Add Geometry#orient_polygons and #orient_polygons!.

lib/ffi-geos.rb

@@ -821,6 +821,11 @@ def self.geos_library_paths
         :int, :pointer, :pointer
       ],
 
+      GEOSOrientPolygons_r: [
+        # -1 on exception, *handle, *geom, exterior_cw
+        :int, :pointer, :pointer, :int
+      ],
+
       GEOSGetInteriorRingN_r: [
         # *geom, *handle, *geom, n
         :pointer, :pointer, :pointer, :int

lib/ffi-geos/geometry.rb

@@ -59,6 +59,18 @@ def normalize!
     end
     alias normalize normalize!
 
+    if FFIGeos.respond_to?(:GEOSOrientPolygons_r)
+      def orient_polygons!(exterior_cw = false)
+        raise Geos::GEOSException, self.class if FFIGeos.GEOSOrientPolygons_r(Geos.current_handle_pointer, ptr, bool_to_int(exterior_cw)) == -1
+
+        self
+      end
+
+      def orient_polygons(exterior_cw = false)
+        dup.orient_polygons!(exterior_cw)
+      end
+    end
+
     def srid
       FFIGeos.GEOSGetSRID_r(Geos.current_handle_pointer, ptr)
     end

test/geometry/orient_polygons_tests.rb

@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+describe '#orient_polygons' do
+  include TestHelper
+
+  def setup
+    super
+    writer.trim = true
+  end
+
+  it 'does not overwrite the original geometry' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    geom = read('POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))')
+
+    result = geom.orient_polygons(true)
+
+    assert_equal('POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))', write(geom))
+    assert_equal('POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))', write(result))
+    refute_same(geom, result)
+  end
+
+  it 'does overwrite the original geometry with bang method' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons!)
+
+    geom = read('POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))')
+
+    result = geom.orient_polygons!(true)
+
+    assert_equal('POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))', write(geom))
+    assert_equal('POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))', write(result))
+    assert_same(geom, result)
+  end
+
+  it 'handles empty polygons' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    simple_tester(
+      :orient_polygons,
+      'POLYGON EMPTY',
+      'POLYGON EMPTY'
+    )
+  end
+
+  it 'hole orientation is opposite to shell' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    simple_tester(
+      :orient_polygons,
+      'POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 1 2, 2 2, 2 1, 1 1))',
+      'POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))'
+    )
+
+    simple_tester(
+      :orient_polygons,
+      'POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))',
+      'POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1))',
+      true
+    )
+  end
+
+  it 'ensures all polygons in collection are processed' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    simple_tester(
+      :orient_polygons,
+      'MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 1 2, 2 2, 2 1, 1 1)), ((100 100, 200 100, 200 200, 100 100)))',
+      'MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), ((100 100, 200 100, 200 200, 100 100)))'
+    )
+
+    simple_tester(
+      :orient_polygons,
+      'MULTIPOLYGON (((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), ((100 100, 200 200, 200 100, 100 100)))',
+      'MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), ((100 100, 200 100, 200 200, 100 100)))',
+      true
+    )
+  end
+
+  it 'polygons in collection are oriented, closed linestring unchanged' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    simple_tester(
+      :orient_polygons,
+      'GEOMETRYCOLLECTION (POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), LINESTRING (100 100, 200 100, 200 200, 100 100))',
+      'GEOMETRYCOLLECTION (POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1)), LINESTRING (100 100, 200 100, 200 200, 100 100))',
+      true
+    )
+  end
+
+  it 'nested collection handled correctly' do
+    skip unless ENV['FORCE_TESTS'] || Geos::Geometry.method_defined?(:orient_polygons)
+
+    simple_tester(
+      :orient_polygons,
+      'GEOMETRYCOLLECTION (GEOMETRYCOLLECTION (MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0)))))',
+      'GEOMETRYCOLLECTION (GEOMETRYCOLLECTION (MULTIPOLYGON (((0 0, 10 0, 10 10, 0 10, 0 0)))))'
+    )
+  end
+end