Merge pull request #4 from swiftui-library/feat/metadata-callback

add callback for view layout
swiftui-library · Nov 24, 2021 · 2634703 · 2634703
2 parents 2153c7d + 845bf70
commit 2634703
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Showing 5 changed files with 75 additions and 50 deletions.
diff --git a/SnapToScrollDemo/Sources/Example 2/Example2ContentView.swift b/SnapToScrollDemo/Sources/Example 2/Example2ContentView.swift
@@ -1,34 +1,48 @@
-import SwiftUI
 import SnapToScroll
+import SwiftUI
 
 // MARK: - Example2ContentView
 
 struct Example2ContentView: View {
+
     var body: some View {
-
         VStack {
-
+            
             Text("Explore Nearby")
                 .font(.system(size: 22, weight: .semibold, design: .rounded))
                 .frame(maxWidth: .infinity, alignment: .leading)
                 .padding([.top, .leading], 16)
 
             HStackSnap(alignment: .leading(16)) {
-
+                
                 ForEach(TripTupleModel.exampleModels) { viewModel in
 
                     TripTupleView(viewModel: viewModel)
                         .frame(maxWidth: 250)
                         .snapAlignmentHelper(id: viewModel.id)
                 }
-            } onSwipe: { index in
-
-                print(index)
+            } eventHandler: { event in
+                
+                handleSnapToScrollEvent(event: event)
             }
             .frame(height: 130)
             .padding(.top, 4)
         }
     }
+
+    func handleSnapToScrollEvent(event: SnapToScrollEvent) {
+
+        switch event {
+
+            case let .didLayout(layoutInfo: layoutInfo):
+
+                print("\(layoutInfo.keys.count) items layed out")
+
+            case let .swipe(index: index):
+
+                print("swiped to index: \(index)")
+        }
+    }
 }
 
 // MARK: - Example2ContentView_Previews

diff --git a/SnapToScrollDemo/Sources/Example3/Example3ContentView.swift b/SnapToScrollDemo/Sources/Example3/Example3ContentView.swift
@@ -5,30 +5,28 @@ import SwiftUI
 
 struct Example3ContentView: View {
 
-    // MARK: Internal
-
     var body: some View {
-
+        
         VStack {
-
+                
             Text("Getting Started")
                 .font(.system(size: 22, weight: .semibold, design: .rounded))
                 .foregroundColor(.white)
                 .frame(maxWidth: .infinity, alignment: .leading)
                 .padding([.top, .leading], 32)
 
             HStackSnap(alignment: .center(32)) {
-
+                
                 ForEach(GettingStartedModel.exampleModels) { viewModel in
 
                     GettingStartedView(
                         selectedIndex: $selectedGettingStartedIndex,
                         viewModel: viewModel)
                         .snapAlignmentHelper(id: viewModel.id)
                 }
-            } onSwipe: { index in
+            } eventHandler: { event in
 
-                selectedGettingStartedIndex = index
+                handleSnapToScrollEvent(event: event)
             }
             .frame(height: 200)
             .padding(.top, 4)
@@ -40,6 +38,19 @@ struct Example3ContentView: View {
             endPoint: .bottom))
     }
 
+    func handleSnapToScrollEvent(event: SnapToScrollEvent) {
+        switch event {
+            case let .didLayout(layoutInfo: layoutInfo):
+
+                print("\(layoutInfo.keys.count) items layed out")
+
+            case let .swipe(index: index):
+
+                print("swiped to index: \(index)")
+                selectedGettingStartedIndex = index
+        }
+    }
+
     // MARK: Private
 
     @State private var selectedGettingStartedIndex: Int = 0

diff --git a/Sources/HStackSnap.swift b/Sources/HStackSnap.swift
@@ -3,21 +3,19 @@ import SwiftUI
 
 public struct HStackSnap<Content: View>: View {
 
-    public typealias SwipeEventHandler = ((Int) -> Void)
-
     // MARK: Lifecycle
 
     public init(
         alignment: SnapAlignment,
         coordinateSpace: String = "SnapToScroll",
         @ViewBuilder content: @escaping () -> Content,
-        onSwipe: SwipeEventHandler? = .none) {
+        eventHandler: SnapToScrollEventHandler? = .none) {
 
         self.content = content
-            self.alignment = alignment
-        leadingOffset = alignment.scrollOffset
+        self.alignment = alignment
+        self.leadingOffset = alignment.scrollOffset
         self.coordinateSpace = coordinateSpace
-        swipeEventHandler = onSwipe
+        self.eventHandler = eventHandler
     }
 
     // MARK: Public
@@ -36,7 +34,7 @@ public struct HStackSnap<Content: View>: View {
                 leadingOffset: leadingOffset,
                 coordinateSpace: coordinateSpace,
                 content: content,
-                onSwipe: swipeEventHandler)
+                eventHandler: eventHandler)
                 .environmentObject(SizeOverride(itemWidth: alignment.shouldSetWidth ? calculatedItemWidth(parentWidth: geometry.size.width, offset: alignment.scrollOffset) : .none))
         }
     }
@@ -52,7 +50,7 @@ public struct HStackSnap<Content: View>: View {
     /// Calculated offset based on `SnapLocation`
     private let leadingOffset: CGFloat
 
-    private var swipeEventHandler: SwipeEventHandler?
+    private var eventHandler: SnapToScrollEventHandler?
 
