New Matrix3F class added in gfx.

ui/gfx/matrix3_f.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_GFX_MATRIX3_F_H_
+#define UI_GFX_MATRIX3_F_H_
+
+#include "base/logging.h"
+#include "ui/gfx/vector3d_f.h"
+
+namespace gfx {
+
+class UI_EXPORT Matrix3F {
+ public:
+  Matrix3F(const Matrix3F& rhs);
+  ~Matrix3F();
+
+  static Matrix3F Zeros();
+  static Matrix3F Ones();
+  static Matrix3F Identity();
+  static Matrix3F FromOuterProduct(const Vector3dF& a, const Vector3dF& bt);
+
+  bool IsEqual(const Matrix3F& rhs) const;
+
+  // Element-wise comparison with given precision.
+  bool IsNear(const Matrix3F& rhs, float precision) const;
+
+  float get(int i, int j) const {
+    return data_[MatrixToArrayCoords(i, j)];
+  }
+
+  void set(int i, int j, float v) {
+    data_[MatrixToArrayCoords(i, j)] = v;
+  }
+
+  void set(float m00, float m01, float m02,
+           float m10, float m11, float m12,
+           float m20, float m21, float m22) {
+    data_[0] = m00;
+    data_[1] = m01;
+    data_[2] = m02;
+    data_[3] = m10;
+    data_[4] = m11;
+    data_[5] = m12;
+    data_[6] = m20;
+    data_[7] = m21;
+    data_[8] = m22;
+  }
+
+  Vector3dF get_column(int i) const {
+    return Vector3dF(
+      data_[MatrixToArrayCoords(0, i)],
+      data_[MatrixToArrayCoords(1, i)],
+      data_[MatrixToArrayCoords(2, i)]);
+  }
+
+  void set_column(int i, const Vector3dF& c) {
+    data_[MatrixToArrayCoords(0, i)] = c.x();
+    data_[MatrixToArrayCoords(1, i)] = c.y();
+    data_[MatrixToArrayCoords(2, i)] = c.z();
+  }
+
+  // Returns an inverse of this if the matrix is non-singular, zero (== Zero())
+  // otherwise.
+  Matrix3F Inverse() const;
+
+  // Value of the determinant of the matrix.
+  float Determinant() const;
+
+  // Trace (sum of diagonal elements) of the matrix.
+  float Trace() const {
+    return data_[MatrixToArrayCoords(0, 0)] +
+        data_[MatrixToArrayCoords(1, 1)] +
+        data_[MatrixToArrayCoords(2, 2)];
+  }
+
+  // Compute eigenvalues and (optionally) normalized eigenvectors of
+  // a positive defnite matrix *this. Eigenvectors are computed only if
+  // non-null |eigenvectors| matrix is passed. If it is NULL, the routine
+  // will not attempt to compute eigenvectors but will still return eigenvalues
+  // if they can be computed.
+  // If eigenvalues cannot be computed (the matrix does not meet constraints)
+  // the 0-vector is returned. Note that to retrieve eigenvalues, the matrix
+  // only needs to be symmetric while eigenvectors require it to be
+  // positive-definite. Passing a non-positive definite matrix will result in
+  // NaNs in vectors which cannot be computed.
+  // Eigenvectors are placed as column in |eigenvectors| in order corresponding
+  // to eigenvalues.
+  Vector3dF SolveEigenproblem(Matrix3F* eigenvectors) const;
+
+ private:
+  float data_[9];

[sky, 2013/02/01 00:25:30]

fields after functions.

[motek., 2013/02/01 15:19:35]

Done.

+
+  Matrix3F();  // Uninitialized default.

[sky, 2013/02/01 00:25:30]

Seems painful not to have this and let it return the identity.

[motek., 2013/02/01 15:19:35]

I don't think making the constructor set identity implicitly is not that useful.
They went through a similar exercise in Skia and ended up deprecating the
default constructor. 
Instead, I have a set of 'creator' static functions that address reasonable
possibilities. I am sure the compiler will make a decent work of it.

+
+  static int MatrixToArrayCoords(int i, int j) {
+    DCHECK(i >= 0 && i < 3);
+    DCHECK(j >= 0 && j < 3);
+    return i * 3 + j;
+  }
+};
+
+inline bool operator==(const Matrix3F& lhs, const Matrix3F& rhs) {
+  return lhs.IsEqual(rhs);
+}
+
+}  // namespace gfx
+
+#endif  // UI_GFX_MATRIX3_F_H_