scroll_snap_data_unittest.cc

// Copyright 2018 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 "cc/input/scroll_snap_data.h"
#include <memory>
#include "cc/input/snap_selection_strategy.h"

#include "testing/gtest/include/gtest/gtest.h"

namespace cc {

class ScrollSnapDataTest : public testing::Test {
 public:
  TargetSnapAreaElementIds target_elements;
};

TEST_F(ScrollSnapDataTest, StartAlignmentCalculation) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(10, 10, 200, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kStart),
                    gfx::RectF(100, 150, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(0, 0), true,
                                                  true);

  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(90, snap_position.x());
  EXPECT_EQ(140, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, CenterAlignmentCalculation) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(10, 10, 200, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kCenter),
                    gfx::RectF(100, 150, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(0, 0), true,
                                                  true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(40, snap_position.x());
  EXPECT_EQ(40, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, EndAlignmentCalculation) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(10, 10, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kEnd),
                    gfx::RectF(150, 200, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(0, 0), true,
                                                  true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(40, snap_position.x());
  EXPECT_EQ(90, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, UnreachableSnapPositionCalculation) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(100, 100));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kEnd, SnapAlignment::kStart),
                    gfx::RectF(200, 0, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(50, 50),
                                                  true, true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  // Aligning to start on x would lead the scroll offset larger than max, and
  // aligning to end on y would lead the scroll offset smaller than zero. So
  // we expect these are clamped.
  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, FindsClosestSnapPositionIndependently) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData snap_x_only(
      ScrollSnapAlign(SnapAlignment::kNone, SnapAlignment::kStart),
      gfx::RectF(80, 0, 150, 150), false, ElementId(10));
  SnapAreaData snap_y_only(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(0, 70, 150, 150), false, ElementId(20));
  SnapAreaData snap_on_both(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(50, 150, 150, 150), false,
                            ElementId(30));
  container.AddSnapAreaData(snap_x_only);
  container.AddSnapAreaData(snap_y_only);
  container.AddSnapAreaData(snap_on_both);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(100, 100),
                                                  true, true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(80, snap_position.x());
  EXPECT_EQ(70, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(20)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, FindsClosestSnapPositionOnAxisValueBoth) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData snap_x_only(
      ScrollSnapAlign(SnapAlignment::kNone, SnapAlignment::kStart),
      gfx::RectF(80, 0, 150, 150), false, ElementId(10));
  SnapAreaData snap_y_only(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(0, 70, 150, 150), false, ElementId(20));
  SnapAreaData snap_on_both(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(50, 150, 150, 150), false,
                            ElementId(30));

  container.AddSnapAreaData(snap_x_only);
  container.AddSnapAreaData(snap_y_only);
  container.AddSnapAreaData(snap_on_both);
  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(40, 120),
                                                  true, true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(50, snap_position.x());
  EXPECT_EQ(150, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(30), ElementId(30)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, DoesNotSnapOnNonScrolledAxis) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData snap_x_only(
      ScrollSnapAlign(SnapAlignment::kNone, SnapAlignment::kStart),
      gfx::RectF(80, 0, 150, 150), false, ElementId(10));
  SnapAreaData snap_y_only(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(0, 70, 150, 150), false, ElementId(20));
  container.AddSnapAreaData(snap_x_only);
  container.AddSnapAreaData(snap_y_only);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(100, 100),
                                                  true, false);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(80, snap_position.x());
  EXPECT_EQ(100, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, DoesNotSnapOnNonVisibleAreas) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData snap_x_only(
      ScrollSnapAlign(SnapAlignment::kNone, SnapAlignment::kStart),
      gfx::RectF(300, 400, 100, 100), false, ElementId(10));
  SnapAreaData snap_y_only(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(400, 300, 100, 100), false, ElementId(20));

  container.AddSnapAreaData(snap_x_only);
  container.AddSnapAreaData(snap_y_only);
  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(0, 0), true,
                                                  true);
  EXPECT_FALSE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(TargetSnapAreaElementIds(), target_elements);
}

TEST_F(ScrollSnapDataTest, SnapOnClosestAxisFirstIfVisibilityConflicts) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));

