/*
 * Copyright (c) 2010, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package javafx.scene.control;

import java.lang.ref.WeakReference;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import com.sun.javafx.scene.control.ControlAcceleratorSupport;
import javafx.application.Application;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.ObjectPropertyBase;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.WritableValue;
import javafx.collections.ObservableList;
import javafx.css.CssParser;
import javafx.event.EventHandler;
import javafx.scene.AccessibleAction;
import javafx.scene.AccessibleAttribute;
import javafx.scene.Node;
import javafx.scene.input.ContextMenuEvent;
import javafx.scene.layout.Region;
import com.sun.javafx.application.PlatformImpl;
import javafx.css.CssMetaData;
import com.sun.javafx.css.StyleManager;
import com.sun.javafx.scene.NodeHelper;
import com.sun.javafx.scene.control.ControlHelper;
import javafx.css.StyleableObjectProperty;
import javafx.css.StyleableStringProperty;
import javafx.css.converter.StringConverter;
import com.sun.javafx.scene.control.Logging;
import javafx.css.Styleable;
import javafx.css.StyleableProperty;
import com.sun.javafx.logging.PlatformLogger;
import com.sun.javafx.logging.PlatformLogger.Level;


Base class for all user interface controls. A "Control" is a node in the
scene graph which can be manipulated by the user. Controls provide
additional variables and behaviors beyond those of Node to support
common user interactions in a manner which is consistent and predictable
for the user.

Additionally, controls support explicit skinning to make it easy to
leverage the functionality of a control while customizing its appearance.

See specific Control subclasses for information on how to use individual
types of controls.
 Most controls have their focusTraversable property set to true by default, however read-only controls such as Label and ProgressIndicator, and some controls that are containers ScrollPane and ToolBar do not. Consult individual control documentation for details. 
Since:
JavaFX 2.0/**
 * Base class for all user interface controls. A "Control" is a node in the
 * scene graph which can be manipulated by the user. Controls provide
 * additional variables and behaviors beyond those of Node to support
 * common user interactions in a manner which is consistent and predictable
 * for the user.
 * <p>
 * Additionally, controls support explicit skinning to make it easy to
 * leverage the functionality of a control while customizing its appearance.
 * <p>
 * See specific Control subclasses for information on how to use individual
 * types of controls.
 * <p> Most controls have their focusTraversable property set to true by default, however
 * read-only controls such as {@link Label} and {@link ProgressIndicator}, and some
 * controls that are containers {@link ScrollPane} and {@link ToolBar} do not.
 * Consult individual control documentation for details.
 * @since JavaFX 2.0
 */
public abstract class Control extends Region implements Skinnable {

    static {
        ControlHelper.setControlAccessor(new ControlHelper.ControlAccessor() {
            @Override
            public void doProcessCSS(Node node) {
                ((Control) node).doProcessCSS();
            }
            @Override
            public StringProperty skinClassNameProperty(Control control) {
                return control.skinClassNameProperty();
            }
        });

        // Ensures that the default application user agent stylesheet is loaded
        if (Application.getUserAgentStylesheet() == null) {
            PlatformImpl.setDefaultPlatformUserAgentStylesheet();
        }
    }

    
Utility for loading a class in a manner that will work with multiple
class loaders, as is typically found in OSGI modular applications.
In particular, this method will attempt to just load the class
identified by className. If that fails, it attempts to load the
class using the current thread's context class loader. If that fails,
it attempts to use the class loader of the supplied "instance", and
if it still fails it walks up the class hierarchy of the instance
and attempts to use the class loader of each class in the super-type
hierarchy.
Params:
className – The name of the class we want to load
instance – An optional instance used to help find the class to load
Throws:
ClassNotFoundException – If the class cannot be found using any technique.
Returns:
The class. Cannot return null/**
     * Utility for loading a class in a manner that will work with multiple
     * class loaders, as is typically found in OSGI modular applications.
     * In particular, this method will attempt to just load the class
     * identified by className. If that fails, it attempts to load the
     * class using the current thread's context class loader. If that fails,
     * it attempts to use the class loader of the supplied "instance", and
     * if it still fails it walks up the class hierarchy of the instance
     * and attempts to use the class loader of each class in the super-type
     * hierarchy.
     *
     * @param className The name of the class we want to load
     * @param instance An optional instance used to help find the class to load
     * @return The class. Cannot return null
     * @throws ClassNotFoundException If the class cannot be found using any technique.
     */
    private static Class<?> loadClass(final String className, final Object instance)
            throws ClassNotFoundException
    {
        try {
            // Try just loading the class
            return Class.forName(className, false, Control.class.getClassLoader());
        } catch (ClassNotFoundException ex) {
            // RT-17525 : Use context class loader only if Class.forName fails.
            if (Thread.currentThread().getContextClassLoader() != null) {
                try {
                    final ClassLoader ccl = Thread.currentThread().getContextClassLoader();
                    return Class.forName(className, false, ccl);
                } catch (ClassNotFoundException ex2) {
                    // Do nothing, just fall through
                }
            }

