Lib/lib-stdwin/rect.py

   1 # Module 'rect'.
   2 #
   3 # Operations on rectangles.
   4 # There is some normalization: all results return the object 'empty'
   5 # if their result would contain no points.
   6
   7
   8 # Exception.
   9 #
  10 error = 'rect.error'
  11
  12
  13 # The empty rectangle.
  14 #
  15 empty = (0, 0), (0, 0)
  16
  17
  18 # Check if a rectangle is empty.
  19 #
  20 def is_empty(r):
  21         (left, top), (right, bottom) = r
  22         return left >= right or top >= bottom
  23
  24
  25 # Compute the intersection or two or more rectangles.
  26 # This works with a list or tuple argument.
  27 #
  28 def intersect(list):
  29         if not list: raise error, 'intersect called with empty list'
  30         if is_empty(list[0]): return empty
  31         (left, top), (right, bottom) = list[0]
  32         for rect in list[1:]:
  33                 if is_empty(rect):
  34                         return empty
  35                 (l, t), (r, b) = rect
  36                 if left < l: left = l
  37                 if top < t: top = t
  38                 if right > r: right = r
  39                 if bottom > b: bottom = b
  40                 if is_empty(((left, top), (right, bottom))):
  41                         return empty
  42         return (left, top), (right, bottom)
  43
  44
  45 # Compute the smallest rectangle containing all given rectangles.
  46 # This works with a list or tuple argument.
  47 #
  48 def union(list):
  49         (left, top), (right, bottom) = list[0]
  50         for (l, t), (r, b) in list[1:]:
  51                 if not is_empty(((l, t), (r, b))):
  52                         if l < left: left = l
  53                         if t < top: top = t
  54                         if r > right: right = r
  55                         if b > bottom: bottom = b
  56         res = (left, top), (right, bottom)
  57         if is_empty(res):
  58                 return empty
  59         return res
  60
  61
  62 # Check if a point is in a rectangle.
  63 #
  64 def pointinrect((h, v), ((left, top), (right, bottom))):
  65         return left <= h < right and top <= v < bottom
  66
  67
  68 # Return a rectangle that is dh, dv inside another
  69 #
  70 def inset(((left, top), (right, bottom)), (dh, dv)):
  71         left = left + dh
  72         top = top + dv
  73         right = right - dh
  74         bottom = bottom - dv
  75         r = (left, top), (right, bottom)
  76         if is_empty(r):
  77                 return empty
  78         else:
  79                 return r
  80
  81
  82 # Conversions between rectangles and 'geometry tuples',
  83 # given as origin (h, v) and dimensions (width, height).
  84 #
  85 def rect2geom((left, top), (right, bottom)):
  86         return (left, top), (right-left, bottom-top)
  87
  88 def geom2rect((h, v), (width, height)):
  89         return (h, v), (h+width, v+height)