[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.

13 files changed, 219 insertions, 128 deletions

diff --git a/platform/darwin/src/MGLBackgroundStyleLayer.mm b/platform/darwin/src/MGLBackgroundStyleLayer.mm
index 38c97e8d46..a4914d3242 100644
--- a/platform/darwin/src/MGLBackgroundStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLCircleStyleLayer.mm b/platform/darwin/src/MGLCircleStyleLayer.mm
index 13eedf3f96..13262a8c9c 100644
--- a/platform/darwin/src/MGLCircleStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLFillStyleLayer.mm b/platform/darwin/src/MGLFillStyleLayer.mm
index 1f8b7402d8..5aed779c86 100644
--- a/platform/darwin/src/MGLFillStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLGeoJSONSource.mm b/platform/darwin/src/MGLGeoJSONSource.mm
index 0dbe1030c6..0213b6a27e 100644
--- a/platform/darwin/src/MGLGeoJSONSource.mm
+++ b/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);
diff --git a/platform/darwin/src/MGLLineStyleLayer.mm b/platform/darwin/src/MGLLineStyleLayer.mm
index aa699ea37d..c7509e2870 100644
--- a/platform/darwin/src/MGLLineStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLRasterSource.mm b/platform/darwin/src/MGLRasterSource.mm
index fc47c23853..92494febff 100644
--- a/platform/darwin/src/MGLRasterSource.mm
+++ b/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
diff --git a/platform/darwin/src/MGLRasterStyleLayer.mm b/platform/darwin/src/MGLRasterStyleLayer.mm
index ba1df40f95..063f5e3384 100644
--- a/platform/darwin/src/MGLRasterStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLSource_Private.h b/platform/darwin/src/MGLSource_Private.h
index dff230ede5..d360e71f3c 100644
--- a/platform/darwin/src/MGLSource_Private.h
+++ b/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
diff --git a/platform/darwin/src/MGLStyle.mm b/platform/darwin/src/MGLStyle.mm
index d59194725b..7e67273a38 100644
--- a/platform/darwin/src/MGLStyle.mm
+++ b/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
diff --git a/platform/darwin/src/MGLStyleLayer.mm.ejs b/platform/darwin/src/MGLStyleLayer.mm.ejs
index 48d013d482..d366a1955b 100644
--- a/platform/darwin/src/MGLStyleLayer.mm.ejs
+++ b/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
diff --git a/platform/darwin/src/MGLStyleLayer_Private.h b/platform/darwin/src/MGLStyleLayer_Private.h
index f61630b8c4..bfce452a4a 100644
--- a/platform/darwin/src/MGLStyleLayer_Private.h
+++ b/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`.
diff --git a/platform/darwin/src/MGLSymbolStyleLayer.mm b/platform/darwin/src/MGLSymbolStyleLayer.mm
index 539e0f2cc7..082743be58 100644
--- a/platform/darwin/src/MGLSymbolStyleLayer.mm
+++ b/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
diff --git a/platform/darwin/src/MGLVectorSource.mm b/platform/darwin/src/MGLVectorSource.mm
index 995565419f..2c7b529d74 100644
--- a/platform/darwin/src/MGLVectorSource.mm
+++ b/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