[Remoting Client] Fix scaling bug in ViewMatrix

remoting/client/desktop_viewport_unittest.cc

 // Copyright 2017 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.
 
 #include "remoting/client/desktop_viewport.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/strings/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 10 matching lines @@
  public:
   void SetUp() override;
   void TearDown() override;
 
  protected:
   void AssertTransformationReceived(const tracked_objects::Location& from_here,
                                     float scale,
                                     float offset_x,
                                     float offset_y);
 
+  ViewMatrix ReleaseReceivedTransformation();
+
   DesktopViewport viewport_;
 
  private:
   void OnTransformationChanged(const ViewMatrix& matrix);
 
   ViewMatrix received_transformation_;
 };
 
 void DesktopViewportTest::SetUp() {
   viewport_.RegisterOnTransformationChangedCallback(
@@ skipping 26 matching lines @@
                               expected_array[0], expected_array[2],
                               expected_array[5])
         << base::StringPrintf("Actual scale: %f, offset: (%f, %f)\n",
                               actual_array[0], actual_array[2], actual_array[5])
         << "Location: " << from_here.ToString();
   }
 
   received_transformation_ = ViewMatrix();
 }
 
+ViewMatrix DesktopViewportTest::ReleaseReceivedTransformation() {
+  EXPECT_FALSE(received_transformation_.IsEmpty());
+  ViewMatrix out = received_transformation_;
+  received_transformation_ = ViewMatrix();
+  return out;
+}
+
 void DesktopViewportTest::OnTransformationChanged(const ViewMatrix& matrix) {
   ASSERT_TRUE(received_transformation_.IsEmpty())
       << "Previous matrix has not been asserted.";
   received_transformation_ = matrix;
 }
 
 TEST_F(DesktopViewportTest, TestViewportInitialization1) {
   // VP < DP. Desktop shrinks to fit.
   // +====+------+
   // | VP | DP   |
@@ skipping 157 matching lines @@
   // |                  |
   // |     DP           |
   // |               +====+
   // |               | VP |
   // +---------------|    |
   //                 +====+
   viewport_.SetViewportCenter(1000.f, 1000.f);
   AssertTransformationReceived(FROM_HERE, 1.25f, -8.f, -4.5f);
 }
 
+TEST_F(DesktopViewportTest, TestScaleDesktop) {
+  // Number in surface coordinate.
+  //
+  // +====+------+
+  // | VP | DP   |
+  // |    |      | 3
+  // +====+------+
+  //        4
+  viewport_.SetDesktopSize(8, 6);
+  viewport_.SetSurfaceSize(2, 3);
+  AssertTransformationReceived(FROM_HERE, 0.5f, 0.f, 0.f);
+
+  ViewMatrix old_transformation(0.5f, {0.f, 0.f});
+
+  ViewMatrix::Point surface_point = old_transformation.MapPoint({1.2f, 1.3f});
+
+  // Scale a little bit at a pivot point.
+  viewport_.ScaleDesktop(surface_point.x, surface_point.y, 1.1f);
+
+  ViewMatrix new_transformation = ReleaseReceivedTransformation();
+
+  // Verify the pivot point is fixed.
+  ViewMatrix::Point new_surface_point =
+      new_transformation.MapPoint({1.2f, 1.3f});
+  ASSERT_FLOAT_EQ(surface_point.x, new_surface_point.x);
+  ASSERT_FLOAT_EQ(surface_point.y, new_surface_point.y);
+
+  // Verify the scale is correct.
+  ASSERT_FLOAT_EQ(old_transformation.GetScale() * 1.1f,
+                  new_transformation.GetScale());
+}
+
 }  // namespace remoting