Add a geometry playground with proportional bars

Author: colemancda

Demo/App.swiftpm/Sources/GeometryPlaygrounds.swift

@@ -0,0 +1,36 @@
+#if canImport(AndroidSwiftUI)
+import AndroidSwiftUI
+#else
+import SwiftUI
+#endif
+
+struct GeometryPlayground: View {
+
+    @State private var tall = false
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 16) {
+            Text("A GeometryReader reports the space its parent offers.")
+
+            GeometryReader { geometry in
+                VStack(alignment: .leading, spacing: 10) {
+                    Text("Offered: \(Int(geometry.size.width)) × \(Int(geometry.size.height))")
+                    // bars sized from the measurement — proof the number is live
+                    Text("half width")
+                    Rectangle()
+                        .fill(.blue)
+                        .frame(width: geometry.size.width / 2, height: 22)
+                    Text("one quarter")
+                    Rectangle()
+                        .fill(.green)
+                        .frame(width: geometry.size.width / 4, height: 22)
+                }
+            }
+            .frame(height: tall ? 320 : 200)
+
+            Button(tall ? "Shrink the reader" : "Grow the reader") { tall.toggle() }
+        }
+        .padding()
+        .navigationTitle("GeometryReader")
+    }
+}