1 /*
2 * Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
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24 */
25
26 package javax.swing.plaf;
27
28 import javax.swing.JComponent;
29 import javax.swing.SwingUtilities;
30 import javax.accessibility.Accessible;
31
32 import java.awt.Component;
33 import java.awt.Container;
34 import java.awt.Dimension;
35 import java.awt.Graphics;
36 import java.awt.Insets;
37
38
39 /**
40 * The base class for all UI delegate objects in the Swing pluggable
41 * look and feel architecture. The UI delegate object for a Swing
42 * component is responsible for implementing the aspects of the
43 * component that depend on the look and feel.
44 * The <code>JComponent</code> class
45 * invokes methods from this class in order to delegate operations
46 * (painting, layout calculations, etc.) that may vary depending on the
47 * look and feel installed. <b>Client programs should not invoke methods
48 * on this class directly.</b>
49 *
50 * @see javax.swing.JComponent
51 * @see javax.swing.UIManager
52 *
53 */
54 public abstract class ComponentUI {
55 /**
56 * Sole constructor. (For invocation by subclass constructors,
57 * typically implicit.)
58 */
59 public ComponentUI() {
60 }
61
62 /**
63 * Configures the specified component appropriately for the look and feel.
64 * This method is invoked when the <code>ComponentUI</code> instance is being installed
65 * as the UI delegate on the specified component. This method should
66 * completely configure the component for the look and feel,
67 * including the following:
68 * <ol>
69 * <li>Install default property values for color, fonts, borders,
70 * icons, opacity, etc. on the component. Whenever possible,
71 * property values initialized by the client program should <i>not</i>
72 * be overridden.
73 * <li>Install a <code>LayoutManager</code> on the component if necessary.
74 * <li>Create/add any required sub-components to the component.
75 * <li>Create/install event listeners on the component.
76 * <li>Create/install a <code>PropertyChangeListener</code> on the component in order
77 * to detect and respond to component property changes appropriately.
78 * <li>Install keyboard UI (mnemonics, traversal, etc.) on the component.
79 * <li>Initialize any appropriate instance data.
80 * </ol>
81 * @param c the component where this UI delegate is being installed
82 *
83 * @see #uninstallUI
84 * @see javax.swing.JComponent#setUI
85 * @see javax.swing.JComponent#updateUI
86 */
87 public void installUI(JComponent c) {
88 }
89
90 /**
91 * Reverses configuration which was done on the specified component during
92 * <code>installUI</code>. This method is invoked when this
93 * <code>UIComponent</code> instance is being removed as the UI delegate
94 * for the specified component. This method should undo the
95 * configuration performed in <code>installUI</code>, being careful to
96 * leave the <code>JComponent</code> instance in a clean state (no
97 * extraneous listeners, look-and-feel-specific property objects, etc.).
98 * This should include the following:
99 * <ol>
100 * <li>Remove any UI-set borders from the component.
101 * <li>Remove any UI-set layout managers on the component.
102 * <li>Remove any UI-added sub-components from the component.
103 * <li>Remove any UI-added event/property listeners from the component.
104 * <li>Remove any UI-installed keyboard UI from the component.
105 * <li>Nullify any allocated instance data objects to allow for GC.
106 * </ol>
107 * @param c the component from which this UI delegate is being removed;
108 * this argument is often ignored,
109 * but might be used if the UI object is stateless
110 * and shared by multiple components
111 *
112 * @see #installUI
113 * @see javax.swing.JComponent#updateUI
114 */
115 public void uninstallUI(JComponent c) {
116 }
117
118 /**
119 * Paints the specified component appropriately for the look and feel.
120 * This method is invoked from the <code>ComponentUI.update</code> method when
121 * the specified component is being painted. Subclasses should override
122 * this method and use the specified <code>Graphics</code> object to
123 * render the content of the component.
124 *
125 * @param g the <code>Graphics</code> context in which to paint
126 * @param c the component being painted;
127 * this argument is often ignored,
128 * but might be used if the UI object is stateless
129 * and shared by multiple components
130 *
131 * @see #update
132 */
133 public void paint(Graphics g, JComponent c) {
134 }
135
136 /**
137 * Notifies this UI delegate that it is time to paint the specified
138 * component. This method is invoked by <code>JComponent</code>
139 * when the specified component is being painted.
