JavaFX 2.2 TextField maxlength

With java8u40 we got a new class TextFormatter: one of its main responsibilities is to provide a hook into any change of text input before it gets comitted to the content. In that hook we can accept/reject or even change the proposed change.

The requirement solved in the OP's self-answer is

• the rule: restrict the length of text to shorter than n chars
• the modification: if the rule is violated, keep the last n chars as the input text and remove the excess chars at its start

Using a TextFormatter, this could be implemented like:

// here we adjust the new text 
TextField adjust = new TextField("scrolling: " + len);
UnaryOperator<Change> modifyChange = c -> {
    if (c.isContentChange()) {
        int newLength = c.getControlNewText().length();
        if (newLength > len) {
            // replace the input text with the last len chars
            String tail = c.getControlNewText().substring(newLength - len, newLength);
            c.setText(tail);
            // replace the range to complete text
            // valid coordinates for range is in terms of old text
            int oldLength = c.getControlText().length();
            c.setRange(0, oldLength);
        }
    }
    return c;
};
adjust.setTextFormatter(new TextFormatter(modifyChange));

Asides:

• modifying a property while listening to its change might lead to unexpected side-effects
• all suggested solutions on the key-level events are broken (they can't handle paste/programatic changes

This is a better way to do the job on a generic text field:

public static void addTextLimiter(final TextField tf, final int maxLength) {
    tf.textProperty().addListener(new ChangeListener<String>() {
        @Override
        public void changed(final ObservableValue<? extends String> ov, final String oldValue, final String newValue) {
            if (tf.getText().length() > maxLength) {
                String s = tf.getText().substring(0, maxLength);
                tf.setText(s);
            }
        }
    });
}

Works perfectly, except for that Undo bug.