            // RT-14177: Try looking up the class using the class loader of the
            //           current class, walking up the list of superclasses
            //           and checking each of them, before bailing and using
            //           the context class loader.
            if (instance != null) {
                Class<?> currentType = instance.getClass();
                while (currentType != null) {
                    try {
                        final ClassLoader loader = currentType.getClassLoader();
                        return Class.forName(className, false, loader);
                    } catch (ClassNotFoundException ex2) {
                        currentType = currentType.getSuperclass();
                    }
                }
            }

            // We failed to find the class using any of the above means, so we're going
            // to just throw the ClassNotFoundException that we caught earlier
            throw ex;
        }
    }

    
                                                                        *
Private fields                                                          *
                                                                        *
/***************************************************************************
     *                                                                         *
     * Private fields                                                          *
     *                                                                         *
     **************************************************************************/

    private List<CssMetaData<? extends Styleable, ?>> styleableProperties;

    
A private reference directly to the SkinBase instance that is used as the
Skin for this Control. A Control's Skin doesn't have to be of type
SkinBase, although 98% of the time or greater it probably will be.
Because instanceof checks and reading a value from a property are
not cheap (on interpreters on slower hardware or mobile devices)
it pays to have a direct reference here to the skinBase. We simply
need to check this variable -- if it is not null then we know the
Skin is a SkinBase and this is a direct reference to it. If it is null
then we know the skin is not a SkinBase and we need to call getSkin().
/**
     * A private reference directly to the SkinBase instance that is used as the
     * Skin for this Control. A Control's Skin doesn't have to be of type
     * SkinBase, although 98% of the time or greater it probably will be.
     * Because instanceof checks and reading a value from a property are
     * not cheap (on interpreters on slower hardware or mobile devices)
     * it pays to have a direct reference here to the skinBase. We simply
     * need to check this variable -- if it is not null then we know the
     * Skin is a SkinBase and this is a direct reference to it. If it is null
     * then we know the skin is not a SkinBase and we need to call getSkin().
     */
    private SkinBase<?> skinBase;

    /***************************************************************************
    *                                                                         *
    * Event Handlers / Listeners                                              *
    *                                                                         *
    **************************************************************************/

    
Handles context menu requests by popping up the menu.
Note that we use this pattern to remove some of the anonymous inner
classes which we'd otherwise have to create. When lambda expressions
are supported, we could do it that way instead (or use MethodHandles).
/**
     * Handles context menu requests by popping up the menu.
     * Note that we use this pattern to remove some of the anonymous inner
     * classes which we'd otherwise have to create. When lambda expressions
     * are supported, we could do it that way instead (or use MethodHandles).
     */
    private final static EventHandler<ContextMenuEvent> contextMenuHandler = event -> {
        if (event.isConsumed()) return;

        // If a context menu was shown, consume the event to prevent multiple context menus
        Object source = event.getSource();
        if (source instanceof Control) {
            Control c = (Control) source;
            if (c.getContextMenu() != null) {
                c.getContextMenu().show(c, event.getScreenX(), event.getScreenY());
                event.consume();
            }
        }
    };



    /***************************************************************************
     *                                                                         *
     * Properties                                                              *
     *                                                                         *
     **************************************************************************/



    // --- skin
    
Skin is responsible for rendering this Control. From the perspective of the Control, the Skin is a black box. It listens and responds to changes in state in a Control. 
 There is a one-to-one relationship between a Control and its Skin. Every Skin maintains a back reference to the Control via the Skin.getSkinnable() method. 

