From 1520a56813f82bbe875774fdc2b3df26392278d6 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Fri, 21 Apr 2017 13:35:34 -0700
Subject: [all] Promote Style to public API

---
 src/mbgl/annotation/annotation_manager.cpp    |   7 +-
 src/mbgl/annotation/annotation_manager.hpp    |   7 +-
 src/mbgl/annotation/fill_annotation_impl.cpp  |   4 +-
 src/mbgl/annotation/fill_annotation_impl.hpp  |   2 +-
 src/mbgl/annotation/line_annotation_impl.cpp  |   4 +-
 src/mbgl/annotation/line_annotation_impl.hpp  |   2 +-
 src/mbgl/annotation/shape_annotation_impl.hpp |   7 +-
 src/mbgl/map/map.cpp                          | 157 +++----------
 src/mbgl/renderer/update_parameters.hpp       |   4 +
 src/mbgl/style/style.cpp                      | 307 +++++-------------------
 src/mbgl/style/style.hpp                      | 130 -----------
 src/mbgl/style/style_impl.cpp                 | 321 ++++++++++++++++++++++++++
 src/mbgl/style/style_impl.hpp                 | 136 +++++++++++
 13 files changed, 570 insertions(+), 518 deletions(-)
 delete mode 100644 src/mbgl/style/style.hpp
 create mode 100644 src/mbgl/style/style_impl.cpp
 create mode 100644 src/mbgl/style/style_impl.hpp

(limited to 'src/mbgl')

diff --git a/src/mbgl/annotation/annotation_manager.cpp b/src/mbgl/annotation/annotation_manager.cpp
index 58bda6052e..a69dba1bf2 100644
--- a/src/mbgl/annotation/annotation_manager.cpp
+++ b/src/mbgl/annotation/annotation_manager.cpp
@@ -4,7 +4,7 @@
 #include <mbgl/annotation/symbol_annotation_impl.hpp>
 #include <mbgl/annotation/line_annotation_impl.hpp>
 #include <mbgl/annotation/fill_annotation_impl.hpp>
-#include <mbgl/style/style.hpp>
+#include <mbgl/style/style_impl.hpp>
 #include <mbgl/style/layers/symbol_layer.hpp>
 #include <mbgl/style/layers/symbol_layer_impl.hpp>
 #include <mbgl/storage/file_source.hpp>
@@ -149,8 +149,9 @@ std::unique_ptr<AnnotationTileData> AnnotationManager::getTileData(const Canonic
     return tileData;
 }
 
-void AnnotationManager::updateStyle(Style& style) {
-    // Create annotation source, point layer, and point bucket
+void AnnotationManager::updateStyle(Style::Impl& style) {
+    // Create annotation source, point layer, and point bucket. We do everything via Style::Impl
+    // because we don't want annotation mutations to trigger Style::Impl::styleMutated to be set.
     if (!style.getSource(SourceID)) {
         style.addSource(std::make_unique<AnnotationSource>());
 
diff --git a/src/mbgl/annotation/annotation_manager.hpp b/src/mbgl/annotation/annotation_manager.hpp
index c2ed5ba89f..6906791db7 100644
--- a/src/mbgl/annotation/annotation_manager.hpp
+++ b/src/mbgl/annotation/annotation_manager.hpp
@@ -4,6 +4,7 @@
 #include <mbgl/annotation/symbol_annotation_impl.hpp>
 #include <mbgl/style/image.hpp>
 #include <mbgl/map/update.hpp>
+#include <mbgl/style/style.hpp>
 #include <mbgl/util/noncopyable.hpp>
 
 #include <mutex>
@@ -20,10 +21,6 @@ class AnnotationTileData;
 class SymbolAnnotationImpl;
 class ShapeAnnotationImpl;
 
-namespace style {
-class Style;
-} // namespace style
-
 class AnnotationManager : private util::noncopyable {
 public:
     AnnotationManager();
@@ -37,7 +34,7 @@ public:
     void removeImage(const std::string&);
     double getTopOffsetPixelsForImage(const std::string&);
 
-    void updateStyle(style::Style&);
+    void updateStyle(style::Style::Impl&);
     void updateData();
 
     void addTile(AnnotationTile&);
diff --git a/src/mbgl/annotation/fill_annotation_impl.cpp b/src/mbgl/annotation/fill_annotation_impl.cpp
index 484870c45c..5dc36edab0 100644
--- a/src/mbgl/annotation/fill_annotation_impl.cpp
+++ b/src/mbgl/annotation/fill_annotation_impl.cpp
@@ -1,6 +1,6 @@
 #include <mbgl/annotation/fill_annotation_impl.hpp>
 #include <mbgl/annotation/annotation_manager.hpp>
-#include <mbgl/style/style.hpp>
+#include <mbgl/style/style_impl.hpp>
 #include <mbgl/style/layers/fill_layer.hpp>
 
 namespace mbgl {
@@ -12,7 +12,7 @@ FillAnnotationImpl::FillAnnotationImpl(AnnotationID id_, FillAnnotation annotati
       annotation({ ShapeAnnotationGeometry::visit(annotation_.geometry, CloseShapeAnnotation{}), annotation_.opacity, annotation_.color, annotation_.outlineColor }) {
 }
 
-void FillAnnotationImpl::updateStyle(Style& style) const {
+void FillAnnotationImpl::updateStyle(Style::Impl& style) const {
     Layer* layer = style.getLayer(layerID);
 
     if (!layer) {
diff --git a/src/mbgl/annotation/fill_annotation_impl.hpp b/src/mbgl/annotation/fill_annotation_impl.hpp
index 6376eee880..5c49e447b8 100644
--- a/src/mbgl/annotation/fill_annotation_impl.hpp
+++ b/src/mbgl/annotation/fill_annotation_impl.hpp
@@ -9,7 +9,7 @@ class FillAnnotationImpl : public ShapeAnnotationImpl {
 public:
     FillAnnotationImpl(AnnotationID, FillAnnotation, uint8_t maxZoom);
 
