add minimum-path-length to text_symbolizer - closes #865

CHANGELOG

@@ -14,6 +14,8 @@ For a complete change history, see the SVN log.
 Mapnik Trunk
 ------------
 
+- Add minimum-path-length property to text_symbolizer to allow labels to be placed only on lines of a certain length (#865)
+
 - Add support for png quantization using fixed palettes (#843)
 
 - Add AlsoFilter functionality - http://trac.mapnik.org/wiki/AlsoFilter

bindings/python/mapnik_text_symbolizer.cpp

@@ -90,6 +90,7 @@ struct text_symbolizer_pickle_suite : boost::python::pickle_suite
         extras.append(t.get_justify_alignment());
         extras.append(t.get_text_opacity());
         extras.append(t.get_minimum_padding());
+        extras.append(t.get_minimum_path_length());
                 
         return boost::python::make_tuple(disp,t.get_label_placement(),
                t.get_vertical_alignment(),t.get_halo_radius(),t.get_halo_fill(),t.get_text_ratio(),
@@ -153,6 +154,7 @@ struct text_symbolizer_pickle_suite : boost::python::pickle_suite
         t.set_justify_alignment(extract<justify_alignment_e>(extras[6]));
         t.set_text_opacity(extract<double>(extras[7]));
         t.set_minimum_padding(extract<double>(extras[8]));
+        t.set_minimum_path_length(extract<double>(extras[9]));
     }
 };
 
@@ -276,6 +278,9 @@ void export_text_symbolizer()
         .add_property("minimum_padding",
                       &text_symbolizer::get_minimum_padding,
                       &text_symbolizer::set_minimum_padding)
+        .add_property("minimum_path_length",
+                      &text_symbolizer::get_minimum_path_length,
+                      &text_symbolizer::set_minimum_path_length)
         .add_property("name",&text_symbolizer::get_name,
                       &text_symbolizer::set_name)
         .add_property("opacity",

include/mapnik/placement_finder.hpp

@@ -70,6 +70,7 @@ struct placement : boost::noncopyable
     double max_char_angle_delta;
     double minimum_distance;
     double minimum_padding;
+    double minimum_path_length;
     bool avoid_edges;
     bool has_dimensions;
     bool allow_overlap;

include/mapnik/text_symbolizer.hpp

@@ -110,6 +110,8 @@ struct MAPNIK_DECL text_symbolizer : public symbolizer_base
     double get_minimum_distance() const;
     void set_minimum_padding(double distance);
     double get_minimum_padding() const;
+    void set_minimum_path_length(double size);
+    double get_minimum_path_length() const;
     void set_allow_overlap(bool overlap);
     bool get_allow_overlap() const;
     void set_text_opacity(double opacity);
@@ -146,6 +148,7 @@ private:
     bool avoid_edges_;
     double minimum_distance_;
     double minimum_padding_;
+    double minimum_path_length_;
     bool overlap_;
     double text_opacity_;
     bool wrap_before_;

src/load_map.cpp

@@ -1204,7 +1204,7 @@ void map_parser::parse_text_symbolizer( rule & rule, ptree const & sym )
       << "halo-radius,text-ratio,wrap-width,wrap-before,"
       << "wrap-character,text-transform,line-spacing,"
       << "label-position-tolerance,character-spacing,"
-      << "spacing,minimum-distance,minimum-padding,"
+      << "spacing,minimum-distance,minimum-padding,minimum-path-length,"
       << "avoid-edges,allow-overlap,opacity,max-char-angle-delta,"
       << "horizontal-alignment,justify-alignment,"
       << "placements,placement-type,"
@@ -1381,6 +1381,13 @@ void map_parser::parse_text_symbolizer( rule & rule, ptree const & sym )
             text_symbol.set_minimum_padding(*min_padding);
         }
         
