ash/wm/workspace/magnetism_matcher.h

   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 #ifndef ASH_WM_WORKSPACE_MAGNETISM_MATCHER_H_
   6 #define ASH_WM_WORKSPACE_MAGNETISM_MATCHER_H_
   7
   8 #include <utility>
   9 #include <vector>
  10
  11 #include "ash/ash_export.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/logging.h"
  14 #include "base/memory/scoped_vector.h"
  15 #include "ui/gfx/geometry/rect.h"
  16
  17 namespace ash {
  18
  19 enum MagnetismEdge {
  20   MAGNETISM_EDGE_TOP    = 1 << 0,
  21   MAGNETISM_EDGE_LEFT   = 1 << 1,
  22   MAGNETISM_EDGE_BOTTOM = 1 << 2,
  23   MAGNETISM_EDGE_RIGHT  = 1 << 3,
  24 };
  25
  26 const uint32 kAllMagnetismEdges =
  27     MAGNETISM_EDGE_TOP | MAGNETISM_EDGE_LEFT | MAGNETISM_EDGE_BOTTOM |
  28     MAGNETISM_EDGE_RIGHT;
  29
  30 // MagnetismEdgeMatcher is used for matching a particular edge of a window. You
  31 // shouldn't need to use this directly, instead use MagnetismMatcher which takes
  32 // care of all edges.
  33 // MagnetismEdgeMatcher maintains a range of the visible portions of the
  34 // edge. As ShouldAttach() is invoked the visible range is updated.
  35 class MagnetismEdgeMatcher {
  36  public:
  37   MagnetismEdgeMatcher(const gfx::Rect& bounds, MagnetismEdge edge);
  38   ~MagnetismEdgeMatcher();
  39
  40   MagnetismEdge edge() const { return edge_; }
  41   const gfx::Rect& bounds() const { return bounds_; }
  42
  43   // Returns true if the edge is completely obscured. If true ShouldAttach()
  44   // will return false.
  45   bool is_edge_obscured() const { return ranges_.empty(); }
  46
  47   // Returns true if should attach to the specified bounds.
  48   bool ShouldAttach(const gfx::Rect& bounds);
  49
  50  private:
  51   typedef std::pair<int,int> Range;
  52   typedef std::vector<Range> Ranges;
  53
  54   // Removes |range| from |ranges_|.
  55   void UpdateRanges(const Range& range);
  56
  57   static int GetPrimaryCoordinate(const gfx::Rect& bounds, MagnetismEdge edge) {
  58     switch (edge) {
  59       case MAGNETISM_EDGE_TOP:
  60         return bounds.y();
  61       case MAGNETISM_EDGE_LEFT:
  62         return bounds.x();
  63       case MAGNETISM_EDGE_BOTTOM:
  64         return bounds.bottom();
  65       case MAGNETISM_EDGE_RIGHT:
  66         return bounds.right();
  67     }
  68     NOTREACHED();
  69     return 0;
  70   }
  71
  72   static MagnetismEdge FlipEdge(MagnetismEdge edge) {
  73     switch (edge) {
  74       case MAGNETISM_EDGE_TOP:
  75         return MAGNETISM_EDGE_BOTTOM;
  76       case MAGNETISM_EDGE_BOTTOM:
  77         return MAGNETISM_EDGE_TOP;
  78       case MAGNETISM_EDGE_LEFT:
  79         return MAGNETISM_EDGE_RIGHT;
  80       case MAGNETISM_EDGE_RIGHT:
  81         return MAGNETISM_EDGE_LEFT;
  82     }
  83     NOTREACHED();
  84     return MAGNETISM_EDGE_LEFT;
  85   }
  86
  87   Range GetPrimaryRange(const gfx::Rect& bounds) const {
  88     switch (edge_) {
  89       case MAGNETISM_EDGE_TOP:
  90       case MAGNETISM_EDGE_BOTTOM:
  91         return Range(bounds.y(), bounds.bottom());
  92       case MAGNETISM_EDGE_LEFT:
  93       case MAGNETISM_EDGE_RIGHT:
  94         return Range(bounds.x(), bounds.right());
  95     }
  96     NOTREACHED();
  97     return Range();
  98   }
  99
 100   Range GetSecondaryRange(const gfx::Rect& bounds) const {
 101     switch (edge_) {
 102       case MAGNETISM_EDGE_TOP:
 103       case MAGNETISM_EDGE_BOTTOM:
 104         return Range(bounds.x(), bounds.right());
 105       case MAGNETISM_EDGE_LEFT:
 106       case MAGNETISM_EDGE_RIGHT:
 107         return Range(bounds.y(), bounds.bottom());
 108     }
 109     NOTREACHED();
 110     return Range();
 111   }
 112
 113   static bool RangesIntersect(const Range& r1, const Range& r2) {
 114     return r2.first < r1.second && r2.second > r1.first;
 115   }
 116
 117   // The bounds of window.
