# Class CssMetaData<S extends Styleable, V>

java.lang.Object
javafx.css.CssMetaData<S,V>

Type Parameters:
  `S` - The type of Styleable
  `V` - The type into which the parsed value is converted.

Direct Known Subclasses:
  `FontCssMetaData`

public abstract class CssMetaData<S extends Styleable, V> extends Object
A CssMetaData instance provides information about the CSS style and provides the hooks that allow CSS to set a property value. It encapsulates the CSS property name, the type into which the CSS value is converted, and the default value of the property.

CssMetaData is the bridge between a value that can be represented syntactically in a .css file, and a `StyleableProperty`. There is a one-to-one correspondence between a CssMetaData and a StyleableProperty. Typically, the CssMetaData of a Node will include the CssMetaData of its ancestors. For example, the CssMetaData of a Rectangle includes the CssMetaData of Shape and also of Node. During CSS processing, the CSS engine iterates over the Node's CssMetaData, looks up the parsed value of each `property`, converts the parsed value, and sets the value on the StyleableProperty.

The method `Node.getCssMetaData()` is called to obtain the List<CssMetaData>. This method is called frequently and it is prudent to return a static list rather than creating the list on each call. By convention, node classes that have CssMetaData will implement a static method `getClassCssMetaData()` and it is customary to have `getCssMetaData()` simply return `getClassCssMetaData()`. The purpose of `getClassCssMetaData()` is to allow sub-classes to easily include the CssMetaData of some ancestor.

The `StyleablePropertyFactory` greatly simplifies creating a StyleableProperty and its corresponding CssMetaData.

This example is a typical implementation.

    private DoubleProperty gapProperty = new StyleableDoubleProperty(0) {
        @Override
         public CssMetaData<MyWidget,Number> getCssMetaData() {
             return GAP_META_DATA;
         }

         @Override
         public Object getBean() {
             return MyWidget.this;
         }

         @Override
         public String getName() {
             return "gap";
         }
    };

    private static final CssMetaData GAP_META_DATA =
        new CssMetaData<MyWidget,Number>("-my-gap", StyleConverter.getSizeConverter(), 0d) {

           @Override
           public boolean isSettable(MyWidget node) {
               return node.gapProperty == null || !node.gapProperty.isBound();
           }

           @Override
           public StyleableProperty<Number> getStyleableProperty(MyWidget node) {
               return (StyleableProperty<Number>)node.gapProperty;
           }
    };

    private static final List<CssMetaData<? extends Node, ?>> cssMetaDataList;
    static {
        List<CssMetaData<? extends Node, ?>> temp =
            new ArrayList<CssMetaData<? extends Node, ?>>(Control.getClassCssMetaData());
        temp.add(GAP_META_DATA);
        cssMetaDataList = Collections.unmodifiableList(temp);
    }

    public static List<CssMetaData<? extends Node, ?>> getClassCssMetaData() {
        return cssMetaDataList;
    }

    @Override
    public List<CssMetaData<? extends Node, ?>> getCssMetaData() {
        return getClassCssMetaData();
    }

Since:
  JavaFX 8.0
See Also:
  - `StyleablePropertyFactory`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `CssMetaData(String property, StyleConverter<?,V> converter)`
  Construct a CssMetaData with the given parameters, initialValue is null, inherit is set to false, and no sub-properties.
  `protected`
  `CssMetaData(String property, StyleConverter<?,V> converter, V initialValue)`
  Construct a CssMetaData with the given parameters, inherit set to false and no sub-properties.
  `protected`
  `CssMetaData(String property, StyleConverter<?,V> converter, V initialValue, boolean inherits)`
  Construct a CssMetaData with the given parameters and no sub-properties.
  `protected`
  `CssMetaData(String property, StyleConverter<?,V> converter, V initialValue, boolean inherits, List<CssMetaData<? extends Styleable, ?>> subProperties)`
  Construct a CssMetaData with the given parameters and no sub-properties.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `equals(Object obj)`
  Two CssMetaData objects are considered to be equal if their `property` values are equal.
  `final StyleConverter<?,V>`
  `getConverter()`
  Gets the CSS converter that handles conversion from a CSS value to a Java Object.
  `V`
  `getInitialValue(S styleable)`
  The initial value of a CssMetaData corresponds to the default value of the StyleableProperty in code.
  `final String`
  `getProperty()`
  Gets the CSS property name.
  `abstract StyleableProperty<V>`
  `getStyleableProperty(S styleable)`
  Return the corresponding `StyleableProperty` for the given Node.
  `final List<CssMetaData<? extends Styleable, ?>>`
  `getSubProperties()`
  The sub-properties refers to the constituent properties of this property, if any.
  `final boolean`
  `isInherits()`
  If true, the value of this property is the same as the parent's computed value of this property.
  `abstract boolean`
  `isSettable(S styleable)`
  Check to see if the corresponding property on the given Node is settable.
  `void`
  `set(S styleable, V value, StyleOrigin origin)`
  Deprecated.
  This method is no longer called from CSS code.

