Question

In Java SWT, is there a way to draw text on a transparent shell so that only the text appears visible? What I would like to do is have the text appear on my desktop without any background window. Using shell.setAlpha() will make the entire shell transparent, including any elements that appear on it (which I am trying to avoid).

Answer 1

Here’s an example displaying an image without the shell. You can fairly easily adapt it to display text.

Update:

OK I got bored. Here’s a basic example that paints “Hello” on a transparent background:

package swttest;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.FontData;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.Region;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class Test {

    public static void main(String[] args) {
        Test test = new Test();

        test.show();
    }

    public void show() {
        Display display = new Display();
        // Create a shell with no trim
        final Shell shell = new Shell(display, SWT.NO_TRIM);
        shell.setForeground(display.getSystemColor(SWT.COLOR_WHITE));

        //set the transparent canvas on the shell
        Canvas canvas = new Canvas(shell, SWT.NO_BACKGROUND);

        //create an area to paint the text
        Rectangle size = new Rectangle(0, 0, 200, 200);
        canvas.setBounds(size);

        Region region = canvas.getRegion();

        //mucking about with fonts
        Font font = display.getSystemFont();

        FontData[] fd = font.getFontData();

        fd[0].setHeight(24);
        fd[0].setStyle(SWT.BOLD);

        Font bigFont = new Font(display, fd[0]);
        canvas.setFont(bigFont);

        // define the shape of the shell using setRegion
        shell.setRegion(region);
        shell.setSize(size.width, size.height);

        canvas.addPaintListener(new PaintListener() {
            public void paintControl(PaintEvent e) {
                e.gc.drawString("Hello", 10, 10, true);
            }
        });

        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        region.dispose();
        display.dispose();
    }
}