[ios, macos] Take back source and layer ownership on removal (#7048)

If a source or layer is removed from the style, recapture the
unique pointer ownership. This makes it safe to add back sources
and layers after they have been removed.

platform/darwin/src/MGLBackgroundStyleLayer.mm

@@ -32,6 +32,31 @@
 }
 
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::BackgroundLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Paint Attributes
 
 - (void)setBackgroundColor:(MGLStyleValue<MGLColor *> *)backgroundColor {
@@ -65,21 +90,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLCircleStyleLayer.mm

@@ -53,6 +53,31 @@
     return [NSPredicate mgl_predicateWithFilter:self.rawLayer->getFilter()];
 }
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::CircleLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Paint Attributes
 
 - (void)setCircleRadius:(MGLStyleValue<NSNumber *> *)circleRadius {
@@ -126,21 +151,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLFillStyleLayer.mm

@@ -53,6 +53,31 @@
     return [NSPredicate mgl_predicateWithFilter:self.rawLayer->getFilter()];
 }
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::FillLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Paint Attributes
 
 - (void)setFillAntialias:(MGLStyleValue<NSNumber *> *)fillAntialias {
@@ -126,21 +151,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLGeoJSONSource.mm

@@ -64,6 +64,14 @@ const MGLGeoJSONSourceOption MGLGeoJSONSourceOptionSimplificationTolerance = @"M
     mapView.mbglMap->addSource(std::move(_pendingSource));
 }
 
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedSource = mapView.mbglMap->removeSource(self.identifier.UTF8String);
+
+    _pendingSource = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::GeoJSONSource> &>(removedSource));
+    self.rawSource = _pendingSource.get();
+}
+
 - (void)commonInit
 {
     auto source = std::make_unique<mbgl::style::GeoJSONSource>(self.identifier.UTF8String, self.geoJSONOptions);

platform/darwin/src/MGLLineStyleLayer.mm

@@ -53,6 +53,31 @@
     return [NSPredicate mgl_predicateWithFilter:self.rawLayer->getFilter()];
 }
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::LineLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Layout Attributes
 
 - (void)setLineCap:(MGLStyleValue<NSValue *> *)lineCap {
@@ -198,21 +223,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLRasterSource.mm

@@ -65,4 +65,12 @@
     mapView.mbglMap->addSource(std::move(_pendingSource));
 }
 
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedSource = mapView.mbglMap->removeSource(self.identifier.UTF8String);
+
+    _pendingSource = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::RasterSource> &>(removedSource));
+    self.rawSource = _pendingSource.get();
+}
+
 @end

platform/darwin/src/MGLRasterStyleLayer.mm

@@ -32,6 +32,31 @@
 }
 
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::RasterLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Paint Attributes
 
 - (void)setRasterOpacity:(MGLStyleValue<NSNumber *> *)rasterOpacity {
@@ -105,21 +130,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLSource_Private.h

@@ -28,4 +28,13 @@
  */
 - (void)addToMapView:(MGLMapView *)mapView;
 
+/**
+ Removes the mbgl source that this object represents from the mbgl map.
+ 
+ When a mbgl source is removed, ownership of the object is transferred back
+ to the `MGLSource` instance and the unique_ptr reference is valid again. It is
+ safe to add the source back to the style after it is removed.
+ */
+- (void)removeFromMapView:(MGLMapView *)mapView;
+
 @end

platform/darwin/src/MGLStyle.mm

@@ -168,7 +168,7 @@ static NSURL *MGLStyleURL_emerald;
 
 - (void)removeLayer:(MGLStyleLayer *)layer
 {
-    self.mapView.mbglMap->removeLayer(layer.identifier.UTF8String);
+    [layer removeFromMapView:self.mapView];    
 }
 
 - (void)addLayer:(MGLStyleLayer *)layer
@@ -209,12 +209,7 @@ static NSURL *MGLStyleURL_emerald;
 
