Re: enable/disable widgets?

Found difficulties in some versions of Opera with exercising CSS properties like .myclass[disabled] {...}. Also I haven't found any solution how to sink events for disabled widgets. Seems like they are totally non-interactive (however :hover property still does some effect) speaking in terms of standard events, available for handling. Manually implemented enabled/disabled state has been the only suitable solution, which I'd found till present.

There's one good article about preview native event. In a nutshell you may examine what current event is about and cancel it before browser starts any propagation. Also I found this article quite useful to keep up on date with modern API. Here's a very concise piece of code:

In some singleton filter class (e.g. NativePreviewHandlerForHasEnabled):
*************************
private final Map<Element, HasEnabled> elementToWidgetMap = new HashMap<Element, HasEnabled>();

private NativePreviewHandlerForHasEnabled() {

assert instance == null : "Only one instance is allowed.";

elementToWidgetMap = new HashMap<Element, HasEnabled>();

Event.addNativePreviewHandler(new Event.NativePreviewHandler() {

           public void onPreviewNativeEvent(NativePreviewEvent pEvent) {

               final Element target = pEvent.getNativeEvent().getEventTarget().cast();

               HasEnabled widget = elementToWidgetMap.get(target);

               if (widget != null && !widget.isEnabled()) {

               

                // Let it work, cause we may need to e.g. hide tool tip when mouse is out

                if (pEvent.getTypeInt() != Event.ONMOUSEOUT) {

                pEvent.cancel();

                }

               }

           }

       }); 
}

public <T extends Widget & HasEnabled> void registerWidget(T widget) {

elementToWidgetMap.put(widget.getElement(), widget);

}

*************************

For our widget:

@Override

public void setEnabled(boolean enabled) {

this.enabled = enabled;

// super.setEnabled(enabled); // don't do this!

}

It's not perfect. Map can grow up fast depending on scale of your app. To enhance the performance store HandlerRegistration objects upon Event.addNativePreviewHandler call for later disposing, when the time comes.

On Thursday, June 17, 2010 10:27:26 PM UTC+5, Magnus wrote:

Hi,

how can I enable/disable a widget (TextBox, Button, etc.)?

I would like to iterate all Widgets of a form and set this status. I
found no appropriate methods in the Widget class...

Magnus

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