TextBubbleBorder.java

package com.horstmann.violet.application.swingextension;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.geom.Area;
import java.awt.geom.RoundRectangle2D;

import javax.swing.border.AbstractBorder;

/**
 * Found on the web, then modified
 * 
 * @author http://stackoverflow.com/questions/15025092/border-with-rounded-corners-transparency
 *
 */
public class TextBubbleBorder extends AbstractBorder
{

    private Color color;
    private int thickness = 4;
    private int radii = 8;
    private int pointerSize = 7;
    private Insets insets = null;
    private BasicStroke stroke = null;
    private int strokePad;
    private int pointerPad = 4;
    private boolean left = true;
    RenderingHints hints;

    public TextBubbleBorder(Color color)
    {
        new TextBubbleBorder(color, 4, 8, 7);
    }

    public TextBubbleBorder(Color color, int thickness, int radii, int pointerSize)
    {
        this.thickness = thickness;
        this.radii = radii;
        this.pointerSize = pointerSize;
        this.color = color;

        stroke = new BasicStroke(thickness);
        strokePad = thickness / 2;

        hints = new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        int pad = radii + strokePad;
        int bottomPad = pad + pointerSize + strokePad;
        insets = new Insets(pad, pad, bottomPad, pad);
    }

    public TextBubbleBorder(Color color, int thickness, int radii, int pointerSize, boolean left)
    {
        this(color, thickness, radii, pointerSize);
        this.left = left;
    }

    @Override
    public Insets getBorderInsets(Component c)
    {
        return insets;
    }

    @Override
    public Insets getBorderInsets(Component c, Insets insets)
    {
        return getBorderInsets(c);
    }

    @Override
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height)
    {

        Graphics2D g2 = (Graphics2D) g;

        int bottomLineY = height - thickness - pointerSize;

        RoundRectangle2D.Double bubble = new RoundRectangle2D.Double(0 + strokePad, 0 + strokePad, width - thickness, bottomLineY,
                radii, radii);

        Polygon pointer = new Polygon();

        if (left)
        {
            // left point
            pointer.addPoint(strokePad + radii + pointerPad, bottomLineY);
            // right point
            pointer.addPoint(strokePad + radii + pointerPad + pointerSize, bottomLineY);
            // bottom point
            pointer.addPoint(strokePad + radii + pointerPad + (pointerSize / 2), height - strokePad);
        }
        else
        {
            // left point
            pointer.addPoint(width - (strokePad + radii + pointerPad), bottomLineY);
            // right point
            pointer.addPoint(width - (strokePad + radii + pointerPad + pointerSize), bottomLineY);
            // bottom point
            pointer.addPoint(width - (strokePad + radii + pointerPad + (pointerSize / 2)), height - strokePad);
        }

        Area area = new Area(bubble);
        area.add(new Area(pointer));

        g2.setRenderingHints(hints);

        // Paint the BG color of the parent, everywhere outside the clip
        // of the text bubble.
        Component parent = c.getParent();
        if (parent != null)
        {
            Color bg = parent.getBackground();
            Rectangle rect = new Rectangle(0, 0, width, height);
            Area borderRegion = new Area(rect);
            borderRegion.subtract(area);
            g2.setClip(borderRegion);
            g2.setColor(bg);
            g2.fillRect(0, 0, width, height);
            g2.setClip(null);
        }

        g2.setColor(color);
        g2.setStroke(stroke);
        g2.draw(area);
    }
}