improve interplay of maximum-extent and map.zoom_all, now properly clipping to maximum-extent - closes #1473

CHANGELOG.md

@@ -6,6 +6,11 @@ Developers: Please commit along with changes.
 
 For a complete change history, see the git log.
 
+## Future
+
+- Fixed zoom_all behavior when Map maximum-extent is provided. Previously maximum-extent was used outright but
+  now the combined layer extents will be again respected: they will be clipped to the maximum-extent if possible
+  and only when back-projecting fails for all layers will the maximum-extent be used as a fallback (#1473)
 
 ## Mapnik 2.1.0
 

src/map.cpp

@@ -340,54 +340,59 @@ void Map::zoom(double factor)
 
 void Map::zoom_all()
 {
-    if (maximum_extent_) {
+    try
-        zoom_to_box(*maximum_extent_);
-    }
-    else
     {
-        try
+        if (!layers_.size() > 0)
+            return;
+        projection proj0(srs_);
+        box2d<double> ext;
+        bool success = false;
+        bool first = true;
+        std::vector<layer>::const_iterator itr = layers_.begin();
+        std::vector<layer>::const_iterator end = layers_.end();
+        while (itr != end)
         {
-            if (!layers_.size() > 0)
+            if (itr->active())
-                return;
-            projection proj0(srs_);
-            box2d<double> ext;
-            bool success = false;
-            bool first = true;
-            std::vector<layer>::const_iterator itr = layers_.begin();
-            std::vector<layer>::const_iterator end = layers_.end();
-            while (itr != end)
             {
-                if (itr->active())
+                std::string const& layer_srs = itr->srs();
+                projection proj1(layer_srs);
+                proj_transform prj_trans(proj0,proj1);
+                box2d<double> layer_ext = itr->envelope();
+                if (prj_trans.backward(layer_ext, PROJ_ENVELOPE_POINTS))
                 {
-                    std::string const& layer_srs = itr->srs();
+                    success = true;
-                    projection proj1(layer_srs);
+                    MAPNIK_LOG_DEBUG(map) << "map: Layer " << itr->name() << " original ext=" << itr->envelope();
-
+                    MAPNIK_LOG_DEBUG(map) << "map: Layer " << itr->name() << " transformed to map srs=" << layer_ext;
-                    proj_transform prj_trans(proj0,proj1);
+                    if (first)
-
-                    box2d<double> layer_ext = itr->envelope();
-                    if (prj_trans.backward(layer_ext, PROJ_ENVELOPE_POINTS))
                     {
-                        success = true;
+                        ext = layer_ext;
-
+                        first = false;
-                        MAPNIK_LOG_DEBUG(map) << "map: Layer " << itr->name() << " original ext=" << itr->envelope();
+                    }
-                        MAPNIK_LOG_DEBUG(map) << "map: Layer " << itr->name() << " transformed to map srs=" << layer_ext;
+                    else
-
+                    {
-                        if (first)
+                        ext.expand_to_include(layer_ext);
-                        {
-                            ext = layer_ext;
-                            first = false;
-                        }
-                        else
-                        {
-                            ext.expand_to_include(layer_ext);
-                        }
                     }
                 }
-                ++itr;
             }
-            if (success) {
+            ++itr;
-                zoom_to_box(ext);
+        }
-            } else {
+        if (success)
+        {
+            if (maximum_extent_) {
+                ext.clip(*maximum_extent_);
+            }
+            zoom_to_box(ext);
+        }
+        else
+        {
+            if (maximum_extent_)
+            {
+                MAPNIK_LOG_ERROR(map) << "could not zoom to combined layer extents"
+                    << " so falling back to maximum-extent for zoom_all result";
+                zoom_to_box(*maximum_extent_);
+            }
+            else
+            {
                 std::ostringstream s;
                 s << "could not zoom to combined layer extents "
                   << "using zoom_all because proj4 could not "
@@ -396,10 +401,10 @@ void Map::zoom_all()
                 throw std::runtime_error(s.str());
             }
         }
-        catch (proj_init_error & ex)
+    }
-        {
+    catch (proj_init_error & ex)
-            throw mapnik::config_error(std::string("Projection error during map.zoom_all: ") + ex.what());
+    {
-        }
+        throw mapnik::config_error(std::string("Projection error during map.zoom_all: ") + ex.what());
     }
 }
 
@@ -544,7 +549,8 @@ featureset_ptr Map::query_point(unsigned index, double x, double y) const
             if (fs)
             {
                 mapnik::box2d<double> map_ex = current_extent_;
-                if (maximum_extent_) {
+                if (maximum_extent_)
+                {
                     map_ex.clip(*maximum_extent_);
                 }
                 if (!prj_trans.backward(map_ex,PROJ_ENVELOPE_POINTS))