Add timeline properties for edited and reactions.

Not yet visible, waiting for timeline API.

ElementX/Sources/Other/SwiftUI/Layout/AlignedScrollView.swift

@@ -0,0 +1,37 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import SwiftUI
+
+/// A horizontal `ScrollView` that will pad the start of it's content
+/// when the alignment is set to `.trailing`.
+struct AlignedScrollView<Content: View>: View {
+    let alignment: HorizontalAlignment
+    var showsIndicators = true
+    
+    @ViewBuilder let content: () -> Content
+    
+    @State private var scrollViewFrame: CGRect = .zero
+    
+    var body: some View {
+        ScrollView(.horizontal, showsIndicators: showsIndicators) {
+            content()
+                .frame(minWidth: scrollViewFrame.width,
+                       alignment: Alignment(horizontal: alignment, vertical: .center))
+        }
+        .background(ViewFrameReader(frame: $scrollViewFrame))
+    }
+}

ElementX/Sources/Other/SwiftUI/Layout/ViewFrameReader.swift

@@ -35,8 +35,9 @@ struct ViewFrameReader: View {
                 .preference(key: FramePreferenceKey.self,
                             value: geometry.frame(in: .local))
         }
-        .onPreferenceChange(FramePreferenceKey.self) {
-            frame = $0
+        .onPreferenceChange(FramePreferenceKey.self) { newValue in
+            guard frame != newValue else { return }
+            frame = newValue
         }
     }
 }