Revert "Fix target content offset edge case (#115)"

This reverts commit c3f346b.
airbnb · Feb 8, 2024 · b0ebcbc · b0ebcbc
1 parent c3f346b
commit b0ebcbc
Showing 1 changed file with 12 additions and 42 deletions.
diff --git a/MagazineLayout/Public/MagazineLayout.swift b/MagazineLayout/Public/MagazineLayout.swift
@@ -265,32 +265,26 @@ public final class MagazineLayout: UICollectionViewLayout {
     supplementaryViewLayoutAttributesForPendingAnimations.removeAll()
 
     targetContentOffsetAnchor = nil
+    preInvalidationContentSize = nil
+    preInvalidationContentInset = nil
 
     super.finalizeCollectionViewUpdates()
   }
 
   override public func prepare(forAnimatedBoundsChange oldBounds: CGRect) {
     super.prepare(forAnimatedBoundsChange: oldBounds)
 
-    let contentSize: CGSize
-    let contentInset: UIEdgeInsets
-    if let metricsSnapshot = metricsSnapshots.first(where: { $0.bounds == oldBounds }) {
-      contentSize = metricsSnapshot.contentSize
-      contentInset = metricsSnapshot.contentInset
-    } else {
-      contentSize = collectionViewContentSize
-      contentInset = self.contentInset
-    }
-
     targetContentOffsetAnchor = targetContentOffsetAnchor(
       bounds: oldBounds,
-      contentHeight: contentSize.height,
-      topInset: contentInset.top,
-      bottomInset: contentInset.bottom)
+      contentHeight: preInvalidationContentSize?.height ?? collectionViewContentSize.height,
+      topInset: preInvalidationContentInset?.top ?? contentInset.top,
+      bottomInset: preInvalidationContentInset?.bottom ?? contentInset.bottom)
   }
 
   override public func finalizeAnimatedBoundsChange() {
     targetContentOffsetAnchor = nil
+    preInvalidationContentSize = nil
+    preInvalidationContentInset = nil
 
     super.finalizeAnimatedBoundsChange()
   }
@@ -760,29 +754,10 @@ public final class MagazineLayout: UICollectionViewLayout {
       return
     }
 
-    // We need to save a few content size and content inset values for different bounds. This
-    // allows us to compute the correct target content offset in `prepareForAnimatedBoundsChange`.
-    // The root issue is that in the aforementioned function, we need a way to know what the content
-    // size and content inset _were_ for a given bounds value.
-    let metricsSnapshot = MetricsSnapshot(
-      bounds: currentCollectionView.bounds,
-      contentSize: collectionViewContentSize,
-      contentInset: lastContentInset ?? contentInset)
-
-    // Replace existing snapshot if the bounds is the same
-    let indexOfExistingMetricsSnapshot = metricsSnapshots.firstIndex {
-      $0.bounds == metricsSnapshot.bounds
-    }
-    if let indexOfExistingMetricsSnapshot {
-      metricsSnapshots[indexOfExistingMetricsSnapshot] = metricsSnapshot
-    } else {
-      metricsSnapshots.append(metricsSnapshot)
-    }
-
-    // Limit to 3 snapshots
-    if metricsSnapshots.count > 3 {
-      metricsSnapshots.removeFirst()
+    if collectionViewContentSize.width > 0, collectionViewContentSize.height > 0 {
+      preInvalidationContentSize = preInvalidationContentSize ?? collectionViewContentSize
     }
+    preInvalidationContentInset = preInvalidationContentInset ?? lastContentInset ?? contentInset
 
     let shouldInvalidateLayoutMetrics = !context.invalidateEverything &&
       !context.invalidateDataSourceCounts
@@ -856,13 +831,8 @@ public final class MagazineLayout: UICollectionViewLayout {
 
   private var lastContentInset: UIEdgeInsets?
   private var cachedCollectionViewWidth: CGFloat?
-
-  private struct MetricsSnapshot {
-    let bounds: CGRect
-    let contentSize: CGSize
-    let contentInset: UIEdgeInsets
-  }
-  private var metricsSnapshots = [MetricsSnapshot]()
+  private var preInvalidationContentSize: CGSize?
+  private var preInvalidationContentInset: UIEdgeInsets?
 
   // These properties are used to prevent scroll jumpiness due to self-sizing after rotation; see
   // comment in `invalidationContext(forPreferredLayoutAttributes:withOriginalAttributes:)` for more