wtk/src/org/apache/pivot/wtk/Skin.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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.apache.pivot.wtk;

/**
 * Interface defining a "skin". A skin is the graphical representation of a
 * component. In MVC terminology, a skin represents the "view" of the "model"
 * data provided by a component. Components delegate a number of methods to the
 * skin, including all methods defined by the <tt>Visual</tt> interface as well
 * as style properties and layout. In conjunction with renderers
 * (implementations of the <tt>Renderer</tt> interface), skins define the
 * overall look and feel of an application. <p> Skins are primarily responsible
 * for the following: <ul> <li>Adding additional subcomponents, if a
 * composite.</li> <li>Painting the component; if a container, this is
 * effectively the background of the container, since a container cannot paint
 * on top of its children.</li> <li>Layout of subcomponents or content.</li>
 * </ul> Skins will often change their appearance in response to events fired by
 * the component; most commonly, this will be in response to data changes within
 * the component but may also be in response to input events (e.g. keyboard,
 * mouse). Skins are not required to register for such events - skin base
 * classes implement all relevant listener interfaces and the component calls
 * them as appropriate. <p> Skins may (but are not required to) expose internal
 * properties that affect the appearance of the component as "style properties",
 * similar to CSS styles. For example, a component might provide styles to let a
 * caller set the foreground color and font. Since callers are not allowed to
 * interact with a component's skin directly, access to styles is via the
 * component's styles collection, which delegates to the dictionary methods in
 * the installed skin. Skins are responsible for invalidating or repainting the
 * component as appropriate in response to events and style changes.
 */
public interface Skin extends ConstrainedVisual {
    /**
     * Associates a skin with a component.
     *
     * @param component The component to which the skin is being attached.
     */
    public void install(Component component);

    /**
     * Returns the component with which a skin is associated.
     * @return This skin's associated component.
     */
    public Component getComponent();

    /**
     * If the component on which the skin is installed is a container, lays out
     * the container's children.
     */
    public void layout();

    /**
     * Returns the skin's focusable state.
     *
     * @return <code>true</code> if this skin is focusable; <code>false</code>,
     * otherwise.
     */
    public boolean isFocusable();

    /**
     * Tells whether or not this skin is fully opaque when painted.
     *
     * @return <code>true</code> if this skin is opaque; <code>false</code> if any part
     * of it is transparent or translucent.
     */
    public boolean isOpaque();
}