https://docs.flutter.dev/development/ui/layout
- Flutter의 layout의 메커니즘은 widgets
- images, icon 이런게 모두 widget
- widget catalog https://docs.flutter.dev/development/ui/widgets
- standard widgets
- container
- gridview
- listview
- Stack
- Widget을 overlap 할때 사용
- scroll 할 수 없음
- flutter gallery https://github.com/flutter/flutter/tree/master/dev/integration_tests/flutter_gallery