Thuban/UI/hittest.py

# Copyright (C) 2003 by Intevation GmbH
# Authors:
# Martin Mueller <[email protected]>
# Bernhard Herzog <[email protected]>
#
# This program is free software under the GPL (>=v2)
# Read the file COPYING coming with the software for details.

"""Hit testing functions"""

__version__ = "$Revision$"
# $Source$
# $Id$

from math import hypot, sqrt

def line_hit(sx, sy, ex, ey, px, py):
    """Determine whether the line fom (SX, SY) to (EX, EY) is `hit' by a
    click at (PX, PY), or whether a polygon containing this line is hit
    in the interior at (PX, PY).

    Return -1 if the line it self his hit. Otherwise, return +1 if a
    horizontal line from (PX, PY) to (-Infinity, PY) intersects the line
    and 0 if it doesn't.

    The nonnegative return values can be used to determine whether (PX, PY)
    is an interior point of a polygon according to the even-odd rule.
    """

    if (ey < sy):
        sx, ex = ex, sx
        sy, ey = ey, sy

    not_horizontal = ey > sy + 2
    if not_horizontal and (py >= ey or py < sy):
        return 0

    vx = ex - sx
    vy = ey - sy

    len = sqrt(vx * vx + vy * vy)
    if not len:
        # degenerate case of coincident end points. Assumes that some
        # other part of the code has already determined whether the end
        # point is hit.
        return 0

    dx = px - sx
    dy = py - sy
    dist = vx * dy - vy * dx

    if ((not_horizontal or (px >= sx and px <= ex) or (px >= ex and px <= sx))
        and abs(dist) <= (len * 2)):
        return -1

    # horizontal lines (vy == 0) always return 0 here.
    return vy and py < ey and py >= sy and dx * abs(vy) > vx * abs(dy)


def polygon_hit(points, x, y):
    """Return whether x, y is in the polygon or on or near the boundary

    The return value is -1 if the point (x, y) is near the boundary, 1
    if the point is inside and 0 if it's outside.

    The points argument should be a list of lists of coordinate pairs.
    """
    crossings = 0
    for ring in points:
        for i in range(len(ring) - 1):
            sx, sy = ring[i]
            ex, ey = ring[i + 1]
            hit = line_hit(sx, sy, ex, ey, x, y)
            if hit < 0:
                return hit
            crossings += hit
    return crossings % 2


def arc_hit(points, x, y):
    """Return whether x, y is on or near the arc's boundary

    The return value is -1 if the point (x, y) is near the boundary, 1
    if the point is inside and 0 if it's outside.

    The points argument should be a list of lists of coordinate pairs.
    """
    return polygon_hit(points, x, y) < 0
1	# Copyright (C) 2003 by Intevation GmbH
2	# Authors:
3	# Martin Mueller <[email protected]>
4	# Bernhard Herzog <[email protected]>
5	#
6	# This program is free software under the GPL (>=v2)
7	# Read the file COPYING coming with the software for details.
8
9	"""Hit testing functions"""
10
11	__version__ = "$Revision$"
12	# $Source$
13	# $Id$
14
15	from math import hypot, sqrt
16
17	def line_hit(sx, sy, ex, ey, px, py):
18	"""Determine whether the line fom (SX, SY) to (EX, EY) is `hit' by a
19	click at (PX, PY), or whether a polygon containing this line is hit
20	in the interior at (PX, PY).
21
22	Return -1 if the line it self his hit. Otherwise, return +1 if a
23	horizontal line from (PX, PY) to (-Infinity, PY) intersects the line
24	and 0 if it doesn't.
25
26	The nonnegative return values can be used to determine whether (PX, PY)
27	is an interior point of a polygon according to the even-odd rule.
28	"""
29
30	if (ey < sy):
31	sx, ex = ex, sx
32	sy, ey = ey, sy
33
34	not_horizontal = ey > sy + 2
35	if not_horizontal and (py >= ey or py < sy):
36	return 0
37
38	vx = ex - sx
39	vy = ey - sy
40
41	len = sqrt(vx * vx + vy * vy)
42	if not len:
43	# degenerate case of coincident end points. Assumes that some
44	# other part of the code has already determined whether the end
45	# point is hit.
46	return 0
47
48	dx = px - sx
49	dy = py - sy
50	dist = vx * dy - vy * dx
51
52	if ((not_horizontal or (px >= sx and px <= ex) or (px >= ex and px <= sx))
53	and abs(dist) <= (len * 2)):
54	return -1
55
56	# horizontal lines (vy == 0) always return 0 here.
57	return vy and py < ey and py >= sy and dx * abs(vy) > vx * abs(dy)
58
59
60	def polygon_hit(points, x, y):
61	"""Return whether x, y is in the polygon or on or near the boundary
62
63	The return value is -1 if the point (x, y) is near the boundary, 1
64	if the point is inside and 0 if it's outside.
65
66	The points argument should be a list of lists of coordinate pairs.
67	"""
68	crossings = 0
69	for ring in points:
70	for i in range(len(ring) - 1):
71	sx, sy = ring[i]
72	ex, ey = ring[i + 1]
73	hit = line_hit(sx, sy, ex, ey, x, y)
74	if hit < 0:
75	return hit
76	crossings += hit
77	return crossings % 2
78
79
80	def arc_hit(points, x, y):
81	"""Return whether x, y is on or near the arc's boundary
82
83	The return value is -1 if the point (x, y) is near the boundary, 1
84	if the point is inside and 0 if it's outside.
85
86	The points argument should be a list of lists of coordinate pairs.
87	"""
88	return polygon_hit(points, x, y) < 0
Name	Value
svn:eol-style	native
svn:keywords	Author Date Id Revision