SiteFrameSelectionManager.java

package com.project.website.canvas.client.canvastools.sitecrop;

import com.google.gwt.dom.client.Element;
import com.google.gwt.event.dom.client.MouseDownEvent;
import com.google.gwt.user.client.ui.Widget;
import com.project.shared.client.events.SimpleEvent;
import com.project.shared.client.events.SimpleEvent.Handler;
import com.project.shared.client.utils.ElementUtils;
import com.project.shared.data.Point2D;
import com.project.shared.data.Rectangle;
import com.project.shared.utils.RectangleUtils;
import com.project.website.canvas.client.worksheet.ElementDragManagerImpl;
import com.project.website.canvas.client.worksheet.interfaces.ElementDragManager.StopCondition;
import com.project.website.canvas.client.worksheet.interfaces.MouseMoveOperationHandler;

public class SiteFrameSelectionManager {
    public final static int MIN_VALID_SELECTION_SIZE_PX = 5;

    private ElementDragManagerImpl _selectionDragManager = null;
	private Widget _selectionPanel = null;
	private Widget _container = null;

	public SiteFrameSelectionManager(Widget container, Widget dragPanel,
	        Widget selectionPanel, SimpleEvent<Void> cancelOperationEvent) {
		this._container = container;
		this._selectionPanel = selectionPanel;
		this._selectionDragManager = new ElementDragManagerImpl(container,
				dragPanel, cancelOperationEvent);
	}

	public void startSelectionDrag(MouseDownEvent event, final Handler<Void> doneHandler) {
        ElementUtils.setTextSelectionEnabled(_container.getElement(), false);

		final Point2D initialPosition =
			ElementUtils.getRelativePosition(event, this._container.getElement());
		ElementUtils.setElementRectangle(this._selectionPanel.getElement(),
				new Rectangle(initialPosition.getX(), initialPosition.getY(), 0));

		this._selectionPanel.setVisible(true);

		MouseMoveOperationHandler handler = new MouseMoveOperationHandler() {
            @Override public void onStop(Point2D pos) {
                if (false == isValidSelection())
                {
                    clearSelection();
                }
                else
                {
                    doneHandler.onFire(null);
                }
            }

            @Override public void onStart() {
            }

            @Override public void onMouseMove(Point2D pos) {
                Element selectionElement = _selectionPanel.getElement();
                ElementUtils.setElementRectangle(selectionElement,
                        RectangleUtils.Build(initialPosition, pos));
            }

            @Override public void onCancel() {
                clearSelection();
            }
        };

		this._selectionDragManager.startMouseMoveOperation(this._container.getElement(),
		        Point2D.zero, handler, StopCondition.STOP_CONDITION_MOVEMENT_STOP);
	}

	public Rectangle getSelectedRectangle()
	{
	    return ElementUtils.getElementOffsetRectangle(_selectionPanel.getElement());
	}

	public void clearSelection() {
		this._selectionPanel.setVisible(false);
		ElementUtils.setElementSize(this._selectionPanel.getElement(), Point2D.zero);
	}

	private boolean isValidSelection()
	{
	    Point2D selectionSize = this.getSelectedRectangle().getSize();
	    if ((selectionSize.getX() > MIN_VALID_SELECTION_SIZE_PX) &&
	        (selectionSize.getY() > MIN_VALID_SELECTION_SIZE_PX))
	    {
	        return true;
	    }
	    return false;
	}
}