Add ExpandingVC Timeout + Explicitly Call updateScrollViewHeight on m…

…ain thread (#182)

* Changes

* verify dispatch main is still necessary

* address noah comments

* keep main thread dispatch for test

* just the timer logic

* address noah comments

* remove anchor changes when timer ends

* delete print

.gitignore

@@ -9,3 +9,6 @@ DerivedData/
 DemoApp/DemoApp.xcodeproj/xcuserdata/
 .xcuserstate
 PreviewsSupport/PreviewsSupport.xcframework/**/*.private.swiftinterface
+
+
+DemoApp/DemoApp.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/

Sources/SnapshotPreviewsCore/ExpandingViewController.swift

@@ -20,13 +20,18 @@ public final class ExpandingViewController: UIHostingController<EmergeModifierVi
     rootView.supportsExpansion
   }
 
+  private let HeightExpansionTimeLimitInSeconds: Double = 30
+
   private var didCall = false
   var previousHeight: CGFloat?
 
   var heightAnchor: NSLayoutConstraint?
   private var widthAnchor: NSLayoutConstraint?
 
-  public var expansionSettled: ((EmergeRenderingMode?, Float?, Bool?) -> Void)? {
+  private var startTime: Date?
+  private var timer: Timer?
+
+  public var expansionSettled: ((EmergeRenderingMode?, Float?, Bool?, Error?) -> Void)? {
     didSet { didCall = false }
   }
 
@@ -69,19 +74,25 @@ public final class ExpandingViewController: UIHostingController<EmergeModifierVi
     }
   }
 
-  private func runCallback() {
+  private func runCallback(_ error: Error? = nil) {
     guard !didCall else { return }
 
     didCall = true
-    expansionSettled?(rootView.emergeRenderingMode, rootView.precision, rootView.accessibilityEnabled)
+    expansionSettled?(rootView.emergeRenderingMode, rootView.precision, rootView.accessibilityEnabled, error)
+    stopAndResetTimer()
   }
 
   public override func viewDidLayoutSubviews() {
     super.viewDidLayoutSubviews()
-    self.updateScrollViewHeight()
+    updateScrollViewHeight()
   }
 
   public func updateScrollViewHeight() {
+    // Timeout limit
+    if timer == nil {
+      startTimer()
+    }
+
     guard expansionSettled != nil else {
       runCallback()
       return
@@ -92,5 +103,32 @@ public final class ExpandingViewController: UIHostingController<EmergeModifierVi
     }
   }
 
+//  MARK: - Timer
+
+  func startTimer() {
+      guard timer == nil else {
+        print("Timer already exists")
+        return
+      }
+      startTime = Date()
+      timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { [weak self] _ in
+          guard let self,
+                let start = startTime,
+                Date().timeIntervalSince(start) >= HeightExpansionTimeLimitInSeconds else {
+              return
+          }
+          let timeoutError = RenderingError.expandingViewTimeout(CGSize(width: UIScreen.main.bounds.size.width,
+                                                                        height: firstScrollView?.visibleContentHeight ?? -1))
+          NSLog("ExpandingViewController: Expanding Scroll View timed out. Current height is \(firstScrollView?.visibleContentHeight ?? -1)")
+          runCallback(timeoutError)
+      }
+  }
+
+  func stopAndResetTimer() {
+      timer?.invalidate()
+      timer = nil
+      startTime = nil
+  }
+
 }
 #endif

Sources/SnapshotPreviewsCore/View+Snapshot.swift

@@ -15,6 +15,7 @@ import SnapshotSharedModels
 public enum RenderingError: Error {
   case failedRendering(CGSize)
   case maxSize(CGSize)
+  case expandingViewTimeout(CGSize)
 }
 
 extension AccessibilityMarker: AccessibilityMark {
@@ -57,8 +58,17 @@ extension View {
     async: Bool,
     completion: @escaping (SnapshotResult) -> Void)
   {
-    controller.expansionSettled = { [weak controller, weak window] renderingMode, precision, accessibilityEnabled in
-      guard let controller, let window, let containerVC = controller.parent else { return }
+    controller.expansionSettled = { [weak controller, weak window] renderingMode, precision, accessibilityEnabled, error in
+      guard let controller, let window, let containerVC = controller.parent else {
+        return
+      }
+
+      if let error {
+        DispatchQueue.main.async {
+          completion(SnapshotResult(image: .failure(error), precision: precision, accessibilityEnabled: accessibilityEnabled, accessibilityMarkers: nil, colorScheme: _colorScheme))
+        }
+        return
+      }
 
       if async {
         DispatchQueue.main.asyncAfter(deadline: .now() + 2) {