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direction.py

# Copyright (C) 2009, 2010  Roman Zimbelmann <romanz@lavabit.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
Directions provide convenience methods for movement operations.

Direction objects are handled just like dicts but provide
methods like up() and down() which give you the correct value
for the vertical direction, even if only the "up" or "down" key
has been defined.

Example application:
d = Direction(down=5)
print(d.up()) # prints -5
print(bool(d.horizontal())) # False, since no horizontal direction is defined
"""

00030 class Direction(dict):
      __doc__ = __doc__  # for nicer pydoc

      def __init__(self, dictionary=None, **keywords):
            if dictionary is not None:
                  dict.__init__(self, dictionary)
            else:
                  dict.__init__(self, keywords)
            if 'to' in self:
                  self['down'] = self['to']
                  self['absolute'] = True

      def copy(self):
            return Direction(**self)

      def _get_bool(self, first, second, fallback=None):
            try: return self[first]
            except:
                  try: return not self[second]
                  except: return fallback

      def _get_direction(self, first, second, fallback=0):
            try: return self[first]
            except:
                  try: return -self[second]
                  except: return fallback

      def up(self):
            return -Direction.down(self)

      def down(self):
            return Direction._get_direction(self, 'down', 'up')

      def right(self):
            return Direction._get_direction(self, 'right', 'left')

      def absolute(self):
            return Direction._get_bool(self, 'absolute', 'relative')

      def left(self):
            return -Direction.right(self)

      def relative(self):
            return not Direction.absolute(self)

      def vertical_direction(self):
            down = Direction.down(self)
            return (down > 0) - (down < 0)

      def horizontal_direction(self):
            right = Direction.right(self)
            return (right > 0) - (right < 0)

      def vertical(self):
            return set(self) & set(['up', 'down'])

      def horizontal(self):
            return set(self) & set(['left', 'right'])

      def pages(self):
            return 'pages' in self and self['pages']

      def percentage(self):
            return 'percentage' in self and self['percentage']

      def multiply(self, n):
            for key in ('up', 'right', 'down', 'left'):
                  try:
                        self[key] *= n
                  except:
                        pass

      def set(self, n):
            for key in ('up', 'right', 'down', 'left'):
                  if key in self:
                        self[key] = n

00107       def move(self, direction, override=None, minimum=0, maximum=9999,
                  current=0, pagesize=1, offset=0):
            """
            Calculates the new position in a given boundary.

            Example:
            d = Direction(pages=True)
            d.move(direction=3) # = 3
            d.move(direction=3, current=2) # = 5
            d.move(direction=3, pagesize=5) # = 15
            d.move(direction=3, pagesize=5, maximum=10) # = 10
            d.move(direction=9, override=2) # = 18
            """
            pos = direction
            if override is not None:
                  if self.absolute():
                        pos = override
                  else:
                        pos *= override
            if self.pages():
                  pos *= pagesize
            elif self.percentage():
                  pos *= maximum / 100.0
            if self.absolute():
                  if pos < minimum:
                        pos += maximum
            else:
                  pos += current
            return int(max(min(pos, maximum + offset - 1), minimum))

      def select(self, lst, current, pagesize, override=None, offset=1):
            dest = self.move(direction=self.down(), override=override,
                  current=current, pagesize=pagesize, minimum=0, maximum=len(lst))
            selection = lst[min(current, dest):max(current, dest) + offset]
            return dest + offset - 1, selection

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