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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package javafx.scene.control.skin;

import javafx.event.EventHandler;
import javafx.scene.control.Control;
import javafx.scene.control.IndexedCell;
import javafx.scene.control.ScrollToEvent;
import javafx.scene.control.SkinBase;

Parent class to control skins whose contents are virtualized and scrollable.
This class handles the interaction with the VirtualFlow class, which is the
main class handling the virtualization of the contents of this container.
Since:
9/**
 * Parent class to control skins whose contents are virtualized and scrollable.
 * This class handles the interaction with the VirtualFlow class, which is the
 * main class handling the virtualization of the contents of this container.
 *
 * @since 9
 */
public abstract class VirtualContainerBase<C extends Control, I extends IndexedCell> extends SkinBase<C> {

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

    private boolean itemCountDirty;

    
The virtualized container which handles the layout and scrolling of
all the cells.
/**
     * The virtualized container which handles the layout and scrolling of
     * all the cells.
     */
    private final VirtualFlow<I> flow;

    private EventHandler<? super ScrollToEvent<Integer>> scrollToEventHandler;


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

    
Params:
control – the control/**
     *
     * @param control the control
     */
    public VirtualContainerBase(final C control) {
        super(control);
        flow = createVirtualFlow();

        scrollToEventHandler = event -> {
            // Fix for RT-24630: The row count in VirtualFlow was incorrect
            // (normally zero), so the scrollTo call was misbehaving.
            if (itemCountDirty) {
                // update row count before we do a scroll
                updateItemCount();
                itemCountDirty = false;
            }
            flow.scrollToTop(event.getScrollTarget());
        };
        control.addEventHandler(ScrollToEvent.scrollToTopIndex(), scrollToEventHandler);
    }



    /***************************************************************************
     *                                                                         *
     * Abstract API                                                            *
     *                                                                         *
     **************************************************************************/

    
Returns the total number of items in this container, including those
that are currently hidden because they are out of view.
Returns:
the total number of items in this container/**
     * Returns the total number of items in this container, including those
     * that are currently hidden because they are out of view.
     * @return the total number of items in this container
     */
    protected abstract int getItemCount();

    
This method is called when it is possible that the item count has changed (i.e. scrolling has occurred, the control has resized, etc). This method should recalculate the item count and store that for future use by the getItemCount method. /**
     * This method is called when it is possible that the item count has changed (i.e. scrolling has occurred,
     * the control has resized, etc). This method should recalculate the item count and store that for future
     * use by the {@link #getItemCount} method.
     */
    protected abstract void updateItemCount();



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

    
Create the virtualized container that handles the layout and scrolling of all the cells. This enables skin subclasses to provide a custom VirtualFlow implementation. If not overridden, this method intantiates a default VirtualFlow instance. 
Returns:
newly created VirtualFlow instance
Since:
10/**
     * Create the virtualized container that handles the layout and scrolling of
     * all the cells. This enables skin subclasses to provide
     * a custom {@link VirtualFlow} implementation.
     * If not overridden, this method intantiates a default VirtualFlow instance.
     * @return newly created VirtualFlow instance
     * @since 10
     */
    protected VirtualFlow<I> createVirtualFlow() {
        return new VirtualFlow<>();
    }

    
{@inheritDoc} 

Overridden to remove EventHandler.
/**
     * {@inheritDoc} <p>
     * Overridden to remove EventHandler.
     */
    @Override
    public void dispose() {
        if (getSkinnable() == null) return;
        getSkinnable().removeEventHandler(ScrollToEvent.scrollToTopIndex(), scrollToEventHandler);
        super.dispose();
    }

    
Get the virtualized container.
Subclasses can invoke this method to get the VirtualFlow instance.
Returns:
the virtualized container
Since:
10/**
     * Get the virtualized container.
     * Subclasses can invoke this method to get the VirtualFlow instance.
     * @return the virtualized container
     * @since 10
     */
    protected final VirtualFlow<I> getVirtualFlow() {
        return flow;
    }

    
Call this method to indicate that the item count should be updated on the next pulse.
/**
     * Call this method to indicate that the item count should be updated on the next pulse.
     */
    protected final void markItemCountDirty() {
        itemCountDirty = true;
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override protected void layoutChildren(double x, double y, double w, double h) {
        checkState();
    }

    
                                                                        *
Private methods                                                         *
                                                                        *
/***************************************************************************
     *                                                                         *
     * Private methods                                                         *
     *                                                                         *
     **************************************************************************/

    double getMaxCellWidth(int rowsToCount) {
        return snappedLeftInset() + flow.getMaxCellWidth(rowsToCount) + snappedRightInset();
    }

    double getVirtualFlowPreferredHeight(int rows) {
        double height = 1.0;

        for (int i = 0; i < rows && i < getItemCount(); i++) {
            height += flow.getCellLength(i);
        }

        return height + snappedTopInset() + snappedBottomInset();
    }

    void checkState() {
        if (itemCountDirty) {
            updateItemCount();
            itemCountDirty = false;
        }
    }

    void requestRebuildCells() {
        flow.rebuildCells();
    }

}