 118   const gfx::Rect bounds_;
 119
 120   // The edge this matcher checks.
 121   const MagnetismEdge edge_;
 122
 123   // Visible ranges of the edge. Initialized with GetSecondaryRange() and
 124   // updated as ShouldAttach() is invoked. When empty the edge is completely
 125   // obscured by other bounds.
 126   Ranges ranges_;
 127
 128   DISALLOW_COPY_AND_ASSIGN(MagnetismEdgeMatcher);
 129 };
 130
 131 enum SecondaryMagnetismEdge {
 132   SECONDARY_MAGNETISM_EDGE_LEADING,
 133   SECONDARY_MAGNETISM_EDGE_TRAILING,
 134   SECONDARY_MAGNETISM_EDGE_NONE,
 135 };
 136
 137 // Used to identify a matched edge. |primary_edge| is relative to the source and
 138 // indicates the edge the two are to share. For example, if |primary_edge| is
 139 // MAGNETISM_EDGE_RIGHT then the right edge of the source should snap to to the
 140 // left edge of the target. |secondary_edge| indicates one of the edges along
 141 // the opposite axis should should also be aligned. For example, if
 142 // |primary_edge| is MAGNETISM_EDGE_RIGHT and |secondary_edge| is
 143 // SECONDARY_MAGNETISM_EDGE_LEADING then the source should snap to the left top
 144 // corner of the target.
 145 struct MatchedEdge {
 146   MagnetismEdge primary_edge;
 147   SecondaryMagnetismEdge secondary_edge;
 148 };
 149
 150 // MagnetismMatcher is used to test if a window should snap to another window.
 151 // To use MagnetismMatcher do the following:
 152 // . Create it with the bounds of the window being dragged.
 153 // . Iterate over the child windows checking if the window being dragged should
 154 //   attach to it using ShouldAttach().
 155 // . Use AreEdgesObscured() to test if no other windows can match (because all
 156 //   edges are completely obscured).
 157 class ASH_EXPORT MagnetismMatcher {
 158  public:
 159   static const int kMagneticDistance;
 160
 161   // |edges| is a bitmask of MagnetismEdges to match against.
 162   MagnetismMatcher(const gfx::Rect& bounds, uint32 edges);
 163   ~MagnetismMatcher();
 164
 165   // Returns true if |bounds| is close enough to the initial bounds that the two
 166   // should be attached. If true is returned |edge| is set to indicates how the
 167   // two should snap together. See description of MatchedEdge for details.
 168   bool ShouldAttach(const gfx::Rect& bounds, MatchedEdge* edge);
 169
 170   // Returns true if no other matches are possible.
 171   bool AreEdgesObscured() const;
 172
 173  private:
 174   // Sets |secondary_edge| based on whether the secondary edges should snap.
 175   void AttachToSecondaryEdge(const gfx::Rect& bounds,
 176                              MagnetismEdge edge,
 177                              SecondaryMagnetismEdge* secondary_edge) const;
 178
 179   // The edges to match against.
 180   const int32 edges_;
 181
 182   ScopedVector<MagnetismEdgeMatcher> matchers_;
 183
 184   DISALLOW_COPY_AND_ASSIGN(MagnetismMatcher);
 185 };
 186
 187 }  // namespace ash
 188
 189 #endif  // ASH_WM_WORKSPACE_MAGNETISM_MATCHER_H_