[core] More efficient layer cloning

src/mbgl/layer/background_layer.cpp

@@ -4,10 +4,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> BackgroundLayer::clone() const {
-    std::unique_ptr<BackgroundLayer> result = std::make_unique<BackgroundLayer>();
-    result->copy(*this);
-    result->paint = paint;
-    return std::move(result);
+    return std::make_unique<BackgroundLayer>(*this);
 }
 
 void BackgroundLayer::parsePaints(const JSVal& layer) {

src/mbgl/layer/circle_layer.cpp

@@ -5,10 +5,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> CircleLayer::clone() const {
-    std::unique_ptr<CircleLayer> result = std::make_unique<CircleLayer>();
-    result->copy(*this);
-    result->paint = paint;
-    return std::move(result);
+    return std::make_unique<CircleLayer>(*this);
 }
 
 void CircleLayer::parsePaints(const JSVal& layer) {

src/mbgl/layer/fill_layer.cpp

@@ -5,10 +5,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> FillLayer::clone() const {
-    std::unique_ptr<FillLayer> result = std::make_unique<FillLayer>();
-    result->copy(*this);
-    result->paint = paint;
-    return std::move(result);
+    return std::make_unique<FillLayer>(*this);
 }
 
 void FillLayer::parsePaints(const JSVal& layer) {

src/mbgl/layer/line_layer.cpp

@@ -6,11 +6,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> LineLayer::clone() const {
-    std::unique_ptr<LineLayer> result = std::make_unique<LineLayer>();
-    result->copy(*this);
-    result->layout = layout;
-    result->paint = paint;
-    return std::move(result);
+    return std::make_unique<LineLayer>(*this);
 }
 
 void LineLayer::parseLayout(const JSVal& value) {

src/mbgl/layer/raster_layer.cpp

@@ -4,10 +4,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> RasterLayer::clone() const {
-    std::unique_ptr<RasterLayer> result = std::make_unique<RasterLayer>();
-    result->copy(*this);
-    result->paint = paint;
-    return std::move(result);
+    return std::make_unique<RasterLayer>(*this);
 }
 
 void RasterLayer::parsePaints(const JSVal& layer) {

src/mbgl/layer/symbol_layer.cpp

@@ -6,12 +6,7 @@
 namespace mbgl {
 
 std::unique_ptr<StyleLayer> SymbolLayer::clone() const {
-    std::unique_ptr<SymbolLayer> result = std::make_unique<SymbolLayer>();
-    result->copy(*this);
-    result->layout = layout;
-    result->paint = paint;
-    result->spriteAtlas = spriteAtlas;
-    return std::move(result);
+    return std::make_unique<SymbolLayer>(*this);
 }
 
 void SymbolLayer::parseLayout(const JSVal& value) {

src/mbgl/style/paint_property.hpp

@@ -8,6 +8,7 @@
 #include <mbgl/style/style_cascade_parameters.hpp>
 #include <mbgl/style/style_calculation_parameters.hpp>
 #include <mbgl/util/interpolate.hpp>
+#include <mbgl/util/std.hpp>
 
 #include <rapidjson/document.h>
 
@@ -23,9 +24,8 @@ class PaintProperty {
 public:
     using Fn = Function<Result>;
 
-    PaintProperty(T fallbackValue_)
-        : fallbackValue(fallbackValue_),
-          value(fallbackValue_) {
+    PaintProperty(T fallbackValue)
+        : value(fallbackValue) {
         values.emplace(ClassID::Fallback, Fn(fallbackValue));
     }
 
@@ -34,14 +34,8 @@ public:
           transitions(other.transitions) {
     }
 
-    void operator=(const PaintProperty& other) {
-        values = other.values;
-        transitions = other.transitions;
-    }
-
     void parse(const char* name, const JSVal& layer) {
-        values.clear();
-        values.emplace(ClassID::Fallback, Fn(fallbackValue));
+        mbgl::util::erase_if(values, [] (const auto& p) { return p.first != ClassID::Fallback; });
 
         std::string transitionName = { name };
         transitionName += "-transition";
@@ -104,9 +98,9 @@ public:
         return cascaded->prior.operator bool();
     }
 
+    void operator=(const T& v) { values.emplace(ClassID::Default, Fn(v)); }
     operator T() const { return value; }
 
-    T fallbackValue;
     std::map<ClassID, Fn> values;
     std::map<ClassID, PropertyTransition> transitions;
 

src/mbgl/style/style_layer.cpp

@@ -35,16 +35,4 @@ bool StyleLayer::hasRenderPass(RenderPass pass) const {
     return bool(passes & pass);
 }
 
-void StyleLayer::copy(const StyleLayer& src) {
-    id = src.id;
-    ref = src.ref;
-    type = src.type;
-    source = src.source;
-    sourceLayer = src.sourceLayer;
-    filter = src.filter;
-    minZoom = src.minZoom;
-    maxZoom = src.maxZoom;
-    visibility = src.visibility;
-}
-
 } // namespace mbgl

src/mbgl/style/style_layer.hpp

@@ -21,7 +21,7 @@ class Bucket;
 
 using JSVal = rapidjson::Value;
 
-class StyleLayer : public util::noncopyable {
+class StyleLayer {
 public:
     static std::unique_ptr<StyleLayer> create(StyleLayerType);
     virtual std::unique_ptr<StyleLayer> clone() const = 0;
@@ -58,11 +58,13 @@ public:
     VisibilityType visibility = VisibilityType::Visible;
 
 protected:
+    StyleLayer() = default;
+    StyleLayer(const StyleLayer&) = default;
+    StyleLayer& operator=(const StyleLayer&) = delete;
+
     // Stores what render passes this layer is currently enabled for. This depends on the
     // evaluated StyleProperties object and is updated accordingly.
     RenderPass passes = RenderPass::None;
-
-    void copy(const StyleLayer& source);
 };
 
 } // namespace mbgl

test/style/style_layer.cpp

@@ -0,0 +1,24 @@
+#include "../fixtures/util.hpp"
+
+#include <mbgl/style/style_layer.hpp>
+#include <mbgl/layer/background_layer.hpp>
+
+using namespace mbgl;
+
+TEST(StyleLayer, Create) {
+    std::unique_ptr<StyleLayer> layer = StyleLayer::create(StyleLayerType::Background);
+    EXPECT_TRUE(reinterpret_cast<BackgroundLayer*>(layer.get()));
+}
+
+TEST(StyleLayer, Clone) {
+    std::unique_ptr<StyleLayer> layer = StyleLayer::create(StyleLayerType::Background);
+    std::unique_ptr<StyleLayer> clone = layer->clone();
+    EXPECT_NE(layer.get(), clone.get());
+    EXPECT_TRUE(reinterpret_cast<BackgroundLayer*>(layer.get()));
+}
+
+TEST(StyleLayer, CloneCopiesBaseProperties) {
+    std::unique_ptr<BackgroundLayer> layer = std::make_unique<BackgroundLayer>();
+    layer->id = "test";
+    EXPECT_EQ("test", layer->clone()->id);
+}

test/test.gypi

@@ -91,6 +91,7 @@
         'style/glyph_store.cpp',
         'style/pending_resources.cpp',
         'style/resource_loading.cpp',
+        'style/style_layer.cpp',
 
         'sprite/sprite_atlas.cpp',
         'sprite/sprite_image.cpp',