-    void updateStyle(style::Style&) const final;
+    void updateStyle(style::Style::Impl&) const final;
     const ShapeAnnotationGeometry& geometry() const final;
 
 private:
diff --git a/src/mbgl/annotation/line_annotation_impl.cpp b/src/mbgl/annotation/line_annotation_impl.cpp
index 65379c42a8..8954ecfa58 100644
--- a/src/mbgl/annotation/line_annotation_impl.cpp
+++ b/src/mbgl/annotation/line_annotation_impl.cpp
@@ -1,6 +1,6 @@
 #include <mbgl/annotation/line_annotation_impl.hpp>
 #include <mbgl/annotation/annotation_manager.hpp>
-#include <mbgl/style/style.hpp>
+#include <mbgl/style/style_impl.hpp>
 #include <mbgl/style/layers/line_layer.hpp>
 
 namespace mbgl {
@@ -12,7 +12,7 @@ LineAnnotationImpl::LineAnnotationImpl(AnnotationID id_, LineAnnotation annotati
       annotation({ ShapeAnnotationGeometry::visit(annotation_.geometry, CloseShapeAnnotation{}), annotation_.opacity, annotation_.width, annotation_.color }) {
 }
 
-void LineAnnotationImpl::updateStyle(Style& style) const {
+void LineAnnotationImpl::updateStyle(Style::Impl& style) const {
     Layer* layer = style.getLayer(layerID);
 
     if (!layer) {
diff --git a/src/mbgl/annotation/line_annotation_impl.hpp b/src/mbgl/annotation/line_annotation_impl.hpp
index 7945da5d97..548a094d53 100644
--- a/src/mbgl/annotation/line_annotation_impl.hpp
+++ b/src/mbgl/annotation/line_annotation_impl.hpp
@@ -9,7 +9,7 @@ class LineAnnotationImpl : public ShapeAnnotationImpl {
 public:
     LineAnnotationImpl(AnnotationID, LineAnnotation, uint8_t maxZoom);
 
-    void updateStyle(style::Style&) const final;
+    void updateStyle(style::Style::Impl&) const final;
     const ShapeAnnotationGeometry& geometry() const final;
 
 private:
diff --git a/src/mbgl/annotation/shape_annotation_impl.hpp b/src/mbgl/annotation/shape_annotation_impl.hpp
index 800b4ec313..ed9e8d015a 100644
--- a/src/mbgl/annotation/shape_annotation_impl.hpp
+++ b/src/mbgl/annotation/shape_annotation_impl.hpp
@@ -4,6 +4,7 @@
 
 #include <mbgl/annotation/annotation.hpp>
 #include <mbgl/util/geometry.hpp>
+#include <mbgl/style/style.hpp>
 
 #include <string>
 #include <memory>
@@ -13,16 +14,12 @@ namespace mbgl {
 class AnnotationTileData;
 class CanonicalTileID;
 
-namespace style {
-class Style;
-} // namespace style
-
 class ShapeAnnotationImpl {
 public:
     ShapeAnnotationImpl(const AnnotationID, const uint8_t maxZoom);
     virtual ~ShapeAnnotationImpl() = default;
 
-    virtual void updateStyle(style::Style&) const = 0;
+    virtual void updateStyle(style::Style::Impl&) const = 0;
     virtual const ShapeAnnotationGeometry& geometry() const = 0;
 
     void updateTileData(const CanonicalTileID&, AnnotationTileData&);
diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 73a540a16a..3aed91cda4 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -6,12 +6,8 @@
 #include <mbgl/map/transform.hpp>
 #include <mbgl/map/transform_state.hpp>
 #include <mbgl/annotation/annotation_manager.hpp>
-#include <mbgl/style/style.hpp>
-#include <mbgl/style/source.hpp>
-#include <mbgl/style/layer.hpp>
-#include <mbgl/style/light.hpp>
+#include <mbgl/style/style_impl.hpp>
 #include <mbgl/style/observer.hpp>
-#include <mbgl/style/transition_options.hpp>
 #include <mbgl/renderer/update_parameters.hpp>
 #include <mbgl/renderer/painter.hpp>
 #include <mbgl/renderer/render_source.hpp>
@@ -101,7 +97,6 @@ public:
 
     std::string styleURL;
     std::string styleJSON;
-    bool styleMutated = false;
     bool cameraMutated = false;
 
     std::unique_ptr<AsyncRequest> styleRequest;
@@ -166,7 +161,7 @@ Map::Impl::Impl(Map& map_,
           }
       }) {
     style = std::make_unique<Style>(scheduler, fileSource, pixelRatio);
-    style->setObserver(this);
+    style->impl->setObserver(this);
 }
 
 Map::~Map() {
@@ -196,8 +191,8 @@ void Map::renderStill(View& view, StillImageCallback callback) {
         return;
     }
 
-    if (impl->style->getLastError()) {
-        callback(impl->style->getLastError());
+    if (impl->style->impl->getLastError()) {
+        callback(impl->style->impl->getLastError());
         return;
     }
 
@@ -228,8 +223,8 @@ void Map::Impl::render(View& view) {
 
     transform.updateTransitions(timePoint);
 
-    if (style->loaded && updateFlags & Update::AnnotationStyle) {
-        annotationManager.updateStyle(*style);
+    if (style->impl->loaded && updateFlags & Update::AnnotationStyle) {
+        annotationManager.updateStyle(*style->impl);
     }
 
     if (updateFlags & Update::AnnotationData) {
@@ -251,19 +246,19 @@ void Map::Impl::render(View& view) {
         debugOptions,
         timePoint,
         transform.getState(),
-        style->getGlyphURL(),
-        style->spriteLoaded,
+        style->impl->getGlyphURL(),
+        style->impl->spriteLoaded,
         style->getTransitionOptions(),
         style->getLight()->impl,
-        style->getImageImpls(),
-        style->getSourceImpls(),
-        style->getLayerImpls(),
+        style->impl->getImageImpls(),
+        style->impl->getSourceImpls(),
+        style->impl->getLayerImpls(),
         scheduler,
         fileSource,
         annotationManager
     });
 
-    bool loaded = style->isLoaded() && renderStyle->isLoaded();
+    bool loaded = style->impl->isLoaded() && renderStyle->isLoaded();
 
     if (mode == MapMode::Continuous) {
         if (renderState == RenderState::Never) {
@@ -334,24 +329,21 @@ void Map::setStyleURL(const std::string& url) {
     }
 
     impl->loading = true;
-
     impl->observer.onWillStartLoadingMap();
 
     impl->styleRequest = nullptr;
     impl->styleURL = url;
     impl->styleJSON.clear();
-
-    impl->style->loaded = false;
-    impl->styleMutated = false;
+    impl->style->impl->loaded = false;
 
     impl->styleRequest = impl->fileSource.request(Resource::style(impl->styleURL), [this](Response res) {
         // Once we get a fresh style, or the style is mutated, stop revalidating.
-        if (res.isFresh() || impl->styleMutated) {
+        if (res.isFresh() || impl->style->impl->mutated) {
             impl->styleRequest.reset();
         }
 