  // Both the areas are currently visible.
  // However, if we snap to them on x and y independently, none is visible after
  // snapping. So we only snap on the axis that has a closer snap point first.
  // After that, we look for another snap point on y axis which does not
  // conflict with the snap point on x.
  SnapAreaData snap_x(
      ScrollSnapAlign(SnapAlignment::kNone, SnapAlignment::kStart),
      gfx::RectF(150, 0, 100, 100), false, ElementId(10));
  SnapAreaData snap_y1(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(0, 180, 100, 100), false, ElementId(20));
  SnapAreaData snap_y2(
      ScrollSnapAlign(SnapAlignment::kStart, SnapAlignment::kNone),
      gfx::RectF(250, 80, 100, 100), false, ElementId(30));
  container.AddSnapAreaData(snap_x);
  container.AddSnapAreaData(snap_y1);
  container.AddSnapAreaData(snap_y2);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(0, 0), true,
                                                  true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(150, snap_position.x());
  EXPECT_EQ(80, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(30)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, DoesNotSnapToPositionsOutsideProximityRange) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  container.set_proximity_range(gfx::ScrollOffset(50, 50));

  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kStart),
                    gfx::RectF(80, 160, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndPosition(gfx::ScrollOffset(100, 100),
                                                  true, true);
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));

  // The snap position on x, 80, is within the proximity range of [50, 150].
  // However, the snap position on y, 160, is outside the proximity range of
  // [50, 150], so we should only snap on x.
  EXPECT_EQ(80, snap_position.x());
  EXPECT_EQ(100, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, MandatoryReturnsToCurrentIfNoValidAreaForward) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(2000, 2000));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kStart),
                    gfx::RectF(600, 0, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);
  gfx::ScrollOffset snap_position;

  std::unique_ptr<SnapSelectionStrategy> direction_strategy =
      SnapSelectionStrategy::CreateForDirection(
          gfx::ScrollOffset(600, 0), gfx::ScrollOffset(5, 0),
          false /* use_fractional_deltas */);
  EXPECT_TRUE(container.FindSnapPosition(*direction_strategy, &snap_position,
                                         &target_elements));
  // The snap direction is right. However, there is no valid snap position on
  // that direction. So we have to stay at the current snap position of 600 as
  // the snap type is mandatory.
  EXPECT_EQ(600, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);

  std::unique_ptr<SnapSelectionStrategy> end_direction_strategy =
      SnapSelectionStrategy::CreateForEndAndDirection(
          gfx::ScrollOffset(600, 0), gfx::ScrollOffset(15, 15),
          false /* use_fractional_deltas */);
  EXPECT_TRUE(container.FindSnapPosition(*end_direction_strategy,
                                         &snap_position, &target_elements));
  // The snap direction is down and right. However, there is no valid snap
  // position on that direction. So we have to stay at the current snap position
  // of (600, 0) as the snap type is mandatory.
  EXPECT_EQ(600, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);

  // If the scroll-snap-type is proximity, we wouldn't consider the current
  // snap area valid even if there is no snap area forward.
  container.set_scroll_snap_type(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kProximity));
  EXPECT_FALSE(container.FindSnapPosition(*direction_strategy, &snap_position,
                                          &target_elements));
  EXPECT_FALSE(container.FindSnapPosition(*end_direction_strategy,
                                          &snap_position, &target_elements));
  EXPECT_EQ(TargetSnapAreaElementIds(), target_elements);
}

TEST_F(ScrollSnapDataTest, MandatorySnapsBackwardIfNoValidAreaForward) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(2000, 2000));
  SnapAreaData area(ScrollSnapAlign(SnapAlignment::kStart),
                    gfx::RectF(600, 0, 100, 100), false, ElementId(10));
  container.AddSnapAreaData(area);
  gfx::ScrollOffset snap_position;

  std::unique_ptr<SnapSelectionStrategy> direction_strategy =
      SnapSelectionStrategy::CreateForDirection(
          gfx::ScrollOffset(650, 0), gfx::ScrollOffset(5, 0),
          false /* use_fractional_deltas */);
  EXPECT_TRUE(container.FindSnapPosition(*direction_strategy, &snap_position,
                                         &target_elements));
  // The snap direction is right. However, there is no valid snap position on
  // that direction. So we have to scroll back to the snap position of 600 as
  // the snap type is mandatory.
  EXPECT_EQ(600, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);

  std::unique_ptr<SnapSelectionStrategy> end_direction_strategy =
      SnapSelectionStrategy::CreateForEndAndDirection(
          gfx::ScrollOffset(650, 10), gfx::ScrollOffset(15, 15),
          false /* use_fractional_deltas */);
  EXPECT_TRUE(container.FindSnapPosition(*end_direction_strategy,
                                         &snap_position, &target_elements));
  // The snap direction is down and right. However, there is no valid snap
  // position on that direction. So we have to scroll back to the snap position
  // of (600, 0) as the snap type is mandatory.
  EXPECT_EQ(600, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(10)),
            target_elements);

