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- /*
- * Copyright 2000-2016 Vaadin Ltd.
- *
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not
- * use this file except in compliance with the License. You may obtain a copy of
- * the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
- * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
- * License for the specific language governing permissions and limitations under
- * the License.
- */
- package com.vaadin.event.dd.acceptcriteria;
-
- import java.io.Serializable;
-
- import com.vaadin.event.Transferable;
- import com.vaadin.event.dd.DragAndDropEvent;
- import com.vaadin.event.dd.DropHandler;
- import com.vaadin.server.PaintException;
- import com.vaadin.server.PaintTarget;
-
- /**
- * Criterion that can be used create policy to accept/discard dragged content
- * (presented by {@link Transferable}).
- *
- * The drag and drop mechanism will verify the criteria returned by
- * {@link DropHandler#getAcceptCriterion()} before calling
- * {@link DropHandler#drop(DragAndDropEvent)}.
- *
- * The criteria can be evaluated either on the client (browser - see
- * {@link ClientSideCriterion}) or on the server (see
- * {@link ServerSideCriterion}). If no constraints are needed, an
- * {@link AcceptAll} can be used.
- *
- * In addition to accepting or rejecting a possible drop, criteria can provide
- * additional hints for client side painting.
- *
- * @see DropHandler
- * @see ClientSideCriterion
- * @see ServerSideCriterion
- *
- * @since 6.3
- */
- public interface AcceptCriterion extends Serializable {
-
- /**
- * Returns whether the criteria can be checked on the client or whether a
- * server request is needed to check the criteria.
- *
- * This requirement may depend on the state of the criterion (e.g. logical
- * operations between criteria), so this cannot be based on a marker
- * interface.
- */
- public boolean isClientSideVerifiable();
-
- public void paint(PaintTarget target) throws PaintException;
-
- /**
- * This needs to be implemented if and only if a criterion does some lazy server side
- * initialization. The UIDL painted in this method will be passed to client
- * side drop handler implementation. Implementation can assume that
- * {@link #accept(DragAndDropEvent)} is called before this method.
- *
- * @param target
- * @throws PaintException
- */
- public void paintResponse(PaintTarget target) throws PaintException;
-
- /**
- * Validates the data in event to be appropriate for the
- * {@link DropHandler#drop(DragAndDropEvent)} method.
- * <p>
- * Note that even if your criterion is validated on client side, you should
- * always validate the data on server side too.
- *
- * @param dragEvent
- * @return
- */
- public boolean accept(DragAndDropEvent dragEvent);
- }
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