core: do not use JSON serialization for layer grouping key

Author: louwers

include/mbgl/style/filter.hpp

@@ -5,9 +5,6 @@
 #include <mbgl/util/geometry.hpp>
 #include <mbgl/style/expression/expression.hpp>
 
-#include <string>
-#include <vector>
-#include <tuple>
 #include <optional>
 
 namespace mbgl {

src/mbgl/plugin/plugin_layer.cpp

@@ -34,8 +34,6 @@ std::unique_ptr<Layer> PluginLayer::cloneRef(const std::string& id_) const {
     return std::make_unique<PluginLayer>(std::move(impl_));
 }
 
-void PluginLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const {}
-
 Value PluginLayer::serialize() const {
     auto result = Layer::serialize();
     return result;

src/mbgl/plugin/plugin_layer_impl.hpp

@@ -87,7 +87,6 @@ class PluginLayer::Impl : public Layer::Impl {
     using Layer::Impl::Impl;
 
     bool hasLayoutDifference(const Layer::Impl&) const override;
-    void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override;
 
     const LayerTypeInfo* getTypeInfo() const noexcept final { return &_layerTypeInfo; }
 

src/mbgl/renderer/group_by_layout.cpp

@@ -1,32 +1,46 @@
 #include <mbgl/renderer/group_by_layout.hpp>
-#include <mbgl/style/conversion/stringify.hpp>
-#include <mbgl/util/rapidjson.hpp>
+#include <mbgl/util/instrumentation.hpp>
+#include <mbgl/util/containers.hpp>
+#include <mbgl/style/layer_properties.hpp>
 
-#include <rapidjson/writer.h>
-#include <rapidjson/stringbuffer.h>
-
-#include <unordered_map>
+#include <string>
 
 namespace mbgl {
 
-std::string layoutKey(const style::Layer::Impl& impl) {
+std::string createLayoutKey(const style::Layer::Impl& impl) {
     using namespace style::conversion;
+    std::string key;
+    key += std::to_string(reinterpret_cast<uint64_t>(impl.getTypeInfo()));
+    key += impl.source;
+    key += impl.sourceLayer;
+    key += std::to_string(impl.maxZoom);
+    key += std::to_string(impl.minZoom);
+    key += std::to_string(static_cast<uint32_t>(impl.visibility));
+    return key;
+}
 
-    rapidjson::StringBuffer s;
-    rapidjson::Writer<rapidjson::StringBuffer> writer(s);
-
-    writer.StartArray();
-    writer.Uint64(reinterpret_cast<uint64_t>(impl.getTypeInfo()));
-    writer.String(impl.source);
-    writer.String(impl.sourceLayer);
-    writer.Double(impl.minZoom);
-    writer.Double(impl.maxZoom);
-    writer.Uint(static_cast<uint32_t>(impl.visibility));
-    stringify(writer, impl.filter);
-    impl.stringifyLayout(writer);
-    writer.EndArray();
-
-    return s.GetString();
+GroupMap groupLayers(const std::vector<Immutable<style::LayerProperties>>& layers) {
+    MLN_TRACE_FUNC();
+
+    mbgl::unordered_map<std::string, std::vector<Immutable<style::LayerProperties>>> groupMap;
+    groupMap.reserve(layers.size());
+
+    for (auto layer : layers) {
+        // this part of the key is unique per filter
+        auto layoutFilterKey = 0;
+        while (true) {
+            auto layoutKey = createLayoutKey(*layer->baseImpl) + std::to_string(layoutFilterKey);
+            if (groupMap.contains(layoutKey)) {
+                if (groupMap[layoutKey].front()->baseImpl->filter != layer->baseImpl->filter) {
+                    ++layoutFilterKey;
+                    continue;
+                }
+            }
+            groupMap[layoutKey].push_back(std::move(layer));
+            break;
+        }
+    }
+    return groupMap;
 }
 
 } // namespace mbgl

src/mbgl/renderer/group_by_layout.hpp

@@ -1,12 +1,15 @@
 #pragma once
 
 #include <mbgl/style/layer_impl.hpp>
+#include <mbgl/util/containers.hpp>
+#include <mbgl/style/layer_properties.hpp>
 
 #include <vector>
-#include <memory>
 
 namespace mbgl {
 
-std::string layoutKey(const style::Layer::Impl& impl);
+using GroupMap = mbgl::unordered_map<std::string, std::vector<Immutable<style::LayerProperties>>>;
+
+GroupMap groupLayers(const std::vector<Immutable<style::LayerProperties>> &);
 
 } // namespace mbgl

src/mbgl/renderer/sources/render_tile_source.cpp

@@ -49,7 +49,6 @@ class PolylineLayerImpl : public Layer::Impl {
     PolylineLayerImpl()
         : Layer::Impl("", "") {}
     bool hasLayoutDifference(const Layer::Impl&) const override { return false; }
-    void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override {}
 
     const LayerTypeInfo* getTypeInfo() const noexcept final { return staticTypeInfo(); }
     static const LayerTypeInfo* staticTypeInfo() noexcept {

src/mbgl/style/layer_impl.hpp

@@ -39,9 +39,6 @@ class Layer::Impl {
     // filter, visibility, layout properties, or data-driven paint properties.
     virtual bool hasLayoutDifference(const Layer::Impl&) const = 0;
 
-    // Utility function for automatic layer grouping.
-    virtual void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const = 0;
-
     // Returns pointer to the statically allocated layer type info structure.
     virtual const LayerTypeInfo* getTypeInfo() const noexcept = 0;
 

src/mbgl/style/layers/background_layer.cpp

@@ -58,9 +58,6 @@ std::unique_ptr<Layer> BackgroundLayer::cloneRef(const std::string& id_) const {
     return std::make_unique<BackgroundLayer>(std::move(impl_));
 }
 
-void BackgroundLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const {
-}
-
 // Layout properties
 
 

src/mbgl/style/layers/background_layer_impl.hpp

@@ -29,7 +29,6 @@ class BackgroundLayer::Impl : public Layer::Impl {
     Impl(const Impl&);
 
     bool hasLayoutDifference(const Layer::Impl&) const override;
-    void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override;
 
 public:
     BackgroundPaintProperties::Transitionable paint;

src/mbgl/style/layers/circle_layer.cpp

@@ -58,10 +58,6 @@ std::unique_ptr<Layer> CircleLayer::cloneRef(const std::string& id_) const {
     return std::make_unique<CircleLayer>(std::move(impl_));
 }
 
-void CircleLayer::Impl::stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>& writer) const {
-    layout.stringify(writer);
-}
-
 // Layout properties
 
 PropertyValue<float> CircleLayer::getDefaultCircleSortKey() {