A skin may be null.
Returns:
the skin property for this control/**
     * Skin is responsible for rendering this {@code Control}. From the
     * perspective of the {@code Control}, the {@code Skin} is a black box.
     * It listens and responds to changes in state in a {@code Control}.
     * <p>
     * There is a one-to-one relationship between a {@code Control} and its
     * {@code Skin}. Every {@code Skin} maintains a back reference to the
     * {@code Control} via the {@link Skin#getSkinnable()} method.
     * <p>
     * A skin may be null.
     * @return the skin property for this control
     */
    @Override public final ObjectProperty<Skin<?>> skinProperty() { return skin; }
    @Override public final void setSkin(Skin<?> value) {
        skinProperty().set(value);
    }
    @Override public final Skin<?> getSkin() { return skinProperty().getValue(); }
    private ObjectProperty<Skin<?>> skin = new StyleableObjectProperty<Skin<?>>() {
        // We store a reference to the oldValue so that we can handle
        // changes in the skin properly in the case of binding. This is
        // only needed because invalidated() does not currently take
        // a reference to the old value.
        private Skin<?> oldValue;

        @Override
        //This code is basically a kind of optimization that prevents a Skin that is equal but not instance equal.
        //Although it's not kosher from the property perspective (bindings won't pass through set), it should not do any harm.
        //But it should be evaluated in the future.
        public void set(Skin<?> v) {
            if (v == null
                ? oldValue == null
                : oldValue != null && v.getClass().equals(oldValue.getClass()))
                return;

            super.set(v);
        }

        @Override protected void invalidated() {
            Skin<?> skin = get();
            // Collect the name of the currently installed skin class. We do this
            // so that subsequent updates from CSS to the same skin class will not
            // result in reinstalling the skin
            currentSkinClassName = skin == null ? null : skin.getClass().getName();

            // if someone calls setSkin, we need to make it look like they
            // called set on skinClassName in order to keep CSS from overwriting
            // the skin.
            skinClassNameProperty().set(currentSkinClassName);


            // Dispose of the old skin
            if (oldValue != null) oldValue.dispose();

            // Get the new value, and save it off as the new oldValue
            oldValue = skin;

            // Reset skinBase to null - it will be set to the new Skin if it
            // is a SkinBase, otherwise it will remain null, as expected
            skinBase = null;

            // We have two paths, one for "legacy" Skins, and one for
            // any Skin which extends from SkinBase. Legacy Skins will
            // produce a single node which will be the only child of
            // the Control via the getNode() method on the Skin. A
            // SkinBase will manipulate the children of the Control
            // directly. Further, we maintain a direct reference to
            // the skinBase for more optimal updates later.
            if (skin instanceof SkinBase) {
                // record a reference of the skin, if it is a SkinBase, for
                // performance reasons
                skinBase = (SkinBase<?>) skin;
                // Note I do not remove any children here, because the
                // skin will have already configured all the children
                // by the time setSkin has been called. This is because
                // our Skin interface was lacking an initialize method (doh!)
                // and so the Skin constructor is where it adds listeners
                // and so forth. For SkinBase implementations, the
                // constructor is also where it will take ownership of
                // the children.
            } else {
                final Node n = getSkinNode();
                if (n != null) {
                    getChildren().setAll(n);
                } else {
                    getChildren().clear();
                }
            }

            // clear out the styleable properties so that the list is rebuilt
            // next time they are requested.
            styleableProperties = null;

            // calling NodeHelper.reapplyCSS() as the styleable properties may now
            // be different, as we will now be able to return styleable properties
            // belonging to the skin. If NodeHelper.reapplyCSS() is not called, the
            // getCssMetaData() method is never called, so the
            // skin properties are never exposed.
            NodeHelper.reapplyCSS(Control.this);

            // DEBUG: Log that we've changed the skin
            final PlatformLogger logger = Logging.getControlsLogger();
            if (logger.isLoggable(Level.FINEST)) {
                logger.finest("Stored skin[" + getValue() + "] on " + this);
            }
        }

        // This method should be CssMetaData<Control,Skin> getCssMetaData(),
        // but SKIN is CssMetaData<Control,String>. This does not matter to
        // the CSS code which doesn't care about the actual type. Hence,
        // we'll suppress the warnings
        @Override @SuppressWarnings({"unchecked", "rawtype"})
        public CssMetaData getCssMetaData() {
            return StyleableProperties.SKIN;
        }

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

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


    // --- tooltip
    
The ToolTip for this control.
Returns:
the tool tip for this control/**
     * The ToolTip for this control.
     * @return the tool tip for this control
     */
    public final ObjectProperty<Tooltip> tooltipProperty() {
        if (tooltip == null) {
            tooltip = new ObjectPropertyBase<Tooltip>() {
                private Tooltip old = null;
                @Override protected void invalidated() {
                    Tooltip t = get();
                    // install / uninstall
                    if (t != old) {
                        if (old != null) {
                            Tooltip.uninstall(Control.this, old);
                        }
                        if (t != null) {
                            Tooltip.install(Control.this, t);
                        }
                        old = t;
                    }
                }

