src/java.desktop/share/classes/javax/swing/plaf/metal/MetalScrollPaneUI.java

/*
 * Copyright (c) 1998, 2024, 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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package javax.swing.plaf.metal;

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;

import java.awt.*;
import java.beans.*;
import java.awt.event.*;


/**
 * A Metal L&F implementation of ScrollPaneUI.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases. The current serialization support is
 * appropriate for short term storage or RMI between applications running
 * the same version of Swing.  As of 1.4, support for long term storage
 * of all JavaBeans
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author Steve Wilson
 */
public class MetalScrollPaneUI extends BasicScrollPaneUI
{

    private PropertyChangeListener scrollBarSwapListener;

    /**
     * Constructs a {@code MetalScrollPaneUI}.
     */
    public MetalScrollPaneUI() {}

    /**
     * Constructs a new {@code MetalScrollPaneUI}.
     *
     * @param x a component
     * @return a new {@code MetalScrollPaneUI}
     */
    public static ComponentUI createUI(JComponent x) {
        return new MetalScrollPaneUI();
    }

    public void installUI(JComponent c) {

        super.installUI(c);

        JScrollPane sp = (JScrollPane)c;
        updateScrollbarsFreeStanding();
    }

    public void uninstallUI(JComponent c) {
        super.uninstallUI(c);

        JScrollPane sp = (JScrollPane)c;
        JScrollBar hsb = sp.getHorizontalScrollBar();
        JScrollBar vsb = sp.getVerticalScrollBar();
        if (hsb != null) {
            hsb.putClientProperty( MetalScrollBarUI.FREE_STANDING_PROP, null);
        }
        if (vsb != null) {
            vsb.putClientProperty( MetalScrollBarUI.FREE_STANDING_PROP, null);
        }
    }

    public void installListeners(JScrollPane scrollPane) {
        super.installListeners(scrollPane);
        scrollBarSwapListener = createScrollBarSwapListener();
        scrollPane.addPropertyChangeListener(scrollBarSwapListener);
    }

    /**
     * {@inheritDoc}
     */
    protected void uninstallListeners(JComponent c) {
        super.uninstallListeners(c);
        c.removePropertyChangeListener(scrollBarSwapListener);
    }

    /**
     * @param scrollPane an instance of the {@code JScrollPane}
     * @deprecated - Replaced by {@link #uninstallListeners(JComponent)}
     */
    @Deprecated
    public void uninstallListeners(JScrollPane scrollPane) {
        super.uninstallListeners(scrollPane);
        scrollPane.removePropertyChangeListener(scrollBarSwapListener);
    }

    /**
     * If the border of the scrollpane is an instance of
     * <code>MetalBorders.ScrollPaneBorder</code>, the client property
     * <code>FREE_STANDING_PROP</code> of the scrollbars
     * is set to false, otherwise it is set to true.
     */
    private void updateScrollbarsFreeStanding() {
        if (scrollpane == null) {
            return;
        }
        Border border = scrollpane.getBorder();
        Object value;

        if (border instanceof MetalBorders.ScrollPaneBorder) {
            value = Boolean.FALSE;
        }
        else {
            value = Boolean.TRUE;
        }
        JScrollBar sb = scrollpane.getHorizontalScrollBar();
        if (sb != null) {
            sb.putClientProperty
                   (MetalScrollBarUI.FREE_STANDING_PROP, value);
        }
        sb = scrollpane.getVerticalScrollBar();
        if (sb != null) {
            sb.putClientProperty
                   (MetalScrollBarUI.FREE_STANDING_PROP, value);
        }
    }

    /**
     * Returns a new {@code PropertyChangeListener} for scroll bar swap events.
     *
     * @return a new {@code PropertyChangeListener} for scroll bar swap events.
     */
    protected PropertyChangeListener createScrollBarSwapListener() {
        return new PropertyChangeListener() {
            public void propertyChange(PropertyChangeEvent e) {
                  String propertyName = e.getPropertyName();
                  if (propertyName.equals("verticalScrollBar") ||
                      propertyName.equals("horizontalScrollBar")) {
                      JScrollBar oldSB = (JScrollBar)e.getOldValue();
                      if (oldSB != null) {
                          oldSB.putClientProperty(
                              MetalScrollBarUI.FREE_STANDING_PROP, null);
                      }
                      JScrollBar newSB = (JScrollBar)e.getNewValue();
                      if (newSB != null) {
                          newSB.putClientProperty(
                              MetalScrollBarUI.FREE_STANDING_PROP,
                              Boolean.FALSE);
                      }
                  }
                  else if ("border".equals(propertyName)) {
                      updateScrollbarsFreeStanding();
                  }
        }};
    }

}