Change SetReverse to GetInverse in CFX_Matrix

CFX_Matrix::GetInverse is much clearer.
Change-Id: Id10ab1723735332e1a78de853f28415ec3a4d834
Reviewed-on: https://pdfium-review.googlesource.com/7090
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Nicolás Peña <npm@chromium.org>

3 files changed, 18 insertions, 22 deletions

diff --git a/core/fxcrt/fx_coordinates.cpp b/core/fxcrt/fx_coordinates.cpp
index 27c0a95ee4..0b6aed44cc 100644
--- a/core/fxcrt/fx_coordinates.cpp
+++ b/core/fxcrt/fx_coordinates.cpp
@@ -197,18 +197,20 @@ CFX_FloatRect CFX_FloatRect::GetBBox(const CFX_PointF* pPoints, int nPoints) {
   return CFX_FloatRect(min_x, min_y, max_x, max_y);
 }
 
-void CFX_Matrix::SetReverse(const CFX_Matrix& m) {
-  float i = m.a * m.d - m.b * m.c;
+CFX_Matrix CFX_Matrix::GetInverse() const {
+  CFX_Matrix inverse;
+  float i = a * d - b * c;
   if (fabs(i) == 0)
-    return;
+    return inverse;
 
   float j = -i;
-  a = m.d / i;
-  b = m.b / j;
-  c = m.c / j;
-  d = m.a / i;
-  e = (m.c * m.f - m.d * m.e) / i;
-  f = (m.a * m.f - m.b * m.e) / j;
+  inverse.a = d / i;
+  inverse.b = b / j;
+  inverse.c = c / j;
+  inverse.d = a / i;
+  inverse.e = (c * f - d * e) / i;
+  inverse.f = (a * f - b * e) / j;
+  return inverse;
 }
 
 void CFX_Matrix::Concat(const CFX_Matrix& m, bool bPrepended) {
@@ -216,9 +218,7 @@ void CFX_Matrix::Concat(const CFX_Matrix& m, bool bPrepended) {
 }
 
 void CFX_Matrix::ConcatInverse(const CFX_Matrix& src, bool bPrepended) {
-  CFX_Matrix m;
-  m.SetReverse(src);
-  Concat(m, bPrepended);
+  Concat(src.GetInverse(), bPrepended);
 }
 
 bool CFX_Matrix::Is90Rotated() const {
diff --git a/core/fxcrt/fx_coordinates.h b/core/fxcrt/fx_coordinates.h
index fc51c458a0..25923f7290 100644
--- a/core/fxcrt/fx_coordinates.h
+++ b/core/fxcrt/fx_coordinates.h
@@ -608,7 +608,7 @@ class CFX_Matrix {
     f = 0;
   }
 
-  void SetReverse(const CFX_Matrix& m);
+  CFX_Matrix GetInverse() const;
 
   void Concat(const CFX_Matrix& m, bool bPrepended = false);
   void ConcatInverse(const CFX_Matrix& m, bool bPrepended = false);
diff --git a/core/fxcrt/fx_coordinates_unittest.cpp b/core/fxcrt/fx_coordinates_unittest.cpp
index 12ddb97330..e998b440f5 100644
--- a/core/fxcrt/fx_coordinates_unittest.cpp
+++ b/core/fxcrt/fx_coordinates_unittest.cpp
@@ -8,10 +8,9 @@
 
 TEST(CFX_Matrix, ReverseIdentity) {
   CFX_Matrix m;
-  CFX_Matrix rev;
-
   m.SetIdentity();
-  rev.SetReverse(m);
+  CFX_Matrix rev = m.GetInverse();
+
   EXPECT_FLOAT_EQ(1.0, rev.a);
   EXPECT_FLOAT_EQ(0.0, rev.b);
   EXPECT_FLOAT_EQ(0.0, rev.c);
@@ -28,9 +27,8 @@ TEST(CFX_Matrix, ReverseIdentity) {
 TEST(CFX_Matrix, Reverse) {
   float data[6] = {3, 0, 2, 3, 1, 4};
   CFX_Matrix m(data);
-  CFX_Matrix rev;
+  CFX_Matrix rev = m.GetInverse();
 
-  rev.SetReverse(m);
   EXPECT_FLOAT_EQ(0.33333334f, rev.a);
   EXPECT_FLOAT_EQ(0.0f, rev.b);
   EXPECT_FLOAT_EQ(-0.22222222f, rev.c);
@@ -50,9 +48,8 @@ TEST(CFX_Matrix, ReverseCR702041) {
   float data[6] = {0.947368443f, -0.108947366f, -0.923076928f,
                    0.106153846f, 18.0f,         787.929993f};
   CFX_Matrix m(data);
-  CFX_Matrix rev;
+  CFX_Matrix rev = m.GetInverse();
 
-  rev.SetReverse(m);
   EXPECT_FLOAT_EQ(14247728.0f, rev.a);
   EXPECT_FLOAT_EQ(14622668.0f, rev.b);
   EXPECT_FLOAT_EQ(1.2389329e+08f, rev.c);
@@ -71,9 +68,8 @@ TEST(CFX_Matrix, ReverseCR714187) {
   // The determinate is < std::numeric_limits<float>::epsilon()
   float data[6] = {0.000037f, 0.0f, 0.0f, -0.000037f, 182.413101f, 136.977646f};
   CFX_Matrix m(data);
-  CFX_Matrix rev;
+  CFX_Matrix rev = m.GetInverse();
 
-  rev.SetReverse(m);
   EXPECT_FLOAT_EQ(27027.025f, rev.a);
   EXPECT_FLOAT_EQ(0.0f, rev.b);
   EXPECT_FLOAT_EQ(0.0f, rev.c);