Mixing Swing/FX with binding - use custom property for mediating between threads?

Question

This is a kind of follow-up of seeing thread-rule violations when mixing Swing/FX and bind both parts to the same model.

Meanwhile I experimented a bit: use a custo

Answer 1

A partial answer (why the misbehaviour of the bidi-bound textfield and what to do against it):

Techically, the behaviour is due to internal flags which get confused when the "back-notification" of a bidi-bound property happens outside of the expected code blocks.

• BidirectionalBinding guards - being the listener to two properties - itself against endless looping by isUpdating to not update the originating property again
• the flag doNotAdjustCaret is used by TextInputControl to mark changes triggered by itself. The control has a custom TextProperty which uses that flag to either set the selection to the start (for external changes) or not (for internal changes)

Now the thread-changing property falls outside the first block, triggers a re-set of the textProperty which in turn isn't recognized as self-triggered, thus resetting the selectin/caret. A work-around is to update the value and "back-fire" directly:

/**
 * Implemented to set the value of this property, immediately 
 * fire a value change if needed and then update the delegate.
 * 
 * The sequence may be crucial if the value is changed by a bidirectionally
 * bound property (like f.i. a TextProperty): that property reacts to 
 * change notifications triggered by its own change in a different 
 * way as by those from the outside, detected by a flag (sigh ...)
 * set while firing.
 */
@Override
public void set(T value) {
    T oldValue = this.value;
    this.value = value;
    if (!areEqual(oldValue, value)) {
        fireValueChangedEvent();
    }
    updateToDelegate(value);
    // PENDING: think about uni-directional binding
}

/**
 * Updates the internal value and notifies its listeners, if needed.
 * Does nothing if the newValue equals the current value.<p>
 * 
 * It runs on the thread it is called from.
 * 
 * @param newValue the new value.
 */
protected void doUpdateFromDelegate(T newValue) {
    if (areEqual(newValue, value)) return;
    value = newValue;
    fireValueChangedEvent();
}