Fix CFX_Matrix.RotateAt()

The translations were in the opposite order they should be.
First the specified (x, y) coord needs to be translated to the
origin, then rotation should be applied, then the translation should
be reversed. To translate (x, y) to the origin, the initial
translation should be Tx = -x, Ty = -y.

Bug: pdfium:987
Change-Id: I7f873c6a20858bf7fd03e5fdb49020b196b44a1d
Reviewed-on: https://pdfium-review.googlesource.com/23210
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: Shirleen Lou <xlou@chromium.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/core/fxcrt/fx_coordinates_unittest.cpp b/core/fxcrt/fx_coordinates_unittest.cpp
index 3368a40e18..6fec10ecac 100644
--- a/core/fxcrt/fx_coordinates_unittest.cpp
+++ b/core/fxcrt/fx_coordinates_unittest.cpp
@@ -289,3 +289,67 @@ TEST(CFX_Matrix, ReverseCR714187) {
   EXPECT_FLOAT_EQ(expected.x, result.x);
   EXPECT_FLOAT_EQ(expected.y, result.y);
 }
+
+TEST(CFX_Matrix, RotateAt) {
+  CFX_Matrix m;
+  m.RotateAt(FX_PI, 10, 20);
+
+  // 180 degree rotation
+  CFX_PointF p(27, 19);
+  CFX_PointF new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(-7, new_p.x);
+  EXPECT_FLOAT_EQ(21, new_p.y);
+
+  p = CFX_PointF(10, 20);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(10, new_p.x);
+  EXPECT_FLOAT_EQ(20, new_p.y);
+
+  p = CFX_PointF(0, 0);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(20, new_p.x);
+  EXPECT_FLOAT_EQ(40, new_p.y);
+
+  // 90 degree rotation
+  m.SetIdentity();
+  m.RotateAt(FX_PI / 2, 10, 20);
+
+  p = CFX_PointF(6, 17);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(13, new_p.x);
+  EXPECT_FLOAT_EQ(16, new_p.y);
+
+  p = CFX_PointF(10, 20);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(10, new_p.x);
+  EXPECT_FLOAT_EQ(20, new_p.y);
+
+  p = CFX_PointF(0, 0);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(30, new_p.x);
+  EXPECT_FLOAT_EQ(10, new_p.y);
+
+  // 60 degree rotation
+  m.SetIdentity();
+  m.RotateAt(FX_PI / 3, 10, 20);
+
+  p = CFX_PointF(20, 20);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(15, new_p.x);
+  EXPECT_FLOAT_EQ(28.660254f, new_p.y);
+
+  p = CFX_PointF(10, 20);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(10, new_p.x);
+  EXPECT_FLOAT_EQ(20, new_p.y);
+
+  p = CFX_PointF(0, 0);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(22.320509f, new_p.x);
+  EXPECT_FLOAT_EQ(1.3397465f, new_p.y);
+
+  p = CFX_PointF(10, -80);
+  new_p = m.Transform(p);
+  EXPECT_FLOAT_EQ(96.602540f, new_p.x);
+  EXPECT_FLOAT_EQ(-30, new_p.y);
+}