1 files changed, 68 insertions, 0 deletions
diff --git a/libs/geometry/doc/src/examples/algorithms/is_valid_failure.cpp b/libs/geometry/doc/src/examples/algorithms/is_valid_failure.cpp
new file mode 100644
index 000000000..f566e23a2
--- /dev/null
+++ b/libs/geometry/doc/src/examples/algorithms/is_valid_failure.cpp
@@ -0,0 +1,68 @@
+// Boost.Geometry (aka GGL, Generic Geometry Library)
+// QuickBook Example
+
+// Copyright (c) 2015, Oracle and/or its affiliates
+
+// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
+
+// Licensed under the Boost Software License version 1.0.
+// http://www.boost.org/users/license.html
+
+//[is_valid_failure
+//` Checks whether a geometry is valid and, if not valid, checks if it could be fixed by bg::correct; if so bg::correct is called on the geometry
+
+#include <iostream>
+
+#include <boost/geometry.hpp>
+#include <boost/geometry/geometries/point_xy.hpp>
+#include <boost/geometry/geometries/polygon.hpp>
+/*<-*/ #include "create_svg_one.hpp" /*->*/
+
+int main()
+{
+    typedef boost::geometry::model::d2::point_xy<double> point_type;
+    typedef boost::geometry::model::polygon<point_type> polygon_type;
+
+    polygon_type poly;
+    boost::geometry::read_wkt("POLYGON((0 0,0 10,10 10,10 0),(0 0,9 2,9 1,0 0),(0 0,2 9,1 9,0 0))", poly);
+
+    std::cout << "original geometry: " << boost::geometry::dsv(poly) << std::endl;
+    boost::geometry::validity_failure_type failure;
+    bool valid = boost::geometry::is_valid(poly, failure);
+
+    // if the invalidity is only due to lack of closing points and/or wrongly oriented rings, then bg::correct can fix it
+    bool could_be_fixed = (failure == boost::geometry::failure_not_closed
+                           || boost::geometry::failure_wrong_orientation);
+    std::cout << "is valid? " << (valid ? "yes" : "no") << std::endl;
+    if (! valid)
+    {
+        std::cout << "can boost::geometry::correct remedy invalidity? " << (could_be_fixed ? "possibly yes" : "no") << std::endl;
+        if (could_be_fixed)
+        {
+            boost::geometry::correct(poly);
+            std::cout << "after correction: " << (boost::geometry::is_valid(poly) ? "valid" : "still invalid") << std::endl;
+            std::cout << "corrected geometry: " << boost::geometry::dsv(poly) << std::endl;
+        }
+    }
+    /*<-*/ create_svg("is_valid_failure_example.svg", poly); /*->*/
+    return 0;
+}
+
+//]
+
+//[is_valid_failure_output
+/*`
+Output:
+[pre
+original geometry: (((0, 0), (0, 10), (10, 10), (10, 0)), ((0, 0), (9, 2), (9, 1), (0, 0)), ((0, 0), (2, 9), (1, 9), (0, 0)))
+is valid? no
+can boost::geometry::correct remedy invalidity? possibly yes
+after correction: valid
+corrected geometry: (((0, 0), (0, 10), (10, 10), (10, 0), (0, 0)), ((0, 0), (9, 1), (9, 2), (0, 0)), ((0, 0), (2, 9), (1, 9), (0, 0)))
+
+[$img/algorithms/is_valid_failure_example.png]
+
+]
+
+*/
+//]