Experimental update - turning Obj-C object into C++ to reduce amount of hand-waving to manage reference counts.

9 files changed, 138 insertions, 325 deletions

diff --git a/include/mbgl/style/layers/custom_layer.hpp b/include/mbgl/style/layers/custom_layer.hpp
index 05d12f47f4..a37ac25b01 100644
--- a/include/mbgl/style/layers/custom_layer.hpp
+++ b/include/mbgl/style/layers/custom_layer.hpp
@@ -61,30 +61,27 @@ using CustomLayerContextAttachFunction = void (*)(void* context);
 using CustomLayerContextDetachFunction = void (*)(void* context);
 
 
-class CustomLayer : public Layer {
-public:
-    CustomLayer(const std::string& id,
-                CustomLayerInitializeFunction,
-                CustomLayerRenderFunction,
-                CustomLayerContextLostFunction,
-                CustomLayerDeinitializeFunction,
+class CustomLayerContext {
+    public:
+    CustomLayerContext() = default;
+    virtual ~CustomLayerContext() = default;
+
+    virtual void initialize() = 0;
+    virtual void render(const CustomLayerRenderParameters&) = 0;
+    virtual void deinitialize() = 0;
 
-                // Wrap these 4?
-                CustomLayerContextOwnerChangedFunction,
-                CustomLayerContextAttachFunction,
-                CustomLayerContextDetachFunction,
-                void* context);
+    virtual void lost() {};
 
+    // could lose these if we go back to having the set/style manage life times for
+    // MGLOpenGLStyleLayers
+    virtual void attach() {}
+    virtual void detach() {}
+};
+
+class CustomLayer : public Layer {
+public:
     CustomLayer(const std::string& id,
-                CustomLayerInitializeFunction,
-                CustomLayerRenderFunction,
-                CustomLayerDeinitializeFunction,
-
-                // Wrap these 4?
-                CustomLayerContextOwnerChangedFunction,
-                CustomLayerContextAttachFunction,
-                CustomLayerContextDetachFunction,
-                void* context);
+                std::unique_ptr<CustomLayerContext> context);
 
     ~CustomLayer() final;
 
diff --git a/platform/darwin/src/MGLOpenGLStyleLayer.h b/platform/darwin/src/MGLOpenGLStyleLayer.h
index ad854eac4d..a6b390b71a 100644
--- a/platform/darwin/src/MGLOpenGLStyleLayer.h
+++ b/platform/darwin/src/MGLOpenGLStyleLayer.h
@@ -12,19 +12,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @class MGLOpenGLStyleLayer;
 
-MGL_EXPORT
-@interface MGLOpenGLStyleLayerRetainer: NSObject
-@property (nonatomic, weak, readonly) MGLOpenGLStyleLayer *layer;
-@property (nonatomic, assign, readonly) NSInteger layerRetainCount;
-@property (nonatomic, unsafe_unretained, nullable) void *owner;
-- (instancetype)initWithLayer:(MGLStyleLayer*)styleLayer;
-- (void)retainLayer;
-- (void)releaseLayer;
-@end
-
-
-
-
 typedef struct MGLStyleLayerDrawingContext {
     CGSize size;
     CLLocationCoordinate2D centerCoordinate;
@@ -38,8 +25,6 @@ MGL_EXPORT
 @interface MGLOpenGLStyleLayer : MGLStyleLayer
 @property (nonatomic, weak, readonly) MGLStyle *style;
 
-- (BOOL)isBeingManaged;
-
 - (instancetype)initWithIdentifier:(NSString *)identifier;
 
 - (void)didMoveToMapView:(MGLMapView *)mapView;
diff --git a/platform/darwin/src/MGLOpenGLStyleLayer.mm b/platform/darwin/src/MGLOpenGLStyleLayer.mm
index ad41958903..c4defddbe2 100644
--- a/platform/darwin/src/MGLOpenGLStyleLayer.mm
+++ b/platform/darwin/src/MGLOpenGLStyleLayer.mm
@@ -7,187 +7,96 @@
 #include <mbgl/style/layers/custom_layer.hpp>
 #include <mbgl/math/wrap.hpp>
 
