src/ash/wm/workspace/magnetism_matcher.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ash/wm/workspace/magnetism_matcher.h"
   6
   7 #include <algorithm>
   8 #include <cmath>
   9
  10 namespace ash {
  11 namespace {
  12
  13 // Returns true if |a| is close enough to |b| that the two edges snap.
  14 bool IsCloseEnough(int a, int b) {
  15   return abs(a - b) <= MagnetismMatcher::kMagneticDistance;
  16 }
  17
  18 // Returns true if the specified SecondaryMagnetismEdge can be matched with a
  19 // primary edge of |primary|. |edges| is a bitmask of the allowed
  20 // MagnetismEdges.
  21 bool CanMatchSecondaryEdge(MagnetismEdge primary,
  22                            SecondaryMagnetismEdge secondary,
  23                            uint32 edges) {
  24   // Convert |secondary| to a MagnetismEdge so we can compare it to |edges|.
  25   MagnetismEdge secondary_as_magnetism_edge = MAGNETISM_EDGE_TOP;
  26   switch (primary) {
  27     case MAGNETISM_EDGE_TOP:
  28     case MAGNETISM_EDGE_BOTTOM:
  29       if (secondary == SECONDARY_MAGNETISM_EDGE_LEADING)
  30         secondary_as_magnetism_edge = MAGNETISM_EDGE_LEFT;
  31       else if (secondary == SECONDARY_MAGNETISM_EDGE_TRAILING)
  32         secondary_as_magnetism_edge = MAGNETISM_EDGE_RIGHT;
  33       else
  34         NOTREACHED();
  35       break;
  36     case MAGNETISM_EDGE_LEFT:
  37     case MAGNETISM_EDGE_RIGHT:
  38       if (secondary == SECONDARY_MAGNETISM_EDGE_LEADING)
  39         secondary_as_magnetism_edge = MAGNETISM_EDGE_TOP;
  40       else if (secondary == SECONDARY_MAGNETISM_EDGE_TRAILING)
  41         secondary_as_magnetism_edge = MAGNETISM_EDGE_BOTTOM;
  42       else
  43         NOTREACHED();
  44       break;
  45   }
  46   return (edges & secondary_as_magnetism_edge) != 0;
  47 }
  48
  49 }  // namespace
  50
  51 // MagnetismEdgeMatcher --------------------------------------------------------
  52
  53 MagnetismEdgeMatcher::MagnetismEdgeMatcher(const gfx::Rect& bounds,
  54                                            MagnetismEdge edge)
  55     : bounds_(bounds),
  56       edge_(edge) {
  57   ranges_.push_back(GetSecondaryRange(bounds_));
  58 }
  59
  60 MagnetismEdgeMatcher::~MagnetismEdgeMatcher() {
  61 }
  62
  63 bool MagnetismEdgeMatcher::ShouldAttach(const gfx::Rect& bounds) {
  64   if (is_edge_obscured())
  65     return false;
  66
  67   if (IsCloseEnough(GetPrimaryCoordinate(bounds_, edge_),
  68                     GetPrimaryCoordinate(bounds, FlipEdge(edge_)))) {
  69     const Range range(GetSecondaryRange(bounds));
  70     Ranges::const_iterator i =
  71         std::lower_bound(ranges_.begin(), ranges_.end(), range);
  72     // Close enough, but only attach if some portion of the edge is visible.
  73     if ((i != ranges_.begin() && RangesIntersect(*(i - 1), range)) ||
  74         (i != ranges_.end() && RangesIntersect(*i, range))) {
  75       return true;
  76     }
  77   }
  78   // NOTE: this checks against the current bounds, we may want to allow some
  79   // flexibility here.
