1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70
   71
   72
   73
   74
   75
   76
   77
   78
   79
   80
   81
   82
   83
   84
   85
   86
   87
   88
   89
   90
   91
   92
   93
   94
   95
   96
   97
   98
   99
  100
  101
  102
  103
  104
  105
  106
  107
  108
  109
  110
  111
  112
  113
  114
  115
  116
  117
  118
  119
  120
  121
  122
  123
  124
  125
  126
  127
  128
  129
  130
  131
  132
  133
  134
  135
  136
  137
  138
  139
  140
  141
  142
  143
  144
  145
  146
  147
  148
  149
  150
  151
  152
  153
  154
  155
  156
  157
  158
  159
  160
  161
  162
  163
  164
  165
  166
  167
  168
  169
  170
  171
  172
  173
  174
  175
  176
  177
  178
  179
  180
  181
  182
  183
  184
  185
  186
  187
  188
  189
  190
  191
  192
  193
  194
  195
  196
  197
  198
  199
  200
  201
  202
  203
  204
  205
  206
  207
  208
  209
  210
  211
  212
  213
  214
  215
  216
  217
  218
  219
  220
  221
  222
  223
  224
  225
  226
  227
  228
  229
  230
  231
  232
  233
  234
  235
  236
  237
  238
  239
  240

cc / input / snap_selection_strategy.cc [blame]

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/input/snap_selection_strategy.h"

#include <cmath>

namespace cc {

std::unique_ptr<SnapSelectionStrategy>
SnapSelectionStrategy::CreateForEndPosition(const gfx::PointF& current_position,
                                            bool scrolled_x,
                                            bool scrolled_y) {
  return std::make_unique<EndPositionStrategy>(current_position, scrolled_x,
                                               scrolled_y);
}

std::unique_ptr<SnapSelectionStrategy>
SnapSelectionStrategy::CreateForDirection(gfx::PointF current_position,
                                          gfx::Vector2dF step,
                                          bool use_fractional_offsets,
                                          SnapStopAlwaysFilter filter) {
  return std::make_unique<DirectionStrategy>(current_position, step, filter,
                                             use_fractional_offsets);
}

std::unique_ptr<SnapSelectionStrategy>
SnapSelectionStrategy::CreateForEndAndDirection(gfx::PointF current_position,
                                                gfx::Vector2dF displacement,
                                                bool use_fractional_offsets) {
  return std::make_unique<EndAndDirectionStrategy>(
      current_position, displacement, use_fractional_offsets);
}

std::unique_ptr<SnapSelectionStrategy>
SnapSelectionStrategy::CreateForTargetElement(gfx::PointF current_position) {
  return std::make_unique<EndPositionStrategy>(
      current_position, true /* scrolled_x */, true /* scrolled_y */,
      SnapTargetsPrioritization::kRequire);
}

bool SnapSelectionStrategy::HasIntendedDirection() const {
  return true;
}

bool SnapSelectionStrategy::ShouldRespectSnapStop() const {
  return false;
}

bool SnapSelectionStrategy::IsValidSnapArea(SearchAxis axis,
                                            const SnapAreaData& area) const {
  return axis == SearchAxis::kX
             ? area.scroll_snap_align.alignment_inline != SnapAlignment::kNone
             : area.scroll_snap_align.alignment_block != SnapAlignment::kNone;
}

bool SnapSelectionStrategy::ShouldPrioritizeSnapTargets() const {
  return false;
}

bool SnapSelectionStrategy::UsingFractionalOffsets() const {
  return false;
}

bool EndPositionStrategy::ShouldSnapOnX() const {
  return scrolled_x_;
}

bool EndPositionStrategy::ShouldSnapOnY() const {
  return scrolled_y_;
}

gfx::PointF EndPositionStrategy::intended_position() const {
  return current_position_;
}

gfx::PointF EndPositionStrategy::base_position() const {
  return current_position_;
}

// |position| is unused in this method.
bool EndPositionStrategy::IsValidSnapPosition(SearchAxis axis,
                                              float position) const {
  return (scrolled_x_ && axis == SearchAxis::kX) ||
         (scrolled_y_ && axis == SearchAxis::kY);
}

bool EndPositionStrategy::HasIntendedDirection() const {
  return false;
}

bool EndPositionStrategy::ShouldPrioritizeSnapTargets() const {
  return snap_targets_prioritization_ == SnapTargetsPrioritization::kRequire;
}

const std::optional<SnapSearchResult>& EndPositionStrategy::PickBestResult(
    const std::optional<SnapSearchResult>& closest,
    const std::optional<SnapSearchResult>& covering) const {
  return covering.has_value() ? covering : closest;
}

std::unique_ptr<SnapSelectionStrategy> EndPositionStrategy::Clone() const {
  return std::make_unique<EndPositionStrategy>(*this);
}