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

                @Override
                public String getName() {
                    return "tooltip";
                }
            };
        }
        return tooltip;
    }
    private ObjectProperty<Tooltip> tooltip;
    public final void setTooltip(Tooltip value) { tooltipProperty().setValue(value); }
    public final Tooltip getTooltip() { return tooltip == null ? null : tooltip.getValue(); }


    // --- context menu
    
The ContextMenu to show for this control.
/**
     * The ContextMenu to show for this control.
     */
    private ObjectProperty<ContextMenu> contextMenu = new SimpleObjectProperty<ContextMenu>(this, "contextMenu") {
        private WeakReference<ContextMenu> contextMenuRef;

        @Override protected void invalidated() {
            ContextMenu oldMenu = contextMenuRef == null ? null : contextMenuRef.get();
            if (oldMenu != null) {
                ControlAcceleratorSupport.removeAcceleratorsFromScene(oldMenu.getItems(), Control.this);
            }

            ContextMenu ctx = get();
            contextMenuRef = new WeakReference<>(ctx);

            if (ctx != null) {
                // set this flag so contextmenu show will be relative to parent window not anchor
                ctx.setShowRelativeToWindow(true); //RT-15160

                // if a context menu is set, we need to install any accelerators
                // belonging to its menu items ASAP into the scene that this
                // Control is in (if the control is not in a Scene, we will need
                // to wait until it is and then do it).
                ControlAcceleratorSupport.addAcceleratorsIntoScene(ctx.getItems(), Control.this);
            }
        }
    };
    public final ObjectProperty<ContextMenu> contextMenuProperty() { return contextMenu; }
    public final void setContextMenu(ContextMenu value) { contextMenu.setValue(value); }
    public final ContextMenu getContextMenu() { return contextMenu == null ? null : contextMenu.getValue(); }



    
                                                                        *
Constructors                                                            *
                                                                        *
/***************************************************************************
     *                                                                         *
     * Constructors                                                            *
     *                                                                         *
     **************************************************************************/

    {
        // To initialize the class helper at the begining each constructor of this class
        ControlHelper.initHelper(this);
    }
    
 Create a new Control.
/**
     *  Create a new Control.
     */
    protected Control() {
        // focusTraversable is styleable through css. Calling setFocusTraversable
        // makes it look to css like the user set the value and css will not
        // override. Initializing focusTraversable by calling applyStyle
        // with null for StyleOrigin ensures that css will be able to override
        // the value.
        final StyleableProperty<Boolean> prop = (StyleableProperty<Boolean>)(WritableValue<Boolean>)focusTraversableProperty();
        prop.applyStyle(null, Boolean.TRUE);

        // we add a listener for menu request events to show the context menu
        // that may be set on the Control
        this.addEventHandler(ContextMenuEvent.CONTEXT_MENU_REQUESTED, contextMenuHandler);

        // TODO re-enable when InputMap moves back to Node / Control
//        // Most controls need an input map, so we set this to be non-null in
//        // Control to save people from running into NPEs.
//        setInputMap(new InputMap(this));
    }



    /***************************************************************************
     *                                                                         *
     * Public API                                                              *
     *                                                                         *
     **************************************************************************/

    // Proposed dispose() API.
    // Note that there is impl code for a dispose method in TableRowSkinBase
    // and TableCell (just search for dispose())
//    public void dispose() {
//        Skin skin = getSkin();
//        if (skin != null) {
//            skin.dispose();
//        }
//    }

    
Returns true since all Controls are resizable.
Returns:
whether this node can be resized by its parent during layout/**
     * Returns <code>true</code> since all Controls are resizable.
     * @return whether this node can be resized by its parent during layout
     */
    @Override public boolean isResizable() {
        return true;
    }

    // Implementation of the Resizable interface.
    // Because only the skin can know the min, pref, and max sizes, these
    // functions are implemented to delegate to skin. If there is no skin then
    // we simply return 0 for all the values since a Control without a Skin
    // doesn't render
    