  // If the scroll-snap-type is proximity, we wouldn't consider the backward
  // snap area valid even if there is no snap area forward.
  container.set_scroll_snap_type(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kProximity));
  EXPECT_FALSE(container.FindSnapPosition(*direction_strategy, &snap_position,
                                          &target_elements));
  EXPECT_FALSE(container.FindSnapPosition(*end_direction_strategy,
                                          &snap_position, &target_elements));
  EXPECT_EQ(TargetSnapAreaElementIds(), target_elements);
}

TEST_F(ScrollSnapDataTest, ShouldNotPassScrollSnapStopAlwaysElement) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(2000, 2000));
  SnapAreaData must_snap_1(ScrollSnapAlign(SnapAlignment::kStart),
                           gfx::RectF(200, 0, 100, 100), true, ElementId(10));
  SnapAreaData must_snap_2(ScrollSnapAlign(SnapAlignment::kStart),
                           gfx::RectF(400, 0, 100, 100), true, ElementId(20));
  SnapAreaData closer_to_target(ScrollSnapAlign(SnapAlignment::kStart),
                                gfx::RectF(600, 0, 100, 100), false,
                                ElementId(30));
  container.AddSnapAreaData(must_snap_1);
  container.AddSnapAreaData(must_snap_2);
  container.AddSnapAreaData(closer_to_target);
  gfx::ScrollOffset snap_position;

  std::unique_ptr<SnapSelectionStrategy> end_direction_strategy =
      SnapSelectionStrategy::CreateForEndAndDirection(
          gfx::ScrollOffset(0, 0), gfx::ScrollOffset(600, 0),
          false /* use_fractional_deltas */);

  EXPECT_TRUE(container.FindSnapPosition(*end_direction_strategy,
                                         &snap_position, &target_elements));

  // Even though closer_to_target and must_snap_2 are closer to the target
  // position of the scroll, the must_snap_1 which is closer to the start
  // shouldn't be passed.
  EXPECT_EQ(200, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapStopAlwaysOverridesCoveringSnapArea) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 200), gfx::ScrollOffset(600, 800));
  SnapAreaData stop_area(ScrollSnapAlign(SnapAlignment::kStart),
                         gfx::RectF(100, 0, 100, 100), true, ElementId(10));
  SnapAreaData covering_area(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(250, 0, 600, 600), false,
                             ElementId(20));
  container.AddSnapAreaData(stop_area);
  container.AddSnapAreaData(covering_area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndAndDirection(
          gfx::ScrollOffset(0, 0), gfx::ScrollOffset(300, 0),
          false /* use_fractional_deltas */);

  // The fling is from (0, 0) to (300, 0), and the destination would make
  // the |covering_area| perfectly cover the snapport. However, another area
  // with snap-stop:always precedes this |covering_area| so we snap at
  // (100, 100).
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapStopAlwaysInReverseDirection) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData stop_area(ScrollSnapAlign(SnapAlignment::kStart),
                         gfx::RectF(100, 0, 100, 100), true, ElementId(10));
  container.AddSnapAreaData(stop_area);

  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForEndAndDirection(
          gfx::ScrollOffset(150, 0), gfx::ScrollOffset(200, 0),
          false /* use_fractional_deltas */);

  // The fling is from (150, 0) to (350, 0), but the snap position is in the
  // reverse direction at (100, 0). Since the container has mandatory for
  // snapstrictness, we should go back to snap at (100, 0).
  EXPECT_TRUE(
      container.FindSnapPosition(*strategy, &snap_position, &target_elements));
  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapStopAlwaysNotInterferingWithDirectionStrategy) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData closer_area(ScrollSnapAlign(SnapAlignment::kStart),
                           gfx::RectF(100, 0, 1, 1), false, ElementId(10));
  SnapAreaData stop_area(ScrollSnapAlign(SnapAlignment::kStart),
                         gfx::RectF(120, 0, 1, 1), true, ElementId(20));
  container.AddSnapAreaData(closer_area);
  container.AddSnapAreaData(stop_area);

