[news.eclipse.platform.swt] Re: Confusing mouseDown / mouseUp / mouseDou

[Matthew Hall <matthall@xxxxxxxxxxxxxxxxx>]

Enric Tordera wrote:
> I've developed a custom widget. It has got a Composite, where I want to 
> catch some mouse events. So I used "addMouseListener" and defined a 
> "MouseListener" that implements "mouseDown", "mouseUp" and 
> "mouseDoubleClick".
>
> I just want to detect single clicks and double clicks on the widget. 
> Single clicks mean different things than double clicks in my 
> application. I wrote my code under "mouseUp" for single clicks and under 
> "mouseDoubleClick" for double clicks.
>
> The problem is that when the user double clicks on the widget, the code 
> at mouseDoubleClick is called, but also the code at mouseUp is called 
> twice.
>
> Which is the best way to detect the double click and avoid the code at 
> "mouseUp" or "mouseDown" being executed in that case?
>
> Thanks in advance
>
> - Enric

Use Display.timerExec to delay the single-click event handler until 
you're sure it's not a double-click.  I've used this technique to delay 
updating of viewer filters until the user stops typing in a filter field.

class CancelableRunnable implements Runnable {
  public void cancel() { ... }

  public boolean isCancelled() { ... }

  public void run() {
    if (!isCancelled()) {
      // single click event handler
    }
  }
}

When you receive a mouse-up event, create a new CancelableRunnable 
instance, assign it to a field where the double-click listener has 
access to it, and then call:

display.timerExec(display.getDoubleClickTime(), runnable);

In the double-click event handler, check to see if the cancelable 
runnable is non-null, and if so, cancel it.

Let me know how it works.

Matthew