mapnik/tests/python_tests/query_tolerance_test.py

#!/usr/bin/env python

from nose.tools import *
from utilities import execution_path

import os, mapnik

def setup():
    # All of the paths used are relative, if we run the tests
    # from another directory we need to chdir()
    os.chdir(execution_path('.'))

if 'shape' in mapnik.DatasourceCache.plugin_names():
    def test_query_tolerance():
        srs = '+init=epsg:4326'
        lyr = mapnik.Layer('test')
        ds = mapnik.Shapefile(file='../data/shp/arrows.shp')
        lyr.datasource = ds
        lyr.srs = srs
        _width = 256
        _map = mapnik.Map(_width,_width, srs)
        _map.layers.append(lyr)
        # zoom determines tolerance
        _map.zoom_all()
        _map_env = _map.envelope()
        tol = (_map_env.maxx - _map_env.minx) / _width * 3
        # 0.046875 for arrows.shp and zoom_all
        eq_(tol,0.046875)
        # check point really exists
        x, y = 2.0, 4.0
        features = _map.query_point(0,x,y).features
        eq_(len(features),1)
        # check inside tolerance limit
        x = 2.0 + tol * 0.9
        features = _map.query_point(0,x,y).features
        eq_(len(features),1)
        # check outside tolerance limit
        x = 2.0 + tol * 1.1
        features = _map.query_point(0,x,y).features
        eq_(len(features),0)

if __name__ == "__main__":
    setup()
    [eval(run)() for run in dir() if 'test_' in run]