add method to check for planar surface

src/Mod/Part/App/GeometrySurfacePy.xml

@@ -71,7 +71,15 @@ the second vector corresponds to the minimum curvature.
 				</UserDocu>
 			</Documentation>
 		</Methode>
-		<Attribute Name="Continuity" ReadOnly="true">
+        <Methode Name="isPlanar">
+            <Documentation>
+                <UserDocu>
+isPlanar([float]) -> Bool
+Checks if the surface is planar within a certain tolerance.
+                </UserDocu>
+            </Documentation>
+        </Methode>
+        <Attribute Name="Continuity" ReadOnly="true">
 			<Documentation>
 				<UserDocu>
 					Returns the global continuity of the surface.

src/Mod/Part/App/GeometrySurfacePyImp.cpp

@@ -40,6 +40,7 @@
 # include <Standard_Version.hxx>
 # include <ShapeAnalysis_Surface.hxx>
 # include <GeomAPI_IntSS.hxx>
+# include <GeomLib_IsPlanarSurface.hxx>
 #endif
 
 #include <Base/GeometryPyCXX.h>
@@ -456,6 +457,30 @@ PyObject* GeometrySurfacePy::curvature(PyObject *args)
     return 0;
 }
 
+PyObject* GeometrySurfacePy::isPlanar(PyObject *args)
+{
+    try {
+        Handle(Geom_Surface) surf = Handle(Geom_Surface)
+            ::DownCast(getGeometryPtr()->handle());
+        if (!surf.IsNull()) {
+            double tol = Precision::Confusion();
+            if (!PyArg_ParseTuple(args, "|d", &tol))
+                return 0;
+
+            GeomLib_IsPlanarSurface check(surf, tol);
+            Standard_Boolean val = check.IsPlanar();
+            return PyBool_FromLong(val ? 1 : 0);
+        }
+    }
+    catch (Standard_Failure& e) {
+        PyErr_SetString(PartExceptionOCCError, e.GetMessageString());
+        return 0;
+    }
+
+    PyErr_SetString(PartExceptionOCCError, "Geometry is not a surface");
+    return 0;
+}
+
 PyObject* GeometrySurfacePy::parameter(PyObject *args)
 {
     Handle(Geom_Surface) surf = Handle(Geom_Surface)