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	bh	1589	# 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
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svn:keywords	Author Date Id Revision