140 *
141 * <p>By default this method fills the specified component with
142 * its background color if its {@code opaque} property is {@code true},
143 * and then immediately calls {@code paint}. In general this method need
144 * not be overridden by subclasses; all look-and-feel rendering code should
145 * reside in the {@code paint} method.
146 *
147 * @param g the <code>Graphics</code> context in which to paint
148 * @param c the component being painted;
149 * this argument is often ignored,
150 * but might be used if the UI object is stateless
151 * and shared by multiple components
152 *
153 * @see #paint
154 * @see javax.swing.JComponent#paintComponent
155 */
156 public void update(Graphics g, JComponent c) {
157 if (c.isOpaque()) {
158 g.setColor(c.getBackground());
159 g.fillRect(0, 0, c.getWidth(),c.getHeight());
160 }
161 paint(g, c);
162 }
163
164 /**
165 * Returns the specified component's preferred size appropriate for
166 * the look and feel. If <code>null</code> is returned, the preferred
167 * size will be calculated by the component's layout manager instead
168 * (this is the preferred approach for any component with a specific
169 * layout manager installed). The default implementation of this
170 * method returns <code>null</code>.
171 *
172 * @param c the component whose preferred size is being queried;
173 * this argument is often ignored,
174 * but might be used if the UI object is stateless
175 * and shared by multiple components
176 *
177 * @see javax.swing.JComponent#getPreferredSize
178 * @see java.awt.LayoutManager#preferredLayoutSize
179 */
180 public Dimension getPreferredSize(JComponent c) {
181 return null;
182 }
183
184 /**
185 * Returns the specified component's minimum size appropriate for
186 * the look and feel. If <code>null</code> is returned, the minimum
187 * size will be calculated by the component's layout manager instead
188 * (this is the preferred approach for any component with a specific
189 * layout manager installed). The default implementation of this
190 * method invokes <code>getPreferredSize</code> and returns that value.
191 *
192 * @param c the component whose minimum size is being queried;
193 * this argument is often ignored,
194 * but might be used if the UI object is stateless
195 * and shared by multiple components
196 *
197 * @return a <code>Dimension</code> object or <code>null</code>
198 *
199 * @see javax.swing.JComponent#getMinimumSize
200 * @see java.awt.LayoutManager#minimumLayoutSize
201 * @see #getPreferredSize
202 */
203 public Dimension getMinimumSize(JComponent c) {
204 return getPreferredSize(c);
205 }
206
207 /**
208 * Returns the specified component's maximum size appropriate for
209 * the look and feel. If <code>null</code> is returned, the maximum
210 * size will be calculated by the component's layout manager instead
211 * (this is the preferred approach for any component with a specific
212 * layout manager installed). The default implementation of this
213 * method invokes <code>getPreferredSize</code> and returns that value.
214 *
215 * @param c the component whose maximum size is being queried;
216 * this argument is often ignored,
217 * but might be used if the UI object is stateless
218 * and shared by multiple components
219 * @return a <code>Dimension</code> object or <code>null</code>
220 *
221 * @see javax.swing.JComponent#getMaximumSize
222 * @see java.awt.LayoutManager2#maximumLayoutSize
223 */
224 public Dimension getMaximumSize(JComponent c) {
225 return getPreferredSize(c);
226 }
227
228 /**
229 * Returns <code>true</code> if the specified <i>x,y</i> location is
230 * contained within the look and feel's defined shape of the specified
231 * component. <code>x</code> and <code>y</code> are defined to be relative
232 * to the coordinate system of the specified component. Although
233 * a component's <code>bounds</code> is constrained to a rectangle,
234 * this method provides the means for defining a non-rectangular
235 * shape within those bounds for the purpose of hit detection.
236 *
237 * @param c the component where the <i>x,y</i> location is being queried;
238 * this argument is often ignored,
239 * but might be used if the UI object is stateless
240 * and shared by multiple components
241 * @param x the <i>x</i> coordinate of the point
242 * @param y the <i>y</i> coordinate of the point
243 *
244 * @see javax.swing.JComponent#contains
245 * @see java.awt.Component#contains
246 */
247 public boolean contains(JComponent c, int x, int y) {
248 return c.inside(x, y);
249 }
250
251 /**
252 * Returns an instance of the UI delegate for the specified component.