-@interface MGLOpenGLStyleLayerRetainer ()
-@property (nonatomic, weak, readwrite) MGLOpenGLStyleLayer *layer;
-@property (nonatomic, assign, readwrite) NSInteger layerRetainCount;
-@end
-
-@implementation MGLOpenGLStyleLayerRetainer
-
-- (void)dealloc {
-    NSLog(@"LayerRetainer dealloc start %p", self);
-
-    while (self.layerRetainCount) {
-        [self releaseLayer];
-    }
-
-    NSLog(@"LayerRetainer dealloc end %p", self);
-}
-
-- (instancetype)initWithLayer:(MGLOpenGLStyleLayer*)styleLayer {
-    if ((self = [super init])) {
-        _layer = styleLayer;
-    }
-    NSLog(@"LayerRetainer %p init with layer %p", self, styleLayer);
-    return self;
-}
-
-- (void)setOwner:(nullable void *)owner {
-    void* oldOwner = _owner;
-
-    _owner = owner;
+class MGLOpenGLStyleLayerContext: public mbgl::style::CustomLayerContext
+{
+public:
+    __weak MGLOpenGLStyleLayer* layer;
+    int layerRetainCount;
+
+    MGLOpenGLStyleLayerContext(MGLOpenGLStyleLayer *layer_) :
+        mbgl::style::CustomLayerContext(),
+        layer(layer_),
+        layerRetainCount(0)
+    {
 
-    if (oldOwner) {
-        NSLog(@"LayerRetainer %p released", self);
-        CFBridgingRelease((__bridge CFTypeRef)(self));
     }
 
-    if (_owner) {
-        NSLog(@"LayerRetainer %p retained", self);
-        CFBridgingRetain(self);
+    ~MGLOpenGLStyleLayerContext()
+    {
+        while (layerRetainCount) {
+            detach();
+        }
     }
-}
 
-- (void)retainLayer {
+    void attach()
+    {
+        if (!layer) return;
 
-    if (!self.layer)
-        return;
+        assert(layerRetainCount >= 0);
 
-    NSAssert(self.layerRetainCount >= 0, @"");
+        @autoreleasepool {
+            CFBridgingRetain(layer);
+        }
+        layerRetainCount++;
 
-    @autoreleasepool {
-        CFBridgingRetain(self.layer);
+        printf("LayerRetainer %p retained %d", this, layerRetainCount);
     }
-    self.layerRetainCount++;
 
-    NSLog(@"LayerRetainer %p retained %ld", self,  self.layerRetainCount);
-}
 
+    void detach()
+    {
+        if (!layer) return;
 
-- (void)releaseLayer {
-    if (!self.layer)
-        return;
+        assert(layerRetainCount > 0);
 
-    NSAssert(self.layerRetainCount > 0, @"");
+        layerRetainCount--;
 
-    self.layerRetainCount--;
+        @autoreleasepool {
+            CFBridgingRelease((__bridge CFTypeRef)layer);
+        }
 
-    @autoreleasepool {
-        CFBridgingRelease((__bridge CFTypeRef)self.layer);
+        printf("LayerRetainer %p released %d", this, layerRetainCount);
     }
 
