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Swing Layout Extensions goal is to make it easy to create professional cross platform layouts with Swing. This project has an eye towards the needs of GUI builders, such as NetBeans. This project consists of the following pieces: * Ability to get the baseline for components. * Ability to get the preferred gap between components. * A new LayoutManager that utilizes both of these concepts and is tuned toward a free-form drag and drop layout model as can be provided by GUI builders.

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/*
 * Copyright (C) 2005-2006 Sun Microsystems, Inc. All rights reserved. Use is
 * subject to license terms.
 */ 

package org.jdesktop.layout;

import java.awt.Container;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.swing.JComponent;

/**
 *
 * @author sky
 */
class SwingLayoutStyle extends LayoutStyle {
    private static final Method SWING_GET_LAYOUT_STYLE_METHOD;
    
    private static final Method SWING_GET_PREFERRED_GAP_METHOD;
    private static final Method SWING_GET_CONTAINER_GAP_METHOD;
    
    private static final Object RELATED_TYPE;
    private static final Object UNRELATED_TYPE;
    private static final Object INDENT_TYPE;
    
    static {
        Method getLayoutStyle = null;
        Method getPreferredGap = null;
        Method getContainerGap = null;
        Object relatedType = null;
        Object unrelatedType = null;
        Object indentType = null;
        try {
            Class swingLayoutStyleClass;
            Class swingComponentPlacementClass;
            
            swingLayoutStyleClass = Class.forName("javax.swing.LayoutStyle");
            swingComponentPlacementClass = Class.forName(
                    "javax.swing.LayoutStyle$ComponentPlacement");
            swingLayoutStyleClass = Class.forName("javax.swing.LayoutStyle");
            getLayoutStyle =
                    swingLayoutStyleClass.getMethod("getInstance", null);
            getPreferredGap =
                    swingLayoutStyleClass.getMethod("getPreferredGap",
                    new Class[] { JComponent.class, JComponent.class,
                    swingComponentPlacementClass,
                    int.class, Container.class } );
            getContainerGap = swingLayoutStyleClass.getMethod("getContainerGap",
                    new Class[] { JComponent.class, int.class,
                    Container.class } );
            relatedType = swingComponentPlacementClass.getField("RELATED").get(null);
            unrelatedType = swingComponentPlacementClass.getField("UNRELATED").get(null);
            indentType = swingComponentPlacementClass.getField("INDENT").get(null);
        } catch (ClassNotFoundException cnfe) {
        } catch (NoSuchMethodException nsme) {
        } catch (NoSuchFieldException nsfe) {
        } catch (IllegalAccessException iae) {
        }
        SWING_GET_LAYOUT_STYLE_METHOD = getLayoutStyle;
        SWING_GET_PREFERRED_GAP_METHOD = getPreferredGap;
        SWING_GET_CONTAINER_GAP_METHOD = getContainerGap;
        RELATED_TYPE = relatedType;
        UNRELATED_TYPE = unrelatedType;
        INDENT_TYPE = indentType;
    }
    
    private static final Object layoutStyleTypeToComponentPlacement(int type) {
        if (type == LayoutStyle.RELATED) {
            return RELATED_TYPE;
        } else if (type == LayoutStyle.UNRELATED) {
            return UNRELATED_TYPE;
        } else {
            assert (type == LayoutStyle.INDENT);
            return INDENT_TYPE;
        }
    }
    
    private static final Object getSwingLayoutStyle() {
        try {
            return SWING_GET_LAYOUT_STYLE_METHOD.invoke(null, null);
        } catch (IllegalAccessException iae) {
        } catch (InvocationTargetException ite) {
        }
        return null;
    }
    
    public int getPreferredGap(JComponent component1, JComponent component2,
            int type, int position, Container parent) {
        super.getPreferredGap(component1, component2, type, position, parent);
        Object componentPlacement = layoutStyleTypeToComponentPlacement(type);
        Object layoutStyle = getSwingLayoutStyle();
        try {
            return ((Integer)SWING_GET_PREFERRED_GAP_METHOD.invoke(layoutStyle,
                    new Object[] { component1, component2, componentPlacement,
                    new Integer(position), parent })).intValue();
        } catch (IllegalAccessException iae) {
        } catch (InvocationTargetException ite) {
        }
        return 0;
    }
    
    public int getContainerGap(JComponent component, int position,
            Container parent) {
        super.getContainerGap(component, position, parent);
        Object layoutStyle = getSwingLayoutStyle();
        try {
            return ((Integer)SWING_GET_CONTAINER_GAP_METHOD.invoke(layoutStyle,
                    new Object[] { component, new Integer(position),
                    parent })).intValue();
        } catch (IllegalAccessException iae) {
        } catch (InvocationTargetException ite) {
        }
        return 0;
    }
}