New timeline (#276) (#280)

* Fixes #276 - Rebuilt room timeline:
    - Removed the need for the ListCollectionViewAdapter
    - Rewrote the TimelineItemList without using introspection
    - Added ReversedScrollView for laying out items at the bottom/trailing
    - Rewrote TimelineProvider diffing through CollectionDifference (similar to the RoomSummaryProvider)
    - Added back `scrollDismissesKeyboard`  behavior
    - Various other tweaks and fixes
- Fixed various warnings:
    - removed async AttributedStringBuilder as AttributedString is non-sendable, made the RoomTimelineItemFactory synchronous
    - removed unused virtual timeline items
    - removed unused isOutgoing property from the FormattedBodyText
* Make TimelineItemContextMenuActions indentifiable and specify contextMenu identifiers
* Bump the matrix-rust-components-swift to v1.0.16-alpha
* Add changes file and changelog contribution guide
* Fix attributed string builder unit tests

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilder.swift

@@ -21,13 +21,7 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
     private let temporaryBlockquoteMarkingColor = UIColor.magenta
     private let temporaryCodeBlockMarkingColor = UIColor.cyan
     private let linkColor = UIColor.blue
-    
-    func fromPlain(_ string: String?) async -> AttributedString? {
-        await Task.dispatch(on: .global()) {
-            fromPlain(string)
-        }
-    }
-    
+        
     func fromPlain(_ string: String?) -> AttributedString? {
         guard let string else {
             return nil
@@ -39,13 +33,7 @@ struct AttributedStringBuilder: AttributedStringBuilderProtocol {
         
         return try? AttributedString(mutableAttributedString, including: \.elementX)
     }
-    
-    func fromHTML(_ htmlString: String?) async -> AttributedString? {
-        await Task.dispatch(on: .global()) {
-            fromHTML(htmlString)
-        }
-    }
-    
+        
     // Do not use the default HTML renderer of NSAttributedString because this method
     // runs on the UI thread which we want to avoid because renderHTMLString is called
     // most of the time from a background thread.

ElementX/Sources/Other/HTMLParsing/AttributedStringBuilderProtocol.swift

@@ -23,10 +23,8 @@ struct AttributedStringBuilderComponent: Hashable {
 
 protocol AttributedStringBuilderProtocol {
     func fromPlain(_ string: String?) -> AttributedString?
-    func fromPlain(_ string: String?) async -> AttributedString?
     
     func fromHTML(_ htmlString: String?) -> AttributedString?
-    func fromHTML(_ htmlString: String?) async -> AttributedString?
     
     func blockquoteCoalescedComponentsFrom(_ attributedString: AttributedString?) -> [AttributedStringBuilderComponent]?
 }

ElementX/Sources/Other/ReversedScrollView.swift

@@ -0,0 +1,82 @@
+//
+// 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 SwiftUI scroll view that lays out its content starting at the bottom or trailing
+/// https://www.thirdrocktechkno.com/blog/implementing-reversed-scrolling-behaviour-in-swiftui/
+struct ReversedScrollView<Content: View>: View {
+    private let axis: Axis.Set
+    private let leadingSpace: CGFloat
+    private let content: Content
+    
+    init(_ axis: Axis.Set = .horizontal, leadingSpace: CGFloat = 0, @ViewBuilder builder: () -> Content) {
+        self.axis = axis
+        self.leadingSpace = leadingSpace
+        content = builder()
+    }
+    
+    var body: some View {
+        GeometryReader { proxy in
+            ScrollView(axis, showsIndicators: false) {
+                Stack(axis) {
+                    Spacer(minLength: leadingSpace)
+                    content
+                }
+                .frame(
+                    minWidth: minWidth(in: proxy, for: axis),
+                    minHeight: minHeight(in: proxy, for: axis)
+                )
+            }
+        }
+    }
+    
+    private func minWidth(in proxy: GeometryProxy, for axis: Axis.Set) -> CGFloat? {
+        axis.contains(.horizontal) ? proxy.size.width : nil
+    }
+    
+    private func minHeight(in proxy: GeometryProxy, for axis: Axis.Set) -> CGFloat? {
+        axis.contains(.vertical) ? proxy.size.height : nil
+    }
+}
+
+private struct Stack<Content: View>: View {
+    var axis: Axis.Set
+    var content: Content
+    
+    init(_ axis: Axis.Set = .vertical, @ViewBuilder builder: () -> Content) {
+        self.axis = axis
+        
+        content = builder()
+    }
+    
+    var body: some View {
+        switch axis {
+        case .horizontal:
+            HStack {
+                content
+            }
+        case .vertical:
+            VStack {
+                content
+            }
+        default:
+            VStack {
+                content
+            }
+        }
+    }
+}