Computes the minimum allowable width of the Control, based on the provided height. The minimum width is not calculated within the Control, instead the calculation is delegated to the Node.minWidth(double) method of the Skin. If the Skin is null, the returned value is 0. 
Params:
height – The height of the Control, in case this value might dictate
     the minimum width.
Returns:
A double representing the minimum width of this control./**
     * Computes the minimum allowable width of the Control, based on the provided
     * height. The minimum width is not calculated within the Control, instead
     * the calculation is delegated to the {@link Node#minWidth(double)} method
     * of the {@link Skin}. If the Skin is null, the returned value is 0.
     *
     * @param height The height of the Control, in case this value might dictate
     *      the minimum width.
     * @return A double representing the minimum width of this control.
     */
    @Override protected double computeMinWidth(final double height) {
        if (skinBase != null) {
            return skinBase.computeMinWidth(height, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.minWidth(height);
        }
    }

    
Computes the minimum allowable height of the Control, based on the provided width. The minimum height is not calculated within the Control, instead the calculation is delegated to the Node.minHeight(double) method of the Skin. If the Skin is null, the returned value is 0. 
Params:
width – The width of the Control, in case this value might dictate
     the minimum height.
Returns:
A double representing the minimum height of this control./**
     * Computes the minimum allowable height of the Control, based on the provided
     * width. The minimum height is not calculated within the Control, instead
     * the calculation is delegated to the {@link Node#minHeight(double)} method
     * of the {@link Skin}. If the Skin is null, the returned value is 0.
     *
     * @param width The width of the Control, in case this value might dictate
     *      the minimum height.
     * @return A double representing the minimum height of this control.
     */
    @Override protected double computeMinHeight(final double width) {
        if (skinBase != null) {
            return skinBase.computeMinHeight(width, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.minHeight(width);
        }
    }

    
Computes the maximum allowable width of the Control, based on the provided height. The maximum width is not calculated within the Control, instead the calculation is delegated to the Node.maxWidth(double) method of the Skin. If the Skin is null, the returned value is 0. 
Params:
height – The height of the Control, in case this value might dictate
     the maximum width.
Returns:
A double representing the maximum width of this control./**
     * Computes the maximum allowable width of the Control, based on the provided
     * height. The maximum width is not calculated within the Control, instead
     * the calculation is delegated to the {@link Node#maxWidth(double)} method
     * of the {@link Skin}. If the Skin is null, the returned value is 0.
     *
     * @param height The height of the Control, in case this value might dictate
     *      the maximum width.
     * @return A double representing the maximum width of this control.
     */
    @Override protected double computeMaxWidth(double height) {
        if (skinBase != null) {
            return skinBase.computeMaxWidth(height, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.maxWidth(height);
        }
    }

    
Computes the maximum allowable height of the Control, based on the provided width. The maximum height is not calculated within the Control, instead the calculation is delegated to the Node.maxHeight(double) method of the Skin. If the Skin is null, the returned value is 0. 
Params:
width – The width of the Control, in case this value might dictate
     the maximum height.
Returns:
A double representing the maximum height of this control./**
     * Computes the maximum allowable height of the Control, based on the provided
     * width. The maximum height is not calculated within the Control, instead
     * the calculation is delegated to the {@link Node#maxHeight(double)} method
     * of the {@link Skin}. If the Skin is null, the returned value is 0.
     *
     * @param width The width of the Control, in case this value might dictate
     *      the maximum height.
     * @return A double representing the maximum height of this control.
     */
    @Override protected double computeMaxHeight(double width) {
        if (skinBase != null) {
            return skinBase.computeMaxHeight(width, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.maxHeight(width);
        }
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override protected double computePrefWidth(double height) {
        if (skinBase != null) {
            return skinBase.computePrefWidth(height, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.prefWidth(height);
        }
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override protected double computePrefHeight(double width) {
        if (skinBase != null) {
            return skinBase.computePrefHeight(width, snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.prefHeight(width);
        }
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override public double getBaselineOffset() {
        if (skinBase != null) {
            return skinBase.computeBaselineOffset(snappedTopInset(), snappedRightInset(), snappedBottomInset(), snappedLeftInset());
        } else {
            final Node skinNode = getSkinNode();
            return skinNode == null ? 0 : skinNode.getBaselineOffset();
        }
    }

    /***************************************************************************
     * Implementation of layout bounds for the Control. We want to preserve    *
     * the lazy semantics of layout bounds. So whenever the width/height       *
     * changes on the node, we end up invalidating layout bounds. We then      *
     * recompute it on demand.                                                 *
     **************************************************************************/

