Label: text aliasing breaks on lines following empty new lines

[iloveeclipse]

I was asked to show a bigger message with some paragraphs in a MessageDialog (that uses 'new Label(SWT.WRAP)') and surprisingly, every second line after a paragraph seem to be rendered with different anti-aliasing settings. Turned out, it is a bug in SWT / GTK. If a line is empty, next non-empty line of text will be rendered with anti-aliasing settings broken (switched off?).

package org.eclipse.swt.tests.manual;

/*
 * Label example snippet: create a label with paragraphs separated by new lines.
 *
 * If the lines are empty, next line text is not properly rendered, breaking font aliasing
 */
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;

public class LabelRenderingTextWithEmptyLines {

	public static void main(String[] args) {
		// Message with new lines containing some spaces
		String goodMessage = "Hello\n  \nworld of good text aliasing\n\n";
		// just trim new lines to be empty
		String badMessage = goodMessage.replaceAll("  ", "");
		// and slightly change text to indicate where the problem is
		badMessage = badMessage.replaceAll("good", "bad");


		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout(SWT.VERTICAL));
		shell.setText("Crazy font rendering");
		shell.setBackground(new Color(255, 255, 255));
		Label badLabel = new Label(shell, SWT.WRAP);
		badLabel.setText(badMessage);
		Label goodLabel = new Label(shell, SWT.WRAP);
		goodLabel.setText(goodMessage);
		shell.setSize(300, 300);
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}
		display.dispose();
	}
}