  80   const Range primary_range(GetPrimaryRange(bounds));
  81   if (primary_range.first <= GetPrimaryCoordinate(bounds_, edge_) &&
  82       primary_range.second >= GetPrimaryCoordinate(bounds_, edge_)) {
  83     UpdateRanges(GetSecondaryRange(bounds));
  84   }
  85   return false;
  86 }
  87
  88 void MagnetismEdgeMatcher::UpdateRanges(const Range& range) {
  89   Ranges::const_iterator it =
  90       std::lower_bound(ranges_.begin(), ranges_.end(), range);
  91   if (it != ranges_.begin() && RangesIntersect(*(it - 1), range))
  92     --it;
  93   if (it == ranges_.end())
  94     return;
  95
  96   for (size_t i = it - ranges_.begin();
  97        i < ranges_.size() && RangesIntersect(ranges_[i], range); ) {
  98     if (range.first <= ranges_[i].first &&
  99         range.second >= ranges_[i].second) {
 100       ranges_.erase(ranges_.begin() + i);
 101     } else if (range.first < ranges_[i].first) {
 102       DCHECK_GT(range.second, ranges_[i].first);
 103       ranges_[i] = Range(range.second, ranges_[i].second);
 104       ++i;
 105     } else {
 106       Range existing(ranges_[i]);
 107       ranges_[i].second = range.first;
 108       ++i;
 109       if (existing.second > range.second) {
 110         ranges_.insert(ranges_.begin() + i,
 111                        Range(range.second, existing.second));
 112         ++i;
 113       }
 114     }
 115   }
 116 }
 117
 118 // MagnetismMatcher ------------------------------------------------------------
 119
 120 // static
 121 const int MagnetismMatcher::kMagneticDistance = 8;
 122
 123 MagnetismMatcher::MagnetismMatcher(const gfx::Rect& bounds, uint32 edges)
 124     : edges_(edges) {
 125   if (edges & MAGNETISM_EDGE_TOP)
 126     matchers_.push_back(new MagnetismEdgeMatcher(bounds, MAGNETISM_EDGE_TOP));
 127   if (edges & MAGNETISM_EDGE_LEFT)
 128     matchers_.push_back(new MagnetismEdgeMatcher(bounds, MAGNETISM_EDGE_LEFT));
 129   if (edges & MAGNETISM_EDGE_BOTTOM) {
 130     matchers_.push_back(new MagnetismEdgeMatcher(bounds,
 131                                                  MAGNETISM_EDGE_BOTTOM));
 132   }
 133   if (edges & MAGNETISM_EDGE_RIGHT)
 134     matchers_.push_back(new MagnetismEdgeMatcher(bounds, MAGNETISM_EDGE_RIGHT));
 135 }
 136
 137 MagnetismMatcher::~MagnetismMatcher() {
 138 }
 139
 140 bool MagnetismMatcher::ShouldAttach(const gfx::Rect& bounds,
 141                                     MatchedEdge* edge) {
 142   for (size_t i = 0; i < matchers_.size(); ++i) {
 143     if (matchers_[i]->ShouldAttach(bounds)) {
 144       edge->primary_edge = matchers_[i]->edge();
 145       AttachToSecondaryEdge(bounds, edge->primary_edge,
 146                             &(edge->secondary_edge));
 147       return true;
 148     }
 149   }
 150   return false;
 151 }
 152
 153 bool MagnetismMatcher::AreEdgesObscured() const {
 154   for (size_t i = 0; i < matchers_.size(); ++i) {
 155     if (!matchers_[i]->is_edge_obscured())
 156       return false;
 157   }
 158   return true;
 159 }
 160
 161 void MagnetismMatcher::AttachToSecondaryEdge(
 162     const gfx::Rect& bounds,
 163     MagnetismEdge edge,
 164     SecondaryMagnetismEdge* secondary_edge) const {
 165   const gfx::Rect& src_bounds(matchers_[0]->bounds());
 166   if (edge == MAGNETISM_EDGE_LEFT || edge == MAGNETISM_EDGE_RIGHT) {
 167     if (CanMatchSecondaryEdge(edge, SECONDARY_MAGNETISM_EDGE_LEADING, edges_) &&
 168         IsCloseEnough(bounds.y(), src_bounds.y())) {
 169       *secondary_edge = SECONDARY_MAGNETISM_EDGE_LEADING;
 170     } else if (CanMatchSecondaryEdge(edge, SECONDARY_MAGNETISM_EDGE_TRAILING,
 171                                      edges_) &&
 172                IsCloseEnough(bounds.bottom(), src_bounds.bottom())) {
 173       *secondary_edge = SECONDARY_MAGNETISM_EDGE_TRAILING;
 174     } else {
 175       *secondary_edge = SECONDARY_MAGNETISM_EDGE_NONE;
 176     }
 177   } else {
 178     if (CanMatchSecondaryEdge(edge, SECONDARY_MAGNETISM_EDGE_LEADING, edges_) &&
 179         IsCloseEnough(bounds.x(), src_bounds.x())) {
 180       *secondary_edge = SECONDARY_MAGNETISM_EDGE_LEADING;
 181     } else if (CanMatchSecondaryEdge(edge, SECONDARY_MAGNETISM_EDGE_TRAILING,
 182                                      edges_) &&
 183                IsCloseEnough(bounds.right(), src_bounds.right())) {
 184       *secondary_edge = SECONDARY_MAGNETISM_EDGE_TRAILING;
 185     } else {
 186       *secondary_edge = SECONDARY_MAGNETISM_EDGE_NONE;
 187     }
 188   }
 189 }
 190
 191 }  // namespace ash