1# Copyright 2015 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"""Objects for convenient manipulation of points and other surface areas."""
6
7import collections
8
9
10class Point(collections.namedtuple('Point', ['x', 'y'])):
11  """Object to represent an (x, y) point on a surface.
12
13  Args:
14    x, y: Two numeric coordinates that define the point.
15  """
16  __slots__ = ()
17
18  def __str__(self):
19    """Get a useful string representation of the object."""
20    return '(%s, %s)' % (self.x, self.y)
21
22  def __add__(self, other):
23    """Sum of two points, e.g. p + q."""
24    if isinstance(other, Point):
25      return Point(self.x + other.x, self.y + other.y)
26    else:
27      return NotImplemented
28
29  def __mul__(self, factor):
30    """Multiplication on the right is not implemented."""
31    # This overrides the default behaviour of a tuple multiplied by a constant
32    # on the right, which does not make sense for a Point.
33    return NotImplemented
34
35  def __rmul__(self, factor):
36    """Multiply a point by a scalar factor on the left, e.g. 2 * p."""
37    return Point(factor * self.x, factor * self.y)
38
39
40class Rectangle(
41    collections.namedtuple('Rectangle', ['top_left', 'bottom_right'])):
42  """Object to represent a rectangle on a surface.
43
44  Args:
45    top_left: A pair of (left, top) coordinates. Might be given as a Point
46      or as a two-element sequence (list, tuple, etc.).
47    bottom_right: A pair (right, bottom) coordinates.
48  """
49  __slots__ = ()
50
51  def __new__(cls, top_left, bottom_right):
52    if not isinstance(top_left, Point):
53      top_left = Point(*top_left)
54    if not isinstance(bottom_right, Point):
55      bottom_right = Point(*bottom_right)
56    return super(Rectangle, cls).__new__(cls, top_left, bottom_right)
57
58  def __str__(self):
59    """Get a useful string representation of the object."""
60    return '[%s, %s]' % (self.top_left, self.bottom_right)
61
62  @property
63  def center(self):
64    """Get the point at the center of the rectangle."""
65    return 0.5 * (self.top_left + self.bottom_right)
66
67  @classmethod
68  def FromDict(cls, d):
69    """Create a rectangle object from a dictionary.
70
71    Args:
72      d: A dictionary (or mapping) of the form, e.g., {'top': 0, 'left': 0,
73         'bottom': 1, 'right': 1}.
74    """
75    return cls(Point(d['left'], d['top']), Point(d['right'], d['bottom']))
76