-    NSLog(@"LayerRetainer %p released %ld", self, self.layerRetainCount);
-}
-@end
-
-void MGLCustomLayerContextOwnerChangedFunction(void *context, void* owner) {
-    MGLOpenGLStyleLayerRetainer *contextRetainer = (__bridge MGLOpenGLStyleLayerRetainer*)context;
-    contextRetainer.owner = owner;
-}
-
-void MGLCustomLayerContextAttachFunction(void *context) {
-    MGLOpenGLStyleLayerRetainer *contextRetainer = (__bridge MGLOpenGLStyleLayerRetainer*)context;
-    [contextRetainer retainLayer];
-}
-
-void MGLCustomLayerContextDetachFunction(void *context) {
-    MGLOpenGLStyleLayerRetainer *contextRetainer = (__bridge MGLOpenGLStyleLayerRetainer*)context;
-    [contextRetainer releaseLayer];
-}
-
-
-
-/**
- Runs the preparation handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
-
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLPrepareCustomStyleLayer(void *context) {
-    // Note, that the layer is retained/released by MGLStyle, ensuring that the layer
-    // is alive during rendering
-//    MGLOpenGLStyleLayer *layer = (__bridge MGLOpenGLStyleLayer*)context;
-
-    MGLOpenGLStyleLayerRetainer *retainer = (__bridge MGLOpenGLStyleLayerRetainer*)context;
-    MGLOpenGLStyleLayer *layer = retainer.layer;
-
-    [layer didMoveToMapView:layer.style.mapView];
-}
+    // Custom stuff
 
-/**
- Runs the drawing handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
+    /**
+     Runs the preparation handler block contained in the given context, which is
+     implicitly an instance of `MGLOpenGLStyleLayer`.
 
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLDrawCustomStyleLayer(void *context, const mbgl::style::CustomLayerRenderParameters &params) {
-//    MGLOpenGLStyleLayer *layer = (__bridge MGLOpenGLStyleLayer *)context;
-    MGLOpenGLStyleLayer *layer = ((__bridge MGLOpenGLStyleLayerRetainer*)context).layer;
-
-    if (!layer)
-    {
-        NSLog(@"no layer");
-        return;
-    }
-
-    MGLStyleLayerDrawingContext drawingContext = {
-        .size = CGSizeMake(params.width, params.height),
-        .centerCoordinate = CLLocationCoordinate2DMake(params.latitude, params.longitude),
-        .zoomLevel = params.zoom,
-        .direction = mbgl::util::wrap(params.bearing, 0., 360.),
-        .pitch = static_cast<CGFloat>(params.pitch),
-        .fieldOfView = static_cast<CGFloat>(params.fieldOfView),
+     */
+    void initialize() {
+        [layer didMoveToMapView:layer.style.mapView];
     };
-    [layer drawInMapView:layer.style.mapView withContext:drawingContext];
-}
 
-/**
- Runs the completion handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
+    /**
+     Runs the drawing handler block contained in the given context, which is
+     implicitly an instance of `MGLOpenGLStyleLayer`.
+
+     */
+    void render(const mbgl::style::CustomLayerRenderParameters& params) {
+
+        MGLStyleLayerDrawingContext drawingContext = {
+            .size = CGSizeMake(params.width, params.height),
+            .centerCoordinate = CLLocationCoordinate2DMake(params.latitude, params.longitude),
+            .zoomLevel = params.zoom,
+            .direction = mbgl::util::wrap(params.bearing, 0., 360.),
+            .pitch = static_cast<CGFloat>(params.pitch),
+            .fieldOfView = static_cast<CGFloat>(params.fieldOfView),
+        };
+        [layer drawInMapView:layer.style.mapView withContext:drawingContext];
+    };
 
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLFinishCustomStyleLayer(void *context) {
-    // Note, that the layer is retained/released by MGLStyle, ensuring that the layer
-    // is alive during rendering
-//    MGLOpenGLStyleLayer *layer = (__bridge MGLOpenGLStyleLayer*)context;
-    MGLOpenGLStyleLayerRetainer *retainer = (__bridge MGLOpenGLStyleLayerRetainer*)context;
-    MGLOpenGLStyleLayer *layer = retainer.layer;
-
-    [layer willMoveFromMapView:layer.style.mapView];
-}
+    /**
+     Runs the completion handler block contained in the given context, which is
+     implicitly an instance of `MGLOpenGLStyleLayer`.
 
