org.cruxframework.crux.smartfaces.client.util.dragdrop.GenericDragEventHandler.java Source code

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Here is the source code for org.cruxframework.crux.smartfaces.client.util.dragdrop.GenericDragEventHandler.java

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/*
 * Copyright 2014 cruxframework.org.
 * 
 * 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 org.cruxframework.crux.smartfaces.client.util.dragdrop;

import org.cruxframework.crux.core.client.utils.StyleUtils;

import com.google.gwt.dom.client.Document;
import com.google.gwt.event.dom.client.HasAllMouseHandlers;
import com.google.gwt.event.dom.client.MouseDownEvent;
import com.google.gwt.event.dom.client.MouseDownHandler;
import com.google.gwt.event.dom.client.MouseMoveEvent;
import com.google.gwt.event.dom.client.MouseMoveHandler;
import com.google.gwt.event.dom.client.MouseUpEvent;
import com.google.gwt.event.dom.client.MouseUpHandler;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.IsWidget;

/**
 * A generic handler which captures mouse events, translates them into drag events and invokes actions associated to them.  
 * @author Gesse Dafe
 */
public class GenericDragEventHandler implements MouseDownHandler, MouseUpHandler, MouseMoveHandler {
    public static final String DRAGGING_STYLE = "dragging";
    private DragAction<?> action;

    private int dragStartX;
    private int dragStartY;
    private int clientLeft;
    private int clientTop;
    private int windowWidth;
    private boolean dragging;

    /**
     * @param action
     */
    public GenericDragEventHandler(DragAction<?> action) {
        this.action = action;
    }

    /**
     * Apply this handler to a given draggable
     * @param draggable
     */
    public void applyTo(Draggable<?> draggable) {
        draggable.getHandle(action.getFeature()).addMouseDownHandler(this);
        draggable.getHandle(action.getFeature()).addMouseMoveHandler(this);
        draggable.getHandle(action.getFeature()).addMouseUpHandler(this);
    }

    @Override
    public void onMouseDown(MouseDownEvent event) {
        if (DOM.getCaptureElement() == null) {
            windowWidth = Window.getClientWidth();
            clientLeft = Document.get().getBodyOffsetLeft();
            clientTop = Document.get().getBodyOffsetTop();

            dragging = true;

            DOM.setCapture(action.getDraggable().getHandle(action.getFeature()).asWidget().getElement());

            dragStartX = event.getClientX();
            dragStartY = event.getClientY();

            action.onStartDrag();
        }
    }

    @Override
    public void onMouseMove(MouseMoveEvent event) {
        if (dragging) {
            int x = event.getClientX();
            int y = event.getClientY();

            if (x < clientLeft || x >= windowWidth || y < clientTop) {
                return;
            }

            action.onDrag(x, y, dragStartX, dragStartY);
        }
    }

    @Override
    public void onMouseUp(MouseUpEvent event) {
        dragging = false;
        action.onEndDrag();
        DOM.releaseCapture(action.getDraggable().getHandle(action.getFeature()).asWidget().getElement());
    }

    /**
     * The contract to implement the logic associated to a drag action
     * @author Gesse Dafe
     */
    public static abstract class DragAction<D extends Draggable<?>> {
        private D draggable;

        /**
         * @param draggable
         * @param move 
         */
        public DragAction(D draggable) {
            this.draggable = draggable;
        }

        /**
         * Action to be taken when drag starts
         */
        public void onStartDrag() {
            StyleUtils.addStyleName(Document.get().getBody(), DRAGGING_STYLE);
        }

        /**
         * Gets the feature associated to this action
         * @return
         */
        public abstract DragAndDropFeature getFeature();

        /**
         * Action to be taken when drag happens
         * @param x
         * @param y
         * @param dragStartX
         * @param dragStartY
         */
        public abstract void onDrag(int x, int y, int dragStartX, int dragStartY);

        /**
         * Action to be taken when drag ends
         */
        public void onEndDrag() {
            StyleUtils.removeStyleName(Document.get().getBody(), DRAGGING_STYLE);
        }

        /**
         * @return
         */
        public D getDraggable() {
            return draggable;
        }
    }

    /**
     * The contract to implement a widget which can be resized  
     * @author Gesse Dafe
     */
    public static interface Draggable<K extends IsWidget & HasAllMouseHandlers> {
        K getHandle(DragAndDropFeature feature);
    }

    /**
     * Features offered by existing drag and drop capabilities 
     * @author Gesse Dafe
     *
     */
    public static enum DragAndDropFeature {
        MOVE, RESIZE
    }
}