         // Don't allow a loaded, mutated style to be overwritten with a new version.
-        if (impl->styleMutated && impl->style->loaded) {
+        if (impl->style->impl->mutated && impl->style->impl->loaded) {
             return;
         }
 
@@ -381,26 +373,25 @@ void Map::setStyleJSON(const std::string& json) {
     }
 
     impl->loading = true;
-
     impl->observer.onWillStartLoadingMap();
 
     impl->styleURL.clear();
     impl->styleJSON.clear();
-    impl->styleMutated = false;
+    impl->style->impl->mutated = false;
 
     impl->loadStyleJSON(json);
 }
 
 void Map::Impl::loadStyleJSON(const std::string& json) {
-    style->setJSON(json);
+    style->impl->setJSON(json);
     styleJSON = json;
 
     if (!cameraMutated) {
         // Zoom first because it may constrain subsequent operations.
-        map.setZoom(map.getDefaultZoom());
-        map.setLatLng(map.getDefaultLatLng());
-        map.setBearing(map.getDefaultBearing());
-        map.setPitch(map.getDefaultPitch());
+        map.setZoom(style->getDefaultZoom());
+        map.setLatLng(style->getDefaultLatLng());
+        map.setBearing(style->getDefaultBearing());
+        map.setPitch(style->getDefaultPitch());
     }
 
     onUpdate(Update::AnnotationStyle);
@@ -414,6 +405,14 @@ std::string Map::getStyleJSON() const {
     return impl->styleJSON;
 }
 
+style::Style& Map::getStyle() {
+    return *impl->style;
+}
+
+const style::Style& Map::getStyle() const {
+    return *impl->style;
+}
+
 #pragma mark - Transitions
 
 void Map::cancelTransitions() {
@@ -872,92 +871,6 @@ AnnotationIDs Map::queryPointAnnotations(const ScreenBox& box) {
     return ids;
 }
 
-#pragma mark - Style API
-
-std::vector<style::Source*> Map::getSources() {
-    return impl->style->getSources();
-}
-
-style::Source* Map::getSource(const std::string& sourceID) {
-    impl->styleMutated = true;
-    return impl->style->getSource(sourceID);
-}
-
-void Map::addSource(std::unique_ptr<style::Source> source) {
-    impl->styleMutated = true;
-    impl->style->addSource(std::move(source));
-}
-
-std::unique_ptr<Source> Map::removeSource(const std::string& sourceID) {
-    impl->styleMutated = true;
-    return impl->style->removeSource(sourceID);
-}
-
-std::vector<style::Layer*> Map::getLayers() {
-    return impl->style->getLayers();
-}
-
-Layer* Map::getLayer(const std::string& layerID) {
-    impl->styleMutated = true;
-    return impl->style->getLayer(layerID);
-}
-
-void Map::addLayer(std::unique_ptr<Layer> layer, const optional<std::string>& before) {
-    impl->styleMutated = true;
-    impl->style->addLayer(std::move(layer), before);
-    impl->onUpdate(Update::Repaint);
-}
-
-std::unique_ptr<Layer> Map::removeLayer(const std::string& id) {
-    impl->styleMutated = true;
-    impl->onUpdate(Update::Repaint);
-    return impl->style->removeLayer(id);
-}
-
-void Map::addImage(std::unique_ptr<style::Image> image) {
-    impl->styleMutated = true;
-    impl->style->addImage(std::move(image));
-}
-
-void Map::removeImage(const std::string& id) {
-    impl->styleMutated = true;
-    impl->style->removeImage(id);
-}
-
-const style::Image* Map::getImage(const std::string& id) {
-    return impl->style->getImage(id);
-}
-
-void Map::setLight(std::unique_ptr<style::Light> light) {
-    impl->style->setLight(std::move(light));
-}
-
-style::Light* Map::getLight() {
-    return impl->style->getLight();
-}
-
-#pragma mark - Defaults
-
-std::string Map::getStyleName() const {
-    return impl->style->getName();
-}
-
-LatLng Map::getDefaultLatLng() const {
-    return impl->style->getDefaultLatLng();
-}
-
-double Map::getDefaultZoom() const {
-    return impl->style->getDefaultZoom();
-}
-
-double Map::getDefaultBearing() const {
-    return impl->style->getDefaultBearing();
-}
-
-double Map::getDefaultPitch() const {
-    return impl->style->getDefaultPitch();
-}
-
 #pragma mark - Toggles
 
 void Map::setDebug(MapDebugOptions debugOptions) {
@@ -994,15 +907,7 @@ MapDebugOptions Map::getDebug() const {
 }
 
 bool Map::isFullyLoaded() const {
-    return impl->style && impl->style->isLoaded() && impl->renderStyle && impl->renderStyle->isLoaded();
-}
-
-style::TransitionOptions Map::getTransitionOptions() const {
-    return impl->style->getTransitionOptions();
-}
-
-void Map::setTransitionOptions(const style::TransitionOptions& options) {
-    impl->style->setTransitionOptions(options);
+    return impl->style->impl->isLoaded() && impl->renderStyle && impl->renderStyle->isLoaded();
 }
 
 void Map::setSourceTileCacheSize(size_t size) {
@@ -1056,7 +961,7 @@ void Map::Impl::onResourceError(std::exception_ptr error) {
 void Map::dumpDebugLogs() const {
     Log::Info(Event::General, "--------------------------------------------------------------------------------");
     Log::Info(Event::General, "MapContext::styleURL: %s", impl->styleURL.c_str());
-    impl->style->dumpDebugLogs();
+    impl->style->impl->dumpDebugLogs();
     if (impl->renderStyle) {
         impl->renderStyle->dumpDebugLogs();
     }
diff --git a/src/mbgl/renderer/update_parameters.hpp b/src/mbgl/renderer/update_parameters.hpp
index 7c44064b0b..ce79a4f31b 100644
--- a/src/mbgl/renderer/update_parameters.hpp
+++ b/src/mbgl/renderer/update_parameters.hpp
@@ -3,6 +3,10 @@
 #include <mbgl/map/mode.hpp>
 #include <mbgl/map/transform_state.hpp>
 #include <mbgl/util/chrono.hpp>
+#include <mbgl/style/light.hpp>
+#include <mbgl/style/image.hpp>
+#include <mbgl/style/source.hpp>
+#include <mbgl/style/layer.hpp>
 
