   const nsStyleTransformMatrix
 108     operator * (const nsStyleTransformMatrix &aOther) const;
 109
 110   /**
 111    * Return the transform function, as an nsCSSKeyword, for the given
 112    * nsCSSValue::Array from a transform list.
 113    */
 114   static nsCSSKeyword TransformFunctionOf(const nsCSSValue::Array* aData);
 115
 116   /**
 117    * Given an nsCSSValue::Array* containing a -moz-transform function,
 118    * updates this matrix to hold the value of that function.
 119    *
 120    * @param aData The nsCSSValue::Array* containing the transform function.
 121    * @param aContext The style context, used for unit conversion.
 122    * @param aPresContext The presentation context, used for unit conversion.
 123    * @param aCanStoreInRuleTree Set to false if the result cannot be cached
 124    *                            in the rule tree, otherwise untouched.
 125    *
 126    * aContext and aPresContext may be null if all of the (non-percent)
 127    * length values in aData are already known to have been converted to
 128    * eCSSUnit_Pixel (as they are in an nsStyleAnimation::Value)
 129    */
 130   void SetToTransformFunction(const nsCSSValue::Array* aData,
 131                               nsStyleContext* aContext,
 132                               nsPresContext* aPresContext,
 133                               PRBool& aCanStoreInRuleTree);
 134
 135   /**
 136    * The same as SetToTransformFunction, but for a list of transform
 137    * functions.
 138    */
 139   static nsStyleTransformMatrix ReadTransforms(const nsCSSValueList* aList,
 140                                                nsStyleContext* aContext,
 141                                                nsPresContext* aPresContext,
 142                                                PRBool &aCanStoreInRuleTree);
 143   /**
 144    * Sets this matrix to be the identity matrix.
 145    */
 146   void SetToIdentity();
 147
 148   /**
 149    * Returns the value of the entry at the 2x2 submatrix of the
 150    * transform matrix that defines the non-affine linear transform.
 151    * The order is given as
 152    * |elem[0]  elem[2]|
 153    * |elem[1]  elem[3]|
 154    *
 155    * @param aIndex The element index.
 156    * @return The value of the element at that index.
 157    */
 158   float GetMainMatrixEntry(PRInt32 aIndex) const
 159   {
 160     NS_PRECONDITION(aIndex >= 0 && aIndex < 4, "Index out of bounds!");
 161     return mMain[aIndex];
 162   }
 163
 164   /**
 165    * Returns the value of the X or Y translation component of the matrix,
 166    * given the specified bounds.
 167    *
 168    * @param aBounds The bounds of the element.
 169    * @return The value of the X or Ytranslation component.
 170    */
 171   nscoord GetXTranslation(const nsRect& aBounds) const;
 172   nscoord GetYTranslation(const nsRect& aBounds) const;
 173
 174   /**
 175    * Get the raw components used for GetXTranslation and GetYTranslation.
 176    */
 177   nscoord GetCoordXTranslation() const { return mDelta[0]; }
 178   nscoord GetCoordYTranslation() const { return mDelta[1]; }
 179   float GetWidthRelativeXTranslation() const { return mX[0]; }
 180   float GetWidthRelativeYTranslation() const { return mX[1]; }
 181   float GetHeightRelativeXTranslation() const { return mY[0]; }
 182   float GetHeightRelativeYTranslation() const { return mY[1]; }
 183
 184   /**
 185    * Returns whether the two matrices are equal or not.
 186    *
 187    * @param aOther The matrix to compare to.
 188    * @return Whether the two matrices are equal.
 189    */
 190   PRBool operator== (const nsStyleTransformMatrix& aOther) const;
 191   PRBool operator!= (const nsStyleTransformMatrix& aOther) const
 192   {
 193     return !(*this == aOther);
 194   }
 195
 196  private:
 197   /* The three matrices look like this:
 198    * |mMain[0] mMain[2] mDelta[0]|
 199    * |mMain[1] mMain[3] mDelta[1]| <-- Constant matrix
 200    * |       0        0         1|
 201    *
 202    * |       0        0     mX[0]|
 203    * |       0        0     mX[1]| <-- Scaled by width of element
 204    * |       0        0         0|
 205    *
 206    * |       0        0     mY[0]|
 207    * |       0        0     mY[1]| <-- Scaled by height of element
 208    * |       0        0         0|
 209    */
 210   float mMain[4];
 211   nscoord mDelta[2];
 212   float mX[2];
 213   float mY[2];
 214 };
 215
 216 #endif