bool DirectionStrategy::ShouldSnapOnX() const {
  return step_.x() != 0;
}

bool DirectionStrategy::ShouldSnapOnY() const {
  return step_.y() != 0;
}

gfx::PointF DirectionStrategy::intended_position() const {
  return current_position_ + step_;
}

gfx::PointF DirectionStrategy::base_position() const {
  return current_position_;
}

bool DirectionStrategy::IsValidSnapPosition(SearchAxis axis,
                                            float position) const {
  // If not using fractional offsets then it is possible for the currently
  // snapped area's offset, which is fractional, to not be equal to the current
  // scroll offset, which is not fractional. Therefore we truncate the offsets
  // so that any position within 1 of the current position is ignored.
  if (axis == SearchAxis::kX) {
    float delta = position - current_position_.x();
    if (!use_fractional_offsets_)
      delta = delta > 0 ? std::floor(delta) : std::ceil(delta);
    return (step_.x() > 0 && delta > 0) ||  // "Right" arrow
           (step_.x() < 0 && delta < 0);    // "Left" arrow
  } else {
    float delta = position - current_position_.y();
    if (!use_fractional_offsets_)
      delta = delta > 0 ? std::floor(delta) : std::ceil(delta);
    return (step_.y() > 0 && delta > 0) ||  // "Down" arrow
           (step_.y() < 0 && delta < 0);    // "Up" arrow
  }
}

bool DirectionStrategy::IsValidSnapArea(SearchAxis axis,
                                        const SnapAreaData& area) const {
  return SnapSelectionStrategy::IsValidSnapArea(axis, area) &&
         (snap_stop_always_filter_ == SnapStopAlwaysFilter::kIgnore ||
          area.must_snap);
}

const std::optional<SnapSearchResult>& DirectionStrategy::PickBestResult(
    const std::optional<SnapSearchResult>& closest,
    const std::optional<SnapSearchResult>& covering) const {
  // We choose the |closest| result only if the default landing position (using
  // the default step) is not a valid snap position (not making a snap area
  // covering the snapport), or the |closest| is closer than the default landing
  // position.
  if (!closest.has_value())
    return covering;
  if (!covering.has_value())
    return closest;

  // "Right" or "Down" arrow.
  if ((step_.x() > 0 || step_.y() > 0) &&
      closest.value().snap_offset() < covering.value().snap_offset()) {
    return closest;
  }
  // "Left" or "Up" arrow.
  if ((step_.x() < 0 || step_.y() < 0) &&
      closest.value().snap_offset() > covering.value().snap_offset()) {
    return closest;
  }

  return covering;
}

bool DirectionStrategy::UsingFractionalOffsets() const {
  return use_fractional_offsets_;
}

std::unique_ptr<SnapSelectionStrategy> DirectionStrategy::Clone() const {
  return std::make_unique<DirectionStrategy>(*this);
}

bool EndAndDirectionStrategy::ShouldSnapOnX() const {
  return displacement_.x() != 0;
}

bool EndAndDirectionStrategy::ShouldSnapOnY() const {
  return displacement_.y() != 0;
}

gfx::PointF EndAndDirectionStrategy::intended_position() const {
  return current_position_ + displacement_;
}

gfx::PointF EndAndDirectionStrategy::base_position() const {
  return current_position_ + displacement_;
}

bool EndAndDirectionStrategy::IsValidSnapPosition(SearchAxis axis,
                                                  float position) const {
  // If not using fractional offsets then it is possible for the currently
  // snapped area's offset, which is fractional, to not be equal to the current
  // scroll offset, which is not fractional. Therefore we round the offsets so
  // that any position within 0.5 of the current position is ignored.
  if (axis == SearchAxis::kX) {
    float delta = position - current_position_.x();
    if (!use_fractional_offsets_)
      delta = std::round(delta);
    return (displacement_.x() > 0 && delta > 0) ||  // Right
           (displacement_.x() < 0 && delta < 0);    // Left
  } else {
    float delta = position - current_position_.y();
    if (!use_fractional_offsets_)
      delta = std::round(delta);
    return (displacement_.y() > 0 && delta > 0) ||  // Down
           (displacement_.y() < 0 && delta < 0);    // Up
  }
}

bool EndAndDirectionStrategy::ShouldRespectSnapStop() const {
  return true;
}

const std::optional<SnapSearchResult>& EndAndDirectionStrategy::PickBestResult(
    const std::optional<SnapSearchResult>& closest,
    const std::optional<SnapSearchResult>& covering) const {
  return covering.has_value() ? covering : closest;
}

bool EndAndDirectionStrategy::UsingFractionalOffsets() const {
  return use_fractional_offsets_;
}

std::unique_ptr<SnapSelectionStrategy> EndAndDirectionStrategy::Clone() const {
  return std::make_unique<EndAndDirectionStrategy>(*this);
}

}  // namespace cc