multitouch/src/geometry.py

from __future__ import division
from math import atan2, pi
import time


class Positionable(object):
    """
    Parent class for any object with a position.
    """
    def __init__(self, x=None, y=None):
        self.x = x
        self.y = y

    def __str__(self):
        return '<%s at (%s, %s)>' % (self.__class__.__name__, self.x, self.y)

    def set_position(self, x, y):
        self.x = x
        self.y = y

    def get_position(self):
        return self.x, self.y

    @property
    def xy(self):
        """
        Shortcut getter for (x, y) position.
        """
        return self.x, self.y

    def distance_to(self, positionable):
        """
        Calculate the Pythagorian distance from this positionable to another.
        """
        x, y = positionable.get_position()
        return ((x - self.x) ** 2 + (y - self.y) ** 2) ** .5


class MovingPositionable(Positionable):
    """
    Parent class for positionable objects that need movement calculations. For
    these calculations, the previous position is also saved.
    """
    def __init__(self, x=None, y=None):
        super(MovingPositionable, self).__init__(x, y)
        self.prev = Positionable(x, y)

    def set_position(self, x, y):
        """
        Set a new position and save the current position as the precious
        position. If no previous position has been set, set is to the new
        position so that the movement is zero.
        """
        if self.x is None or self.y is None:
            self.prev.set_position(x, y)
        else:
            self.prev.set_position(self.x, self.y)

        Positionable.set_position(self, x, y)

    def get_previous_position(self):
        return self.prev

    def rotation_around(self, center):
        """
        Calculate rotation of this positionable relative to a center
        positionable.
        """
        cx, cy = center.get_position()
        px, py = self.prev.get_position()
        prev_angle = atan2(px - cx, py - cy)
        current_angle = atan2(self.x - cx, self.y - cy)
        rotation = current_angle - prev_angle

        if rotation >= pi:
            return 2 * pi - rotation

        if rotation <= -pi:
            return -2 * pi - rotation

        return rotation

    def translation(self):
        """
        Calculate the movement relative to the last position as a vector
        positionable.
        """
        px, py = self.prev.get_position()
        return Positionable(self.x - px, self.y - py)

    def movement_distance(self):
        return self.distance_to(self.prev)


class AcceleratedPositionable(MovingPositionable):
    """
    Parent class for positionable objects that need acceleration calculations.
    For these calculations, timestamps are saved for both the current and
    previous position.
    """
    def __init__(self, x=None, y=None):
        super(AcceleratedPositionable, self).__init__(x, y)
        self.prev_timestamp = self.current_timestamp = None

    def set_position(self, x, y):
        MovingPositionable.set_position(self, x, y)

        if self.current_timestamp is None:
            self.prev_timestamp = self.current_timestamp = time.time()
            return

        self.prev_timestamp = self.current_timestamp
        self.current_timestamp = time.time()

    def movement_time(self):
        return self.timestamp - self.prev_timestamp

    def acceleration(self):
        """
        Calculate the acceleration in pixels/second.
        """
        return self.movement_distance() / self.movement_time()


class Surface(Positionable):
    """
    Interface class for surfaces with a position. Defines a function
    'contains', which calculates whether a position is located in the surface.
    """
    def contains(self, point):
        raise NotImplemented


class RectangularSurface(Surface):
    """
    Rectangle, represented by a left-top position (x, y) and a size (width,
    height).
    """
    def __init__(self, x, y, width, height):
        super(RectangularSurface, self).__init__(x, y)
        self.set_size(width, height)

    def __str__(self):
        return '<%s at (%s, %s) size=(%s, %s)>' \
               % (self.__class__.__name__, self.x, self.y, self.width,
                  self.height)

    def set_size(self, width, height):
        self.width = width
        self.height = height

    def get_size(self):
        return self.width, self.height

    def contains(self, point):
        x, y = point.get_position()
        return self.x <= x <= self.x + self.width \
               and self.y <= y <= self.y + self.height


class CircularSurface(Surface):
    """
    Circle, represented by a center position (x, y) and a radius.
    """
    def __init__(self, x, y, radius):
        super(CircularSurface, self).__init__(x, y)
        self.set_radius(radius)

    def __str__(self):
        return '<%s at (%s, %s) size=(%s, %s)>' \
               % (self.__class__.__name__, self.x, self.y, self.width,
                  self.height)

    def set_radius(self, radius):
        self.radius = radius

    def get_radius(self):
        return self.radius

    def contains(self, point):
        return self.distance_to(point) <= self.radius