    
{@inheritDoc} /** {@inheritDoc} */
    @Override protected void layoutChildren() {
        if (skinBase != null) {
            final double x = snappedLeftInset();
            final double y = snappedTopInset();
            final double w = snapSizeX(getWidth()) - x - snappedRightInset();
            final double h = snapSizeY(getHeight()) - y - snappedBottomInset();
            skinBase.layoutChildren(x, y, w, h);
        } else {
            Node n = getSkinNode();
            if (n != null) {
                n.resizeRelocate(0, 0, getWidth(), getHeight());
            }
        }
    }

    /***************************************************************************
     * Forward the following to the skin                                       *
     **************************************************************************/

    
Create a new instance of the default skin for this control. This is called to create a skin for the control if no skin is provided via CSS -fx-skin or set explicitly in a sub-class with  setSkin(...). 
Returns:
 new instance of default skin for this control. If null then the control will have no skin unless one
         is provided by css.
Since:
JavaFX 8.0/**
     * Create a new instance of the default skin for this control. This is called to create a skin for the control if
     * no skin is provided via CSS {@code -fx-skin} or set explicitly in a sub-class with {@code  setSkin(...)}.
     *
     * @return  new instance of default skin for this control. If null then the control will have no skin unless one
     *          is provided by css.
     * @since JavaFX 8.0
     */
    protected Skin<?> createDefaultSkin() {
        return null;
    }

    
                                                                        *
Package API for SkinBase                                                *
                                                                        *
/***************************************************************************
     *                                                                         *
     * Package API for SkinBase                                                *
     *                                                                         *
     **************************************************************************/

    // package private for SkinBase
    ObservableList<Node> getControlChildren() {
        return getChildren();
    }


    /***************************************************************************
     *                                                                         *
     * Private implementation                                                  *
     *                                                                         *
     **************************************************************************/

    
Gets the Skin's node, or returns null if there is no Skin.
Convenience method for getting the node of the skin. This is null-safe,
meaning if skin is null then it will return null instead of throwing
a NullPointerException.
Returns:
The Skin's node, or null./**
     * Gets the Skin's node, or returns null if there is no Skin.
     * Convenience method for getting the node of the skin. This is null-safe,
     * meaning if skin is null then it will return null instead of throwing
     * a NullPointerException.
     *
     * @return The Skin's node, or null.
     */
    private Node getSkinNode() {
        assert skinBase == null;
        Skin<?> skin = getSkin();
        return skin == null ? null : skin.getNode();
    }

    
Keeps a reference to the name of the class currently acting as the skin.
/**
     * Keeps a reference to the name of the class currently acting as the skin.
     */
    private String currentSkinClassName = null;
    private StringProperty skinClassName;

    StringProperty skinClassNameProperty() {
        if (skinClassName == null) {
            skinClassName = new StyleableStringProperty() {

                @Override
                public void set(String v) {
                    // do not allow the skin to be set to null through CSS
                    if (v == null || v.isEmpty() || v.equals(get())) return;
                    super.set(v);
                }

                @Override
                public void invalidated() {

                    if (get() != null) {
                        if (!get().equals(currentSkinClassName)) {
                            loadSkinClass(Control.this, skinClassName.get());
                        }
                        // Note: CSS should not set skin to null
                    }
                }

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

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

                @Override
                public CssMetaData<Control,String> getCssMetaData() {
                    return StyleableProperties.SKIN;
                }

            };
        }
        return skinClassName;
    }

    static void loadSkinClass(final Skinnable control, final String skinClassName) {
        if (skinClassName == null || skinClassName.isEmpty()) {
            final String msg =
                "Empty -fx-skin property specified for control " + control;
            final List<CssParser.ParseError> errors = StyleManager.getErrors();
            if (errors != null) {
                CssParser.ParseError error = new CssParser.ParseError(msg);
                errors.add(error); // RT-19884
            }
            Logging.getControlsLogger().severe(msg);
            return;
        }

        try {
            final Class<?> skinClass = Control.loadClass(skinClassName, control);
            if (!Skin.class.isAssignableFrom(skinClass)) {
                final String msg =
                    "'" + skinClassName + "' is not a valid Skin class for control " + control;
                final List<CssParser.ParseError> errors = StyleManager.getErrors();
                if (errors != null) {
                    CssParser.ParseError error = new CssParser.ParseError(msg);
                    errors.add(error); // RT-19884
                }
                Logging.getControlsLogger().severe(msg);
                return;
            }
            Constructor<?>[] constructors = skinClass.getConstructors();
            Constructor<?> skinConstructor = null;
            for (Constructor<?> c : constructors) {
                Class<?>[] parameterTypes = c.getParameterTypes();
                if (parameterTypes.length == 1 && Skinnable.class.isAssignableFrom(parameterTypes[0])) {
                    skinConstructor = c;
                    break;
                }
            }

