Update raw keyboard example (#6871)

We now center the body correctly and handle Fuchsia key events. Also, add
support for modifiers.

dev/manual_tests/raw_keyboard.dart

@@ -14,7 +14,7 @@ void main() {
       appBar: new AppBar(
         title: new Text("Hardware Key Demo")
       ),
-      body: new Material(
+      body: new Center(
         child: new RawKeyboardDemo(
           key: _key
         )
@@ -42,28 +42,28 @@ class _HardwareKeyDemoState extends State<RawKeyboardDemo> {
   @override
   Widget build(BuildContext context)  {
     final TextTheme textTheme = Theme.of(context).textTheme;
-    bool focused = Focus.at(context);
+    final bool focused = Focus.at(context);
     Widget child;
     if (!focused) {
       child = new GestureDetector(
         onTap: () {
           Focus.moveTo(config.key);
         },
-        child: new Center(
-          child: new Text('Tap to focus', style: textTheme.display1),
-        ),
+        child: new Text('Tap to focus', style: textTheme.display1),
       );
     } else if (_event == null) {
-      child = new Center(
-        child: new Text('Press a key', style: textTheme.display1),
-      );
+      child = new Text('Press a key', style: textTheme.display1);
     } else {
       int codePoint;
       int keyCode;
+      int hidUsage;
       final RawKeyEventData data = _event.data;
       if (data is RawKeyEventDataAndroid) {
         codePoint = data.codePoint;
         keyCode = data.keyCode;
+      } else if (data is RawKeyEventDataFuchsia) {
+        codePoint = data.codePoint;
+        hidUsage = data.hidUsage;
       }
       child = new Column(
         mainAxisAlignment: MainAxisAlignment.center,
@@ -71,6 +71,7 @@ class _HardwareKeyDemoState extends State<RawKeyboardDemo> {
           new Text('${_event.runtimeType}', style: textTheme.body2),
           new Text('codePoint: $codePoint', style: textTheme.display4),
           new Text('keyCode: $keyCode', style: textTheme.display4),
+          new Text('hidUsage: $hidUsage', style: textTheme.display4),
         ],
       );
     }
@@ -81,3 +82,4 @@ class _HardwareKeyDemoState extends State<RawKeyboardDemo> {
     );
   }
 }
+

packages/flutter/lib/src/services/raw_keyboard.dart

@@ -70,6 +70,7 @@ class RawKeyEventDataFuchsia extends RawKeyEventData {
   const RawKeyEventDataFuchsia({
     this.hidUsage: 0,
     this.codePoint: 0,
+    this.modifiers: 0,
   });
 
   /// The USB HID usage.
@@ -81,6 +82,12 @@ class RawKeyEventDataFuchsia extends RawKeyEventData {
   ///
   /// If there is no unicode code point, this value is zero.
   final int codePoint;
+
+  /// The modifiers that we present when the key event occured.
+  ///
+  /// See <https://fuchsia.googlesource.com/mozart/+/master/services/input/input_event_constants.fidl>
+  /// for the numerical values of the modifiers.
+  final int modifiers;
 }
 
 /// Base class for raw key events.
@@ -138,6 +145,7 @@ RawKeyEvent _toRawKeyEvent(Map<String, dynamic> message) {
       data = new RawKeyEventDataFuchsia(
         hidUsage: message['hidUsage'] ?? 0,
         codePoint: message['codePoint'] ?? 0,
+        modifiers: message['modifiers'] ?? 0,
       );
       break;
     default:

packages/flutter/test/widgets/raw_keyboard_listener_test.dart

@@ -38,6 +38,7 @@ void main() {
       'keymap': 'fuchsia',
       'hidUsage': 0x04,
       'codePoint': 0x64,
+      'modifiers': 0x08,
     });
 
     await tester.idle();
@@ -48,5 +49,6 @@ void main() {
     RawKeyEventDataFuchsia typedData = events[0].data;
     expect(typedData.hidUsage, 0x04);
     expect(typedData.codePoint, 0x64);
+    expect(typedData.modifiers, 0x08);
   });
 }