Enable layer insertion below symbols (#70)

Author: ianthetechie

CHANGELOG.md

@@ -5,6 +5,17 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Version 0.7.0 - 2025-02-02
+
+### Added
+
+- Adds support for a `belowSymbols` layer order. The `renderBelowSymbols` modifier on layers will insert the new layer below the first symbol layer in the style. This allows for rendering below labels and icons.
+- BREAKING: Refactored the layer position modifiers to accept enum variants to enable better extensibility.
+
+### Fixed
+
+- Moved modifiers on `StyleLayer` to `StyleLayerDefinition`. The previous extension of `StyleLayer` was a mistake, since `StyleLayerDefinition` is the supertype, and none of the behavior was specific to `StyleLayer`.
+
 ## Version 0.6.0 - 2025-01-14
 
 - Potentially BREAKING: Upgrades Mockable to 0.2.0. If you're using mockable in your project, this may require you to upgrade there as well.

Sources/MapLibreSwiftDSL/Style Layers/Background.swift

@@ -7,7 +7,7 @@ import MapLibreSwiftMacros
 @MLNStyleProperty<Float>("backgroundOpacity", supportsInterpolation: true)
 public struct BackgroundLayer: StyleLayer {
     public let identifier: String
-    public var insertionPosition: LayerInsertionPosition = .belowOthers
+    public var insertionPosition: LayerInsertionPosition = .below(.all)
     public var isVisible: Bool = true
     public var maximumZoomLevel: Float? = nil
     public var minimumZoomLevel: Float? = nil

Sources/MapLibreSwiftDSL/Style Layers/Circle.swift

@@ -10,7 +10,7 @@ import MapLibreSwiftMacros
 public struct CircleStyleLayer: SourceBoundVectorStyleLayerDefinition {
     public let identifier: String
     public let sourceLayerIdentifier: String?
-    public var insertionPosition: LayerInsertionPosition = .aboveOthers
+    public var insertionPosition: LayerInsertionPosition = .above(.all)
     public var isVisible: Bool = true
     public var maximumZoomLevel: Float? = nil
     public var minimumZoomLevel: Float? = nil

Sources/MapLibreSwiftDSL/Style Layers/FillStyleLayer.swift

@@ -10,7 +10,7 @@ import MapLibreSwiftMacros
 public struct FillStyleLayer: SourceBoundVectorStyleLayerDefinition {
     public let identifier: String
     public let sourceLayerIdentifier: String?
-    public var insertionPosition: LayerInsertionPosition = .aboveOthers
+    public var insertionPosition: LayerInsertionPosition = .above(.all)
     public var isVisible: Bool = true
     public var maximumZoomLevel: Float? = nil
     public var minimumZoomLevel: Float? = nil

Sources/MapLibreSwiftDSL/Style Layers/Line.swift

@@ -11,7 +11,7 @@ import MapLibreSwiftMacros
 public struct LineStyleLayer: SourceBoundVectorStyleLayerDefinition {
     public let identifier: String
     public let sourceLayerIdentifier: String?
-    public var insertionPosition: LayerInsertionPosition = .aboveOthers
+    public var insertionPosition: LayerInsertionPosition = .above(.all)
     public var isVisible: Bool = true
     public var maximumZoomLevel: Float? = nil
     public var minimumZoomLevel: Float? = nil

Sources/MapLibreSwiftDSL/Style Layers/Style Layer.swift

@@ -1,20 +1,34 @@
 import InternalUtils
 import MapLibre
 
+/// A layer reference specifying which layer we should insert a new layer above.
+public enum LayerReferenceAbove: Equatable {
+    /// A specific layer, referenced by ID.
+    case layer(layerId: String)
+    /// The group of all layers currently in the style.
+    case all
+}
+
+/// A layer reference specifying which layer we should insert a new layer below.
+public enum LayerReferenceBelow: Equatable {
+    /// A specific layer, referenced by ID.
+    case layer(layerId: String)
+    /// The group of all layers currently in the style.
+    case all
+    /// The group of symbol layers currently in the style.
+    case symbols
+}
+
 /// Specifies a preference for where the layer should be inserted in the hierarchy.
 public enum LayerInsertionPosition: Equatable {
     /// The layer should be inserted above the layer with ID ``layerID``.
     ///
     /// If no such layer exists, the layer will be added above others and an error will be logged.
-    case above(layerID: String)
+    case above(LayerReferenceAbove)
     /// The layer should be inserted below the layer with ID ``layerID``.
     ///
     /// If no such layer exists, the layer will be added above others and an error will be logged.
-    case below(layerID: String)
-    /// The layer should be inserted above other existing layers.
-    case aboveOthers
-    /// The layer should be inserted below other existing layers.
-    case belowOthers
+    case below(LayerReferenceBelow)
 }
 
 /// Internal style enum that wraps a source reference.
@@ -132,7 +146,7 @@ public extension StyleLayer {
     }
 }
 
-public extension StyleLayer {
+public extension StyleLayerDefinition {
     // MARK: - Common modifiers
 
     func visible(_ value: Bool) -> Self {
@@ -147,29 +161,11 @@ public extension StyleLayer {
         modified(self) { $0.maximumZoomLevel = value }
     }
 