  // The DirectionStrategy should always choose the first snap position
  // regardless its scroll-snap-stop value.
  gfx::ScrollOffset snap_position;
  std::unique_ptr<SnapSelectionStrategy> direction_strategy =
      SnapSelectionStrategy::CreateForDirection(
          gfx::ScrollOffset(90, 0), gfx::ScrollOffset(50, 0),
          false /* use_fractional_deltas */);
  snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*direction_strategy, &snap_position,
                                         &target_elements));
  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId()),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapToOneTargetElementOnX) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 300), gfx::ScrollOffset(600, 800));

  SnapAreaData closer_area_x(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(100, 0, 1, 1), false, ElementId(10));
  SnapAreaData target_area_x(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(200, 100, 1, 1), false, ElementId(20));
  SnapAreaData closer_area_y(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(300, 50, 1, 1), false, ElementId(30));

  container.AddSnapAreaData(closer_area_x);
  container.AddSnapAreaData(target_area_x);
  container.AddSnapAreaData(closer_area_y);
  container.SetTargetSnapAreaElementIds(
      TargetSnapAreaElementIds(ElementId(20), ElementId()));

  // Even though closer_area_x is closer to the scroll offset, the container
  // should snap to the target for the x-axis. However, since the target is not
  // set for the y-axis, the target on the y-axis should be closer_area_y.
  std::unique_ptr<SnapSelectionStrategy> target_element_strategy =
      SnapSelectionStrategy::CreateForTargetElement(gfx::ScrollOffset(0, 0));

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*target_element_strategy,
                                         &snap_position, &target_elements));

  EXPECT_EQ(200, snap_position.x());
  EXPECT_EQ(50, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(20), ElementId(30)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapToOneTargetElementOnY) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 200, 300), gfx::ScrollOffset(600, 800));

  SnapAreaData closer_area_y(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(0, 100, 1, 1), false, ElementId(10));
  SnapAreaData target_area_y(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(100, 200, 1, 1), false, ElementId(20));
  SnapAreaData closer_area_x(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(50, 300, 1, 1), false, ElementId(30));

  container.AddSnapAreaData(closer_area_y);
  container.AddSnapAreaData(target_area_y);
  container.AddSnapAreaData(closer_area_x);
  container.SetTargetSnapAreaElementIds(
      TargetSnapAreaElementIds(ElementId(), ElementId(20)));

  // Even though closer_area_y is closer to the scroll offset, the container
  // should snap to the target for the y-axis. However, since the target is not
  // set for the x-axis, the target on the x-axis should be closer_area_x.
  std::unique_ptr<SnapSelectionStrategy> target_element_strategy =
      SnapSelectionStrategy::CreateForTargetElement(gfx::ScrollOffset(0, 0));

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*target_element_strategy,
                                         &snap_position, &target_elements));

  EXPECT_EQ(50, snap_position.x());
  EXPECT_EQ(200, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(30), ElementId(20)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapToTwoTargetElementsMutualVisible) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 300, 300), gfx::ScrollOffset(600, 800));

  SnapAreaData target_area_x(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(100, 200, 1, 1), false, ElementId(10));
  SnapAreaData target_area_y(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(200, 100, 1, 1), false, ElementId(20));
  SnapAreaData closer_area_both(ScrollSnapAlign(SnapAlignment::kStart),
                                gfx::RectF(0, 0, 1, 1), false, ElementId(30));

  container.AddSnapAreaData(target_area_x);
  container.AddSnapAreaData(target_area_y);
  container.AddSnapAreaData(closer_area_both);
  container.SetTargetSnapAreaElementIds(
      TargetSnapAreaElementIds(ElementId(10), ElementId(20)));

  // The container should snap to both target areas since they are mutually
  // visible, while ignoring the snap area that is closest to the scroll offset.
  std::unique_ptr<SnapSelectionStrategy> target_element_strategy =
      SnapSelectionStrategy::CreateForTargetElement(gfx::ScrollOffset(0, 0));

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*target_element_strategy,
                                         &snap_position, &target_elements));

  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(100, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(20)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapToTwoTargetElementsNotMutualVisible) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 300, 300), gfx::ScrollOffset(600, 800));

  SnapAreaData target_area_x(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(100, 500, 1, 1), false, ElementId(10));
  SnapAreaData target_area_y(ScrollSnapAlign(SnapAlignment::kStart),
                             gfx::RectF(500, 100, 1, 1), false, ElementId(20));
  SnapAreaData area_mutually_visible_to_targets(
      ScrollSnapAlign(SnapAlignment::kStart), gfx::RectF(350, 350, 1, 1), false,
      ElementId(30));

  container.AddSnapAreaData(target_area_x);
  container.AddSnapAreaData(target_area_y);
  container.AddSnapAreaData(area_mutually_visible_to_targets);
  container.SetTargetSnapAreaElementIds(
      TargetSnapAreaElementIds(ElementId(10), ElementId(20)));

