Justin Tulloss goes in-depth with JavaScript and webOS.

2. Advanced webOS
Justin Tulloss
Sr. Software Engineer
April 24, 2010

3. Overview
• Multi-Stage basics
• Dashboards
• Popups
• Relaunching
• The Future
• Q&A

4. Why Is This So Complicated?
The web isn’t designed for multi-window apps
• Big departure from normal browser behavior
• webOS offers a lot of different interactions
• Performance issues led to complications
• Expected globals (document, window, etc.)
• Late recognition of the problem by Palm. Sorry.

5. Multi-Stage Basics

6. Things to Consider
• Do you need another stage? Every time?
• What is the most appropriate stage type?
• How often do you rely on globals?
• Prototype, jquery, document?
• What state is shared between children?

7. Basic APIs

8. From a Scene Assistant

9. Stage Types
• Card
• Dashboard
• Popup

10. Dashboards
and Banners

11. Example: MainAssistant

12. Example: DashboardStageAssistant

13. Example: Message View

14. Example: MessageAssistant

15. Popups

16. Some New Twists
• Refactor child stage assistant to be generic
• Not all stylesheets are loaded
• Some styles are changed to assume a notification
• Popups can have their height specified
• Closing child windows is easy

17. Example: New ChildStageAssistant

18. Example: Pushing Dashboard Scene
Moved

19. Example: Creating a Popup

20. Example: Popup Scene

21. Example: Popup Assistant

22. Example: Very Simple Popup

23. Relaunching

24. Relaunching Basics
• Certain actions cause your app to be “relaunched”
• The appManager service passes in arguments
• Your AppAssistant can change default launch
behavior
• You should never have to worry about whether or
not your app was already open

25. AppAssistant
• Shared across all child stages
• Handles relaunching
• Convenient place to stick shared state
• Try not to share state

26. Example: App Assistant

27. Example: Setting Default Stage

28. Example: Launch Parameters in
Banner

29. The Future

30. Upcoming API Improvements
• Default dashboards no longer require markup
boilerplate
• Just provide an icon, some text, and a count
• Handles going from single item to multiple
• SingletonStages
• No more stageProxy shenanigans
• Failure cases are handled more elegantly

31. Q &A