New widget code...

    /**
     * Set a single attribute.
     * @param key the attribute to set
     * @param value the value to set it to
     * @return if successful
     */
    boolean setAttr(Attr key, Object value);

    /**
     * Get an attribute but return our own default if it doesn't exist.
     * @param key the attribute to get
     * @param def the default if it doesn't exist
     * @return the value
     */
    Object getAttr(Attr key, Object def);

    /**
     * Get an attribute, return null if not found.
     * @param key the attribute to get
     * @return the value
     */
    Object getAttr(Attr key);

    /**
     * Check if an attribute has been set.
     * @param key the attribute to check
     * @return if it exists
     */
    boolean hasAttr(Attr key);

    /** All attribute enums need to implement this. */
    interface Attr {

        /**
         * Get the allowed types for an attribute.
         * By default attributes should accept Integer, however String and Enum
         * are both common types.
         * @return the allowed class
         */
        Class getType();

        /**
         * Get the default value for an attribute (if set).
         * @return the default value
         */
        Object getDefault();
    }

    /**
     * Used for set/get etc.
     */
    enum WidgetAttr implements Attr {

        /** Widget top offset. */
        TOP,
        /** Widget right offset. */
        RIGHT,
        /** Widget bottom offset. */
        BOTTOM,
        /** Widget left offset. */
        LEFT,
        /** Widget width. */
        WIDTH,
        /** Widget minimum width. */
        MIN_WIDTH,
        /** Widget maximum width. */
        MAX_WIDTH,
        /** Widget height. */
        HEIGHT,
        /** Widget minimum height. */
        MIN_HEIGHT,
        /** Widget maximum height. */
        MAX_HEIGHT,
        /** Tooltip on mouse hover. */
        TOOLTIP(String.class),
        /** How to display the widget "box". */
        DISPLAY(Display.class),
        /** What to do when the content overflows the box. */
        OVERFLOW(Overflow.class),
        /** Where to layout. */
        POSITION(Position.class),
        /** Padding top size. */
        PADDING_TOP,
        /** Padding right size. */
        PADDING_RIGHT,
        /** Padding bottom size. */
        PADDING_BOTTOM,
        /** Padding left size. */
        PADDING_LEFT,
        /** Border top size. */
        BORDER_TOP,
        /** Border top color. */
        BORDER_TOP_COLOR(Color.class),
        /** Border top style. */
        BORDER_TOP_STYLE(Border.class),
        /** Border right size. */
        BORDER_RIGHT,
        /** Border right color. */
        BORDER_RIGHT_COLOR(Color.class),
        /** Border right style. */
        BORDER_RIGHT_STYLE(Border.class),
        /** Border bottom size. */
        BORDER_BOTTOM,
        /** Border bottom color. */
        BORDER_BOTTOM_COLOR(Color.class),
        /** Border bottom style. */
        BORDER_BOTTOM_STYLE(Border.class),
        /** Border left size. */
        BORDER_LEFT,
        /** Border left color. */
        BORDER_LEFT_COLOR(Color.class),
        /** Border left style. */
        BORDER_LEFT_STYLE(Border.class),
        /** Margin top size. */
        MARGIN_TOP,
        /** Margin right size. */
        MARGIN_RIGHT,
        /** Margin bottom size. */
        MARGIN_BOTTOM,
        /** Margin left size. */
        MARGIN_LEFT,;
        /** The allowed type of data - Integer.class as default. */
        private final Class type;
        /** The default value - null by default. */
        private final Object def;

        /**
         * Default type is Integer.
         */
        private WidgetAttr() {
            this(Integer.class, null);
        }

        /**
         * Set the type explicitely.
         * @param allow this class and subclasses only
         */
        private WidgetAttr(final Class allow) {
            this(allow, null);
        }

        /**
         * Set the default value for an int attribute.
         * @param defValue default value
         */
        private WidgetAttr(final int defValue) {
            this(Integer.class, defValue);
        }

        /**
         * Set the type and default.
         * @param allow class
         * @param defValue default value
         */
        private WidgetAttr(final Class allow, final Object defValue) {
            type = allow;
            def = defValue;
        }

        @Override
        public final Class getType() {
            return type;
        }

        @Override
        public final Object getDefault() {
            return def;
        }
    }