 namespace mbgl {
 
diff --git a/src/mbgl/style/style.cpp b/src/mbgl/style/style.cpp
index 41b4310dcf..f8dfd48b5c 100644
--- a/src/mbgl/style/style.cpp
+++ b/src/mbgl/style/style.cpp
@@ -1,308 +1,129 @@
 #include <mbgl/style/style.hpp>
-#include <mbgl/style/observer.hpp>
-#include <mbgl/style/source_impl.hpp>
-#include <mbgl/style/layers/symbol_layer.hpp>
-#include <mbgl/style/layers/custom_layer.hpp>
-#include <mbgl/style/layers/background_layer.hpp>
-#include <mbgl/style/layers/fill_layer.hpp>
-#include <mbgl/style/layers/fill_extrusion_layer.hpp>
-#include <mbgl/style/layers/line_layer.hpp>
-#include <mbgl/style/layers/circle_layer.hpp>
-#include <mbgl/style/layers/raster_layer.hpp>
-#include <mbgl/style/layer_impl.hpp>
-#include <mbgl/style/parser.hpp>
-#include <mbgl/style/transition_options.hpp>
-#include <mbgl/sprite/sprite_loader.hpp>
-#include <mbgl/util/exception.hpp>
-#include <mbgl/util/string.hpp>
-#include <mbgl/util/logging.hpp>
+#include <mbgl/style/style_impl.hpp>
+#include <mbgl/style/light.hpp>
+#include <mbgl/style/image.hpp>
+#include <mbgl/style/source.hpp>
+#include <mbgl/style/layer.hpp>
 
 namespace mbgl {
 namespace style {
 
-static Observer nullObserver;
-
-Style::Style(Scheduler& scheduler_, FileSource& fileSource_, float pixelRatio)
-    : scheduler(scheduler_),
-      fileSource(fileSource_),
-      spriteLoader(std::make_unique<SpriteLoader>(pixelRatio)),
-      light(std::make_unique<Light>()),
-      observer(&nullObserver) {
-    spriteLoader->setObserver(this);
-    light->setObserver(this);
+Style::Style(Scheduler& scheduler, FileSource& fileSource, float pixelRatio)
+    : impl(std::make_unique<Impl>(scheduler, fileSource, pixelRatio)) {
 }
 
 Style::~Style() = default;
 
-void Style::setTransitionOptions(const TransitionOptions& options) {
-    transitionOptions = options;
-}
-
-TransitionOptions Style::getTransitionOptions() const {
-    return transitionOptions;
-}
-
-void Style::setJSON(const std::string& json) {
-    sources.clear();
-    layers.clear();
-    images.clear();
-
-    transitionOptions = {};
-    transitionOptions.duration = util::DEFAULT_TRANSITION_DURATION;
-
-    Parser parser;
-    auto error = parser.parse(json);
-
-    if (error) {
-        std::string message = "Failed to parse style: " + util::toString(error);
-        Log::Error(Event::ParseStyle, message.c_str());
-        observer->onStyleError(std::make_exception_ptr(util::StyleParseException(message)));
-        observer->onResourceError(error);
-        return;
-    }
-
-    for (auto& source : parser.sources) {
-        addSource(std::move(source));
-    }
-
-    for (auto& layer : parser.layers) {
-        addLayer(std::move(layer));
-    }
-
-    name = parser.name;
-    defaultLatLng = parser.latLng;
-    defaultZoom = parser.zoom;
-    defaultBearing = parser.bearing;
-    defaultPitch = parser.pitch;
-    setLight(std::make_unique<Light>(parser.light));
-
-    spriteLoader->load(parser.spriteURL, scheduler, fileSource);
-    glyphURL = parser.glyphURL;
-
-    loaded = true;
-
-    observer->onStyleLoaded();
-}
-
-void Style::addSource(std::unique_ptr<Source> source) {
-    if (sources.get(source->getID())) {
-        std::string msg = "Source " + source->getID() + " already exists";
-        throw std::runtime_error(msg.c_str());
-    }
-
-    source->setObserver(this);
-    source->loadDescription(fileSource);
-
-    sources.add(std::move(source));
-}
-
-struct SourceIdUsageEvaluator {
-    const std::string& sourceId;
-
-    bool operator()(BackgroundLayer&) { return false; }
-    bool operator()(CustomLayer&) { return false; }
-
-    template <class LayerType>
-    bool operator()(LayerType& layer) {
-        return layer.getSourceID() == sourceId;
-    }
-};
-
-std::unique_ptr<Source> Style::removeSource(const std::string& id) {
-    // Check if source is in use
-    SourceIdUsageEvaluator sourceIdEvaluator {id};
-    auto layerIt = std::find_if(layers.begin(), layers.end(), [&](const auto& layer) {
-        return layer->accept(sourceIdEvaluator);
-    });
-
-    if (layerIt != layers.end()) {
-        Log::Warning(Event::General, "Source '%s' is in use, cannot remove", id.c_str());
-        return nullptr;
-    }
-
-    std::unique_ptr<Source> source = sources.remove(id);
-
-    if (source) {
-        source->setObserver(nullptr);
-    }
-
-    return source;
-}
-
-std::vector<Layer*> Style::getLayers() {
-    return layers.getWrappers();
-}
-
-Layer* Style::getLayer(const std::string& id) const {
-    return layers.get(id);
-}
-
-Layer* Style::addLayer(std::unique_ptr<Layer> layer, optional<std::string> before) {
-    // TODO: verify source
-
-    if (layers.get(layer->getID())) {
-        throw std::runtime_error(std::string{"Layer "} + layer->getID() + " already exists");
-    }
-
-    layer->setObserver(this);
-
-    return layers.add(std::move(layer), before);
-}
-
-std::unique_ptr<Layer> Style::removeLayer(const std::string& id) {
-    std::unique_ptr<Layer> layer = layers.remove(id);
-
-    if (layer) {
-        layer->setObserver(nullptr);
-    }
-
-    return layer;
-}
-
-void Style::setLight(std::unique_ptr<Light> light_) {
-    light = std::move(light_);
-    light->setObserver(this);
-    onLightChanged(*light);
-}
-
-Light* Style::getLight() const {
-    return light.get();
-}
-
 std::string Style::getName() const {
-    return name;
+    return impl->getName();
 }
 
