[ios, macos] Layer ownership refactor (#6904)

`MGLStyleLayer` was updated to support a raw pointer to the mbgl object, which is always initialized, either to the  value returned by `mbgl::Map getLayer`, or for independently created objects,  to the pointer value held in `pendingLayer`. In the latter case, this raw  pointer value stays even after ownership of the object is transferred via  `mbgl::Map addLayer`.

1 files changed, 33 insertions, 8 deletions

diff --git a/platform/darwin/src/MGLBackgroundStyleLayer.mm b/platform/darwin/src/MGLBackgroundStyleLayer.mm
index 33a105e5d5..38c97e8d46 100644
--- a/platform/darwin/src/MGLBackgroundStyleLayer.mm
+++ b/platform/darwin/src/MGLBackgroundStyleLayer.mm
@@ -2,6 +2,7 @@
 // Edit platform/darwin/scripts/generate-style-code.js, then run `make style-code-darwin`.
 
 #import "MGLSource.h"
+#import "MGLMapView_Private.h"
 #import "NSPredicate+MGLAdditions.h"
 #import "MGLStyleLayer_Private.h"
 #import "MGLStyleValue_Private.h"
@@ -11,50 +12,74 @@
 
 @interface MGLBackgroundStyleLayer ()
 
-@property (nonatomic) mbgl::style::BackgroundLayer *layer;
+@property (nonatomic) mbgl::style::BackgroundLayer *rawLayer;
 
 @end
 
 @implementation MGLBackgroundStyleLayer
+{
+    std::unique_ptr<mbgl::style::BackgroundLayer> _pendingLayer;
+}
 
 - (instancetype)initWithIdentifier:(NSString *)identifier
 {
     if (self = [super initWithIdentifier:identifier]) {
-        _layer = new mbgl::style::BackgroundLayer(identifier.UTF8String);
+        auto layer = std::make_unique<mbgl::style::BackgroundLayer>(identifier.UTF8String);
+        _pendingLayer = std::move(layer);
+        self.rawLayer = _pendingLayer.get();
     }
     return self;
 }
 
+
 #pragma mark - Accessing the Paint Attributes
 
 - (void)setBackgroundColor:(MGLStyleValue<MGLColor *> *)backgroundColor {
     auto mbglValue = MGLStyleValueTransformer<mbgl::Color, MGLColor *>().toPropertyValue(backgroundColor);
-    self.layer->setBackgroundColor(mbglValue);
+    self.rawLayer->setBackgroundColor(mbglValue);
 }
 
 - (MGLStyleValue<MGLColor *> *)backgroundColor {
-    auto propertyValue = self.layer->getBackgroundColor() ?: self.layer->getDefaultBackgroundColor();
+    auto propertyValue = self.rawLayer->getBackgroundColor() ?: self.rawLayer->getDefaultBackgroundColor();
     return MGLStyleValueTransformer<mbgl::Color, MGLColor *>().toStyleValue(propertyValue);
 }
 
 - (void)setBackgroundPattern:(MGLStyleValue<NSString *> *)backgroundPattern {
     auto mbglValue = MGLStyleValueTransformer<std::string, NSString *>().toPropertyValue(backgroundPattern);
-    self.layer->setBackgroundPattern(mbglValue);
+    self.rawLayer->setBackgroundPattern(mbglValue);
 }
 
 - (MGLStyleValue<NSString *> *)backgroundPattern {
-    auto propertyValue = self.layer->getBackgroundPattern() ?: self.layer->getDefaultBackgroundPattern();
+    auto propertyValue = self.rawLayer->getBackgroundPattern() ?: self.rawLayer->getDefaultBackgroundPattern();
     return MGLStyleValueTransformer<std::string, NSString *>().toStyleValue(propertyValue);
 }
 
 - (void)setBackgroundOpacity:(MGLStyleValue<NSNumber *> *)backgroundOpacity {
     auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toPropertyValue(backgroundOpacity);
-    self.layer->setBackgroundOpacity(mbglValue);
+    self.rawLayer->setBackgroundOpacity(mbglValue);
 }
 
 - (MGLStyleValue<NSNumber *> *)backgroundOpacity {
-    auto propertyValue = self.layer->getBackgroundOpacity() ?: self.layer->getDefaultBackgroundOpacity();
+    auto propertyValue = self.rawLayer->getBackgroundOpacity() ?: self.rawLayer->getDefaultBackgroundOpacity();
     return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(propertyValue);
 }
 
+
+#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