 - (void)removeSource:(MGLSource *)source
 {
-    self.mapView.mbglMap->removeSource(source.identifier.UTF8String);
-    
-    // Once a mbgl source is removed from the map, ownership does not return
-    // to the MGL source. Therefore, the rawSource pointer is set to NULL
-    // so that the implementation of MGL source can avoid using it again.
-    source.rawSource = NULL;
+    [source removeFromMapView:self.mapView];
 }
 
 - (NS_ARRAY_OF(NSString *) *)styleClasses

platform/darwin/src/MGLStyleLayer.mm.ejs

@@ -73,6 +73,31 @@
 }
 
 <% } -%>
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::<%- camelize(type) %>Layer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 <% if (layoutProperties.length) { -%>
 #pragma mark - Accessing the Layout Attributes
 
@@ -106,21 +131,4 @@
 <% } -%>
 <% } -%>
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLStyleLayer_Private.h

@@ -29,11 +29,18 @@
  */
 - (void)addToMapView:(MGLMapView *)mapView;
 
-
+/**
+ Removes the mbgl style layer that this object represents from the mbgl map.
+ 
+ When a mbgl style layer is removed, ownership of the object is transferred back
+ to the `MGLStyleLayer` instance and the unique_ptr reference is valid again. It 
+ is safe to add the layer back to the style after it is removed.
+ */
+- (void)removeFromMapView:(MGLMapView *)mapView;
 
 /**
  Adds the mbgl style layer that this object represents to the mbgl map below the specified `otherLayer`.
- 
+
  Once a mbgl style layer is added, ownership of the object is transferred to the
  `mbgl::Map` and this object no longer has an active unique_ptr reference to the
  `mbgl::style::Layer`.

platform/darwin/src/MGLSymbolStyleLayer.mm

@@ -53,6 +53,31 @@
     return [NSPredicate mgl_predicateWithFilter:self.rawLayer->getFilter()];
 }
 
+
+#pragma mark -  Adding to and removing from a map view
+
+- (void)addToMapView:(MGLMapView *)mapView
+{
+    [self addToMapView:mapView belowLayer:nil];
+}
+
+- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
+{
+    if (otherLayer) {
+        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
+        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
+    } else {
+        mapView.mbglMap->addLayer(std::move(_pendingLayer));
+    }
+}
+
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedLayer = mapView.mbglMap->removeLayer(self.identifier.UTF8String);
+    _pendingLayer = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::SymbolLayer> &>(removedLayer));
+    self.rawLayer = _pendingLayer.get();
+}
+
 #pragma mark - Accessing the Layout Attributes
 
 - (void)setSymbolPlacement:(MGLStyleValue<NSValue *> *)symbolPlacement {
@@ -538,21 +563,4 @@
 }
 
 
-#pragma mark - Add style layer to map
-
-- (void)addToMapView:(MGLMapView *)mapView
-{
-    [self addToMapView:mapView belowLayer:nil];
-}
-
-- (void)addToMapView:(MGLMapView *)mapView belowLayer:(MGLStyleLayer *)otherLayer
-{
-    if (otherLayer) {
-        const mbgl::optional<std::string> belowLayerId{otherLayer.identifier.UTF8String};
-        mapView.mbglMap->addLayer(std::move(_pendingLayer), belowLayerId);
-    } else {
-        mapView.mbglMap->addLayer(std::move(_pendingLayer));
-    }
-}
-
 @end

platform/darwin/src/MGLVectorSource.mm

@@ -64,4 +64,12 @@ static NSString *MGLVectorSourceType   = @"vector";
     mapView.mbglMap->addSource(std::move(_pendingSource));
 }
 
+- (void)removeFromMapView:(MGLMapView *)mapView
+{
+    auto removedSource = mapView.mbglMap->removeSource(self.identifier.UTF8String);
+
+    _pendingSource = std::move(reinterpret_cast<std::unique_ptr<mbgl::style::VectorSource> &>(removedSource));
+    self.rawSource = _pendingSource.get();
+}
+
 @end