-    func renderAbove(_ layerID: String) -> Self {
-        modified(self) { $0.insertionPosition = .above(layerID: layerID) }
-    }
-
-    func renderBelow(_ layerID: String) -> Self {
-        modified(self) { $0.insertionPosition = .below(layerID: layerID) }
-    }
-
-    func renderAboveOthers() -> Self {
-        modified(self) { $0.insertionPosition = .aboveOthers }
+    func renderAbove(_ layerReference: LayerReferenceAbove) -> Self {
+        modified(self) { $0.insertionPosition = .above(layerReference) }
     }
 
-    func renderBelowOthers() -> Self {
-        modified(self) { $0.insertionPosition = .belowOthers }
-    }
-}
-
-public extension StyleLayerDefinition {
-    func minimumZoomLevel(_ value: Float) -> Self {
-        modified(self) { $0.minimumZoomLevel = value }
-    }
-
-    func maximumZoomLevel(_ value: Float) -> Self {
-        modified(self) { $0.maximumZoomLevel = value }
+    func renderBelow(_ layerReference: LayerReferenceBelow) -> Self {
+        modified(self) { $0.insertionPosition = .below(layerReference) }
     }
 }

Sources/MapLibreSwiftDSL/Style Layers/Symbol.swift

@@ -23,7 +23,7 @@ import MapLibreSwiftMacros
 public struct SymbolStyleLayer: SourceBoundVectorStyleLayerDefinition {
     public let identifier: String
     public let sourceLayerIdentifier: String?
-    public var insertionPosition: LayerInsertionPosition = .aboveOthers
+    public var insertionPosition: LayerInsertionPosition = .above(.all)
     public var isVisible: Bool = true
     public var maximumZoomLevel: Float? = nil
     public var minimumZoomLevel: Float? = nil

Sources/MapLibreSwiftUI/Examples/Layers.swift

@@ -38,7 +38,7 @@ let clustered = ShapeSource(identifier: "points", options: [.clustered: true, .c
         // Silly example: a background layer on top of everything to create a tint effect
         BackgroundLayer(identifier: "rose-colored-glasses")
             .backgroundColor(.systemPink.withAlphaComponent(0.3))
-            .renderAboveOthers()
+            .renderAbove(.all)
     }
     .ignoresSafeArea(.all)
 }

Sources/MapLibreSwiftUI/Examples/Polyline.swift

@@ -26,6 +26,7 @@ struct PolylineMapView: View {
                            curveType: .exponential,
                            parameters: NSExpression(forConstantValue: 1.5),
                            stops: NSExpression(forConstantValue: [14: 6, 18: 24]))
+                .renderBelow(.symbols)
 
             // Add an inner (blue) polyline
             LineStyleLayer(identifier: "polyline-inner", source: polylineSource)
@@ -36,6 +37,7 @@ struct PolylineMapView: View {
                            curveType: .exponential,
                            parameters: NSExpression(forConstantValue: 1.5),
                            stops: NSExpression(forConstantValue: [14: 3, 18: 16]))
+                .renderBelow(.symbols)
         }
     }
 }

Sources/MapLibreSwiftUI/MapViewCoordinator.swift

@@ -268,6 +268,10 @@ public class MapViewCoordinator<T: MapViewHostViewController>: NSObject, MLNMapV
     }
 
     func addLayers(to mglStyle: MLNStyle) {
+        let firstSymbolLayer = mglStyle.layers.first { layer in
+            layer is MLNSymbolStyleLayer
+        }
+
         for layerSpec in parent.userLayers {
             // DISCUSS: What preventions should we try to put in place against the user accidentally adding the same layer twice?
             let newLayer = layerSpec.makeStyleLayer(style: mglStyle).makeMLNStyleLayer()
@@ -284,24 +288,30 @@ public class MapViewCoordinator<T: MapViewHostViewController>: NSObject, MLNMapV
             }
 
             switch layerSpec.insertionPosition {
-            case let .above(layerID: id):
+            case let .above(.layer(layerId: id)):
                 if let layer = mglStyle.layer(withIdentifier: id) {
                     mglStyle.insertLayer(newLayer, above: layer)
                 } else {
                     NSLog("Failed to find layer with ID \(id). Adding layer on top.")
                     mglStyle.addLayer(newLayer)
                 }
-            case let .below(layerID: id):
+            case .above(.all):
+                mglStyle.addLayer(newLayer)
+            case let .below(.layer(layerId: id)):
                 if let layer = mglStyle.layer(withIdentifier: id) {
                     mglStyle.insertLayer(newLayer, below: layer)
                 } else {
                     NSLog("Failed to find layer with ID \(id). Adding layer on top.")
                     mglStyle.addLayer(newLayer)
                 }
-            case .aboveOthers:
-                mglStyle.addLayer(newLayer)
-            case .belowOthers:
+            case .below(.all):
                 mglStyle.insertLayer(newLayer, at: 0)
+            case .below(.symbols):
+                if let firstSymbolLayer {
+                    mglStyle.insertLayer(newLayer, below: firstSymbolLayer)
+                } else {
+                    mglStyle.addLayer(newLayer)
+                }
             }
         }
     }