            if (skinConstructor == null) {
                final String msg =
                    "No valid constructor defined in '" + skinClassName + "' for control " + control +
                        ".\r\nYou must provide a constructor that accepts a single "
                        + "Skinnable (e.g. Control or PopupControl) parameter in " + skinClassName + ".";
                final List<CssParser.ParseError> errors = StyleManager.getErrors();
                if (errors != null) {
                    CssParser.ParseError error = new CssParser.ParseError(msg);
                    errors.add(error); // RT-19884
                }
                Logging.getControlsLogger().severe(msg);
            } else {
                Skin<?> skinInstance = (Skin<?>) skinConstructor.newInstance(control);
                // Do not call setSkin here since it has the side effect of
                // also setting the skinClassName!
                control.skinProperty().set(skinInstance);
            }
        } catch (InvocationTargetException e) {
            final String msg =
                "Failed to load skin '" + skinClassName + "' for control " + control;
            final List<CssParser.ParseError> errors = StyleManager.getErrors();
            if (errors != null) {
                CssParser.ParseError error = new CssParser.ParseError(msg + " :" + e.getLocalizedMessage());
                errors.add(error); // RT-19884
            }
            Logging.getControlsLogger().severe(msg, e.getCause());
        } catch (Exception e) {
            final String msg =
                "Failed to load skin '" + skinClassName + "' for control " + control;
            final List<CssParser.ParseError> errors = StyleManager.getErrors();
            if (errors != null) {
                CssParser.ParseError error = new CssParser.ParseError(msg + " :" + e.getLocalizedMessage());
                errors.add(error); // RT-19884
            }
            Logging.getControlsLogger().severe(msg, e);
        }
    }

    
                                                                        *
StyleSheet Handling                                                     *
                                                                        *
/***************************************************************************
     *                                                                         *
     * StyleSheet Handling                                                     *
     *                                                                         *
     **************************************************************************/

    private static class StyleableProperties {
        private static final CssMetaData<Control,String> SKIN =
            new CssMetaData<Control,String>("-fx-skin",
                StringConverter.getInstance()) {

            @Override
            public boolean isSettable(Control n) {
                return (n.skin == null || !n.skin.isBound());
            }

            @Override
            public StyleableProperty<String> getStyleableProperty(Control n) {
                return (StyleableProperty<String>)(WritableValue<String>)n.skinClassNameProperty();
            }
        };

        private static final List<CssMetaData<? extends Styleable, ?>> STYLEABLES;
        static {
            final List<CssMetaData<? extends Styleable, ?>> styleables =
                new ArrayList<CssMetaData<? extends Styleable, ?>>(Region.getClassCssMetaData());
            styleables.add(SKIN);
            STYLEABLES = Collections.unmodifiableList(styleables);
        }
    }

    
Returns:
The CssMetaData associated with this class, which may include the
CssMetaData of its superclasses.
Since:
JavaFX 8.0/**
     * @return The CssMetaData associated with this class, which may include the
     * CssMetaData of its superclasses.
     * @since JavaFX 8.0
     */
    public static List<CssMetaData<? extends Styleable, ?>> getClassCssMetaData() {
        return StyleableProperties.STYLEABLES;
    }

    
This method returns a List containing all CssMetaData for both this Control (returned from getControlCssMetaData() and its Skin, assuming the skin property is a SkinBase. 
Developers who wish to provide custom CssMetaData are therefore encouraged to override getControlCssMetaData() or SkinBase.getCssMetaData(), depending on where the CssMetaData resides. 
Since:
JavaFX 8.0/**
     * This method returns a {@link List} containing all {@link CssMetaData} for
     * both this Control (returned from {@link #getControlCssMetaData()} and its
     * {@link Skin}, assuming the {@link #skinProperty() skin property} is a
     * {@link SkinBase}.
     *
     * <p>Developers who wish to provide custom CssMetaData are therefore
     * encouraged to override {@link Control#getControlCssMetaData()} or
     * {@link SkinBase#getCssMetaData()}, depending on where the CssMetaData
     * resides.
     * @since JavaFX 8.0
     */
    @Override
    public final List<CssMetaData<? extends Styleable, ?>> getCssMetaData() {
        if (styleableProperties == null) {