+     */
+    void deinitialize() {
+        [layer willMoveFromMapView:layer.style.mapView];
+    };
+};
 
-/**
- Function to be called when the core `CustomLayer` (not the Impl) gets deallocated.
- It's possible taht at this stage the Obj-C style layer is being deallocated (but that case is detected).
- */
-//void MGLDeallocateCustomStyleLayer(mbgl::util::unique_any *peer) {
-//
-//    // We know that the peer object contains a LayerWrapper with a weak pointer to
-//    // our custom layer. We can use this to safely access the layer, and clear out the
-//    // raw pointer.
-//    //
-//    // If we don't do this rawLayer can become a dangling pointer (which was previously being
-//    // accessed via the description method)
-//
-//    if (!(peer && peer->has_value()))
-//        return;
-//
-//    LayerWrapper *wrapper = mbgl::util::any_cast<LayerWrapper>(peer);
-//
-//    if (!wrapper)
-//        return;
-//
-//    // If the MGLStyleLayer is currently being dealloc'd (and trigger the CustomLayer destructor, and
-//    // this function) then layer here will be nil (even though wrapper->layer may appear to be non-nil)
-//    MGLStyleLayer *layer = wrapper->layer;
-//
-//    layer.rawLayer = NULL;
-//}
 
 
 /**
@@ -224,6 +133,11 @@ void MGLFinishCustomStyleLayer(void *context) {
 
 @implementation MGLOpenGLStyleLayer
 
+- (void)dealloc
+{
+    NSLog(@"MGLOpenGLStyleLayer dealloc %p\n", self);
+}
+
 /**
  Returns an OpenGL style layer object initialized with the given identifier.
 
@@ -236,44 +150,15 @@ void MGLFinishCustomStyleLayer(void *context) {
  @return An initialized OpenGL style layer.
  */
 
-- (BOOL)isBeingManaged {
-    if (self.rawLayer == NULL) {
-        return NO;
-    }
-
-    auto customLayer = self.rawLayer->template as<mbgl::style::CustomLayer>();
-
-    if (!customLayer) {
-        return NO;
-    }
-
-    MGLOpenGLStyleLayerRetainer *retainer = (__bridge MGLOpenGLStyleLayerRetainer*)(customLayer->getContext());
-
-    return retainer.layerRetainCount > 0;
-}
-
-- (void)dealloc
-{
-    NSLog(@"MGLOpenGLStyleLayer dealloc %p\n", self);
-}
-
 - (instancetype)initWithIdentifier:(NSString *)identifier {
 
     NSLog(@"MGLOpenGLStyleLayer init %p\n", self);
 
-    MGLOpenGLStyleLayerRetainer *retainer = [[MGLOpenGLStyleLayerRetainer alloc] initWithLayer:self];
+    auto context = std::make_unique<MGLOpenGLStyleLayerContext>(self);
 
     // Note, do not retain self here, otherwise MGLOpenGLStyleLayer will never be dealloc'd
     auto layer = std::make_unique<mbgl::style::CustomLayer>(identifier.UTF8String,
-                                                            MGLPrepareCustomStyleLayer,
-                                                            MGLDrawCustomStyleLayer,
-                                                            MGLFinishCustomStyleLayer,
-
-                                                            MGLCustomLayerContextOwnerChangedFunction,
-                                                            MGLCustomLayerContextAttachFunction,
-                                                            MGLCustomLayerContextDetachFunction,
-
-                                                            (__bridge void*)retainer);
+                                                            std::move(context));
 
     return self = [super initWithPendingLayer:std::move(layer)];
 }
diff --git a/platform/ios/Integration Tests/MBGLIntegrationTests.mm b/platform/ios/Integration Tests/MBGLIntegrationTests.mm
index 449adb5dbc..a25cc81782 100644
--- a/platform/ios/Integration Tests/MBGLIntegrationTests.mm
+++ b/platform/ios/Integration Tests/MBGLIntegrationTests.mm
@@ -78,12 +78,12 @@
     //    }
 }
 
