#40: Add the login screen from EI.

- Remove SSO and replace fallback with OIDC.

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

@@ -0,0 +1,42 @@
+// 
+// Copyright 2021 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 Foundation
+import SwiftUI
+
+/// Used to calculate the frame of a view.
+///
+/// Useful in situations as with `ZStack` where you might want to layout views using alignment guides.
+/// ```
+/// @State private var frame: CGRect = CGRect.zero
+/// ...
+/// SomeView()
+///    .background(ViewFrameReader(frame: $frame))
+/// ```
+struct ViewFrameReader: View {
+    @Binding var frame: CGRect
+    
+    var body: some View {
+        GeometryReader { geometry in
+            Color.clear
+                .preference(key: FramePreferenceKey.self,
+                            value: geometry.frame(in: .local))
+        }
+        .onPreferenceChange(FramePreferenceKey.self) {
+            frame = $0
+        }
+    }
+}