Question

I’m experiencing an intermittent problem with a class that extends javax.swing.text.DefaultStyledDocument. This document is being sent to a printer. Most of the time the formatting of the document looks correct, but once in a while it doesn’t. It looks like some of the changes in the formatting have not been applied.

I took a look at the DefaultStyledDocument.styleChanged(Style style) code:

/**
 * Called when any of this document's styles have changed.
 * Subclasses may wish to be intelligent about what gets damaged.
 *
 * @param style The Style that has changed.
 */
protected void styleChanged(Style style) {
    // Only propagate change updated if have content
    if (getLength() != 0) {
        // lazily create a ChangeUpdateRunnable
        if (updateRunnable == null) {
            updateRunnable = new ChangeUpdateRunnable();
        }

        // We may get a whole batch of these at once, so only
        // queue the runnable if it is not already pending
        synchronized(updateRunnable) {
            if (!updateRunnable.isPending) {
                SwingUtilities.invokeLater(updateRunnable);
                updateRunnable.isPending = true;
            }
        }
    }
}

/**
 * When run this creates a change event for the complete document
 * and fires it.
 */
class ChangeUpdateRunnable implements Runnable {
    boolean isPending = false;

public void run() {
        synchronized(this) {
            isPending = false;
        }

    try {
    writeLock();
    DefaultDocumentEvent dde = new DefaultDocumentEvent(0,
                      getLength(),
                      DocumentEvent.EventType.CHANGE);
    dde.end();
    fireChangedUpdate(dde);
    } finally {
    writeUnlock();
    }
}
}

Does the fact that SwingUtilities.invokeLater(updateRunnable) is called, rather than invokeAndWait(updateRunnable), mean that I can’t count on my formatting changes appearing in the document before it is rendered?

If that is the case, is there a way to ensure that I don’t proceed with rendering until the updates have occurred?

Answer 1

You see a fireChangedUpdate(dde); at the end of the code. Try to append yourself as a DocumentListener. Inside the DocumentListener.changedUpdate method you should be save to print your document with all changes included.