CSS metadata boilerplate

[David Grieve]

The reason things are as they are is because most properties in the core classes are lazily created and I didn't want cause the property to be created just to see if it was bound. But that is a particular concern for the core classes and not so much for controls. 

I'm not sure if you are aware of the javafx.css.SimpleStyleableXXXProperty classes. I'd be interested to see how your custom classes dovetail into these as I'd be more than willing to consider taking  your additions and calling them my own… uh, um, I mean, rolling them into the source code. 

Have you looked at the initialization-on-demand holder pattern for creating the List?
 
On Jan 7, 2014, at 9:34 PM, John Hendrikx <hjohn at xs4all.nl> wrote:

> Hi List,
> 
> I'm in the process of adding CSS metadata to a new control, and I noticed there is a lot of boilerplate.
> 
> In order to reduce this, I've created some custom classes StyleableProperty classes (SimpleStyleableXXXProperty), which reduces the boilerplate significantly without sacrificing much (if any) performance.  The only thing that I cannot easily provide in this fashion is the static getClassCssMetaData method.  From the documentation I understand it is there just for convience for subclass creators and is not used by the CSS engine at all -- atleast, everything seems to work.
> 
> The shortened version for CSS aware properties basically looks like:
> 
>  private final SimpleStyleableDoubleProperty cellAlignment = new SimpleStyleableDoubleProperty(this, "cellAlignment", "-fx-cell-alignment", 0.8);
>  private final SimpleStyleableDoubleProperty density= new SimpleStyleableDoubleProperty(this, "density", "-fx-density", 0.02);
>  private final SimpleStyleableBooleanProperty reflectionEnabled= new SimpleStyleableBooleanProperty(this, "reflectionEnabled", "-fx-reflection-enabled", true);
>  private final SimpleStyleableBooleanProperty clipReflections= new SimpleStyleableBooleanProperty(this, "clipReflections", "-fx-clip-reflections", true);
> 
> With one small bit of supporting code in the relevant class (Skin or Control), which is basically a non-static implementation of the standard CSS List example code:
> 
>  private static List<CssMetaData<? extends Styleable, ?>> cssMetaData;
> 
>  @Override
>  public List<CssMetaData<? extends Styleable, ?>> getCssMetaData() {  // Unsynchronized. WC: list gets initialized multiple times.
>    if(cssMetaData == null) {
>      List<CssMetaData<? extends Styleable, ?>> metaData = new ArrayList<>(super.getCssMetaData());
>      Collections.addAll(metaData,
>          cellAlignment.getCssMetaData(),
>          density.getCssMetaData(),
>          reflectionEnabled.getCssMetaData(),
>          clipReflections.getCssMetaData()
>      );
>      cssMetaData = Collections.unmodifiableList(metaData);
>    }
> 
>    return cssMetaData;
>  }
> 
> Note that the List is static and lazy-final.  The same goes for the getCssMetaData method in the SimpleStyleableXXXProperty classes.  There is a slight performance decrease in those classes as getCssMetaData is looked up from a static Map (indexed by Class + css property name) and lazily created as needed -- a Map lookup however should be quite fast enough.
> 
> I'm sure the design had good reason to do things as they are, and I'm wondering if reducing the boilerplate has left me missing something important.
> 
> I welcome any insights!
> 
> --John