src/java.desktop/share/classes/javax/swing/tree/TreeCellRenderer.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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package javax.swing.tree;

import java.awt.Component;
import javax.swing.JTree;

/**
 * Defines the requirements for an object that displays a tree node.
 * See <a
 href="https://docs.oracle.com/javase/tutorial/uiswing/components/tree.html">How to Use Trees</a>
 * in <em>The Java Tutorial</em>
 * for an example of implementing a tree cell renderer
 * that displays custom icons.
 *
 * @author Rob Davis
 * @author Ray Ryan
 * @author Scott Violet
 */
public interface TreeCellRenderer {

    /**
     * Sets the value of the current tree cell to <code>value</code>.
     * If <code>selected</code> is true, the cell will be drawn as if
     * selected. If <code>expanded</code> is true the node is currently
     * expanded and if <code>leaf</code> is true the node represents a
     * leaf and if <code>hasFocus</code> is true the node currently has
     * focus. <code>tree</code> is the <code>JTree</code> the receiver is being
     * configured for.  Returns the <code>Component</code> that the renderer
     * uses to draw the value.
     * <p>
     * The <code>TreeCellRenderer</code> is also responsible for rendering the
     * the cell representing the tree's current DnD drop location if
     * it has one. If this renderer cares about rendering
     * the DnD drop location, it should query the tree directly to
     * see if the given row represents the drop location:
     * <pre>
     *     JTree.DropLocation dropLocation = tree.getDropLocation();
     *     if (dropLocation != null
     *             &amp;&amp; dropLocation.getChildIndex() == -1
     *             &amp;&amp; tree.getRowForPath(dropLocation.getPath()) == row) {
     *
     *         // this row represents the current drop location
     *         // so render it specially, perhaps with a different color
     *     }
     * </pre>
     *
     * @param tree      the receiver is being configured for
     * @param value     the value to render
     * @param selected  whether node is selected
     * @param expanded  whether node is expanded
     * @param leaf      whether node is a lead node
     * @param row       row index
     * @param hasFocus  whether node has focus
     * @return          the {@code Component} that the renderer uses to draw the value
     */
    Component getTreeCellRendererComponent(JTree tree, Object value,
                                   boolean selected, boolean expanded,
                                   boolean leaf, int row, boolean hasFocus);

}