[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.

1 files changed, 7 insertions, 5 deletions

diff --git a/src/mbgl/style/layers/custom_layer_impl.cpp b/src/mbgl/style/layers/custom_layer_impl.cpp
index 124d6b0ce9..1126d57552 100644
--- a/src/mbgl/style/layers/custom_layer_impl.cpp
+++ b/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);