 LatLng Style::getDefaultLatLng() const {
-    return defaultLatLng;
+    return impl->getDefaultLatLng();
 }
 
 double Style::getDefaultZoom() const {
-    return defaultZoom;
+    return impl->getDefaultZoom();
 }
 
 double Style::getDefaultBearing() const {
-    return defaultBearing;
+    return impl->getDefaultBearing();
 }
 
 double Style::getDefaultPitch() const {
-    return defaultPitch;
+    return impl->getDefaultPitch();
 }
 
-std::vector<Source*> Style::getSources() {
-    return sources.getWrappers();
+TransitionOptions Style::getTransitionOptions() const {
+    return impl->getTransitionOptions();
 }
 
-Source* Style::getSource(const std::string& id) const {
-    return sources.get(id);
+void Style::setTransitionOptions(const TransitionOptions& options) {
+    impl->mutated = true;
+    impl->setTransitionOptions(options);
 }
 
-bool Style::isLoaded() const {
-    if (!loaded) {
-        return false;
-    }
-
-    if (!spriteLoaded) {
-        return false;
-    }
-
-    for (const auto& source: sources) {
-        if (!source->loaded) {
-            return false;
-        }
-    }
-
-    return true;
+void Style::setLight(std::unique_ptr<Light> light) {
+    impl->setLight(std::move(light));
 }
 
-void Style::addImage(std::unique_ptr<style::Image> image) {
-    images.remove(image->getID()); // We permit using addImage to update.
-    images.add(std::move(image));
+Light* Style::getLight() {
+    impl->mutated = true;
+    return impl->getLight();
 }
 
-void Style::removeImage(const std::string& id) {
-    images.remove(id);
+const Light* Style::getLight() const {
+    return impl->getLight();
 }
 
-const style::Image* Style::getImage(const std::string& id) const {
-    return images.get(id);
+const Image* Style::getImage(const std::string& name) const {
+    return impl->getImage(name);
 }
 
-void Style::setObserver(style::Observer* observer_) {
-    observer = observer_;
+void Style::addImage(std::unique_ptr<Image> image) {
+    impl->mutated = true;
+    impl->addImage(std::move(image));
 }
 
-void Style::onSourceLoaded(Source& source) {
-    sources.update(source);
-    observer->onSourceLoaded(source);
-    observer->onUpdate(Update::Repaint);
+void Style::removeImage(const std::string& name) {
+    impl->mutated = true;
+    impl->removeImage(name);
 }
 
-void Style::onSourceChanged(Source& source) {
-    sources.update(source);
-    observer->onSourceChanged(source);
-    observer->onUpdate(Update::Repaint);
+std::vector<Source*> Style::getSources() {
+    impl->mutated = true;
+    return impl->getSources();
 }
 
-void Style::onSourceError(Source& source, std::exception_ptr error) {
-    lastError = error;
-    Log::Error(Event::Style, "Failed to load source %s: %s",
-               source.getID().c_str(), util::toString(error).c_str());
-    observer->onSourceError(source, error);
-    observer->onResourceError(error);
+std::vector<const Source*> Style::getSources() const {
+    return const_cast<const Impl&>(*impl).getSources();
 }
 
-void Style::onSourceDescriptionChanged(Source& source) {
-    sources.update(source);
-    observer->onSourceDescriptionChanged(source);
-    if (!source.loaded) {
-        source.loadDescription(fileSource);
-    }
+Source* Style::getSource(const std::string& id) {
+    impl->mutated = true;
+    return impl->getSource(id);
 }
 
-void Style::onSpriteLoaded(std::vector<std::unique_ptr<Image>>&& images_) {
-    for (auto& image : images_) {
-        addImage(std::move(image));
-    }
-    spriteLoaded = true;
-    observer->onUpdate(Update::Repaint); // For *-pattern properties.
+const Source* Style::getSource(const std::string& id) const {
+    return impl->getSource(id);
 }
 
-void Style::onSpriteError(std::exception_ptr error) {
-    lastError = error;
-    Log::Error(Event::Style, "Failed to load sprite: %s", util::toString(error).c_str());
-    observer->onResourceError(error);
+void Style::addSource(std::unique_ptr<Source> source) {
+    impl->mutated = true;
+    impl->addSource(std::move(source));
 }
 
-void Style::onLayerChanged(Layer& layer) {
-    layers.update(layer);
-    observer->onUpdate(Update::Repaint);
+std::unique_ptr<Source> Style::removeSource(const std::string& sourceID) {
+    impl->mutated = true;
+    return impl->removeSource(sourceID);
 }
 
-void Style::onLightChanged(const Light&) {
-    observer->onUpdate(Update::Repaint);
+std::vector<Layer*> Style::getLayers() {
+    impl->mutated = true;
+    return impl->getLayers();
 }
 
-void Style::dumpDebugLogs() const {
-    for (const auto& source : sources) {
-        source->dumpDebugLogs();
-    }
+std::vector<const Layer*> Style::getLayers() const {
+    return const_cast<const Impl&>(*impl).getLayers();
 }
 
-const std::string& Style::getGlyphURL() const {
-    return glyphURL;
+Layer* Style::getLayer(const std::string& layerID) {
+    impl->mutated = true;
+    return impl->getLayer(layerID);
 }
 
-Immutable<std::vector<Immutable<Image::Impl>>> Style::getImageImpls() const {
-    return images.getImpls();
+const Layer* Style::getLayer(const std::string& layerID) const {
+    return impl->getLayer(layerID);
 }
 
-Immutable<std::vector<Immutable<Source::Impl>>> Style::getSourceImpls() const {
-    return sources.getImpls();
+void Style::addLayer(std::unique_ptr<Layer> layer, const optional<std::string>& before) {
+    impl->mutated = true;
+    impl->addLayer(std::move(layer), before);
 }
 
-Immutable<std::vector<Immutable<Layer::Impl>>> Style::getLayerImpls() const {
-    return layers.getImpls();
+std::unique_ptr<Layer> Style::removeLayer(const std::string& id) {
+    impl->mutated = true;
+    return impl->removeLayer(id);
 }
 