253 * Each subclass must provide its own static <code>createUI</code>
254 * method that returns an instance of that UI delegate subclass.
255 * If the UI delegate subclass is stateless, it may return an instance
256 * that is shared by multiple components. If the UI delegate is
257 * stateful, then it should return a new instance per component.
258 * The default implementation of this method throws an error, as it
259 * should never be invoked.
260 */
261 public static ComponentUI createUI(JComponent c) {
262 throw new Error("ComponentUI.createUI not implemented.");
263 }
264
265 /**
266 * Returns the baseline. The baseline is measured from the top of
267 * the component. This method is primarily meant for
268 * <code>LayoutManager</code>s to align components along their
269 * baseline. A return value less than 0 indicates this component
270 * does not have a reasonable baseline and that
271 * <code>LayoutManager</code>s should not align this component on
272 * its baseline.
273 * <p>
274 * This method returns -1. Subclasses that have a meaningful baseline
275 * should override appropriately.
276 *
277 * @param c <code>JComponent</code> baseline is being requested for
278 * @param width the width to get the baseline for
279 * @param height the height to get the baseline for
280 * @throws NullPointerException if <code>c</code> is <code>null</code>
281 * @throws IllegalArgumentException if width or height is < 0
282 * @return baseline or a value < 0 indicating there is no reasonable
283 * baseline
284 * @see javax.swing.JComponent#getBaseline(int,int)
285 * @since 1.6
286 */
287 public int getBaseline(JComponent c, int width, int height) {
288 if (c == null) {
289 throw new NullPointerException("Component must be non-null");
290 }
291 if (width < 0 || height < 0) {
292 throw new IllegalArgumentException(
293 "Width and height must be >= 0");
294 }
295 return -1;
296 }
297
298 /**
299 * Returns an enum indicating how the baseline of he component
300 * changes as the size changes. This method is primarily meant for
301 * layout managers and GUI builders.
302 * <p>
303 * This method returns <code>BaselineResizeBehavior.OTHER</code>.
304 * Subclasses that support a baseline should override appropriately.
305 *
306 * @param c <code>JComponent</code> to return baseline resize behavior for
307 * @return an enum indicating how the baseline changes as the component
308 * size changes
309 * @throws NullPointerException if <code>c</code> is <code>null</code>
310 * @see javax.swing.JComponent#getBaseline(int, int)
311 * @since 1.6
312 */
313 public Component.BaselineResizeBehavior getBaselineResizeBehavior(
314 JComponent c) {
315 if (c == null) {
316 throw new NullPointerException("Component must be non-null");
317 }
318 return Component.BaselineResizeBehavior.OTHER;
319 }
320
321 /**
322 * Returns the number of accessible children in the object. If all
323 * of the children of this object implement <code>Accessible</code>,
324 * this
325 * method should return the number of children of this object.
326 * UIs might wish to override this if they present areas on the
327 * screen that can be viewed as components, but actual components
328 * are not used for presenting those areas.
329 *
330 * Note: As of v1.3, it is recommended that developers call
331 * <code>Component.AccessibleAWTComponent.getAccessibleChildrenCount()</code> instead
332 * of this method.
333 *
334 * @see #getAccessibleChild
335 * @return the number of accessible children in the object
336 */
337 public int getAccessibleChildrenCount(JComponent c) {
338 return SwingUtilities.getAccessibleChildrenCount(c);
339 }
340
341 /**
342 * Returns the <code>i</code>th <code>Accessible</code> child of the object.
343 * UIs might need to override this if they present areas on the
344 * screen that can be viewed as components, but actual components
345 * are not used for presenting those areas.
346 *
347 * <p>
348 *
349 * Note: As of v1.3, it is recommended that developers call
350 * <code>Component.AccessibleAWTComponent.getAccessibleChild()</code> instead of
351 * this method.
352 *
353 * @see #getAccessibleChildrenCount
354 * @param i zero-based index of child
355 * @return the <code>i</code>th <code>Accessible</code> child of the object
356 */
357 public Accessible getAccessibleChild(JComponent c, int i) {
358 return SwingUtilities.getAccessibleChild(c, i);
359 }
360 }