1. Under the hood of the FlexJS framework
FlexJS: Deeper Dive
Under the hood of the FlexJS framework
Alex Harui
Apache Flex PMC Chair
August 4, 2013

2. Who am I? One of the original Flex SDK developers at Macromedia
VP of Apache Flex
Apache Flex PMC Chair
30+ years experience
11+ years at Macromedia/Adobe

3. Disclaimer
Even though I am a full-time Adobe employee and spend my whole day on Apache Flex, everything I say here is just my opinion, and not an official statement on behalf of Adobe Systems Inc., or the Apache Software Foundation, or even the Apache Flex project itself.

4. FlexJS
Use MXML and ActionScript to create either SWFs that run in Flash/AIR or HTML/JS/CSS files that run in browsers (or anywhere HTML/JS/CSS runs) without Flash.
IE8, 9, 10, Chrome, Firefox, Android, IOS
Mobile Apps via PhoneGap/Apache Cordova

5. DEMO
dingTest/bin/js-release/
Shortened URL:
JS debug and SWF versions:

6. Terminology
API Surface – The total set of public properties, methods and events on a component
Component Developer – Someone who is developing components for use by an Application Developer
Application Developer – Someone who is building an Application by taking a set of components and gluing them together with ActionScript.

7. More Terminology
Falcon – The name for the code-base for Adobe’s ASC2.0 that was donated to Apache Flex.
FalconJS – The cross-compiler based on Falcon that was donated by Adobe to Apache Flex. Early prototypes used this compiler, but this code base is not under development at this time.
FalconJX – A cross-compiler developed by Apache Flex committers that is currently being used to compiler FlexJS applications.

8. Philosophy Parallel Frameworks Plug-ins Composition over Inheritance
Multiple Component Sets
Just-in-time, not Just-in-case
Rapid prototyping is important, but end-game optimization is critical

9. Parallel Frameworks The component developer does the hard work:
Creates both a button.as and button.js
Essentially, writes the component twice, once in AS and once in JS.
Button.as can use Flash APIs
Button.js uses HTMLElements, JS, and CSS
The application developer writes one set of code
Compiles and debugs in Flash
Cross-compiles to HTML/JS/CSS

10. Beads (Plug-Ins)
Instead of one Button with every property imaginable, Button optional properties are packaged into “Beads”.
Beads are the name for plug-ins
They should be highly-reusable
Prompt for TextArea, TextInput, ComboBox, for example.
Component when used as sub-components don’t need as much as when used at top-level
Border on TextInput in ComboBox

11. Beads (cont’d) Different code for different runtime environments
Toss out mouseover code on mobile, swap in touch code instead
Use CSS to choose beads
Wrap up a bunch of beads into a top-level component and proxy the model to the component API surface

12. Composition JIT compilers are used in the runtimes.
The more you re-use code, the more efficient JIT is
Flex startup is actually faster without JIT because it doesn’t re-use as much code
A single feature can be written once and applied in several places.
Text prompt example

13. Multiple Component Sets
A one-size-fits-all Button works in most places, but not all

14. Multiple Component Sets
A one-size-fits-all Button works in most places, but not all

15. Multiple Component Sets
A one-size-fits-all Button works in most places, but not all
A choice of Buttons means you have more decisions to make, but you don’t have to carry around excess code.
And some folks have requirements to use JQuery or other frameworks.

16. Prototyping vs Optimization
How do you choose from so many different buttons?
Need utility to help you choose
Maybe a few heavy buttons with lots of options baked in
You will be able to toss out code you are not using.
Debug-mode beads can give more warnings and do more parameter checking.

17. Just-in-Time
Flex initializes a bunch of managers at startup that prepare for overlapping top-level windows, tooltips, and custom cursors.
None of these are likely to be found in mobile apps
You don’t even need PopUpManager unless you have floating non-modal popups
Choose the right PopUpManager, and only instantiate it when you actually get around to showing a popup.

18. Component Patterns MVC Model Bead – stores properties
Spark model is baked into the component
View Bead – assembles sub-components, if any
Spark Skins combine sub-components and the actual visuals
Controller Bead – manages events, updates model and dispatches other events

19. Button.as Has no model. There are no properties!
CSS for Button specifies a ButtonView as the view.
ButtonView.as only knows how to display whatever is specified by the background-image style.
That’s what the HTML Button does so that what we’ll encapsulate and present in AS.
Flex buttons used for scrollbar arrows still think about text label layout. That’s not pay-as-you-go.

20. TextButton.as Wrapper that proxies label property to model.
CSS for Button specifies model with label property.
ButtonView.as only knows how to display the label.
Different ButtonView could know how to display an icon with a label.
Then you’d use a different model as well that supports an “icon” property or style.

21. Button.js Thin wrapper around HTML Button element
TextButton.js is same since text behavior is built-in to HTML.

22. Button Skin
For the basic component set, the skins are images you can specify as a background-image in HTML.
Gif, png, jpg
They are loaded on the fly, no embedding
But the HTML5 Button set can load SVG as background-image
You choose different components sets based on target devices.

23. Panel.as Specifies a PanelView that creates a TitleBar and ContentPane
Another PanelView would create a TitleBar, ContentPane and ControlBar.
Other PanelViews would include a StatusBar
TitleBar is a Sprite with a TextField
Some other TitleBar could be a Sprite with FTE Text

24. Panel.js
Also specifies a PanelView. This one also creates a TitleBar and ContentPane.
TitleBar is a DIV with some text in it.

25. TextPromptBead.as Overlays Text widget
Different TextPromptBead can have different strategy for when to appear/disappear/reappear.
Different implementation could change styles and text in a single text widget.

26. CSS in FlexJS CSS compliant
Custom properties are prefixed
AS-only properties are hidden in a custom media type in a media query.
Need to create more and more sophisticated CSS implementations in the AS side

27. ValuesManager Abstraction for getting default values.
CSS Styles, Resources, etc.
If your app doesn’t use an expensive CSS feature, you may choose a less expensive ValuesManager

28. Compiling and Linking A Flex project contains MXML, AS, and SWCs
The Compiler creates compilation units for every class defined in MXML, AS and SWCs
FalconJX generates JS only for MXML and AS classes.
It assumes that external JS files exist for every class in a SWC.

29. Block Diagram ApplicationMXML & AS Falcon Button.as (SWC) SWF
HTTPService.as
(SWC)

30. Block Diagram ApplicationMXML & AS FalconJX Button.js Button.as (SWC)
Google
Closure
HTTPService.as
(SWC)
HTTPService.js

31. Next Steps More components More compiler work Release early versions
Metadata
Interfaces and other introspection
Release early versions
Basic features first, more features later
Over time, we should be able to replicate most but not all of the current Flex SDK APIs

32. Summary
We need help!
All kinds of contributions welcome
Testing
Development
Documentation
Examples
Look for me in the Apache Flex Discovery Room and on the Apache mailing lists.

33. Questions? http://flex.apache.org/ mailto:dev@flex.apache.org
X/Alex%27s+FlexJS+Prototype