Implement find_points_on_line().

include/mapnik/path_processor.hpp

@@ -0,0 +1,61 @@
+#ifndef MAPNIK_PATH_PROCESSOR_HPP
+#define MAPNIK_PATH_PROCESSOR_HPP
+
+//mapnik
+#include "pixel_position.hpp"
+
+// agg
+#include "agg_path_length.h"
+namespace mapnik
+{
+template <typename T>
+class path_processor
+{
+public:
+    path_processor(T &path)
+        : path_(path), length_(agg::path_length(path_)), valid_(true)
+    {
+        rewind();
+    }
+
+    double length() const { return length_ ;}
+
+    bool next()
+    {
+        if (!valid_) return false;
+        valid_ = path_.vertex(&current_point_.x, &current_point_.y);
+        return valid_;
+    }
+
+    pixel_position const& current_point() const
+    {
+        return current_point_;
+    }
+
+    void rewind()
+    {
+        path_.rewind(0);
+        valid_ = true;
+    }
+
+    bool valid() const { return valid_; }
+
+    /** Skip a certain amount of space.
+     *
+     * This function automatically calculates new points if the position is not exactly
+     * on a point on the path.
+     */
+    bool skip(double length)
+    {
+        //TODO
+        return valid_;
+    }
+
+private:
+    T &path_;
+    double length_;
+    bool valid_;
+    pixel_position current_point_;
+};
+}
+#endif // PATH_PROCESSOR_HPP

include/mapnik/text/placement_finder_ng.hpp

@@ -32,6 +32,7 @@
 
 //stl
 #include <vector>
+#include <list>
 
 //boost
 #include <boost/utility.hpp>
@@ -85,7 +86,8 @@ private:
 };
 typedef boost::shared_ptr<glyph_positions> glyph_positions_ptr;
 
-struct text_symbolizer_properties;
+typedef std::list<glyph_positions_ptr> placements_list;
+typedef boost::shared_ptr<placements_list> placements_list_ptr;
 
 class placement_finder_ng : boost::noncopyable
 {
@@ -101,10 +103,10 @@ public:
     glyph_positions_ptr find_point_placement(pixel_position pos);
     /** Iterate over the given path, placing line-following labels with respect to label_spacing. */
     template <typename T>
-    glyph_positions_ptr find_line_placements(T & path);
+    placements_list_ptr find_line_placements(T & path);
     /** Iterate over the given path, placing point labels with respect to label_spacing. */
     template <typename T>
-    glyph_positions_ptr find_point_on_line_placements(T & path);
+    placements_list_ptr find_point_on_line_placements(T & path);
     /** Try next position alternative from placement_info. */
     bool next_position();
 private:

src/text/placement_finder_ng.cpp

@@ -26,6 +26,7 @@
 #include <mapnik/debug.hpp>
 #include <mapnik/label_collision_detector.hpp>
 #include <mapnik/ctrans.hpp>
+#include <mapnik/path_processor.hpp>
 
 //boost
 #include <boost/make_shared.hpp>
@@ -222,15 +223,39 @@ glyph_positions_ptr placement_finder_ng::find_point_placement(pixel_position pos
 
 
 template <typename T>
-glyph_positions_ptr placement_finder_ng::find_point_on_line_placements(T & path)
+placements_list_ptr placement_finder_ng::find_point_on_line_placements(T & path)
 {
-    return glyph_positions_ptr();
+    path_processor<T> pp(path);
+    placements_list_ptr list = boost::make_shared<placements_list>();
+    if (!pp.valid() || !layout_.size()) return list;
+    if (pp.length() == 0.0)
+    {
+        list->push_back(find_point_placement(pp.current_point()));
+        return list;
+    }
+
+    int num_labels = 1;
+    if (info_->properties.label_spacing > 0)
+        num_labels = static_cast<int> (floor(pp.length() / info_->properties.label_spacing * scale_factor_));
+
+    if (info_->properties.force_odd_labels && num_labels % 2 == 0)
+        num_labels--;
+    if (num_labels <= 0)
+        num_labels = 1;
+
+    double spacing = pp.length() / num_labels;
+    pp.skip(spacing/2.); // first label should be placed at half the spacing
+    do
+    {
+        list->push_back(find_point_placement(pp.current_point()));
+    } while (pp.skip(spacing));
+    return list;
 }
 
 template <typename T>
-glyph_positions_ptr placement_finder_ng::find_line_placements(T & path)
+placements_list_ptr placement_finder_ng::find_line_placements(T & path)
 {
-    return glyph_positions_ptr();
+    return placements_list_ptr();
 }
 
 
@@ -291,10 +316,10 @@ void glyph_positions::set_base_point(pixel_position base_point)
 typedef agg::conv_clip_polyline<geometry_type> clipped_geometry_type;
 typedef coord_transform<CoordTransform,clipped_geometry_type> ClippedPathType;
 typedef coord_transform<CoordTransform,geometry_type> PathType;
-template glyph_positions_ptr placement_finder_ng::find_point_on_line_placements<ClippedPathType>(ClippedPathType &);
-template glyph_positions_ptr placement_finder_ng::find_line_placements<ClippedPathType>(ClippedPathType &);
-template glyph_positions_ptr placement_finder_ng::find_point_on_line_placements<PathType>(PathType &);
-template glyph_positions_ptr placement_finder_ng::find_line_placements<PathType>(PathType &);
+template placements_list_ptr placement_finder_ng::find_point_on_line_placements<ClippedPathType>(ClippedPathType &);
+template placements_list_ptr placement_finder_ng::find_line_placements<ClippedPathType>(ClippedPathType &);
+template placements_list_ptr placement_finder_ng::find_point_on_line_placements<PathType>(PathType &);
+template placements_list_ptr placement_finder_ng::find_line_placements<PathType>(PathType &);
 
 
 }// ns mapnik