Dragging with NONE accept-criterion blocks / freezes application indefinitely (on client side)

[vaadin-bot]

Originally by @jtreml

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With a drop handler that returns NONE as an accept criterion (Not((ClientSideCriterion) AcceptAll.get())), dragging anything in the UI will stop the application from responding to any more events indefinitely until you refresh the browser.[[BR]]
[[BR]]

Online demo:[[BR]]
[http://env-2724817.jelastic.servint.net/drag-freeze/]

To reproduce:

1. Click the button; Works as expected, brings up a notification.
2. Drag the image (nowhere special, just a few inches from its original location).
3. Try to click the button again; no longer works.

Demo code:

package drag.freeze;

import com.vaadin.event.dd.DragAndDropEvent;
import com.vaadin.event.dd.DropHandler;
import com.vaadin.event.dd.acceptcriteria.AcceptAll;
import com.vaadin.event.dd.acceptcriteria.AcceptCriterion;
import com.vaadin.event.dd.acceptcriteria.ClientSideCriterion;
import com.vaadin.event.dd.acceptcriteria.Not;
import com.vaadin.server.ThemeResource;
import com.vaadin.server.VaadinRequest;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.DragAndDropWrapper;
import com.vaadin.ui.DragAndDropWrapper.DragStartMode;
import com.vaadin.ui.Image;
import com.vaadin.ui.Notification;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

@SuppressWarnings("serial")
public class DragTestUI extends UI implements DropHandler {

    @Override
    protected void init(VaadinRequest request) {
        Image sample = new Image();
        sample.setSource(new ThemeResource("../runo/icons/64/document.png"));

        Button button = new Button("Click me!");
        button.addClickListener(new Button.ClickListener() {

            @Override
            public void buttonClick(ClickEvent event) {
                Notification.show("click");
            }
        });

        VerticalLayout wrapperLayout = new VerticalLayout();
        wrapperLayout.setSizeFull();
        wrapperLayout.addComponent(button);

        DragAndDropWrapper wrapper = new DragAndDropWrapper(wrapperLayout);
        wrapper.setSizeFull();
        wrapper.setDragStartMode(DragStartMode.NONE);
        wrapper.setDropHandler(this);

        VerticalLayout content = new VerticalLayout();
        content.addComponent(sample);
        content.addComponent(wrapper);
        content.setExpandRatio(wrapper, 1);
        content.setSizeFull();
        setContent(content);

    }

    @Override
    public void drop(DragAndDropEvent event) {
        // Don't do anything here. It's just an example,
    }

    @Override
    public AcceptCriterion getAcceptCriterion() {
        return new Not((ClientSideCriterion) AcceptAll.get());
    }
}

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Imported from https://dev.vaadin.com/ issue #12013

[vaadin-bot]

Originally by @Wnt

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Unfortunatelly I don't have time to work on this in the next few weeks.

[vaadin-bot]

Originally by @Artur-

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A lot of tickets have been left hanging in the issue tracker through the years. Some of them are still relevant, some of them have been fixed a long time ago and some are no longer valid. To get a better look on what is important and still relevant, we are closing old tickets which have not been touched in a long time.

No further work will be done on this ticket unless someone indicates that it's still relevant.

If this ticket is still relevant to you, please reopen it.

[nickarls]

NB this issue is still around in the currently latest Vaadin-release