add polylabel placement method

.gitmodules

@@ -18,3 +18,6 @@
 	path = deps/mapbox/protozero
 	url = https://github.com/mapbox/protozero.git
         branch = master
+[submodule "deps/mapbox/polylabel"]
+	path = deps/mapbox/polylabel
+	url = https://github.com/mapbox/polylabel.git

SConstruct

@@ -1756,6 +1756,7 @@ if not preconfigured:
     env.Prepend(CPPPATH = '#deps/mapbox/variant/include')
     env.Prepend(CPPPATH = '#deps/mapbox/geometry/include')
     env.Prepend(CPPPATH = '#deps/mapbox/protozero/include')
+    env.Prepend(CPPPATH = '#deps/mapbox/polylabel/include')
     # prepend deps dir for auxillary headers
     env.Prepend(CPPPATH = '#deps')
 

deps/mapbox/polylabel

@@ -0,0 +1 @@
+Subproject commit 51f09d04c21e7b7faf94e2300ca1fe6e1f12fa7f

include/mapnik/geometry/polygon_vertex_processor.hpp

@@ -0,0 +1,62 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2017 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_GEOMETRY_POLYGON_VERTEX_PROCESSOR_HPP
+#define MAPNIK_GEOMETRY_POLYGON_VERTEX_PROCESSOR_HPP
+
+// geometry
+#include <mapnik/geometry/polygon.hpp>
+
+namespace mapnik { namespace geometry {
+
+template <typename T>
+struct polygon_vertex_processor
+{
+    template <typename Path>
+    void add_path(Path & path)
+    {
+        point<T> p;
+        unsigned cmd;
+        linear_ring<T> ring;
+        while ((cmd = path.vertex(&p.x, &p.y)) != SEG_END)
+        {
+            switch (cmd)
+            {
+                case SEG_MOVETO:
+                case SEG_LINETO:
+                    ring.emplace_back(p);
+                    break;
+                case SEG_CLOSE:
+                    ring.emplace_back(ring.front());
+                    polygon_.emplace_back(std::move(ring));
+                    ring = linear_ring<T>();
+                    break;
+            }
+        }
+    }
+
+    polygon<T> polygon_;
+};
+
+} }
+
+#endif // MAPNIK_GEOMETRY_POLYGON_VERTEX_PROCESSOR_HPP

include/mapnik/geometry/polylabel.hpp

@@ -0,0 +1,39 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2017 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_GEOMETRY_POLYLABEL_HPP
+#define MAPNIK_GEOMETRY_POLYLABEL_HPP
+
+#include <mapnik/geometry/polygon.hpp>
+#include <mapnik/geometry/point.hpp>
+
+namespace mapnik { namespace geometry {
+
+template <class T>
+point<T> polylabel(polygon<T> const& polygon, T precision);
+
+template <class T>
+T polylabel_precision(polygon<T> const& polygon, double scale_factor);
+
+} }
+
+#endif // MAPNIK_GEOMETRY_POLYLABEL_HPP

include/mapnik/markers_placement.hpp

@@ -28,6 +28,7 @@
 #include <mapnik/markers_placements/interior.hpp>
 #include <mapnik/markers_placements/vertex_first.hpp>
 #include <mapnik/markers_placements/vertex_last.hpp>
+#include <mapnik/markers_placements/polylabel.hpp>
 #include <mapnik/symbolizer_enumerations.hpp>
 
 namespace mapnik
@@ -65,6 +66,9 @@ public:
         case MARKER_VERTEX_LAST_PLACEMENT:
             construct(&vertex_last_, locator, detector, params);
             break;
+        case MARKER_POLYLABEL_PLACEMENT:
+            construct(&polylabel_, locator, detector, params);
+            break;
         }
     }
 
@@ -89,6 +93,9 @@ public:
         case MARKER_VERTEX_LAST_PLACEMENT:
             destroy(&vertex_last_);
             break;
+        case MARKER_POLYLABEL_PLACEMENT:
+            destroy(&polylabel_);
+            break;
         }
     }
 
@@ -109,6 +116,8 @@ public:
             return vertex_first_.get_point(x, y, angle, ignore_placement);
         case MARKER_VERTEX_LAST_PLACEMENT:
             return vertex_last_.get_point(x, y, angle, ignore_placement);
+        case MARKER_POLYLABEL_PLACEMENT:
+            return polylabel_.get_point(x, y, angle, ignore_placement);
         }
     }
 
@@ -122,6 +131,7 @@ private:
         markers_interior_placement<Locator, Detector> interior_;
         markers_vertex_first_placement<Locator, Detector> vertex_first_;
         markers_vertex_last_placement<Locator, Detector> vertex_last_;
+        markers_polylabel_placement<Locator, Detector> polylabel_;
     };
 
     template <typename T>

include/mapnik/markers_placements/basic.hpp

@@ -46,6 +46,7 @@ struct markers_placement_params
     bool allow_overlap;
     bool avoid_edges;
     direction_enum direction;
+    double scale_factor;
 };
 
