Merge pull request #1610 from strk/2.1.x-whole-centroid

Fix "whole" multi centroid computation (#1606)

include/mapnik/geom_util.hpp

@@ -340,12 +340,10 @@ bool centroid_geoms(Iter start, Iter end, double & x, double & y)
   double start_x = x0;
   double start_y = y0;
 
-  bool empty = true;
-
   double atmp = 0.0;
   double xtmp = 0.0;
   double ytmp = 0.0;
-  unsigned count = 1;
+  unsigned count = 0;
 
   while (start!=end)
   {
@@ -353,7 +351,11 @@ bool centroid_geoms(Iter start, Iter end, double & x, double & y)
     path.rewind(0);
     unsigned command = path.vertex(&x0, &y0);
     if (command == SEG_END) continue;
-    empty = false;
+
+    if ( ! count++ ) {
+      start_x = x0;
+      start_y = y0;
+    }
 
     while (SEG_END != (command = path.vertex(&x1, &y1)))
     {
@@ -369,9 +371,10 @@ bool centroid_geoms(Iter start, Iter end, double & x, double & y)
         y0 = y1;
         ++count;
     }
+
   }
 
-  if ( empty ) return false;
+  if (count == 0) return false;
 
   if (count <= 2) {
       x = (start_x + x0) * 0.5;

tests/visual_tests/styles/whole-centroid.xml

@@ -0,0 +1,21 @@
+<Map maximum-extent="736908, 4390316, 2060771, 5942346">
+<Style name="whole">
+  <Rule>
+    <MarkersSymbolizer placement="point" multi-policy="whole" fill="yellow" width="20" allow-overlap="true"/>
+  </Rule>
+</Style>
+<Style name="boundary">
+  <Rule>
+    <LineSymbolizer />
+  </Rule>
+</Style>
+<Layer name="multi">
+    <StyleName>boundary</StyleName>
+    <StyleName>whole</StyleName>
+    <Datasource>
+       <Parameter name="type">csv</Parameter>
+       <Parameter name="file">../data/whole-centroid.csv</Parameter>
+       <Parameter name="separator">|</Parameter>
+    </Datasource>
+  </Layer>
+</Map>

tests/visual_tests/test.py

@@ -28,6 +28,8 @@ files = [
     {'name': "lines-3", 'sizes': sizes_few_square},
     {'name': "lines-shield", 'sizes': sizes_few_square},
     {'name': "marker-multi-policy", 'sizes':[(600,400)]},
+    {'name': "whole-centroid", 'sizes':[(600,400)],
+        'bbox': mapnik.Box2d(736908, 4390316, 2060771, 5942346)},
     {'name': "simple-E"},
     {'name': "simple-NE"},
     {'name': "simple-NW"},