1// Copyright 2014 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 "cc/base/simple_enclosed_region.h"
6
7#include "base/logging.h"
8#include "cc/base/region.h"
9
10namespace cc {
11
12static bool RectIsLargerArea(const gfx::Rect& a, const gfx::Rect b) {
13  int64 a_area = static_cast<int64>(a.width()) * a.height();
14  int64 b_area = static_cast<int64>(b.width()) * b.height();
15  return a_area > b_area;
16}
17
18SimpleEnclosedRegion::SimpleEnclosedRegion(const Region& region) {
19  for (Region::Iterator it(region); it.has_rect(); it.next())
20    Union(it.rect());
21}
22
23SimpleEnclosedRegion::~SimpleEnclosedRegion() {
24}
25
26void SimpleEnclosedRegion::Subtract(const gfx::Rect& sub_rect) {
27  // We want to keep as much of the current rect as we can, so find the one
28  // largest rectangle inside |rect_| that does not intersect with |sub_rect|.
29  if (!rect_.Intersects(sub_rect))
30    return;
31  if (sub_rect.Contains(rect_)) {
32    rect_ = gfx::Rect();
33    return;
34  }
35
36  int left = rect_.x();
37  int right = rect_.right();
38  int top = rect_.y();
39  int bottom = rect_.bottom();
40
41  int delta_left = sub_rect.x() - left;
42  int delta_right = right - sub_rect.right();
43  int delta_top = sub_rect.y() - top;
44  int delta_bottom = bottom - sub_rect.bottom();
45
46  // The horizontal rect is the larger of the two rectangles above or below
47  // |sub_rect| and inside rect_.
48  int horizontal_top = top;
49  int horizontal_bottom = bottom;
50  if (delta_top > delta_bottom)
51    horizontal_bottom = sub_rect.y();
52  else
53    horizontal_top = sub_rect.bottom();
54  // The vertical rect is the larger of the two rectangles to the left or the
55  // right of |sub_rect| and inside rect_.
56  int vertical_left = left;
57  int vertical_right = right;
58  if (delta_left > delta_right)
59    vertical_right = sub_rect.x();
60  else
61    vertical_left = sub_rect.right();
62
63  rect_.SetRect(
64      left, horizontal_top, right - left, horizontal_bottom - horizontal_top);
65
66  gfx::Rect vertical_rect(
67      vertical_left, top, vertical_right - vertical_left, bottom - top);
68  if (RectIsLargerArea(vertical_rect, rect_))
69    rect_ = vertical_rect;
70}
71
72void SimpleEnclosedRegion::Union(const gfx::Rect& new_rect) {
73  // We want to keep track of a region but bound its complexity at a constant
74  // size. We keep track of the largest rectangle seen by area. If we can add
75  // the |new_rect| to this rectangle then we do that, as that is the cheapest
76  // way to increase the area returned without increasing the complexity.
77  if (new_rect.IsEmpty())
78    return;
79  if (rect_.Contains(new_rect))
80    return;
81  if (new_rect.Contains(rect_)) {
82    rect_ = new_rect;
83    return;
84  }
85
86  int left = rect_.x();
87  int top = rect_.y();
88  int right = rect_.right();
89  int bottom = rect_.bottom();
90
91  int new_left = new_rect.x();
92  int new_top = new_rect.y();
93  int new_right = new_rect.right();
94  int new_bottom = new_rect.bottom();
95
96  // This attempts to expand each edge of |rect_| if the |new_rect| entirely
97  // covers or is adjacent to an entire edge of |rect_|. If this is true for
98  // an edge of |rect_| then it can be expanded out to share that edge with the
99  // same edge of |new_rect|. After, the same thing is done to try expand
100  // |new_rect| relative to |rect_|.
101  if (new_top <= top && new_bottom >= bottom) {
102    if (new_left < left && new_right >= left)
103      left = new_left;
104    if (new_right > right && new_left <= right)
105      right = new_right;
106  } else if (new_left <= left && new_right >= right) {
107    if (new_top < top && new_bottom >= top)
108      top = new_top;
109    if (new_bottom > bottom && new_top <= bottom)
110      bottom = new_bottom;
111  } else if (top <= new_top && bottom >= new_bottom) {
112    if (left < new_left && right >= new_left)
113      new_left = left;
114    if (right > new_right && left <= new_right)
115      new_right = right;
116  } else if (left <= new_left && right >= new_right) {
117    if (top < new_top && bottom >= new_top)
118      new_top = top;
119    if (bottom > new_bottom && top <= new_bottom)
120      new_bottom = bottom;
121  }
122
123  rect_.SetRect(left, top, right - left, bottom - top);
124
125  gfx::Rect adjusted_new_rect(
126      new_left, new_top, new_right - new_left, new_bottom - new_top);
127  if (RectIsLargerArea(adjusted_new_rect, rect_))
128    rect_ = adjusted_new_rect;
129}
130
131gfx::Rect SimpleEnclosedRegion::GetRect(size_t i) const {
132  DCHECK_LT(i, GetRegionComplexity());
133  return rect_;
134}
135
136}  // namespace cc
137