-- (BOOL)isLayerBeingManaged:(MGLStyleLayer*)layer {
-
-    MGLOpenGLStyleLayer *glLayer = [layer isKindOfClass:[MGLOpenGLStyleLayer class]] ? (MGLOpenGLStyleLayer*)layer : nil;
-
-    return [glLayer isBeingManaged];
-}
+//- (BOOL)isLayerBeingManaged:(MGLStyleLayer*)layer {
+//
+//    MGLOpenGLStyleLayer *glLayer = [layer isKindOfClass:[MGLOpenGLStyleLayer class]] ? (MGLOpenGLStyleLayer*)layer : nil;
+//
+//    return [glLayer isBeingManaged];
+//}
 
 - (MGLStyle *)style {
     return self.mapView.style;
@@ -91,7 +91,7 @@
 
 #pragma mark - Tests
 
-
+/*
 - (void)testLayerRetainer {
 
     __weak MGLOpenGLStyleLayer *weaklayer1 = nil;
@@ -191,6 +191,7 @@
 
     #undef ASSERT_RETAIN_COUNT
 }
+ */
 
 
 - (void)testStoringOpenGLLayerInCollections {
@@ -432,7 +433,7 @@
     MGLStyleLayer *layer2 = weakLayer;
 
     XCTAssertNotNil(weakLayer);
-    XCTAssert([self isLayerBeingManaged:weakLayer]);
+//    XCTAssert([self isLayerBeingManaged:weakLayer]);
     [self waitForMapViewToBeRendered];
 
 
@@ -441,7 +442,7 @@
     //    [self waitForMapViewToBeRendered];
 
     XCTAssertNotNil(weakLayer);
-    XCTAssert(![self isLayerBeingManaged:weakLayer]);
+//    XCTAssert(![self isLayerBeingManaged:weakLayer]);
 
     layer2 = nil;
     XCTAssertNil(weakLayer);
diff --git a/src/mbgl/renderer/layers/render_custom_layer.cpp b/src/mbgl/renderer/layers/render_custom_layer.cpp
index eab87b19c5..f137afdeeb 100644
--- a/src/mbgl/renderer/layers/render_custom_layer.cpp
+++ b/src/mbgl/renderer/layers/render_custom_layer.cpp
@@ -16,14 +16,24 @@ RenderCustomLayer::RenderCustomLayer(Immutable<style::CustomLayer::Impl> _impl)
 
 RenderCustomLayer::~RenderCustomLayer() {
     assert(BackendScope::exists());
-    if (initialized) {
-        if (contextDestroyed && impl().contextLostFn ) {
-            impl().contextLostFn(impl().context);
-        } else if (!contextDestroyed && impl().deinitializeFn) {
-            impl().deinitializeFn(impl().context);
+    if (initialized && impl().context.get()) {
+
+        if (contextDestroyed) {
+            impl().context->lost();
+        }
+        else {
+            impl().context->deinitialize();
         }
 
-        impl().detachFn(impl().context);
+        impl().context->detach();
+
+//        if (contextDestroyed && impl().contextLostFn ) {
+//            impl().contextLostFn(impl().context);
+//        } else if (!contextDestroyed && impl().deinitializeFn) {
+//            impl().deinitializeFn(impl().context);
+//        }
+//
+//        impl().detachFn(impl().context);
     }
 }
 
@@ -46,23 +56,19 @@ std::unique_ptr<Bucket> RenderCustomLayer::createBucket(const BucketParameters&,
 
 void RenderCustomLayer::render(PaintParameters& paintParameters, RenderSource*) {
     if (context != impl().context || !initialized) {
-        //If the context changed, deinitialize the previous one before initializing the new one.
-        if (context && !contextDestroyed && impl().deinitializeFn) {
-            impl().deinitializeFn(context);
 