 } // namespace style
diff --git a/src/mbgl/style/style.hpp b/src/mbgl/style/style.hpp
deleted file mode 100644
index 7e8f6f640b..0000000000
--- a/src/mbgl/style/style.hpp
+++ /dev/null
@@ -1,130 +0,0 @@
-#pragma once
-
-#include <mbgl/style/transition_options.hpp>
-#include <mbgl/style/observer.hpp>
-#include <mbgl/style/source_observer.hpp>
-#include <mbgl/style/layer_observer.hpp>
-#include <mbgl/style/light_observer.hpp>
-#include <mbgl/sprite/sprite_loader_observer.hpp>
-#include <mbgl/style/image.hpp>
-#include <mbgl/style/source.hpp>
-#include <mbgl/style/layer.hpp>
-#include <mbgl/style/collection.hpp>
-
-#include <mbgl/util/noncopyable.hpp>
-#include <mbgl/util/optional.hpp>
-#include <mbgl/util/geo.hpp>
-
-#include <memory>
-#include <string>
-#include <vector>
-#include <unordered_map>
-
-namespace mbgl {
-
-class Scheduler;
-class FileSource;
-class SpriteLoader;
-
-namespace style {
-
-class Style : public SpriteLoaderObserver,
-              public SourceObserver,
-              public LayerObserver,
-              public LightObserver,
-              public util::noncopyable {
-public:
-    Style(Scheduler&, FileSource&, float pixelRatio);
-    ~Style() override;
-
-    void setJSON(const std::string&);
-
-    void setObserver(Observer*);
-
-    bool isLoaded() const;
-
-    std::exception_ptr getLastError() const {
-        return lastError;
-    }
-
-    std::vector<Source*> getSources();
-    Source* getSource(const std::string& id) const;
-    void addSource(std::unique_ptr<Source>);
-    std::unique_ptr<Source> removeSource(const std::string& sourceID);
-
-    std::vector<Layer*> getLayers();
-    Layer* getLayer(const std::string& id) const;
-    Layer* addLayer(std::unique_ptr<Layer>,
-                    optional<std::string> beforeLayerID = {});
-    std::unique_ptr<Layer> removeLayer(const std::string& layerID);
-
-    std::string getName() const;
-    LatLng getDefaultLatLng() const;
-    double getDefaultZoom() const;
-    double getDefaultBearing() const;
-    double getDefaultPitch() const;
-
-    TransitionOptions getTransitionOptions() const;
-    void setTransitionOptions(const TransitionOptions&);
-
-    void setLight(std::unique_ptr<Light>);
-    Light* getLight() const;
-
-    const style::Image* getImage(const std::string&) const;
-    void addImage(std::unique_ptr<style::Image>);
-    void removeImage(const std::string&);
-
-    const std::string& getGlyphURL() const;
-
-    Immutable<std::vector<Immutable<Image::Impl>>> getImageImpls() const;
-    Immutable<std::vector<Immutable<Source::Impl>>> getSourceImpls() const;
-    Immutable<std::vector<Immutable<Layer::Impl>>> getLayerImpls() const;
-
-    void dumpDebugLogs() const;
-
-    bool loaded = false;
-    bool spriteLoaded = false;
-
-private:
-    Scheduler& scheduler;
-    FileSource& fileSource;
-    std::unique_ptr<SpriteLoader> spriteLoader;
-    std::string glyphURL;
-
-    Collection<style::Image> images;
-    Collection<Source> sources;
-    Collection<Layer> layers;
-    TransitionOptions transitionOptions;
-    std::unique_ptr<Light> light;
-
-    // Defaults
-    std::string name;
-    LatLng defaultLatLng;
-    double defaultZoom = 0;
-    double defaultBearing = 0;
-    double defaultPitch = 0;
-
-    // SpriteLoaderObserver implementation.
-    void onSpriteLoaded(std::vector<std::unique_ptr<Image>>&&) override;
-    void onSpriteError(std::exception_ptr) override;
-
-    // SourceObserver implementation.
-    void onSourceLoaded(Source&) override;
-    void onSourceChanged(Source&) override;
-    void onSourceError(Source&, std::exception_ptr) override;
-    void onSourceDescriptionChanged(Source&) override;
-
-    // LayerObserver implementation.
-    void onLayerChanged(Layer&) override;
-
-    // LightObserver implementation.
-    void onLightChanged(const Light&) override;
-
-    Observer nullObserver;
-    Observer* observer = &nullObserver;
-
-    std::exception_ptr lastError;
-};
-
-} // namespace style
-} // namespace mbgl
diff --git a/src/mbgl/style/style_impl.cpp b/src/mbgl/style/style_impl.cpp
new file mode 100644
index 0000000000..7235226f84
--- /dev/null
+++ b/src/mbgl/style/style_impl.cpp
@@ -0,0 +1,321 @@
+#include <mbgl/style/style_impl.hpp>
+#include <mbgl/style/observer.hpp>
+#include <mbgl/style/source_impl.hpp>
+#include <mbgl/style/layers/symbol_layer.hpp>
+#include <mbgl/style/layers/custom_layer.hpp>
+#include <mbgl/style/layers/background_layer.hpp>
+#include <mbgl/style/layers/fill_layer.hpp>
+#include <mbgl/style/layers/fill_extrusion_layer.hpp>
+#include <mbgl/style/layers/line_layer.hpp>
+#include <mbgl/style/layers/circle_layer.hpp>
+#include <mbgl/style/layers/raster_layer.hpp>
+#include <mbgl/style/layer_impl.hpp>
+#include <mbgl/style/parser.hpp>
+#include <mbgl/style/transition_options.hpp>
+#include <mbgl/sprite/sprite_loader.hpp>
+#include <mbgl/util/exception.hpp>
+#include <mbgl/util/string.hpp>
+#include <mbgl/util/logging.hpp>
+
+namespace mbgl {
+namespace style {
+
+static Observer nullObserver;
+
+Style::Impl::Impl(Scheduler& scheduler_, FileSource& fileSource_, float pixelRatio)
+    : scheduler(scheduler_),
+      fileSource(fileSource_),
+      spriteLoader(std::make_unique<SpriteLoader>(pixelRatio)),
+      light(std::make_unique<Light>()),
+      observer(&nullObserver) {
+    spriteLoader->setObserver(this);
+    light->setObserver(this);
+}
+
+Style::Impl::~Impl() = default;
+
+void Style::Impl::setTransitionOptions(const TransitionOptions& options) {
+    transitionOptions = options;
+}
+
+TransitionOptions Style::Impl::getTransitionOptions() const {
+    return transitionOptions;
+}
+
+void Style::Impl::setJSON(const std::string& json) {
+    sources.clear();
+    layers.clear();
+    images.clear();
+
