code cleanup and simplification

Author: Trent Guillory

SnapToScrollDemo/Sources/ContentView.swift

@@ -10,16 +10,26 @@ struct ContentView: View {
     var body: some View {
         VStack {
 
-            HStackSnap {
+            HStackSnap(leadingOffset: 16) {
 
                 ForEach(items, id: \.1) { item in
 
                     Text(item.0)
                         .font(.largeTitle)
-                        .padding()
+                        .padding(16)
                         .overlay(GeometryReaderOverlay(id: item.1))
                 }
             }
+//            HStackSnap(snapLocation: .center) {
+//                
+//                ForEach(items, id: \.1) { item in
+//                    
+//                    Text(item.0)
+//                        .font(.largeTitle)
+//                        .padding()
+//                        .overlay(GeometryReaderOverlay(id: item.1))
+//                }
+//            }
         }
 
         /// SnapHStack {

Sources/HStackSnap.swift

@@ -5,16 +5,23 @@ public struct HStackSnap<Content: View>: View {
 
     // MARK: Lifecycle
 
-    public init(@ViewBuilder content: @escaping () -> Content) {
+    public init(
+        leadingOffset: CGFloat,
+        coordinateSpace: String = "SnapToScroll",
+        @ViewBuilder content: @escaping () -> Content) {
 
         self.content = content
+        targetOffset = leadingOffset
+        scrollOffset = leadingOffset
+        self.coordinateSpace = coordinateSpace
     }
 
     // MARK: Public
 
     public var body: some View {
 
         GeometryReader { geometry in
+
             ScrollView(.horizontal) {
 
                 HStack(content: content)
@@ -27,11 +34,12 @@ public struct HStackSnap<Content: View>: View {
 
                     itemFrames[pref.id] = pref
                 }
+
             })
             .disabled(true)
             .gesture(snapDrag)
         }
-            .coordinateSpace(name: ContentPreferenceKey.coordinateSpace)
+        .coordinateSpace(name: coordinateSpace)
     }
 
     // MARK: Internal
@@ -66,7 +74,7 @@ public struct HStackSnap<Content: View>: View {
                     scrollOffset += distanceToTarget(
                         x: closestFrame.rect.minX)
                 }
-                
+
                 prevScrollOffset = scrollOffset
             }
     }
@@ -79,13 +87,15 @@ public struct HStackSnap<Content: View>: View {
     // MARK: Private
 
     /// Current scroll offset.
-    @State private var scrollOffset: CGFloat = 0
-    
+    @State private var scrollOffset: CGFloat
+
     /// Stored offset of previous scroll, so scroll state is resumed between drags.
     @State private var prevScrollOffset: CGFloat = 0
-    
-    ///
-    @State private var targetOffset: CGFloat = 0
+
+    /// Calculated offset based on `SnapLocation`
+    @State private var targetOffset: CGFloat
 
     @State private var itemFrames: [UUID: ContentPreferenceData] = [:]
+
+    private let coordinateSpace: String
 }

Sources/Model/ContentPreferenceKey.swift

@@ -19,8 +19,6 @@ struct ContentPreferenceKey: PreferenceKey {
 
     static var defaultValue: [ContentPreferenceData] = []
 
-    static var coordinateSpace: String = "ContentPreferenceKey"
-
     static func reduce(
         value: inout Value,
         nextValue: () -> Value) {

Sources/Model/SnapLocation.swift

@@ -3,23 +3,31 @@ import SwiftUI
 
 public struct GeometryReaderOverlay: View {
 
-    let id: UUID
-    
-    public init(id: UUID) {
-        
+    // MARK: Lifecycle
+
+    public init(id: UUID, coordinateSpace: String = "SnapToScroll") {
+
         self.id = id
+        self.coordinateSpace = coordinateSpace
     }
-    
+
+    // MARK: Public
+
     public var body: some View {
-        
+
         GeometryReader { geometry in
-            
+
             Rectangle().fill(Color.blue.opacity(0.5))
                 .preference(
                     key: ContentPreferenceKey.self,
                     value: [ContentPreferenceData(
                         id: id,
-                        rect: geometry.frame(in: .named(ContentPreferenceKey.coordinateSpace)))])
+                        rect: geometry.frame(in: .named(coordinateSpace)))])
         }
     }
+
+    // MARK: Internal
+
+    let id: UUID
+    let coordinateSpace: String
 }