-            if (impl().detachFn) {
-                impl().detachFn(context);
-            }
+        if (!contextDestroyed && context.get()) {
+            context->deinitialize();
+            context->detach();
         }
+
         context = impl().context;
 
-        if (impl().attachFn) {
-            impl().attachFn(context);
+        if (context.get()) {
+            context->attach();
+            context->initialize();
         }
 
-        assert(impl().initializeFn);
-        impl().initializeFn(impl().context);
-
         initialized = true;
     }
 
@@ -86,8 +92,9 @@ void RenderCustomLayer::render(PaintParameters& paintParameters, RenderSource*)
     parameters.pitch = state.getPitch();
     parameters.fieldOfView = state.getFieldOfView();
 
-    assert(impl().renderFn);
-    impl().renderFn(context, parameters);
+//    assert(impl().renderFn);
+    context->render(parameters);
+//    impl().renderFn(context, parameters);
 
     // Reset the view back to our original one, just in case the CustomLayer changed
     // the viewport or Framebuffer.
diff --git a/src/mbgl/renderer/layers/render_custom_layer.hpp b/src/mbgl/renderer/layers/render_custom_layer.hpp
index 6d1fea99d3..3e3aa6d365 100644
--- a/src/mbgl/renderer/layers/render_custom_layer.hpp
+++ b/src/mbgl/renderer/layers/render_custom_layer.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/renderer/render_layer.hpp>
 #include <mbgl/style/layers/custom_layer_impl.hpp>
+#include <mbgl/style/layers/custom_layer.hpp>
 
 namespace mbgl {
 
@@ -26,7 +27,7 @@ public:
 private:
     bool initialized = false;
     bool contextDestroyed = false;
-    void * context = nullptr;
+    std::shared_ptr<style::CustomLayerContext> context;
 };
 
 template <>
diff --git a/src/mbgl/style/layers/custom_layer.cpp b/src/mbgl/style/layers/custom_layer.cpp
index 234aa13b83..ee8695b6c3 100644
--- a/src/mbgl/style/layers/custom_layer.cpp
+++ b/src/mbgl/style/layers/custom_layer.cpp
@@ -13,43 +13,17 @@ CustomLayer::~CustomLayer()
 }
 
 CustomLayer::CustomLayer(const std::string& layerID,
-                         CustomLayerInitializeFunction init,
-                         CustomLayerRenderFunction render,
-                         CustomLayerContextLostFunction contextLost,
-                         CustomLayerDeinitializeFunction deinit,
-
-                         CustomLayerContextOwnerChangedFunction ownerChanged,
-                         CustomLayerContextAttachFunction attach,
-                         CustomLayerContextDetachFunction detach,
-                         void* context)
-    : Layer(makeMutable<Impl>(layerID, init, render, contextLost, deinit, ownerChanged, attach, detach, context))
+                         std::unique_ptr<CustomLayerContext> context):
+    Layer(makeMutable<Impl>(layerID, std::move(context)))
 {
     printf("CustomLayer::CustomLayer %p\n", this);
 
 }
 
-CustomLayer::CustomLayer(const std::string& layerID,
-                         CustomLayerInitializeFunction init,
-                         CustomLayerRenderFunction render,
-                         CustomLayerDeinitializeFunction deinit,
-
-                         CustomLayerContextOwnerChangedFunction ownerChanged,
-                         CustomLayerContextAttachFunction attach,
-                         CustomLayerContextDetachFunction detach,
-                         void* context)
-    : Layer(makeMutable<Impl>(layerID, init, render, nullptr, deinit, ownerChanged, attach, detach, context))
-{
-    printf("CustomLayer::CustomLayer %p\n", this);
-}
-
 const CustomLayer::Impl& CustomLayer::impl() const {
     return static_cast<const Impl&>(*baseImpl);
 }
 