+    transitionOptions = {};
+    transitionOptions.duration = util::DEFAULT_TRANSITION_DURATION;
+
+    Parser parser;
+    auto error = parser.parse(json);
+
+    if (error) {
+        std::string message = "Failed to parse style: " + util::toString(error);
+        Log::Error(Event::ParseStyle, message.c_str());
+        observer->onStyleError(std::make_exception_ptr(util::StyleParseException(message)));
+        observer->onResourceError(error);
+        return;
+    }
+
+    for (auto& source : parser.sources) {
+        addSource(std::move(source));
+    }
+
+    for (auto& layer : parser.layers) {
+        addLayer(std::move(layer));
+    }
+
+    name = parser.name;
+    defaultLatLng = parser.latLng;
+    defaultZoom = parser.zoom;
+    defaultBearing = parser.bearing;
+    defaultPitch = parser.pitch;
+    setLight(std::make_unique<Light>(parser.light));
+
+    spriteLoader->load(parser.spriteURL, scheduler, fileSource);
+    glyphURL = parser.glyphURL;
+
+    loaded = true;
+
+    observer->onStyleLoaded();
+}
+
+void Style::Impl::addSource(std::unique_ptr<Source> source) {
+    if (sources.get(source->getID())) {
+        std::string msg = "Source " + source->getID() + " already exists";
+        throw std::runtime_error(msg.c_str());
+    }
+
+    source->setObserver(this);
+    source->loadDescription(fileSource);
+
+    sources.add(std::move(source));
+}
+
+struct SourceIdUsageEvaluator {
+    const std::string& sourceId;
+
+    bool operator()(BackgroundLayer&) { return false; }
+    bool operator()(CustomLayer&) { return false; }
+
+    template <class LayerType>
+    bool operator()(LayerType& layer) {
+        return layer.getSourceID() == sourceId;
+    }
+};
+
+std::unique_ptr<Source> Style::Impl::removeSource(const std::string& id) {
+    // Check if source is in use
+    SourceIdUsageEvaluator sourceIdEvaluator {id};
+    auto layerIt = std::find_if(layers.begin(), layers.end(), [&](const auto& layer) {
+        return layer->accept(sourceIdEvaluator);
+    });
+
+    if (layerIt != layers.end()) {
+        Log::Warning(Event::General, "Source '%s' is in use, cannot remove", id.c_str());
+        return nullptr;
+    }
+
+    std::unique_ptr<Source> source = sources.remove(id);
+
+    if (source) {
+        source->setObserver(nullptr);
+    }
+
+    return source;
+}
+
+std::vector<Layer*> Style::Impl::getLayers() {
+    return layers.getWrappers();
+}
+
+std::vector<const Layer*> Style::Impl::getLayers() const {
+    auto wrappers = layers.getWrappers();
+    return std::vector<const Layer*>(wrappers.begin(), wrappers.end());
+}
+
+Layer* Style::Impl::getLayer(const std::string& id) const {
+    return layers.get(id);
+}
+
+Layer* Style::Impl::addLayer(std::unique_ptr<Layer> layer, optional<std::string> before) {
+    // TODO: verify source
+
+    if (layers.get(layer->getID())) {
+        throw std::runtime_error(std::string{"Layer "} + layer->getID() + " already exists");
+    }
+
+    layer->setObserver(this);
+    observer->onUpdate(Update::Repaint);
+
+    return layers.add(std::move(layer), before);
+}
+
+std::unique_ptr<Layer> Style::Impl::removeLayer(const std::string& id) {
+    std::unique_ptr<Layer> layer = layers.remove(id);
+
+    if (layer) {
+        layer->setObserver(nullptr);
+        observer->onUpdate(Update::Repaint);
+    }
+
+    return layer;
+}
+
+void Style::Impl::setLight(std::unique_ptr<Light> light_) {
+    light = std::move(light_);
+    light->setObserver(this);
+    onLightChanged(*light);
+}
+
+Light* Style::Impl::getLight() const {
+    return light.get();
+}
+
+std::string Style::Impl::getName() const {
+    return name;
+}
+
+LatLng Style::Impl::getDefaultLatLng() const {
+    return defaultLatLng;
+}
+
+double Style::Impl::getDefaultZoom() const {
+    return defaultZoom;
+}
+
+double Style::Impl::getDefaultBearing() const {
+    return defaultBearing;
+}
+
+double Style::Impl::getDefaultPitch() const {
+    return defaultPitch;
+}
+
+std::vector<Source*> Style::Impl::getSources() {
+    return sources.getWrappers();
+}
+
+std::vector<const Source*> Style::Impl::getSources() const {
+    auto wrappers = sources.getWrappers();
+    return std::vector<const Source*>(wrappers.begin(), wrappers.end());
+}
+
+Source* Style::Impl::getSource(const std::string& id) const {
+    return sources.get(id);
+}
+
+bool Style::Impl::isLoaded() const {
+    if (!loaded) {
+        return false;
+    }
+
+    if (!spriteLoaded) {
+        return false;
+    }
+
+    for (const auto& source: sources) {
+        if (!source->loaded) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+void Style::Impl::addImage(std::unique_ptr<style::Image> image) {
+    images.remove(image->getID()); // We permit using addImage to update.
+    images.add(std::move(image));
+}
+
+void Style::Impl::removeImage(const std::string& id) {
+    images.remove(id);
+}
+
+const style::Image* Style::Impl::getImage(const std::string& id) const {
+    return images.get(id);
+}
+
+void Style::Impl::setObserver(style::Observer* observer_) {
+    observer = observer_;
+}
+
+void Style::Impl::onSourceLoaded(Source& source) {
+    sources.update(source);
+    observer->onSourceLoaded(source);
+    observer->onUpdate(Update::Repaint);
+}
+
+void Style::Impl::onSourceChanged(Source& source) {
+    sources.update(source);
+    observer->onSourceChanged(source);
+    observer->onUpdate(Update::Repaint);
+}
+
+void Style::Impl::onSourceError(Source& source, std::exception_ptr error) {
+    lastError = error;
+    Log::Error(Event::Style, "Failed to load source %s: %s",
+               source.getID().c_str(), util::toString(error).c_str());
+    observer->onSourceError(source, error);
+    observer->onResourceError(error);
+}
+
+void Style::Impl::onSourceDescriptionChanged(Source& source) {
