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      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/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_
    190