     private let coordinateSpace: String
 }
diff --git a/Sources/Model/SnapToScrollEvent.swift b/Sources/Model/SnapToScrollEvent.swift
@@ -0,0 +1,11 @@
+import Foundation
+import SwiftUI
+
+public enum SnapToScrollEvent {
+
+    /// Swiped to index.
+    case swipe(index: Int)
+
+    /// HStackSnap completed layout calculations. (item index, item leading offset)
+    case didLayout(layoutInfo: [Int: CGFloat])
+}
diff --git a/Sources/Views/HStackSnapCore.swift b/Sources/Views/HStackSnapCore.swift
@@ -1,33 +1,32 @@
 import Foundation
 import SwiftUI
 
-public struct HStackSnapCore<Content: View>: View {
+public typealias SnapToScrollEventHandler = ((SnapToScrollEvent) -> Void)
 
-    public typealias SwipeEventHandler = ((Int) -> Void)
+// MARK: - HStackSnapCore
 
+public struct HStackSnapCore<Content: View>: View {
     // MARK: Lifecycle
 
     public init(
         leadingOffset: CGFloat,
         coordinateSpace: String = "SnapToScroll",
         @ViewBuilder content: @escaping () -> Content,
-        onSwipe: SwipeEventHandler? = .none) {
-
+        eventHandler: SnapToScrollEventHandler? = .none) {
+            
         self.content = content
-        targetOffset = leadingOffset
-        scrollOffset = leadingOffset
+        self.targetOffset = leadingOffset
+        self.scrollOffset = leadingOffset
         self.coordinateSpace = coordinateSpace
-        swipeEventHandler = onSwipe
+        self.eventHandler = eventHandler
     }
 
     // MARK: Public
 
     public var body: some View {
-
         GeometryReader { geometry in
 
             HStack {
-
                 HStack(content: content)
                     .offset(x: scrollOffset, y: .zero)
                     .animation(.easeOut(duration: 0.2))
@@ -41,25 +40,22 @@ public struct HStackSnapCore<Content: View>: View {
                 // Calculate all values once, on render. On-the-fly calculations with GeometryReader
                 // proved occasionally unstable in testing.
                 if !hasCalculatedFrames {
-
                     let screenWidth = geometry.frame(in: .named(coordinateSpace)).width
 
                     var itemScrollPositions: [Int: CGFloat] = [:]
 
                     var frameMaxXVals: [CGFloat] = []
 
-                    for pref in preferences {
-
-                        itemScrollPositions[pref.id.hashValue] = scrollOffset(for: pref.rect.minX)
-                        frameMaxXVals.append(pref.rect.maxX)
+                    for (index, preference) in preferences.enumerated() {
+                        itemScrollPositions[index] = scrollOffset(for: preference.rect.minX)
+                        frameMaxXVals.append(preference.rect.maxX)
                     }
 
                     // Array of content widths from currentElement.minX to lastElement.maxX
                     var contentFitMap: [CGFloat] = []
 
                     // Calculate content widths (used to trim snap positions later)
                     for currMinX in preferences.map({ $0.rect.minX }) {
-
                         guard let maxX = preferences.last?.rect.maxX else { break }
                         let widthToEnd = maxX - currMinX
 
@@ -71,24 +67,24 @@ public struct HStackSnapCore<Content: View>: View {
 
                     // Calculate how many snap locations should be trimmed.
                     for i in 0 ..< reversedFitMap.count {
-
                         if reversedFitMap[i] > screenWidth {
-
                             frameTrim = max(i - 1, 0)
                             break
                         }
                     }
 
                     // Write valid snap locations to state.
                     for (i, item) in itemScrollPositions.sorted(by: { $0.value > $1.value })
-                        .enumerated() {
-
+                        .enumerated()
+                    {
                         guard i < (itemScrollPositions.count - frameTrim) else { break }
 
                         snapLocations[item.key] = item.value
                     }
 
                     hasCalculatedFrames = true
+
+                    eventHandler?(.didLayout(layoutInfo: itemScrollPositions))
                 }
             })
             .gesture(snapDrag)
@@ -101,21 +97,18 @@ public struct HStackSnapCore<Content: View>: View {
     var content: () -> Content
 
     var snapDrag: some Gesture {
-
         DragGesture()
             .onChanged { gesture in
 
                 self.scrollOffset = gesture.translation.width + prevScrollOffset
-            }.onEnded { event in
+            }.onEnded { _ in
 
                 let currOffset = scrollOffset
                 var closestSnapLocation: CGFloat = snapLocations.first?.value ?? targetOffset
 
                 // Calculate closest snap location
                 for (_, offset) in snapLocations {
-
                     if abs(offset - currOffset) < abs(closestSnapLocation - currOffset) {
-
                         closestSnapLocation = offset
                     }
                 }
@@ -125,8 +118,7 @@ public struct HStackSnapCore<Content: View>: View {
                     .firstIndex(of: closestSnapLocation) ?? 0
 
                 if selectedIndex != previouslySentIndex {
-
-                    swipeEventHandler?(selectedIndex)
+                    eventHandler?(.swipe(index: selectedIndex))
                     previouslySentIndex = selectedIndex
                 }
 
@@ -135,9 +127,8 @@ public struct HStackSnapCore<Content: View>: View {
                 prevScrollOffset = scrollOffset
             }
     }
-
-    func scrollOffset(for x: CGFloat) -> CGFloat {
 
+    func scrollOffset(for x: CGFloat) -> CGFloat {
         return (targetOffset * 2) - x
     }
 
@@ -157,7 +148,7 @@ public struct HStackSnapCore<Content: View>: View {
     /// The original offset of each frame, used to calculate `scrollOffset`
     @State private var snapLocations: [Int: CGFloat] = [:]
 
-    private var swipeEventHandler: SwipeEventHandler?
+    private var eventHandler: SnapToScrollEventHandler?
 
     @State private var previouslySentIndex: Int = 0