Provides API for making properties styleable via CSS and for supporting
pseudo-class state.
The JavaFX Scene Graph provides the facility to style nodes using
CSS (Cascading Style Sheets).
The {@link javafx.scene.Node Node} class contains {@code id}, {@code styleClass}, and
{@code style} variables which are used by CSS selectors to find nodes
to which styles should be applied. The {@link javafx.scene.Scene Scene} class and
{@link javafx.scene.Parent Parent} class contain a
the {@code stylesheets} variable which is a list of URLs that
reference CSS style sheets that are to be applied to the nodes within
that scene or parent.
The primary classes in this package are:
- {@link javafx.css.CssMetaData CssMetaData}
- Defines the CSS property and provides a link back to the 
    {@link javafx.css.StyleableProperty StyleableProperty}.
    By convention, classes that have CssMetaData implement a 
    {@code public static List> getClassCssMetaData()} method that
    allows other classes to include CssMetaData from an inherited class. The
    method {@link javafx.scene.Node#getCssMetaData() getCssMetaData()} should 
    be overridden to return {@code getClassCssMetaData()}. The CSS implementation
    frequently calls {@code getCssMetaData()}. It is strongly recommended that
    the returned list be a {@code final static}.
- {@link javafx.css.StyleableProperty StyleableProperty}
- Defines the interface that the CSS implementation uses to set values on a
    property and provides a link back to the {@code CssMetaData} that 
    corresponds to the property. The {@link javafx.css.StyleablePropertyFactory StyleablePropertyFactory}
    greatly simplifies creating a StyleableProperty and its corresponding CssMetaData.
- {@link javafx.css.PseudoClass PseudoClass}
- Defines a pseudo-class which can be set or cleared via the method 
    {@link javafx.scene.Node#pseudoClassStateChanged(javafx.css.PseudoClass, boolean)
    pseudoClassStateChanged}. 
For further information about CSS, how to apply CSS styles
to nodes, and what properties are available for styling, see the
CSS Reference Guide.