BasicUndo.java

package oripa.paint.core;

import oripa.ORIPA;

public class BasicUndo {

	/**
	 * executes undo of the state if some vertex or line is picked.
	 * If the context has no such element (we assume it the starting point), 
	 * undo of input is executed. 
	 * @param state
	 * @param context
	 * @return next state defined by the given state.
	 */
	public static ActionState undo(ActionState state, PaintContext context){
		ActionState next = state;
		
		if(context.getLineCount() > 0 || context.getVertexCount() > 0){
			next = state.undo(context);
		}
		else {
			ORIPA.doc.loadUndoInfo();
		}
		
		return next;
	}
}