+    sources.update(source);
+    observer->onSourceDescriptionChanged(source);
+    if (!source.loaded) {
+        source.loadDescription(fileSource);
+    }
+}
+
+void Style::Impl::onSpriteLoaded(std::vector<std::unique_ptr<Image>>&& images_) {
+    for (auto& image : images_) {
+        addImage(std::move(image));
+    }
+    spriteLoaded = true;
+    observer->onUpdate(Update::Repaint); // For *-pattern properties.
+}
+
+void Style::Impl::onSpriteError(std::exception_ptr error) {
+    lastError = error;
+    Log::Error(Event::Style, "Failed to load sprite: %s", util::toString(error).c_str());
+    observer->onResourceError(error);
+}
+
+void Style::Impl::onLayerChanged(Layer& layer) {
+    layers.update(layer);
+    observer->onUpdate(Update::Repaint);
+}
+
+void Style::Impl::onLightChanged(const Light&) {
+    observer->onUpdate(Update::Repaint);
+}
+
+void Style::Impl::dumpDebugLogs() const {
+    for (const auto& source : sources) {
+        source->dumpDebugLogs();
+    }
+}
+
+const std::string& Style::Impl::getGlyphURL() const {
+    return glyphURL;
+}
+
+Immutable<std::vector<Immutable<Image::Impl>>> Style::Impl::getImageImpls() const {
+    return images.getImpls();
+}
+
+Immutable<std::vector<Immutable<Source::Impl>>> Style::Impl::getSourceImpls() const {
+    return sources.getImpls();
+}
+
+Immutable<std::vector<Immutable<Layer::Impl>>> Style::Impl::getLayerImpls() const {
+    return layers.getImpls();
+}
+
+} // namespace style
+} // namespace mbgl
diff --git a/src/mbgl/style/style_impl.hpp b/src/mbgl/style/style_impl.hpp
new file mode 100644
index 0000000000..2bdb51a26c
--- /dev/null
+++ b/src/mbgl/style/style_impl.hpp
@@ -0,0 +1,136 @@
+#pragma once
+
+#include <mbgl/style/style.hpp>
+#include <mbgl/style/transition_options.hpp>
+#include <mbgl/style/observer.hpp>
+#include <mbgl/style/source_observer.hpp>
+#include <mbgl/style/layer_observer.hpp>
+#include <mbgl/style/light_observer.hpp>
+#include <mbgl/sprite/sprite_loader_observer.hpp>
+#include <mbgl/style/image.hpp>
+#include <mbgl/style/source.hpp>
+#include <mbgl/style/layer.hpp>
+#include <mbgl/style/collection.hpp>
+
+#include <mbgl/util/noncopyable.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/geo.hpp>
+
+#include <memory>
+#include <string>
+#include <vector>
+#include <unordered_map>
+
+namespace mbgl {
+
+class Scheduler;
+class FileSource;
+class SpriteLoader;
+
+namespace style {
+
+class Style::Impl : public SpriteLoaderObserver,
+                    public SourceObserver,
+                    public LayerObserver,
+                    public LightObserver,
+                    public util::noncopyable {
+public:
+    Impl(Scheduler&, FileSource&, float pixelRatio);
+    ~Impl() override;
+
+    void setJSON(const std::string&);
+
+    void setObserver(Observer*);
+
+    bool isLoaded() const;
+
+    std::exception_ptr getLastError() const {
+        return lastError;
+    }
+
+    std::vector<      Source*> getSources();
+    std::vector<const Source*> getSources() const;
+    Source* getSource(const std::string& id) const;
+
+    void addSource(std::unique_ptr<Source>);
+    std::unique_ptr<Source> removeSource(const std::string& sourceID);
+
+    std::vector<      Layer*> getLayers();
+    std::vector<const Layer*> getLayers() const;
+    Layer* getLayer(const std::string& id) const;
+
+    Layer* addLayer(std::unique_ptr<Layer>,
+                    optional<std::string> beforeLayerID = {});
+    std::unique_ptr<Layer> removeLayer(const std::string& layerID);
+
+    std::string getName() const;
+    LatLng getDefaultLatLng() const;
+    double getDefaultZoom() const;
+    double getDefaultBearing() const;
+    double getDefaultPitch() const;
+
+    TransitionOptions getTransitionOptions() const;
+    void setTransitionOptions(const TransitionOptions&);
+
+    void setLight(std::unique_ptr<Light>);
+    Light* getLight() const;
+
+    const style::Image* getImage(const std::string&) const;
+    void addImage(std::unique_ptr<style::Image>);
+    void removeImage(const std::string&);
+
+    const std::string& getGlyphURL() const;
+
+    Immutable<std::vector<Immutable<Image::Impl>>> getImageImpls() const;
+    Immutable<std::vector<Immutable<Source::Impl>>> getSourceImpls() const;
+    Immutable<std::vector<Immutable<Layer::Impl>>> getLayerImpls() const;
+
+    void dumpDebugLogs() const;
+
+    bool mutated = false;
+    bool loaded = false;
+    bool spriteLoaded = false;
+
+private:
+    Scheduler& scheduler;
+    FileSource& fileSource;
+    std::unique_ptr<SpriteLoader> spriteLoader;
+    std::string glyphURL;
+
+    Collection<style::Image> images;
+    Collection<Source> sources;
+    Collection<Layer> layers;
+    TransitionOptions transitionOptions;
+    std::unique_ptr<Light> light;
+
+    // Defaults
+    std::string name;
+    LatLng defaultLatLng;
+    double defaultZoom = 0;
+    double defaultBearing = 0;
+    double defaultPitch = 0;
+
+    // SpriteLoaderObserver implementation.
+    void onSpriteLoaded(std::vector<std::unique_ptr<Image>>&&) override;
+    void onSpriteError(std::exception_ptr) override;
+
+    // SourceObserver implementation.
+    void onSourceLoaded(Source&) override;
+    void onSourceChanged(Source&) override;
+    void onSourceError(Source&, std::exception_ptr) override;
+    void onSourceDescriptionChanged(Source&) override;
+
+    // LayerObserver implementation.
+    void onLayerChanged(Layer&) override;
+
+    // LightObserver implementation.
+    void onLightChanged(const Light&) override;
+
+    Observer nullObserver;
+    Observer* observer = &nullObserver;
+
+    std::exception_ptr lastError;
+};
+
+} // namespace style
+} // namespace mbgl
-- 
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