+        // minimum path length
+        optional<unsigned> min_path_length = get_opt_attr<unsigned>(sym, "minimum-path-length");
+        if (min_path_length)
+        {
+            text_symbol.set_minimum_path_length(*min_path_length);
+        }
+
         // do not render labels around edges
         optional<boolean> avoid_edges =
             get_opt_attr<boolean>(sym, "avoid-edges");

src/placement_finder.cpp

@@ -66,6 +66,7 @@ placement::placement(string_info & info_,
       max_char_angle_delta(sym.get_max_char_angle_delta()),
       minimum_distance(scale_factor_ * sym.get_minimum_distance()),
       minimum_padding(scale_factor_ * sym.get_minimum_padding()),
+      minimum_path_length(0),
       avoid_edges(sym.get_avoid_edges()),
       has_dimensions(has_dimensions_),
       allow_overlap(false),
@@ -90,6 +91,7 @@ placement::placement(string_info & info_,
       max_char_angle_delta(sym.get_max_char_angle_delta()),
       minimum_distance(scale_factor_ * sym.get_minimum_distance()),
       minimum_padding(scale_factor_ * sym.get_minimum_padding()),
+      minimum_path_length(scale_factor_ * sym.get_minimum_path_length()),
       avoid_edges(sym.get_avoid_edges()),
       has_dimensions(false),
       allow_overlap(sym.get_allow_overlap()),
@@ -517,6 +519,10 @@ void placement_finder<DetectorT>::find_line_placements(placement & p, text_place
     //Now path_positions is full and total_distance is correct
     //shape_path shouldn't be used from here
 
+    // Ensure lines have a minimum length.
+    if (total_distance < p.minimum_path_length)
+        return;
+
     double distance = 0.0;
     std::pair<double, double> string_dimensions = p.info.get_dimensions();
 

src/save_map.cpp

@@ -532,6 +532,10 @@ private:
         {
             set_attr( node, "minimum-padding", sym.get_minimum_padding() );
         }
+        if (sym.get_minimum_path_length() != dfl.get_minimum_path_length() || explicit_defaults_ )
+        {
+            set_attr( node, "minimum-path-length", sym.get_minimum_path_length() );
+        }
         if (sym.get_allow_overlap() != dfl.get_allow_overlap() || explicit_defaults_ )
         {
             set_attr( node, "allow-overlap", sym.get_allow_overlap() );

src/text_symbolizer.cpp

@@ -111,6 +111,7 @@ text_symbolizer::text_symbolizer(expression_ptr name, std::string const& face_na
       avoid_edges_(false),
       minimum_distance_(0.0),
       minimum_padding_(0.0),
+      minimum_path_length_(0.0),
       overlap_(false),
       text_opacity_(1.0),
       wrap_before_(false),
@@ -143,6 +144,7 @@ text_symbolizer::text_symbolizer(expression_ptr name, unsigned size, color const
       avoid_edges_(false),
       minimum_distance_(0.0),
       minimum_padding_(0.0),
+      minimum_path_length_(0.0),
       overlap_(false),
       text_opacity_(1.0),
       wrap_before_(false),
@@ -175,6 +177,7 @@ text_symbolizer::text_symbolizer(text_symbolizer const& rhs)
       avoid_edges_(rhs.avoid_edges_),
       minimum_distance_(rhs.minimum_distance_),
       minimum_padding_(rhs.minimum_padding_),
+      minimum_path_length_(rhs.minimum_path_length_),
       overlap_(rhs.overlap_),
       text_opacity_(rhs.text_opacity_),
       wrap_before_(rhs.wrap_before_),
@@ -206,6 +209,7 @@ text_symbolizer& text_symbolizer::operator=(text_symbolizer const& other)
     avoid_edges_ = other.avoid_edges_;
     minimum_distance_ = other.minimum_distance_;
     minimum_padding_ = other.minimum_padding_;
+    minimum_path_length_ = other.minimum_path_length_;
     overlap_ = other.overlap_;
     text_opacity_ = other.text_opacity_;
     wrap_before_ = other.wrap_before_;
@@ -473,7 +477,17 @@ void text_symbolizer::set_minimum_padding(double distance)
 {
     minimum_padding_ = distance;
 }
- 
+
+double text_symbolizer::get_minimum_path_length() const
+{
+    return minimum_path_length_;
+}
+
+void text_symbolizer::set_minimum_path_length(double size)
+{
+    minimum_path_length_ = size;
+}
+
 void text_symbolizer::set_allow_overlap(bool overlap)
 {
     overlap_ = overlap;