Apply media bottom padding to CupertinoTabBar (#13372)

This adjusts the CupertinoTabBar height in the presence of bottom
padding. On the iPhone X, this will increase the height to account for
the home indicator widget.

packages/flutter/lib/src/cupertino/bottom_tab_bar.dart

@@ -92,6 +92,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
 
   @override
   Widget build(BuildContext context) {
+    final double bottomPadding = MediaQuery.of(context).padding.bottom;
     Widget result = new DecoratedBox(
       decoration: new BoxDecoration(
         border: const Border(
@@ -105,7 +106,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
       ),
       // TODO(xster): allow icons-only versions of the tab bar too.
       child: new SizedBox(
-        height: _kTabBarHeight,
+        height: _kTabBarHeight + bottomPadding,
         child: IconTheme.merge( // Default with the inactive state.
           data: new IconThemeData(
             color: inactiveColor,
@@ -119,6 +120,8 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
               fontWeight: FontWeight.w500,
               color: inactiveColor,
             ),
+            child: new Padding(
+              padding: new EdgeInsets.only(bottom: bottomPadding),
               child: new Row(
                 // Align bottom since we want the labels to be aligned.
                 crossAxisAlignment: CrossAxisAlignment.end,
@@ -127,6 +130,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
             ),
           ),
         ),
+      ),
     );
 
     if (!opaque) {

packages/flutter/test/cupertino/bottom_tab_bar_test.dart

@@ -35,7 +35,9 @@ void main() {
   });
 
   testWidgets('Active and inactive colors', (WidgetTester tester) async {
-    await pumpWidgetWithBoilerplate(tester, new CupertinoTabBar(
+    await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+      data: const MediaQueryData(),
+      child: new CupertinoTabBar(
         items: <BottomNavigationBarItem>[
           const BottomNavigationBarItem(
             icon: const ImageIcon(const TestImageProvider(24, 24)),
@@ -49,6 +51,7 @@ void main() {
         currentIndex: 1,
         activeColor: const Color(0xFF123456),
         inactiveColor: const Color(0xFF654321),
+      ),
     ));
 
     final RichText actualInactive = tester.widget(find.descendant(
@@ -64,8 +67,49 @@ void main() {
     expect(actualActive.text.style.color, const Color(0xFF123456));
   });
 
+  testWidgets('Adjusts height to account for bottom padding', (WidgetTester tester) async {
+    final CupertinoTabBar tabBar = new CupertinoTabBar(
+      items: <BottomNavigationBarItem>[
+        const BottomNavigationBarItem(
+          icon: const ImageIcon(const TestImageProvider(24, 24)),
+          title: const Text('Aka'),
+        ),
+        const BottomNavigationBarItem(
+          icon: const ImageIcon(const TestImageProvider(24, 24)),
+          title: const Text('Shiro'),
+        ),
+      ],
+    );
+
+    // Verify height with no bottom padding.
+    await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+      data: const MediaQueryData(),
+      child: new CupertinoTabScaffold(
+        tabBar: tabBar,
+        tabBuilder: (BuildContext context, int index) {
+          return const Placeholder();
+        },
+      ),
+    ));
+    expect(tester.getSize(find.byType(CupertinoTabBar)).height, 50.0);
+
+    // Verify height with bottom padding.
+    await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+      data: const MediaQueryData(padding: const EdgeInsets.only(bottom: 40.0)),
+      child: new CupertinoTabScaffold(
+        tabBar: tabBar,
+        tabBuilder: (BuildContext context, int index) {
+          return const Placeholder();
+        },
+      ),
+    ));
+    expect(tester.getSize(find.byType(CupertinoTabBar)).height, 90.0);
+  });
+
   testWidgets('Opaque background does not add blur effects', (WidgetTester tester) async {
-    await pumpWidgetWithBoilerplate(tester, new CupertinoTabBar(
+    await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+      data: const MediaQueryData(),
+      child: new CupertinoTabBar(
         items: <BottomNavigationBarItem>[
           const BottomNavigationBarItem(
             icon: const ImageIcon(const TestImageProvider(24, 24)),
@@ -76,11 +120,14 @@ void main() {
             title: const Text('Tab 2'),
           ),
         ],
+      ),
     ));
 
     expect(find.byType(BackdropFilter), findsOneWidget);
 
-    await pumpWidgetWithBoilerplate(tester, new CupertinoTabBar(
+    await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+      data: const MediaQueryData(),
+      child: new CupertinoTabBar(
         items: <BottomNavigationBarItem>[
           const BottomNavigationBarItem(
             icon: const ImageIcon(const TestImageProvider(24, 24)),
@@ -92,6 +139,7 @@ void main() {
           ),
         ],
         backgroundColor: const Color(0xFFFFFFFF), // Opaque white.
+      ),
     ));
 
     expect(find.byType(BackdropFilter), findsNothing);
@@ -100,7 +148,9 @@ void main() {
   testWidgets('Tap callback', (WidgetTester tester) async {
     int callbackTab;
 
-      await pumpWidgetWithBoilerplate(tester, new CupertinoTabBar(
+      await pumpWidgetWithBoilerplate(tester, new MediaQuery(
+        data: const MediaQueryData(),
+        child: new CupertinoTabBar(
           items: <BottomNavigationBarItem>[
             const BottomNavigationBarItem(
               icon: const ImageIcon(const TestImageProvider(24, 24)),
@@ -113,6 +163,7 @@ void main() {
           ],
           currentIndex: 1,
           onTap: (int tab) { callbackTab = tab; },
+        ),
     ));
 
     await tester.tap(find.text('Tab 1'));