-const void* CustomLayer::getContext() const {
-    return impl().context;
-}
-
 Mutable<CustomLayer::Impl> CustomLayer::mutableImpl() const {
     return makeMutable<Impl>(impl());
 }
diff --git a/src/mbgl/style/layers/custom_layer_impl.cpp b/src/mbgl/style/layers/custom_layer_impl.cpp
index 5d1e1f6ab5..3fdeb156a2 100644
--- a/src/mbgl/style/layers/custom_layer_impl.cpp
+++ b/src/mbgl/style/layers/custom_layer_impl.cpp
@@ -4,41 +4,21 @@ namespace mbgl {
 namespace style {
 
 CustomLayer::Impl::~Impl() {
-    if (changeOwnerFn)
-        changeOwnerFn(context, NULL);
 }
 
 CustomLayer::Impl::Impl(const std::string& id_,
-                        CustomLayerInitializeFunction initializeFn_,
-                        CustomLayerRenderFunction renderFn_,
-                        CustomLayerContextLostFunction contextLostFn_,
-                        CustomLayerDeinitializeFunction deinitializeFn_,
-
-                        CustomLayerContextOwnerChangedFunction changeOwnerFn_,
-                        CustomLayerContextAttachFunction attachFn_,
-                        CustomLayerContextDetachFunction detachFn_,
-
-                        void* context_):
+                        std::unique_ptr<CustomLayerContext> context_):
     Layer::Impl(LayerType::Custom, id_, std::string()),
-    initializeFn(initializeFn_),
-    renderFn(renderFn_),
-    contextLostFn(contextLostFn_),
-    deinitializeFn(deinitializeFn_),
-    changeOwnerFn(changeOwnerFn_),
-    attachFn(attachFn_),
-    detachFn(detachFn_),
-    context(context_) {
-
-        if (changeOwnerFn)
-            changeOwnerFn(context, this);
+    context(std::move(context_)) {
+
 }
 
 void CustomLayer::Impl::didSetObserver(bool didSet) const {
     if (didSet) {
-        if (attachFn) attachFn(context);
+        context->attach();
     }
     else {
-        if (detachFn) detachFn(context);
+        context->detach();
     }
 }
 
diff --git a/src/mbgl/style/layers/custom_layer_impl.hpp b/src/mbgl/style/layers/custom_layer_impl.hpp
index 6bc23f0759..5524b6a75e 100644
--- a/src/mbgl/style/layers/custom_layer_impl.hpp
+++ b/src/mbgl/style/layers/custom_layer_impl.hpp
@@ -14,29 +14,12 @@ public:
     virtual ~Impl();
 
     Impl(const std::string& id,
-         CustomLayerInitializeFunction,
-         CustomLayerRenderFunction,
-         CustomLayerContextLostFunction,
-         CustomLayerDeinitializeFunction,
-
-         CustomLayerContextOwnerChangedFunction,
-         CustomLayerContextAttachFunction,
-         CustomLayerContextDetachFunction,
-         void* context);
+         std::unique_ptr<CustomLayerContext> context);
 
     bool hasLayoutDifference(const Layer::Impl&) const override;
     void stringifyLayout(rapidjson::Writer<rapidjson::StringBuffer>&) const override;
 
-    CustomLayerInitializeFunction initializeFn = nullptr;
-    CustomLayerRenderFunction renderFn = nullptr;
-    CustomLayerContextLostFunction contextLostFn = nullptr;
-    CustomLayerDeinitializeFunction deinitializeFn = nullptr;
-
-    CustomLayerContextOwnerChangedFunction changeOwnerFn = nullptr;
-    CustomLayerContextAttachFunction attachFn = nullptr;
-    CustomLayerContextDetachFunction detachFn = nullptr;
-
-    void* context = nullptr;
+    std::shared_ptr<CustomLayerContext> context;
 
     void didSetObserver(bool didSet) const;
 };