Java Swing UIManager installGtkPopupBugWorkaround()

Description

Swing menus are looking pretty bad on Linux when the GTK LaF is used (See bug #6925412).

License

Apache License

Declaration

public static void installGtkPopupBugWorkaround() 

Method Source Code

//package com.java2s;
/*//from w  ww  . j a v  a  2s.c  o  m
 * PlatformHelper.java
 *
 * This file is part of SQL Workbench/J, http://www.sql-workbench.net
 *
 * Copyright 2002-2017, Thomas Kellerer
 *
 * Licensed under a modified Apache License, Version 2.0
 * that restricts the use for certain governments.
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at.
 *
 *     http://sql-workbench.net/manual/license.html
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * To contact the author please send an email to: support@sql-workbench.net
 *
 */

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import javax.swing.JComponent;
import javax.swing.JPopupMenu;
import javax.swing.JSeparator;
import javax.swing.LookAndFeel;
import javax.swing.UIManager;

public class Main {
    /**
     * Swing menus are looking pretty bad on Linux when the GTK LaF is used (See bug #6925412). It will most likely never
     * be fixed anytime soon so this method provides a workaround for it. It uses reflection to change the GTK style
     * objects of Swing so popup menu borders have a minimum thickness of 1 and menu separators have a minimum vertical
     * thickness of 1.
     *
     * Taken from https://www.ailis.de/~k/archives/67-Workaround-for-borderless-Java-Swing-menus-on-Linux.html
     */
    public static void installGtkPopupBugWorkaround() {
        // Get current look-and-feel implementation class
        LookAndFeel laf = UIManager.getLookAndFeel();
        Class<?> lafClass = laf.getClass();

        // Do nothing when not using the problematic LaF
        if (!lafClass.getName().equals("com.sun.java.swing.plaf.gtk.GTKLookAndFeel")) {
            return;
        }

        // We do reflection from here on. Failure is silently ignored. The
        // workaround is simply not installed when something goes wrong here
        try {
            // Access the GTK style factory
            Field field = lafClass.getDeclaredField("styleFactory");
            boolean accessible = field.isAccessible();
            field.setAccessible(true);
            Object styleFactory = field.get(laf);
            field.setAccessible(accessible);

            // Fix the horizontal and vertical thickness of popup menu style
            Object style = getGtkStyle(styleFactory, new JPopupMenu(), "POPUP_MENU");
            fixGtkThickness(style, "yThickness");
            fixGtkThickness(style, "xThickness");

            // Fix the vertical thickness of the popup menu separator style
            style = getGtkStyle(styleFactory, new JSeparator(), "POPUP_MENU_SEPARATOR");
            fixGtkThickness(style, "yThickness");
        } catch (Exception e) {
            // Silently ignored. Workaround can't be applied.
        }
    }

    /**
     * Called internally by installGtkPopupBugWorkaround. Returns a specific GTK style object.
     *
     * @param styleFactory The GTK style factory.
     * @param component The target component of the style.
     * @param regionName The name of the target region of the style.
     * @return The GTK style.
     * @throws Exception When reflection fails.
     */
    private static Object getGtkStyle(Object styleFactory, JComponent component, String regionName)
            throws Exception {
        // Create the region object
        Class<?> regionClass = Class.forName("javax.swing.plaf.synth.Region");
        Field field = regionClass.getField(regionName);
        Object region = field.get(regionClass);

        // Get and return the style
        Class<?> styleFactoryClass = styleFactory.getClass();
        Method method = styleFactoryClass.getMethod("getStyle", new Class<?>[] { JComponent.class, regionClass });
        boolean accessible = method.isAccessible();
        method.setAccessible(true);
        Object style = method.invoke(styleFactory, component, region);
        method.setAccessible(accessible);
        return style;
    }

    /**
     * Called internally by installGtkPopupBugWorkaround to fix the thickness of a GTK style field by setting it to a
     * minimum value of 1.
     *
     * @param style The GTK style object.
     * @param fieldName The field name.
     * @throws Exception When reflection fails.
     */
    private static void fixGtkThickness(Object style, String fieldName) throws Exception {
        Field field = style.getClass().getDeclaredField(fieldName);
        boolean accessible = field.isAccessible();
        field.setAccessible(true);
        field.setInt(style, Math.max(1, field.getInt(style)));
        field.setAccessible(accessible);
    }
}

Related

1. initGui()
2. initialize()
3. initLnF()
4. initNimbusStyle()
5. installDefaults()
6. installGtkPopupBugWorkaround()
7. isFlat(String id)
8. isMetalLnF()
9. isMnemonicHidden()