Add typed gesture utility

Author: li3zhen1

Examples/ForceDirectedGraphExample/ForceDirectedGraphExample/Lattice.swift

@@ -57,7 +57,7 @@ struct Lattice: View {
         }
         .graphOverlay(content: { proxy in
             Rectangle().fill(.clear).contentShape(Rectangle())
-                .withGraphDragGesture(proxy)
+                .withGraphDragGesture(proxy, of: Int.self)
         })
         .toolbar {
             GraphStateToggle(graphStates: graphStates)

Examples/ForceDirectedGraphExample/ForceDirectedGraphExample/MermaidVisualization.swift

@@ -107,7 +107,7 @@ struct MermaidVisualization: View {
         }
         .graphOverlay(content: { proxy in
             Rectangle().fill(.clear).contentShape(Rectangle())
-                .withGraphDragGesture(proxy)
+                .withGraphDragGesture(proxy, of: String.self)
                 .onTapGesture { value in
                     if let nodeID = proxy.node(of: String.self, at: value) {
                         model.tappedNode = nodeID

Examples/ForceDirectedGraphExample/ForceDirectedGraphExample/MyRing.swift

@@ -59,18 +59,17 @@ struct MyRing: View {
         }
         .graphOverlay { proxy in
             Rectangle().fill(.clear).contentShape(Rectangle())
-                .withGraphDragGesture(proxy, action: describe)
+                .withGraphDragGesture(proxy, of: Int.self, action: describe)
                 .withGraphMagnifyGesture(proxy)
         }
         .toolbar {
             GraphStateToggle(graphStates: graphStates)
         }
     }
 
-    func describe(_ state: GraphDragState?) {
+    func describe(_ state: GraphDragState<Int>?) {
         switch state {
-        case .node(let anyHashable):
-            let id = anyHashable as! Int
+        case .node(let id):
             if draggingNodeID != id {
                 draggingNodeID = id
                 print("Dragging \(id)")

Sources/Grape/Gestures/GraphDragGesture.swift

@@ -1,15 +1,15 @@
 import ForceSimulation
 import SwiftUI
 
-public enum GraphDragState {
-    case node(AnyHashable)
-    case background(start: SIMD2<Double>)
+public enum GraphDragState<NodeID: Hashable> {
+    case node(NodeID)
+    case background(SIMD2<Double>)
 }
 
 #if !os(tvOS)
 
 @usableFromInline
-struct GraphDragModifier: ViewModifier {
+struct GraphDragModifier<NodeID: Hashable>: ViewModifier {
 
     @inlinable
     public var dragGesture: some Gesture {
@@ -28,18 +28,18 @@ struct GraphDragModifier: ViewModifier {
 
     @inlinable
     @State
-    public var dragState: GraphDragState?
+    public var dragState: GraphDragState<NodeID>?
 
     @usableFromInline
     let graphProxy: GraphProxy
 
     @usableFromInline
-    let action: ((GraphDragState?) -> Void)?
+    let action: ((GraphDragState<NodeID>?) -> Void)?
 
     @inlinable
     init(
         graphProxy: GraphProxy,
-        action: ((GraphDragState?) -> Void)? = nil
+        action: ((GraphDragState<NodeID>?) -> Void)? = nil
     ) {
         self.graphProxy = graphProxy
         self.action = action
@@ -62,7 +62,7 @@ struct GraphDragModifier: ViewModifier {
             case .background(let start):
                 let delta = value.location.simd - start
                 graphProxy.modelTransform.translate += delta
-                dragState = .background(start: value.location.simd)
+                dragState = .background(value.location.simd)
             case .none:
                 break
             }
@@ -79,11 +79,11 @@ struct GraphDragModifier: ViewModifier {
         value: DragGesture.Value
     ) {
         if dragState == nil {
-            if let nodeID = graphProxy.node(at: value.startLocation) {
+            if let nodeID = graphProxy.node(of: NodeID.self, at: value.startLocation) {
                 dragState = .node(nodeID)
                 graphProxy.setNodeFixation(nodeID: nodeID, fixation: value.startLocation)
             } else {
-                dragState = .background(start: value.location.simd)
+                dragState = .background(value.location.simd)
             }
         } else {
             switch dragState {
@@ -92,7 +92,7 @@ struct GraphDragModifier: ViewModifier {
             case .background(let start):
                 let delta = value.location.simd - start
                 graphProxy.modelTransform.translate += delta
-                dragState = .background(start: value.location.simd)
+                dragState = .background(value.location.simd)
             case .none:
                 break
             }
@@ -105,10 +105,17 @@ struct GraphDragModifier: ViewModifier {
 }
 
 extension View {
+
+    /// Attach a drag gesture to an overlay or a background view created with ``SwiftUICore/View/graphOverlay(alignment:content:)``.
+    /// - Parameters:
+    ///  - proxy: The graph proxy that provides the graph context.
+    ///  - type: The type of the node ID. The drag gesture will look for the node ID of this type.
+    ///  - action: The action to perform when the drag gesture changes.
     @inlinable
-    public func withGraphDragGesture(
+    public func withGraphDragGesture<NodeID>(
         _ proxy: GraphProxy,
-        action: ((GraphDragState?) -> Void)? = nil
+        of type: NodeID.Type,
+        action: ((GraphDragState<NodeID>?) -> Void)? = nil
     ) -> some View {
         self.modifier(GraphDragModifier(graphProxy: proxy, action: action))
     }

Sources/Grape/Gestures/GraphTapGesture.swift

@@ -3,12 +3,13 @@ import SwiftUI
 extension View {
     @inlinable
     @available(tvOS, unavailable)
-    public func withGraphTapGesture(
+    public func withGraphTapGesture<NodeID: Hashable>(
         _ proxy: GraphProxy,
-        action: @escaping (AnyHashable) -> Void
+        of type: NodeID.Type,
+        action: @escaping (NodeID) -> Void
     ) -> some View {
         self.onTapGesture { value in
-            if let nodeID = proxy.node(at: .init(x: value.x, y: value.y)) {
+            if let nodeID = proxy.node(of: type, at: value) {
                 action(nodeID)
             }
         }