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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package com.sun.javafx.scene.control.skin;

import javafx.scene.control.Control;
import javafx.scene.control.IndexedCell;
import javafx.scene.control.ScrollToEvent;

import com.sun.javafx.scene.control.behavior.BehaviorBase;

/**
 * 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.
 *
 * @profile common
 */
public abstract class VirtualContainerBase<C extends Control, B extends BehaviorBase<C>, I extends IndexedCell> extends BehaviorSkinBase<C, B> {

    protected boolean rowCountDirty;

    public VirtualContainerBase(final C control, B behavior) {
        super(control, behavior);
        flow = createVirtualFlow();

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

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

    /**
     * Returns a Cell available to be used in the virtual flow. This means you
     * may return either a previously used, but now unrequired cell, or alternatively
     * create a new Cell instance.
     *
     * Preference is obviously given to reusing cells whenever possible, to keep
     * performance costs down.
     */
    public abstract I createCell();

    /**
     * This enables skin subclasses to provide a custom VirtualFlow implementation,
     * rather than have VirtualContainerBase instantiate the default instance.
     */
    protected VirtualFlow<I> createVirtualFlow() {
        return new VirtualFlow<I>();
    }

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

    protected abstract void updateRowCount();

    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();
    }

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

    protected void checkState() {
        if (rowCountDirty) {
            updateRowCount();
            rowCountDirty = false;
        }
    }
}
