ThinSplitPane.java

package tk.amberide.ide.swing.misc;

import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JSplitPane;
import javax.swing.UIManager;
import javax.swing.border.Border;
import javax.swing.plaf.basic.BasicSplitPaneDivider;
import javax.swing.plaf.basic.BasicSplitPaneUI;

/**
 *
 * @author Tudor
 */
public class ThinSplitPane extends JSplitPane {

    private int dividerDragSize = 9;
    private int dividerDragOffset = 4;

    public ThinSplitPane() {
        setDividerSize(1);
        setContinuousLayout(true);
    }

    @Override
    public void doLayout() {
        super.doLayout();

        // increase divider width or height
        BasicSplitPaneDivider divider = ((BasicSplitPaneUI) getUI()).getDivider();
        Rectangle bounds = divider.getBounds();
        if (orientation == HORIZONTAL_SPLIT) {
            bounds.x -= dividerDragOffset;
            bounds.width = dividerDragSize;
        } else {
            bounds.y -= dividerDragOffset;
            bounds.height = dividerDragSize;
        }
        divider.setBounds(bounds);
    }

    @Override
    public void updateUI() {
        setUI(new SplitPaneWithZeroSizeDividerUI());
        revalidate();
    }

    private class SplitPaneWithZeroSizeDividerUI extends BasicSplitPaneUI {

        @Override
        public BasicSplitPaneDivider createDefaultDivider() {
            return new ZeroSizeDivider(this);
        }
    }

    private class ZeroSizeDivider extends BasicSplitPaneDivider {

        public ZeroSizeDivider(BasicSplitPaneUI ui) {
            super(ui);
            super.setBorder(null);
            setBackground(UIManager.getColor("controlShadow"));
        }

        @Override
        public void setBorder(Border border) {
            // ignore
        }

        @Override
        public void paint(Graphics g) {
            g.setColor(getBackground());
            if (orientation == HORIZONTAL_SPLIT) {
                g.drawLine(dividerDragOffset, 0, dividerDragOffset, getHeight() - 1);
            } else {
                g.drawLine(0, dividerDragOffset, getWidth() - 1, dividerDragOffset);
            }
        }

        @Override
        protected void dragDividerTo(int location) {
            super.dragDividerTo(location + dividerDragOffset);
        }

        @Override
        protected void finishDraggingTo(int location) {
            super.finishDraggingTo(location + dividerDragOffset);
        }
    }
}