Figure out a way to attach to scrolling in pages (#690)

Mastodon/Scene/Onboarding/Welcome/View/WelcomeIllustrationView.swift

@@ -205,32 +205,10 @@ extension WelcomeIllustrationView {
             }
         }
     }
-    
+
+  func update(currentPage: WelcomeContentPage, contentOffset: CGFloat) {
+    // why does it jump back???
+    print("\(contentOffset) — \(currentPage)")
+    //TODO: @zeitschlag update frames
+  }
 }
-
-#if canImport(SwiftUI) && DEBUG
-import SwiftUI
-
-struct WelcomeIllustrationView_Previews: PreviewProvider {
-    
-    static var previews: some View {
-        Group {
-            UIViewPreview(width: 375) {
-                let view = WelcomeIllustrationView()
-                view.layout = .compact
-                return view
-            }
-            .previewLayout(.fixed(width: 375, height: 1500))
-            UIViewPreview(width: 547) {
-                let view = WelcomeIllustrationView()
-                view.layout = .regular
-                return view
-            }
-            .previewLayout(.fixed(width: 547, height: 1500))
-        }
-    }
-    
-}
-
-#endif
-

Mastodon/Scene/Onboarding/Welcome/WelcomeViewController.swift

@@ -145,6 +145,13 @@ extension WelcomeViewController {
     view.addSubview(pageViewController.view)
     pageViewController.didMove(toParent: self)
 
+
+    let scrollviews = pageViewController.view.subviews.filter { type(of: $0).isSubclass(of: UIScrollView.self) }.compactMap { $0 as? UIScrollView }
+
+    for scrollView in scrollviews {
+      scrollView.delegate = self
+    }
+
     NSLayoutConstraint.activate([
       pageViewController.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
       pageViewController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
@@ -398,6 +405,8 @@ extension WelcomeViewController: UIPageViewControllerDelegate {
     guard let currentViewController = pageViewController.viewControllers?.first as? WelcomeContentViewController else { return }
 
     currentPage = currentViewController.page
+    //FIXME: @zeitschlag fix
+//    welcomeIllustrationView.update(for: currentPage, contentOffset: 1000)
   }
 }
 
@@ -443,3 +452,11 @@ extension WelcomeViewController: UIPageViewControllerDataSource {
     }
   }
 }
+
+extension WelcomeViewController: UIScrollViewDelegate {
+  func scrollViewDidScroll(_ scrollView: UIScrollView) {
+    print(scrollView.contentOffset.x)
+    //TODO: @zeitschlag sync view
+    welcomeIllustrationView.update(currentPage: currentPage, contentOffset: scrollView.contentOffset.x)
+  }
+}