[Android] Port Scroller.java to C++ and use for fling animations

ui/gfx/android/scroller_unittest.cc

+// Copyright 2014 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 "base/time/time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/android/scroller.h"
+
+namespace gfx {
+
+namespace {
+
+const float kDefaultStartX = 7.f;
+const float kDefaultStartY = 25.f;
+const float kDefaultDeltaX = -20.f;
+const float kDefaultDeltaY = 73.f;
+const float kDefaultVelocityX = -35.f;
+const float kDefaultVelocityY = 22.f;
+const float kEpsilon = 1e-3f;
+
+Scroller::Config DefaultConfig() {
+  return Scroller::Config();
+}
+
+}  // namespace
+
+class ScrollerTest : public testing::Test {};
+
+TEST_F(ScrollerTest, Scroll) {
+  Scroller scroller(DefaultConfig());
+  base::TimeTicks start_time = base::TimeTicks::Now();
+
+  // Start a scroll and verify initialized values.
+  scroller.StartScroll(kDefaultStartX,
+                       kDefaultStartY,
+                       kDefaultDeltaX,
+                       kDefaultDeltaY,
+                       start_time);
+
+  EXPECT_EQ(kDefaultStartX, scroller.GetStartX());
+  EXPECT_EQ(kDefaultStartY, scroller.GetStartY());
+  EXPECT_EQ(kDefaultStartX, scroller.GetCurrX());
+  EXPECT_EQ(kDefaultStartY, scroller.GetCurrY());
+  EXPECT_EQ(kDefaultStartX + kDefaultDeltaX, scroller.GetFinalX());
+  EXPECT_EQ(kDefaultStartY + kDefaultDeltaY, scroller.GetFinalY());
+  EXPECT_FALSE(scroller.IsFinished());
+  EXPECT_EQ(base::TimeDelta(), scroller.GetTimePassed());
+
+  // Advance halfway through the scroll.
+  const base::TimeDelta scroll_duration = scroller.GetDuration();
+  scroller.ComputeScrollOffset(start_time + scroll_duration / 2);
+
+  // Ensure we've moved in the direction of the delta, but have yet to reach
+  // the target.
+  EXPECT_GT(kDefaultStartX, scroller.GetCurrX());
+  EXPECT_LT(kDefaultStartY, scroller.GetCurrY());
+  EXPECT_LT(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_GT(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_FALSE(scroller.IsFinished());
+
+  // Ensure our velocity is non-zero and in the same direction as the delta.
+  EXPECT_GT(0.f, scroller.GetCurrVelocityX() * kDefaultDeltaX);
+  EXPECT_GT(0.f, scroller.GetCurrVelocityY() * kDefaultDeltaY);
+  EXPECT_TRUE(scroller.IsScrollingInDirection(kDefaultDeltaX, kDefaultDeltaY));
+
+  // Advance to the end.
+  scroller.ComputeScrollOffset(start_time + scroll_duration);
+  EXPECT_EQ(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_EQ(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_TRUE(scroller.IsFinished());
+  EXPECT_EQ(scroll_duration, scroller.GetTimePassed());
+  EXPECT_NEAR(0.f, scroller.GetCurrVelocityX(), kEpsilon);
+  EXPECT_NEAR(0.f, scroller.GetCurrVelocityY(), kEpsilon);
+
+  // Try to advance further; nothing should change.
+  scroller.ComputeScrollOffset(start_time + scroll_duration * 2);
+  EXPECT_EQ(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_EQ(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_TRUE(scroller.IsFinished());
+  EXPECT_EQ(scroll_duration, scroller.GetTimePassed());
+}
+
+TEST_F(ScrollerTest, Fling) {
+  Scroller scroller(DefaultConfig());
+  base::TimeTicks start_time = base::TimeTicks::Now();
+
+  // Start a fling and verify initialized values.
+  scroller.Fling(kDefaultStartX,
+                 kDefaultStartY,
+                 kDefaultVelocityX,
+                 kDefaultVelocityY,
+                 INT_MIN,
+                 INT_MAX,
+                 INT_MIN,
+                 INT_MAX,
+                 start_time);
+
+  EXPECT_EQ(kDefaultStartX, scroller.GetStartX());
+  EXPECT_EQ(kDefaultStartY, scroller.GetStartY());
+  EXPECT_EQ(kDefaultStartX, scroller.GetCurrX());
+  EXPECT_EQ(kDefaultStartY, scroller.GetCurrY());
+  EXPECT_GT(kDefaultStartX, scroller.GetFinalX());
+  EXPECT_LT(kDefaultStartY, scroller.GetFinalY());
+  EXPECT_FALSE(scroller.IsFinished());
+  EXPECT_EQ(base::TimeDelta(), scroller.GetTimePassed());
+
+  // Advance halfway through the fling.
+  const base::TimeDelta scroll_duration = scroller.GetDuration();
+  scroller.ComputeScrollOffset(start_time + scroll_duration / 2);
+
+  // Ensure we've moved in the direction of the velocity, but have yet to reach
+  // the target.
+  EXPECT_GT(kDefaultStartX, scroller.GetCurrX());
+  EXPECT_LT(kDefaultStartY, scroller.GetCurrY());
+  EXPECT_LT(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_GT(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_FALSE(scroller.IsFinished());
+
+  // Ensure our velocity is non-zero and in the same direction as the original
+  // velocity.
+  EXPECT_LT(0.f, scroller.GetCurrVelocityX() * kDefaultVelocityX);
+  EXPECT_LT(0.f, scroller.GetCurrVelocityY() * kDefaultVelocityY);
+  EXPECT_TRUE(
+      scroller.IsScrollingInDirection(kDefaultVelocityX, kDefaultVelocityY));
+
+  // Advance to the end.
+  scroller.ComputeScrollOffset(start_time + scroll_duration);
+  EXPECT_EQ(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_EQ(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_TRUE(scroller.IsFinished());
+  EXPECT_EQ(scroll_duration, scroller.GetTimePassed());
+  EXPECT_NEAR(0.f, scroller.GetCurrVelocityX(), kEpsilon);
+  EXPECT_NEAR(0.f, scroller.GetCurrVelocityY(), kEpsilon);
+
+  // Try to advance further; nothing should change.
+  scroller.ComputeScrollOffset(start_time + scroll_duration * 2);
+  EXPECT_EQ(scroller.GetFinalX(), scroller.GetCurrX());
+  EXPECT_EQ(scroller.GetFinalY(), scroller.GetCurrY());
+  EXPECT_TRUE(scroller.IsFinished());
+  EXPECT_EQ(scroll_duration, scroller.GetTimePassed());
+}
+
+}  // namespace gfx