Why does HTMLDocument ignore white spaces

Question

I have a problem. It looks like that HTMLEditorKit just ignore white spaces. There is my sample code:

public class TestEditor extends JFrame {

public TestEditor(){
    createConnection();
    createGUI();
}
private void createGUI(){
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    JScrollPane scroll1=new JScrollPane(text);
    JScrollPane scroll2=new JScrollPane(html);
    JSplitPane split=new JSplitPane();
    split.setLeftComponent(scroll1);
    split.setRightComponent(scroll2);
    split.setDividerLocation(0.5);
    split.setResizeWeight(0.5);
    getContentPane().add(split);
    setTitle("Test");
    setPreferredSize(new Dimension(600,300));
    pack();
}
private void createConnection(){
    text=new JTextPane();
    html=new JTextPane();
    html.setContentType("text/html");
    html.getStyledDocument().addDocumentListener(new DocumentListener() {
        @Override
        public void insertUpdate(DocumentEvent e) {
            update();
        }
        @Override
        public void removeUpdate(DocumentEvent e) {
            update();
        }
        @Override
        public void changedUpdate(DocumentEvent e) {
            update();
        }
        private void update(){
            if(fromText) return;
            fromHtml=true;
            text.setText(html.getText());
            fromHtml=false;
        }
    });
    text.getStyledDocument().addDocumentListener(new DocumentListener() {
        @Override
        public void insertUpdate(DocumentEvent e) {
            update();
        }
        @Override
        public void removeUpdate(DocumentEvent e) {
            update();
        }
        @Override
        public void changedUpdate(DocumentEvent e) {
            update();
        }
        private void update(){
            if(fromHtml) return;
            fromText=true;
            html.setText(text.getText());
            fromText=false;
        }
    });
}
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            new TestEditor().setVisible(true);
        }
    });
}
private JTextPane text;
private JTextPane html;
private boolean fromHtml, fromText;
}

This code creates a simple application containing two JTextPane text fields. User is allowed to write in the right editor and then he can see a HTML code on the left side. Additionally, he can edit the code and see the changes on the right side.

There is the problem. Let's assume that I wrote the text

"     aaaa"

in the right editor (five spaces before "aaaa"). This would present itself well. However if I add next 'a' in HTML editor (on the left side) I lose my 5 spaces and see only "aaaaa" on the right side.

Is there any way to fix this problem, so that my 5 spaces wouldn't be lost?

Answer 1

HTML strips all tabs, spaces and makes them in a single space.

The HTML code/entity for a space is   and for a tab 	

If you wish to preserve all spaces when double space is used you could consider using this:

String spaces = text.getText()
                .replace("  ","  ")
                .replace("\t","	");
html.setText(spaces);

This way you replace tabs for 	 HTML entity, and double spaces for two HTML spaces. Single spaces will be left alone as they will render properly.