[core] split off render layers

1 files changed, 48 insertions, 0 deletions

diff --git a/src/mbgl/renderer/group_by_layout.cpp b/src/mbgl/renderer/group_by_layout.cpp
new file mode 100644
index 0000000000..df1eb7c7dd
--- /dev/null
+++ b/src/mbgl/renderer/group_by_layout.cpp
@@ -0,0 +1,48 @@
+#include <mbgl/renderer/group_by_layout.hpp>
+#include <mbgl/renderer/render_layer.hpp>
+#include <mbgl/style/layer_impl.hpp>
+#include <mbgl/style/conversion/stringify.hpp>
+#include <mbgl/util/rapidjson.hpp>
+
+#include <rapidjson/writer.h>
+#include <rapidjson/stringbuffer.h>
+
+#include <unordered_map>
+
+namespace mbgl {
+
+std::string layoutKey(const RenderLayer& layer) {
+    using namespace style::conversion;
+
+    rapidjson::StringBuffer s;
+    rapidjson::Writer<rapidjson::StringBuffer> writer(s);
+
+    writer.StartArray();
+    writer.Uint(static_cast<uint32_t>(layer.type));
+    writer.String(layer.baseImpl.source);
+    writer.String(layer.baseImpl.sourceLayer);
+    writer.Double(layer.baseImpl.minZoom);
+    writer.Double(layer.baseImpl.maxZoom);
+    writer.Uint(static_cast<uint32_t>(layer.baseImpl.visibility));
+    stringify(writer, layer.baseImpl.filter);
+    layer.baseImpl.stringifyLayout(writer);
+    writer.EndArray();
+
+    return s.GetString();
+}
+
+std::vector<std::vector<const RenderLayer*>> groupByLayout(const std::vector<std::unique_ptr<RenderLayer>>& layers) {
+    std::unordered_map<std::string, std::vector<const RenderLayer*>> map;
+    for (auto& layer : layers) {
+        map[layoutKey(*layer)].push_back(layer.get());
+    }
+
+    std::vector<std::vector<const RenderLayer*>> result;
+    for (auto& pair : map) {
+        result.push_back(pair.second);
+    }
+
+    return result;
+}
+
+} // namespace mbgl