  // The container cannot snap to both targets, so it should snap to the one
  // closer to the scroll offset, and then snap to the closest mutually visible
  // snap area on the other axis.
  std::unique_ptr<SnapSelectionStrategy> target_element_strategy =
      SnapSelectionStrategy::CreateForTargetElement(gfx::ScrollOffset(10, 0));

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*target_element_strategy,
                                         &snap_position, &target_elements));

  EXPECT_EQ(100, snap_position.x());
  EXPECT_EQ(350, snap_position.y());
  EXPECT_EQ(TargetSnapAreaElementIds(ElementId(10), ElementId(30)),
            target_elements);
}

TEST_F(ScrollSnapDataTest, SnapToFocusedElementHorizontal) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kX, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 300, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData snapped_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(0, 0, 100, 100), false, ElementId(10));
  SnapAreaData focused_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(0, 100, 100, 100), false, ElementId(20));
  container.AddSnapAreaData(snapped_area);
  container.AddSnapAreaData(focused_area);

  // Initially both snap areas are horizontally aligned with the snap position.
  gfx::ScrollOffset origin(0, 0);
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForTargetElement(origin);

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(0, snap_position.x());
  EXPECT_TRUE(container.SetTargetSnapAreaElementIds(target_elements));

  // Simulate layout change. The focused area is no longer aligned, but was
  // previously aligned. It should take precedence over the targeted area.
  focused_area.rect = gfx::RectF(100, 0, 100, 100);
  container.UpdateSnapAreaForTesting(ElementId(20), focused_area);

  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(100, snap_position.x());
}

TEST_F(ScrollSnapDataTest, SnapToFocusedElementVertical) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kY, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 300, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData snapped_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(0, 0, 100, 100), false, ElementId(10));
  SnapAreaData focused_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(100, 0, 100, 100), false, ElementId(20));
  container.AddSnapAreaData(snapped_area);
  container.AddSnapAreaData(focused_area);

  // Initially both snap areas are vertically aligned with the snap position.
  gfx::ScrollOffset origin(0, 0);
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForTargetElement(origin);

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(0, snap_position.y());
  EXPECT_TRUE(container.SetTargetSnapAreaElementIds(target_elements));

  // Simulate layout change. The focused area is no longer aligned, but was
  // previously aligned. It should take precedence over the targeted area.
  focused_area.rect = gfx::RectF(0, 100, 100, 100);
  container.UpdateSnapAreaForTesting(ElementId(20), focused_area);

  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(100, snap_position.y());
}

TEST_F(ScrollSnapDataTest, SnapToFocusedElementBoth) {
  SnapContainerData container(
      ScrollSnapType(false, SnapAxis::kBoth, SnapStrictness::kMandatory),
      gfx::RectF(0, 0, 300, 300), gfx::ScrollOffset(600, 800));
  SnapAreaData snapped_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(0, 0, 100, 100), false, ElementId(10));
  SnapAreaData focused_area(ScrollSnapAlign(SnapAlignment::kStart),
                            gfx::RectF(0, 0, 100, 100), false, ElementId(20));
  container.AddSnapAreaData(snapped_area);
  container.AddSnapAreaData(focused_area);

  // Initially both snap areas are coincident with the snap position.
  gfx::ScrollOffset origin(0, 0);
  std::unique_ptr<SnapSelectionStrategy> strategy =
      SnapSelectionStrategy::CreateForTargetElement(origin);

  gfx::ScrollOffset snap_position = gfx::ScrollOffset();
  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(0, snap_position.x());
  EXPECT_EQ(0, snap_position.y());
  EXPECT_TRUE(container.SetTargetSnapAreaElementIds(target_elements));

  // Simulate layout change. The focused area is no longer aligned, but was
  // previously aligned. It should take precedence over the targeted area.
  focused_area.rect = gfx::RectF(200, 100, 100, 100);
  container.UpdateSnapAreaForTesting(ElementId(20), focused_area);

  EXPECT_TRUE(container.FindSnapPosition(*strategy, &snap_position,
                                         &target_elements, ElementId(20)));
  EXPECT_EQ(200, snap_position.x());
  EXPECT_EQ(100, snap_position.y());
}

}  // namespace cc