Bug 320338 SplitDropAgent should not use client area for preview rectangle
bundles/org.eclipse.e4.ui.workbench.addons.swt/src/org/eclipse/e4/ui/workbench/addons/dndaddon/SplitDropAgent.java
* @param modelService
	 *            The model service related to this agent
	 * 
	 */
	public SplitDropAgent(EModelService modelService) {
		this.modelService = modelService;
	}
	@Override
	public boolean canDrop(MUIElement dragElement, CursorInfo info) {
		if (!(dragElement instanceof MPart))
			return false;
		MPart part = (MPart) dragElement;
		MStackElement stackElement = part.getCurSharedRef() != null ? part.getCurSharedRef() : part;
		
		if (info.curElement == stackElement) {
			if (stackElement.getParent().getWidget() instanceof CTabFolder) {
				CTabFolder ctf = (CTabFolder) stackElement.getParent().getWidget();
				return ctf.getItemCount() > 1;
			}
		}
		if (info.curElement instanceof MStackElement)
			return true;
		
		
		if (info.curElement instanceof MPartStack
				&& info.curElement.getTags().contains("EditorStack")) 
			return true;
		return false;
	}
	private int whereToDrop(Control ctrl, Point cursorPos) {