org.eclipse.swt.snippets.Snippet254.java Source code

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Here is the source code for org.eclipse.swt.snippets.Snippet254.java

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/*******************************************************************************
 * Copyright (c) 2000, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.snippets;

/*
 * Tree example snippet: compute the number of visible rows in a tree
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 */
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class Snippet254 {

    static TreeItem nextItem(Tree tree, TreeItem item) {
        if (item == null)
            return null;
        if (item.getExpanded() && item.getItemCount() > 0)
            return item.getItem(0);
        TreeItem childItem = item;
        TreeItem parentItem = childItem.getParentItem();
        int index = parentItem == null ? tree.indexOf(childItem) : parentItem.indexOf(childItem);
        int count = parentItem == null ? tree.getItemCount() : parentItem.getItemCount();
        while (true) {
            if (index + 1 < count)
                return parentItem == null ? tree.getItem(index + 1) : parentItem.getItem(index + 1);
            if (parentItem == null)
                return null;
            childItem = parentItem;
            parentItem = childItem.getParentItem();
            index = parentItem == null ? tree.indexOf(childItem) : parentItem.indexOf(childItem);
            count = parentItem == null ? tree.getItemCount() : parentItem.getItemCount();
        }
    }

    public static void main(String[] args) {
        final Display display = new Display();
        final Shell shell = new Shell(display);
        shell.setText("Snippet 254");
        RowLayout layout = new RowLayout(SWT.VERTICAL);
        layout.fill = true;
        layout.wrap = false;
        shell.setLayout(layout);
        final Tree tree = new Tree(shell, SWT.NONE);
        for (int i = 0; i < 32; i++) {
            TreeItem item0 = new TreeItem(tree, SWT.NONE);
            item0.setText("Item " + i + " is quite long");
            for (int j = 0; j < 3; j++) {
                TreeItem item1 = new TreeItem(item0, SWT.NONE);
                item1.setText("Item " + i + " " + j + " is quite long");
                for (int k = 0; k < 3; k++) {
                    TreeItem item2 = new TreeItem(item1, SWT.NONE);
                    item2.setText("Item " + i + " " + j + " " + k + " is quite long");
                    for (int l = 0; l < 3; l++) {
                        TreeItem item3 = new TreeItem(item2, SWT.NONE);
                        item3.setText("Item " + i + " " + j + " " + k + " " + l + " is quite long");
                    }
                }
            }
        }
        tree.setLayoutData(new RowData(200, 200));
        final Button button = new Button(shell, SWT.PUSH);
        button.setText("Visible Items []");
        button.addListener(SWT.Selection, e -> {
            int visibleCount = 0;
            Rectangle rect = tree.getClientArea();
            TreeItem item = tree.getTopItem();
            while (item != null) {
                visibleCount++;
                Rectangle itemRect = item.getBounds();
                if (itemRect.y + itemRect.height > rect.y + rect.height) {
                    break;
                }
                item = nextItem(tree, item);
            }
            button.setText("Visible Items [" + visibleCount + "]");
        });
        shell.pack();
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        display.dispose();
    }
}