Add perspective support to SkMatrix44 initializers.

include/utils/SkMatrix44.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkMatrix44_DEFINED
 #define SkMatrix44_DEFINED
 
@@ skipping 119 matching lines @@
             fTypeMask = src.fTypeMask;
         }
         return *this;
     }
 
     bool operator==(const SkMatrix44& other) const;
     bool operator!=(const SkMatrix44& other) const {
         return !(other == *this);
     }
 
+    /* When converting from SkMatrix44 to SkMatrix, the third row and
+     * column is dropped.  When converting from SkMatrix to SkMatrix44
+     * the third row and column remain as identity:
+     * [ a b c ]      [ a b 0 c ]
+     * [ d e f ]  ->  [ d e 0 f ]
+     * [ g h i ]      [ 0 0 1 0 ]
+     *                [ g h 0 i ]
+     */
     SkMatrix44(const SkMatrix&);
     SkMatrix44& operator=(const SkMatrix& src);
     operator SkMatrix() const;
 
     /**
      *  Return a reference to a const identity matrix
      */
     static const SkMatrix44& I();
 
     enum TypeMask {
@@ skipping 96 matching lines @@
     void setRowMajord(const double[]);
 
 #ifdef SK_MSCALAR_IS_FLOAT
     void setColMajor(const SkMScalar data[]) { this->setColMajorf(data); }
     void setRowMajor(const SkMScalar data[]) { this->setRowMajorf(data); }
 #else
     void setColMajor(const SkMScalar data[]) { this->setColMajord(data); }
     void setRowMajor(const SkMScalar data[]) { this->setRowMajord(data); }
 #endif
 
+    /* This sets the top-left of the matrix, i.e. the translation and
+     * perspective components remain untouched. */

[reed1, 2013/10/03 09:00:40]

the i.e. section is incorrect: set3x3 sets *all* elements of the matrix: the
top-left corner is set by the params, but translate and perspective elements are
set to 0 (with [3][3] set to 1).

This is consistent with skia's general matrix naming convention. all of its
set... methods always overwrite the entire matrix, as opposed to its various
concat/preconcat/postconcat methods, which may ignore some fields, or
read-modify others.

[aelias_OOO_until_Jul13, 2013/10/03 19:05:36]

Right, fixed the comment.

     void set3x3(SkMScalar m00, SkMScalar m01, SkMScalar m02,
                 SkMScalar m10, SkMScalar m11, SkMScalar m12,
                 SkMScalar m20, SkMScalar m21, SkMScalar m22);
 
     void setTranslate(SkMScalar dx, SkMScalar dy, SkMScalar dz);
     void preTranslate(SkMScalar dx, SkMScalar dy, SkMScalar dz);
     void postTranslate(SkMScalar dx, SkMScalar dy, SkMScalar dz);
 
     void setScale(SkMScalar sx, SkMScalar sy, SkMScalar sz);
     void preScale(SkMScalar sx, SkMScalar sy, SkMScalar sz);
@@ skipping 130 matching lines @@
     /**
      *  Does not take the time to 'compute' the typemask. Only returns true if
      *  we already know that this matrix is identity.
      */
     inline bool isTriviallyIdentity() const {
         return 0 == fTypeMask;
     }
 };
 
 #endif