/* * Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing.plaf; import javax.swing.JComponent;import javax.swing.SwingUtilities;import javax.accessibility.Accessible; import java.awt.Component;import java.awt.Container;import java.awt.Dimension;import java.awt.Graphics;import java.awt.Insets;  /** * The base class for all UI delegate objects in the Swing pluggable * look and feel architecture.  The UI delegate object for a Swing * component is responsible for implementing the aspects of the * component that depend on the look and feel. * The <code>JComponent</code> class * invokes methods from this class in order to delegate operations * (painting, layout calculations, etc.) that may vary depending on the * look and feel installed.  <b>Client programs should not invoke methods * on this class directly.</b> * * @see javax.swing.JComponent * @see javax.swing.UIManager * */public abstract class ComponentUI {    /**     * Sole constructor. (For invocation by subclass constructors,     * typically implicit.)     */    public ComponentUI() {    }     /**     * Configures the specified component appropriately for the look and feel.     * This method is invoked when the <code>ComponentUI</code> instance is being installed     * as the UI delegate on the specified component.  This method should     * completely configure the component for the look and feel,     * including the following:     * <ol>     * <li>Install default property values for color, fonts, borders,     *     icons, opacity, etc. on the component.  Whenever possible,     *     property values initialized by the client program should <i>not</i>     *     be overridden.     * <li>Install a <code>LayoutManager</code> on the component if necessary.     * <li>Create/add any required sub-components to the component.     * <li>Create/install event listeners on the component.     * <li>Create/install a <code>PropertyChangeListener</code> on the component in order     *     to detect and respond to component property changes appropriately.     * <li>Install keyboard UI (mnemonics, traversal, etc.) on the component.     * <li>Initialize any appropriate instance data.     * </ol>     * @param c the component where this UI delegate is being installed     *     * @see #uninstallUI     * @see javax.swing.JComponent#setUI     * @see javax.swing.JComponent#updateUI     */    public void installUI(JComponent c) {    }     /**     * Reverses configuration which was done on the specified component during     * <code>installUI</code>.  This method is invoked when this     * <code>UIComponent</code> instance is being removed as the UI delegate     * for the specified component.  This method should undo the     * configuration performed in <code>installUI</code>, being careful to     * leave the <code>JComponent</code> instance in a clean state (no     * extraneous listeners, look-and-feel-specific property objects, etc.).     * This should include the following:     * <ol>     * <li>Remove any UI-set borders from the component.     * <li>Remove any UI-set layout managers on the component.     * <li>Remove any UI-added sub-components from the component.     * <li>Remove any UI-added event/property listeners from the component.     * <li>Remove any UI-installed keyboard UI from the component.     * <li>Nullify any allocated instance data objects to allow for GC.     * </ol>     * @param c the component from which this UI delegate is being removed;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     *     * @see #installUI     * @see javax.swing.JComponent#updateUI     */    public void uninstallUI(JComponent c) {    }     /**     * Paints the specified component appropriately for the look and feel.     * This method is invoked from the <code>ComponentUI.update</code> method when     * the specified component is being painted.  Subclasses should override     * this method and use the specified <code>Graphics</code> object to     * render the content of the component.     *     * @param g the <code>Graphics</code> context in which to paint     * @param c the component being painted;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     *     * @see #update     */    public void paint(Graphics g, JComponent c) {    }     /**     * Notifies this UI delegate that it is time to paint the specified     * component.  This method is invoked by <code>JComponent</code>     * when the specified component is being painted.     *     * <p>By default this method fills the specified component with     * its background color if its {@code opaque} property is {@code true},     * and then immediately calls {@code paint}. In general this method need     * not be overridden by subclasses; all look-and-feel rendering code should     * reside in the {@code paint} method.     *     * @param g the <code>Graphics</code> context in which to paint     * @param c the component being painted;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     *     * @see #paint     * @see javax.swing.JComponent#paintComponent     */    public void update(Graphics g, JComponent c) {        if (c.isOpaque()) {            g.setColor(c.getBackground());            g.fillRect(0, 0, c.getWidth(),c.getHeight());        }        paint(g, c);    }     /**     * Returns the specified component's preferred size appropriate for     * the look and feel.  If <code>null</code> is returned, the preferred     * size will be calculated by the component's layout manager instead     * (this is the preferred approach for any component with a specific     * layout manager installed).  The default implementation of this     * method returns <code>null</code>.     *     * @param c the component whose preferred size is being queried;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     *     * @see javax.swing.JComponent#getPreferredSize     * @see java.awt.LayoutManager#preferredLayoutSize     */    public Dimension getPreferredSize(JComponent c) {        return null;    }     /**     * Returns the specified component's minimum size appropriate for     * the look and feel.  If <code>null</code> is returned, the minimum     * size will be calculated by the component's layout manager instead     * (this is the preferred approach for any component with a specific     * layout manager installed).  The default implementation of this     * method invokes <code>getPreferredSize</code> and returns that value.     *     * @param c the component whose minimum size is being queried;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     *     * @return a <code>Dimension</code> object or <code>null</code>     *     * @see javax.swing.JComponent#getMinimumSize     * @see java.awt.LayoutManager#minimumLayoutSize     * @see #getPreferredSize     */    public Dimension getMinimumSize(JComponent c) {        return getPreferredSize(c);    }     /**     * Returns the specified component's maximum size appropriate for     * the look and feel.  If <code>null</code> is returned, the maximum     * size will be calculated by the component's layout manager instead     * (this is the preferred approach for any component with a specific     * layout manager installed).  The default implementation of this     * method invokes <code>getPreferredSize</code> and returns that value.     *     * @param c the component whose maximum size is being queried;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     * @return a <code>Dimension</code> object or <code>null</code>     *     * @see javax.swing.JComponent#getMaximumSize     * @see java.awt.LayoutManager2#maximumLayoutSize     */    public Dimension getMaximumSize(JComponent c) {        return getPreferredSize(c);    }     /**     * Returns <code>true</code> if the specified <i>x,y</i> location is     * contained within the look and feel's defined shape of the specified     * component. <code>x</code> and <code>y</code> are defined to be relative     * to the coordinate system of the specified component.  Although     * a component's <code>bounds</code> is constrained to a rectangle,     * this method provides the means for defining a non-rectangular     * shape within those bounds for the purpose of hit detection.     *     * @param c the component where the <i>x,y</i> location is being queried;     *          this argument is often ignored,     *          but might be used if the UI object is stateless     *          and shared by multiple components     * @param x the <i>x</i> coordinate of the point     * @param y the <i>y</i> coordinate of the point     *     * @see javax.swing.JComponent#contains     * @see java.awt.Component#contains     */    public boolean contains(JComponent c, int x, int y) {        return c.inside(x, y);    }     /**     * Returns an instance of the UI delegate for the specified component.     * Each subclass must provide its own static <code>createUI</code>     * method that returns an instance of that UI delegate subclass.     * If the UI delegate subclass is stateless, it may return an instance     * that is shared by multiple components.  If the UI delegate is     * stateful, then it should return a new instance per component.     * The default implementation of this method throws an error, as it     * should never be invoked.     */    public static ComponentUI createUI(JComponent c) {        throw new Error("ComponentUI.createUI not implemented.");    }     /**     * Returns the baseline.  The baseline is measured from the top of     * the component.  This method is primarily meant for     * <code>LayoutManager</code>s to align components along their     * baseline.  A return value less than 0 indicates this component     * does not have a reasonable baseline and that     * <code>LayoutManager</code>s should not align this component on     * its baseline.     * <p>     * This method returns -1.  Subclasses that have a meaningful baseline     * should override appropriately.     *     * @param c <code>JComponent</code> baseline is being requested for     * @param width the width to get the baseline for     * @param height the height to get the baseline for     * @throws NullPointerException if <code>c</code> is <code>null</code>     * @throws IllegalArgumentException if width or height is &lt; 0     * @return baseline or a value &lt; 0 indicating there is no reasonable     *                  baseline     * @see javax.swing.JComponent#getBaseline(int,int)     * @since 1.6     */    public int getBaseline(JComponent c, int width, int height) {        if (c == null) {            throw new NullPointerException("Component must be non-null");        }        if (width < 0 || height < 0) {            throw new IllegalArgumentException(                    "Width and height must be >= 0");        }        return -1;    }     /**     * Returns an enum indicating how the baseline of he component     * changes as the size changes.  This method is primarily meant for     * layout managers and GUI builders.     * <p>     * This method returns <code>BaselineResizeBehavior.OTHER</code>.     * Subclasses that support a baseline should override appropriately.     *     * @param c <code>JComponent</code> to return baseline resize behavior for     * @return an enum indicating how the baseline changes as the component     *         size changes     * @throws NullPointerException if <code>c</code> is <code>null</code>     * @see javax.swing.JComponent#getBaseline(int, int)     * @since 1.6     */    public Component.BaselineResizeBehavior getBaselineResizeBehavior(            JComponent c) {        if (c == null) {            throw new NullPointerException("Component must be non-null");        }        return Component.BaselineResizeBehavior.OTHER;    }     /**     * Returns the number of accessible children in the object.  If all     * of the children of this object implement <code>Accessible</code>,     * this     * method should return the number of children of this object.     * UIs might wish to override this if they present areas on the     * screen that can be viewed as components, but actual components     * are not used for presenting those areas.     *     * Note: As of v1.3, it is recommended that developers call     * <code>Component.AccessibleAWTComponent.getAccessibleChildrenCount()</code> instead     * of this method.     *     * @see #getAccessibleChild     * @return the number of accessible children in the object     */    public int getAccessibleChildrenCount(JComponent c) {        return SwingUtilities.getAccessibleChildrenCount(c);    }     /**     * Returns the <code>i</code>th <code>Accessible</code> child of the object.     * UIs might need to override this if they present areas on the     * screen that can be viewed as components, but actual components     * are not used for presenting those areas.     *     * <p>     *     * Note: As of v1.3, it is recommended that developers call     * <code>Component.AccessibleAWTComponent.getAccessibleChild()</code> instead of     * this method.     *     * @see #getAccessibleChildrenCount     * @param i zero-based index of child     * @return the <code>i</code>th <code>Accessible</code> child of the object     */    public Accessible getAccessibleChild(JComponent c, int i) {        return SwingUtilities.getAccessibleChild(c, i);    }}