  ### Methods declared in class Object

  `clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### CssMetaData

    protected CssMetaData(String property, StyleConverter<?,V> converter, V initialValue, boolean inherits, List<CssMetaData<? extends Styleable, ?>> subProperties)
    Construct a CssMetaData with the given parameters and no sub-properties.
    Parameters:
      `property` - the CSS property
      `converter` - the StyleConverter used to convert the CSS parsed value to a Java object.
      `initialValue` - The initial or default value of the corresponding StyleableProperty
      `inherits` - true if this property uses CSS inheritance
      `subProperties` - the sub-properties of this property. For example, the -fx-font property has the sub-properties -fx-font-family, -fx-font-size, -fx-font-weight, and -fx-font-style.

  - ### CssMetaData

    protected CssMetaData(String property, StyleConverter<?,V> converter, V initialValue, boolean inherits)
    Construct a CssMetaData with the given parameters and no sub-properties.
    Parameters:
      `property` - the CSS property
      `converter` - the StyleConverter used to convert the CSS parsed value to a Java object.
      `initialValue` - The initial or default value of the corresponding StyleableProperty
      `inherits` - true if this property uses CSS inheritance

  - ### CssMetaData

    protected CssMetaData(String property, StyleConverter<?,V> converter, V initialValue)
    Construct a CssMetaData with the given parameters, inherit set to false and no sub-properties.
    Parameters:
      `property` - the CSS property
      `converter` - the StyleConverter used to convert the CSS parsed value to a Java object.
      `initialValue` - The initial or default value of the corresponding StyleableProperty

  - ### CssMetaData

    protected CssMetaData(String property, StyleConverter<?,V> converter)
    Construct a CssMetaData with the given parameters, initialValue is null, inherit is set to false, and no sub-properties.
    Parameters:
      `property` - the CSS property
      `converter` - the StyleConverter used to convert the CSS parsed value to a Java object.

- ## Method Details

  - ### set

    @Deprecated(since="8") public void set(S styleable, V value, StyleOrigin origin)
    Deprecated.
    This method is no longer called from CSS code. Use `StyleableProperty.applyStyle(javafx.css.StyleOrigin, java.lang.Object)`
    Sets the value of the corresponding property on the given Node.
    Parameters:
      `styleable` - The Styleable on which the property value is being set
      `value` - The value to which the property is set
      `origin` - the origin

  - ### isSettable

    public abstract boolean isSettable(S styleable)
    Check to see if the corresponding property on the given Node is settable. This method is called before any styles are looked up for the given property. It is abstract so that the code can check if the property is settable without expanding the property. Generally, the property is settable if it is not null or is not bound.
    Parameters:
      `styleable` - The Styleable on which the property value is being set
    Returns:
      true if the property can be set.

  - ### getStyleableProperty

    public abstract StyleableProperty<V> getStyleableProperty(S styleable)
    Return the corresponding `StyleableProperty` for the given Node. Note that calling this method will cause the property to be expanded.
    Parameters:
      `styleable` - The Styleable for which the property is returned
    Returns:
      The StyleableProperty corresponding to this CssMetaData for the given Styleable

  - ### getProperty

    public final String getProperty()
    Gets the CSS property name.
    Returns:
      the CSS property name

  - ### getConverter

    public final StyleConverter<?,V> getConverter()
    Gets the CSS converter that handles conversion from a CSS value to a Java Object.
    Returns:
      the CSS converter

  - ### getInitialValue

    public V getInitialValue(S styleable)
    The initial value of a CssMetaData corresponds to the default value of the StyleableProperty in code. For example, the default value of Shape.fill is Color.BLACK and the initialValue of Shape.StyleableProperties.FILL is also Color.BLACK.

    There may be exceptions to this, however. The initialValue may depend on the state of the Node. A ScrollBar has a default orientation of horizontal. If the ScrollBar is vertical, however, this method should return Orientation.VERTICAL. Otherwise, a vertical ScrollBar would be incorrectly set to a horizontal ScrollBar when the initial value is applied.

    Parameters:
      `styleable` - the styleable
    Returns:
      The initial value of the property, possibly null

  - ### getSubProperties

    public final List<CssMetaData<? extends Styleable, ?>> getSubProperties()
    The sub-properties refers to the constituent properties of this property, if any. For example, "-fx-font-weight" is sub-property of "-fx-font".
    Returns:
      the list of sub-properties

  - ### isInherits

    public final boolean isInherits()
    If true, the value of this property is the same as the parent's computed value of this property.
    Returns:
      false by default unless inherits is true
    See Also:
      - CSS Inheritance

  - ### equals

    public boolean equals(Object obj)
    Two CssMetaData objects are considered to be equal if their `property` values are equal.
    Overrides:
      `equals` in class `Object`
    Returns:
      true if the obj is equaled, false otherwise