Can't remove extra line spacing in JTextPane for html content

Question

I can't squeeze together the lines in a Java JTextPane if I set the content-type to text/html. I would like them as close together as they are when the content-type is text/plain, the default.

The line-height, top-margin, ... CSS properties don't seem to help :(.

This is the output of my sample program, that shows that the lines do take more space when a HTML editor handles the rendering:

The code that generates the frame is:

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.text.StyleConstants;
import javax.swing.text.html.HTMLEditorKit;
import javax.swing.text.html.StyleSheet;

public class DemoSimplestGui extends JFrame  {
    private static final long serialVersionUID = 1L;

    private static final int WINDOW_WIDTH = 800;
    private static final int WINDOW_HEIGHT = 130;

    private static final String PLAIN_TEXT = "" +
        "This is some <b>plain text</b>\n" +
        "separated by backslash-n characters\n" +
        "There's no empty space between lines\n" +
        "which is exactly what we need.";

    private static final String DIV_BASED_HTML_TEXT = "" +
        "<div>This is some <b>html text</b></div>" +
        "<div>that usses DIV tags.</div>" +
        "<div>There's too much blank space</div>" +
        "<div>and that sucks for my application</div>";

    private static final String PRE_BASED_HTML_TEXT = "" +
        "<pre>This is some <b>html text</b></pre>" +
        "<pre>that usses PRE tags</pre>" +
        "<pre>There's too much blank space grr</pre>" +
        "<pre>and that sucks for my application</pre>";

    public static void main(String[] args) {
        final DemoSimplestGui frame = new DemoSimplestGui();
        frame.setPreferredSize(new Dimension(WINDOW_WIDTH, WINDOW_HEIGHT));
        frame.setSize(frame.getPreferredSize());
        frame.setMinimumSize(new Dimension(WINDOW_WIDTH / 2, WINDOW_HEIGHT / 2));
        frame.init();
        frame.setVisible(true);
    }

    public void init() {
        setLayout(new BorderLayout(10, 10));
        add(createPlainTextPane(), BorderLayout.WEST);
        add(createDivBasedHtmlTextPane(), BorderLayout.CENTER);
        add(createPreBasedHtmlTextPane(), BorderLayout.EAST);
    }

    private JTextPane createPlainTextPane() {
        final JTextPane textPane = new JTextPane();
        textPane.setContentType("text/plain");
        StyleConstants.setFontFamily(textPane.getInputAttributes(), "Courier New");
        textPane.setText(PLAIN_TEXT);
        return textPane;
    }

    private JTextPane createDivBasedHtmlTextPane() {
        final JTextPane textPane = new JTextPane();
        textPane.setContentType("text/html");
        textPane.setEditorKit(configureHtmlEditorKit(textPane));
        textPane.setText(DIV_BASED_HTML_TEXT);
        return textPane;
    }

    private JTextPane createPreBasedHtmlTextPane() {
        final JTextPane textPane = new JTextPane();
        textPane.setContentType("text/html");
        textPane.setEditorKit(configureHtmlEditorKit(textPane));
        textPane.setText(PRE_BASED_HTML_TEXT);
        return textPane;
    }

    private HTMLEditorKit configureHtmlEditorKit(JTextPane textPane) {
        final HTMLEditorKit kit = (HTMLEditorKit) textPane.getEditorKit();
        final StyleSheet css = new StyleSheet();
        css.addRule("body { font-family: monospaced; margin-top: 0; margin-down: 0; line-height: 0; }");
        css.addRule("div, pre { margin-top: 0; margin-down: 0; line-height: 0; }");
        kit.setStyleSheet(css);
        return kit;
    }

}

I'd really appreciate some hint :D

Answer 1

This may be platform dependent:

Answer 2

Try something like this

StyledDocument doc= textPane.getStyledDocument();
MutableAttributeSet attr= new SimpleAttributeSet();
StyleConstants.setLineSpacing(attr, -0.2f); //NOTE: negative value.

Looks like you are running windows. What version of JDK/JRE is in use?

Answer 3

Solved! If I use Courier New instead of monospace for the font-family, the line spacing is exactly the same as in the text-plain version under Windows. Thanks everyone!