            // RT-29162: make sure properties only show up once in the list
            java.util.Map<String, CssMetaData<? extends Styleable, ?>> map =
                new java.util.HashMap<String, CssMetaData<? extends Styleable, ?>>();

            List<CssMetaData<? extends Styleable, ?>> list =  getControlCssMetaData();

            for (int n=0, nMax = list != null ? list.size() : 0; n<nMax; n++) {

                CssMetaData<? extends Styleable, ?> metaData = list.get(n);
                if (metaData == null) continue;

                map.put(metaData.getProperty(), metaData);
            }

            //
            // if both control and skin base have the same property, use the
            // one from skin base since it may be a specialization of the
            // property in the control. For instance, Label has -fx-font and
            // so does LabeledText which is Label's skin.
            //
            list =  skinBase != null ? skinBase.getCssMetaData() : null;

            for (int n=0, nMax = list != null ? list.size() : 0; n<nMax; n++) {

                CssMetaData<? extends Styleable, ?> metaData = list.get(n);
                if (metaData == null) continue;

                map.put(metaData.getProperty(), metaData);
            }

            styleableProperties = new ArrayList<CssMetaData<? extends Styleable, ?>>();
            styleableProperties.addAll(map.values());
        }
        return styleableProperties;
    }

    
Returns:
unmodifiable list of the controls css styleable properties
Since:
JavaFX 8.0/**
     * @return unmodifiable list of the controls css styleable properties
     * @since JavaFX 8.0
     */
    protected List<CssMetaData<? extends Styleable, ?>> getControlCssMetaData() {
        return getClassCssMetaData();
    }

    /*
     * Note: This method MUST only be called via its accessor method.
     */
    private boolean skinCreationLocked = false;
    private void doProcessCSS() {

        ControlHelper.superProcessCSS(this);

        if (getSkin() == null) {
            if (skinCreationLocked) {
                return;
            }

            try {
                skinCreationLocked = true;

                // try to create default skin
                final Skin<?> defaultSkin = createDefaultSkin();
                if (defaultSkin != null) {
                    skinProperty().set(defaultSkin);
                    ControlHelper.superProcessCSS(this);
                } else {
                    final String msg = "The -fx-skin property has not been defined in CSS for " + this +
                            " and createDefaultSkin() returned null.";
                    final List<CssParser.ParseError> errors = StyleManager.getErrors();
                    if (errors != null) {
                        CssParser.ParseError error = new CssParser.ParseError(msg);
                        errors.add(error); // RT-19884
                    }
                    Logging.getControlsLogger().severe(msg);
                }
            } finally {
                skinCreationLocked = false;
            }
        }
    }

    
Returns the initial focus traversable state of this control, for use
by the JavaFX CSS engine to correctly set its initial value. By default all
UI controls are focus traversable, so this method is overridden in Control
to set the initial traversable state to true.
Returns:
the initial focus traversable state of this control
Since:
9/**
     * Returns the initial focus traversable state of this control, for use
     * by the JavaFX CSS engine to correctly set its initial value. By default all
     * UI controls are focus traversable, so this method is overridden in Control
     * to set the initial traversable state to true.
     *
     * @return the initial focus traversable state of this control
     * @since 9
     */
    @Override protected Boolean getInitialFocusTraversable() {
        return Boolean.TRUE;
    }


    /***************************************************************************
     *                                                                         *
     * Accessibility handling                                                  *
     *                                                                         *
     **************************************************************************/

    
{@inheritDoc} /** {@inheritDoc} */
    @Override
    public Object queryAccessibleAttribute(AccessibleAttribute attribute, Object... parameters) {
        switch (attribute) {
            case HELP:
                String help = getAccessibleHelp();
                if (help != null && !help.isEmpty()) return help;
                Tooltip tooltip = getTooltip();
                return tooltip == null ? "" : tooltip.getText();
            default:
        }
        if (skinBase != null) {
            Object result = skinBase.queryAccessibleAttribute(attribute, parameters);
            if (result != null) return result;
        }
        return super.queryAccessibleAttribute(attribute, parameters);
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override
    public void executeAccessibleAction(AccessibleAction action, Object... parameters) {
        if (skinBase != null) {
            skinBase.executeAccessibleAction(action, parameters);
        }
        super.executeAccessibleAction(action, parameters);
    }
}