 class markers_basic_placement : util::noncopyable

include/mapnik/markers_placements/polylabel.hpp

@@ -0,0 +1,77 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2017 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_MARKERS_PLACEMENTS_POLYLABEL_HPP
+#define MAPNIK_MARKERS_PLACEMENTS_POLYLABEL_HPP
+
+#include <mapnik/markers_placements/point.hpp>
+#include <mapnik/geom_util.hpp>
+#include <mapnik/geometry/geometry_types.hpp>
+#include <mapnik/geometry/polygon_vertex_processor.hpp>
+
+#include <mapnik/geometry/point.hpp>
+#include <mapnik/geometry/polylabel.hpp>
+
+namespace mapnik {
+
+template <typename Locator, typename Detector>
+class markers_polylabel_placement : public markers_point_placement<Locator, Detector>
+{
+public:
+    using point_placement = markers_point_placement<Locator, Detector>;
+    using point_placement::point_placement;
+
+    bool get_point(double &x, double &y, double &angle, bool ignore_placement)
+    {
+        if (this->done_)
+        {
+            return false;
+        }
+
+        if (this->locator_.type() != geometry::geometry_types::Polygon)
+        {
+            return point_placement::get_point(x, y, angle, ignore_placement);
+        }
+
+        geometry::polygon_vertex_processor<double> vertex_processor;
+        vertex_processor.add_path(this->locator_);
+        double precision = geometry::polylabel_precision(vertex_processor.polygon_,
+                                                         this->params_.scale_factor);
+        geometry::point<double> placement = geometry::polylabel(vertex_processor.polygon_, precision);
+
+        x = placement.x;
+        y = placement.y;
+        angle = 0;
+
+        if (!this->push_to_detector(x, y, angle, ignore_placement))
+        {
+            return false;
+        }
+
+        this->done_ = true;
+        return true;
+    }
+};
+
+}
+
+#endif // MAPNIK_MARKERS_PLACEMENTS_POLYLABEL_HPP

include/mapnik/symbolizer_enumerations.hpp

@@ -106,6 +106,7 @@ enum marker_placement_enum : std::uint8_t
     MARKER_VERTEX_FIRST_PLACEMENT,
     MARKER_VERTEX_LAST_PLACEMENT,
     MARKER_ANGLED_POINT_PLACEMENT,
+    MARKER_POLYLABEL_PLACEMENT,
     marker_placement_enum_MAX
 };
 
@@ -139,6 +140,7 @@ enum label_placement_enum : std::uint8_t
     LINE_PLACEMENT,
     VERTEX_PLACEMENT,
     INTERIOR_PLACEMENT,
+    POLYLABEL_PLACEMENT,
     label_placement_enum_MAX
 };
 

src/build.py

@@ -173,6 +173,7 @@ source = Split(
     geometry/closest_point.cpp
     geometry/reprojection.cpp
     geometry/envelope.cpp
+    geometry/polylabel.cpp
     expression_node.cpp
     expression_string.cpp
     expression.cpp

src/geometry/polylabel.cpp

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2017 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#include <mapnik/geometry/polylabel.hpp>
+#include <mapnik/geometry/envelope.hpp>
+#include <mapbox/polylabel.hpp>
+
+namespace mapnik { namespace geometry {
+
+template <class T>
+T polylabel_precision(polygon<T> const& polygon, double scale_factor)
+{
+    // This precision has been chosen to work well in the map (viewport) coordinates.
+    return 10.0 * scale_factor;
+}
+
+template <class T>
+point<T> polylabel(polygon<T> const& polygon, T precision)
+{
+    return mapbox::polylabel(polygon, precision);
+}
+
+template
+point<double> polylabel(polygon<double> const& polygon, double precision);
+
+template
+double polylabel_precision(polygon<double> const& polygon, double scale_factor);
+
+} }
+

src/marker_helpers.cpp

@@ -250,7 +250,7 @@ void apply_markers_multi(feature_impl const& feature, attributes const& vars,
                 converter.apply(va, proc);
             }
         }
-        else if ((placement == MARKER_POINT_PLACEMENT || placement == MARKER_INTERIOR_PLACEMENT) &&
+        else if ((placement == MARKER_POINT_PLACEMENT || placement == MARKER_INTERIOR_PLACEMENT || placement == MARKER_POLYLABEL_PLACEMENT) &&
                  multi_policy == MARKER_LARGEST_MULTI)
         {
             // Only apply to path with largest envelope area

src/symbolizer_enumerations.cpp

@@ -68,6 +68,7 @@ static const char * marker_placement_strings[] = {
     "vertex-first",
     "vertex-last",
     "angled-point",
+    "polylabel",
     ""
 };
 
@@ -117,6 +118,7 @@ static const char * label_placement_strings[] = {
     "line",
     "vertex",
     "interior",
+    "polylabel",
     ""
 };
 

src/text/symbolizer_helpers.cpp

@@ -31,6 +31,7 @@
 #include <mapnik/geometry.hpp>
 #include <mapnik/geometry/geometry_type.hpp>
 #include <mapnik/geometry/centroid.hpp>
+#include <mapnik/geometry/polylabel.hpp>
 #include <mapnik/vertex_processor.hpp>
 #include <mapnik/geom_util.hpp>
 #include <mapnik/parse_path.hpp>
@@ -307,6 +308,12 @@ void base_symbolizer_helper::initialize_points() const
                         points_.emplace_back(label_x, label_y);
                     }
                 }
+                else if (how_placed == POLYLABEL_PLACEMENT)
+                {
+                    double precision = geometry::polylabel_precision(tranformed_poly, scale_factor_);
+                    geometry::point<double> pt = geometry::polylabel(tranformed_poly, precision);
+                    points_.emplace_back(pt.x, pt.y);
+                }
                 continue;
             }
             else