[core] Return source and layer ownership (#7014)

When a source or layer is removed transfer ownership back to the
caller so it can (optionally) take it. Preserve the behavior that 
removing a CustomLayer triggers deinitialization.  Deinitialize all 
custom layers when a style is destroyed in case those layers are not 
explicitly removed.

include/mbgl/map/map.hpp

@@ -159,12 +159,12 @@ class Map : private util::noncopyable {
  // Sources
  style::Source* getSource(const std::string& sourceID);
  void addSource(std::unique_ptr<style::Source>);
- void removeSource(const std::string& sourceID);
+ std::unique_ptr<style::Source> removeSource(const std::string& sourceID);
 
  // Layers
  style::Layer* getLayer(const std::string& layerID);
  void addLayer(std::unique_ptr<style::Layer>, const optional<std::string>& beforeLayerID = {});
- void removeLayer(const std::string& layerID);
+ std::unique_ptr<style::Layer> removeLayer(const std::string& layerID);
 
  // Add image, bound to the style
  void addImage(const std::string&, std::unique_ptr<const SpriteImage>);

src/mbgl/map/map.cpp

@@ -851,11 +851,12 @@ void Map::addSource(std::unique_ptr<style::Source> source) {
  }
 }
 
-void Map::removeSource(const std::string& sourceID) {
+std::unique_ptr<Source> Map::removeSource(const std::string& sourceID) {
  if (impl->style) {
  impl->styleMutated = true;
- impl->style->removeSource(sourceID);
+ return impl->style->removeSource(sourceID);
  }
+ return nullptr;
 }
 
 style::Layer* Map::getLayer(const std::string& layerID) {
@@ -880,18 +881,20 @@ void Map::addLayer(std::unique_ptr<Layer> layer, const optional<std::string>& be
  impl->backend.deactivate();
 }
 
-void Map::removeLayer(const std::string& id) {
+std::unique_ptr<Layer> Map::removeLayer(const std::string& id) {
  if (!impl->style) {
- return;
+ return nullptr;
  }
 
  impl->styleMutated = true;
  impl->backend.activate();
 
- impl->style->removeLayer(id);
+ auto removedLayer = impl->style->removeLayer(id);
  impl->onUpdate(Update::Classes);
 
  impl->backend.deactivate();
+
+ return removedLayer;
 }
 
 void Map::addImage(const std::string& name, std::unique_ptr<const SpriteImage> image) {

src/mbgl/style/layers/custom_layer_impl.cpp

@@ -23,11 +23,7 @@ CustomLayer::Impl::Impl(const CustomLayer::Impl& other)
  // Don't copy anything else.
 }
 
-CustomLayer::Impl::~Impl() {
- if (deinitializeFn) {
- deinitializeFn(context);
- }
-}
+CustomLayer::Impl::~Impl() = default;
 
 std::unique_ptr<Layer> CustomLayer::Impl::clone() const {
  return std::make_unique<CustomLayer>(*this);
@@ -43,6 +39,12 @@ void CustomLayer::Impl::initialize() {
  initializeFn(context);
 }
 
+void CustomLayer::Impl::deinitialize() {
+ if (deinitializeFn) {
+ deinitializeFn(context);
+ }
+}
+
 void CustomLayer::Impl::render(const TransformState& state) const {
  assert(renderFn);
 

src/mbgl/style/layers/custom_layer_impl.hpp

@@ -21,6 +21,7 @@ class CustomLayer::Impl : public Layer::Impl {
  ~Impl() final;
 
  void initialize();
+ void deinitialize();
  void render(const TransformState&) const;
 
 private:

src/mbgl/style/style.cpp

@@ -51,6 +51,12 @@ Style::~Style() {
  source->baseImpl->setObserver(nullptr);
  }
 
+ for (const auto& layer : layers) {
+ if (CustomLayer* customLayer = layer->as<CustomLayer>()) {
+ customLayer->impl->deinitialize();
+ }
+ }
+
  glyphAtlas->setObserver(nullptr);
  spriteAtlas->setObserver(nullptr);
 }
@@ -134,7 +140,7 @@ void Style::addSource(std::unique_ptr<Source> source) {
  sources.emplace_back(std::move(source));
 }
 
-void Style::removeSource(const std::string& id) {
+std::unique_ptr<Source> Style::removeSource(const std::string& id) {
  auto it = std::find_if(sources.begin(), sources.end(), [&](const auto& source) {
  return source->getID() == id;
  });
@@ -143,8 +149,11 @@ void Style::removeSource(const std::string& id) {
  throw std::runtime_error("no such source");
  }
 
+ auto source = std::move(*it);
  sources.erase(it);
  updateBatch.sourceIDs.erase(id);
+
+ return source;
 }
 
 std::vector<const Layer*> Style::getLayers() const {
@@ -185,11 +194,22 @@ Layer* Style::addLayer(std::unique_ptr<Layer> layer, optional<std::string> befor
  return layers.emplace(before ? findLayer(*before) : layers.end(), std::move(layer))->get();
 }
 
-void Style::removeLayer(const std::string& id) {
- auto it = findLayer(id);
+std::unique_ptr<Layer> Style::removeLayer(const std::string& id) {
+ auto it = std::find_if(layers.begin(), layers.end(), [&](const auto& layer) {
+ return layer->baseImpl->id == id;
+ });
+
  if (it == layers.end())
  throw std::runtime_error("no such layer");
+
+ auto layer = std::move(*it);
+
+ if (CustomLayer* customLayer = layer->as<CustomLayer>()) {
+ customLayer->impl->deinitialize();
+ }
+
  layers.erase(it);
+ return layer;
 }
 
 std::string Style::getName() const {

src/mbgl/style/style.hpp

@@ -66,13 +66,13 @@ class Style : public GlyphAtlasObserver,
 
  Source* getSource(const std::string& id) const;
  void addSource(std::unique_ptr<Source>);
- void removeSource(const std::string& sourceID);
+ std::unique_ptr<Source> removeSource(const std::string& sourceID);
 
  std::vector<const Layer*> getLayers() const;
  Layer* getLayer(const std::string& id) const;
  Layer* addLayer(std::unique_ptr<Layer>,
  optional<std::string> beforeLayerID = {});
- void removeLayer(const std::string& layerID);
+ std::unique_ptr<Layer> removeLayer(const std::string& layerID);
 
  std::string getName() const;
  LatLng getDefaultLatLng() const;