title: Use ThemeData as theme for CupertinoApp
body: <p>My app was built using a <code>MaterialApp</code> as the root widget. To this material app, I've added a theme as follows:</p>
  
  <pre><code>MaterialApp(
    theme: myTheme,
    home: MyHomePage(),
    ...
  )
  
  final ThemeData myTheme = _buildTheme();
  
  ThemeData _buildTheme() {
    final ThemeData base = ThemeData.light();
    return base.copyWith(
      ...
        textTheme: _buildMyTextTheme(base.textTheme),
        primaryTextTheme: _buildMyTextTheme(base.primaryTextTheme),
        accentTextTheme: _buildMyTextTheme(base.accentTextTheme),
        pageTransitionsTheme: PageTransitionsTheme(builders: {
          TargetPlatform.iOS: CupertinoPageTransitionsBuilder(),
        }));
  }
  
  TextTheme _buildMyTextTheme(TextTheme base) {
    return base
        .copyWith(
          headline:
              base.headline.copyWith(fontSize: 20.0, fontWeight: FontWeight.w500),
          title: base.title.copyWith(fontSize: 18.0, fontWeight: FontWeight.w400),
          subhead:
              base.subhead.copyWith(fontSize: 16.0, fontWeight: FontWeight.w400),
          body1: base.body1.copyWith(fontSize: 14.0, fontWeight: FontWeight.w400),
          body2: base.body2.copyWith(fontSize: 14.0, fontWeight: FontWeight.w500),
          caption: base.caption.copyWith(
            fontWeight: FontWeight.w400,
            fontSize: 12.0,
          ),
        )
        .apply(
          fontFamily: 'myfont',
          displayColor: Colors.black,
          bodyColor: Colors.black,
        );
  }
  </code></pre>
  
  <p>I've used <code>Theme.of(context.textTheme</code> to style the text in the whole app down the widget tree.</p>
  
  <p>for example :
  to a title I used</p>
  
  <pre><code>Text('Title', style:Theme.of(context).textTheme.title),
  </code></pre>
  
  <p>to a subtitle I used</p>
  
  <pre><code>Text('Title', style:Theme.of(context).textTheme.subhead),
  </code></pre>
  
  <p>It works as intended.
  But now I want to use a <code>CupertinoApp</code> if the current platform is ios as it provides with native ios feel like</p>
  
  <ul>
  <li>List item</li>
  <li>Pages will be dismissible via a back swipe.
  Scrolling past extremities will trigger iOS-style spring overscrolls.</li>
  </ul>
  
  <p>How shall I add the CupertionApp applying the same text theming?</p>