3 files changed, 26 insertions, 0 deletions
diff --git a/Sora/Data/PostGridViewState/PostGridViewState.swift b/Sora/Data/PostGridViewState/PostGridViewState.swift
index 266d05c..ff7a32a 100644
--- a/Sora/Data/PostGridViewState/PostGridViewState.swift
+++ b/Sora/Data/PostGridViewState/PostGridViewState.swift
@@ -4,5 +4,6 @@ struct PostGridViewState: Equatable {
   var posts: [BooruPost] = []
   var currentPage: Int = 1
   var selectedPost: BooruPost?
+  var scrollPosition: BooruPost.ID?
   let createdAt = Date()
 }
diff --git a/Sora/Data/Scroll/ScrollPositionPreference.swift b/Sora/Data/Scroll/ScrollPositionPreference.swift
new file mode 100644
index 0000000..fb36bb1
--- /dev/null
+++ b/Sora/Data/Scroll/ScrollPositionPreference.swift
@@ -0,0 +1,6 @@
+import SwiftUI
+
+struct ScrollPositionPreference: Equatable {
+  let id: BooruPost.ID
+  let yPosition: CGFloat
+}
diff --git a/Sora/Data/Scroll/ScrollPositionPreferenceKey.swift b/Sora/Data/Scroll/ScrollPositionPreferenceKey.swift
new file mode 100644
index 0000000..6b78bdc
--- /dev/null
+++ b/Sora/Data/Scroll/ScrollPositionPreferenceKey.swift
@@ -0,0 +1,19 @@
+import SwiftUI
+
+struct ScrollPositionPreferenceKey: PreferenceKey {
+  typealias Value = ScrollPositionPreference?
+
+  static var defaultValue: Value = nil
+
+  static func reduce(value: inout Value, nextValue: () -> Value) {
+    guard let next = nextValue() else { return }
+
+    if let current = value {
+      if abs(next.yPosition) < abs(current.yPosition) {
+        value = next
+      }
+    } else {
+      value = next
+    }
+  }
+}