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34 <h1>AWT Desktop Properties</h1>
35
36 The following refers to standard AWT desktop properties that
37 may be obtained via the
38 <a href="../Toolkit.html#getDesktopProperty(java.lang.String)">
39 <code>Toolkit.getDesktopProperty</code></a> method.
40 <p>
41 Each desktop property is named by a unique string, which
42 is the "name" of that property.
43 <p>
44 Desktop properties supported by the AWT but not documented
45 elsewhere - typically because there is no suitable
46 method or class - are documented here.
47 <p>
48 Desktop properties documented elsewhere are those which are
49 tightly coupled with a method or class which documents them.
50 <p>
51 Since desktop properties abstract an underlying platform
52 setting, they may not be available in environments that do
53 not support them. In the event that a desktop property is
54 unavailable for any reason, the implementation will return
55 <code>null</code>.
56 <p>
57 The following table summarizes the desktop properties documented
58 here, and their value types.
59 <br><br>
60 <table border=1>
61 <thead>
62 <tr>
63 <th scope="col">Property Name</th>
64 <th scope="col">Value Type</th>
65 <th scope="col">Summary Description</th>
66 </tr>
67 </thead>
68 <tbody>
69 <tr>
70 <th scope="row"><A href="#awt.font.desktophints">awt.font.desktophints</A></th>
71 <td>{@link java.util.Map java.util.Map}</td>
72 <td>Font smoothing (text antialiasing) settings.</td>
73 </tr>
74 <tr>
75 <th scope="row"><A href="#sun.awt.enableExtraMouseButtons">sun.awt.enableExtraMouseButtons</A></th>
76 <td>{@link java.lang.Boolean java.lang.Boolean}</td>
77 <td>Controls if mouse events from extra buttons are to be generated or not</td>
78 </tr>
79 </tbody>
80 </table>
81
82 <h2>Desktop Font Rendering Hints</h2>
83 <b>Desktop Property: <a id="awt.font.desktophints">"awt.font.desktophints"</A></b>
84 <p>
85 Modern desktops support various forms of text antialiasing (font smoothing).
86 <p>
87 These are applied by platform-specific heavyweight components.
88 However an application may want to render text using the same text
89 antialiasing on a drawing surface or lightweight (non-platform) component using
90 <a href="../Graphics2D.html"> <code>Graphics2D</code></a> methods.
91 This is particularly important when creating
92 <a href="../../../javax/swing/JComponent.html"> Swing components</a> which
93 are required to appear consistent with native desktop components or other
94 Swing components.
95
96 <h3>Basic Usage</h3>
97 The standard desktop property named
98 <b>"awt.font.desktophints"</b>
99 can be used to obtain the rendering hints that best match the desktop settings.
100
101 The return value is a
102 <a href="../../util/Map.html"> Map</a> of
103 <a href="../RenderingHints.html"> <code>RenderingHints</code></a> which
104 can be directly applied to a <code>Graphics2D</code>.
105 <p>
106 It is a <code>Map</code> as more than one hint may be needed.
107 If non-null this can be directly applied to the <code>Graphics2D</code>.
108 <pre><code>
109 Toolkit tk = Toolkit.getDefaultToolkit();
110 Map map = (Map)(tk.getDesktopProperty("awt.font.desktophints"));
111 if (map != null) {
112 graphics2D.addRenderingHints(map);
113 }
114 </code></pre>
115 <h3>Advanced Usage Tips</h3>
116
117 <h4>Listening for changes</h4>
118 <p>
119 An application can listen for changes in the property
120 using a <a href="../../beans/PropertyChangeListener.html">
121 <code>PropertyChangeListener</code></a> :
122 <pre><code>
123 tk.addPropertyChangeListener("awt.font.desktophints", pcl);
124 </code></pre>
125 Listening for changes is recommended as users can, on rare occasions,
126 reconfigure a desktop environment whilst applications are running
127 in a way that may affect the selection of these hints, and furthermore
128 many desktop environments support dynamic reconfiguration of these
129 running applications to conform to the new settings.
130 <p>
131 There is no direct way to discover if dynamic reconfiguration
132 is expected of running applications but the default assumption
133 should be that it is expected, since most modern desktop environments
134 do provide this capability.
135 <h4>Text Measurement</h4>
136 <p>
137 Text always needs to be measured using the same
138 <a href="../font/FontRenderContext.html"> <code>FontRenderContext</code></a>
139 as used for rendering. The text anti-aliasing hint is a component of
140 the <code>FontRenderContext</code>.
141 A <a href="../FontMetrics.html"> <code>FontMetrics</code></a>
142 obtained from the <code>Graphics</code> object on which the hint
143 has been set will measure text appropriately.
144 This is not a unique requirement for clients that specify this hint
145 directly, since the value of the <code>FontRenderContext</code> should
146 never be assumed, so is discussed here principally as a reminder.
147 <h4>Saving and restoring Graphics State</h4>
148 <p>
149 Sometimes an application may need to apply these hints on a shared
150 Graphics only temporarily, restoring the previous values after they
151 have been applied to text rendering operations.
152 The following sample code shows one way to do this.
153 <pre><code>
154 /**
155 * Get rendering hints from a Graphics instance.
156 * "hintsToSave" is a Map of RenderingHint key-values.
157 * For each hint key present in that map, the value of that
158 * hint is obtained from the Graphics and stored as the value
159 * for the key in savedHints.
160 */
161 RenderingHints getRenderingHints(Graphics2D g2d,
162 RenderingHints hintsToSave,
163 RenderingHints savedHints) {
164 if (savedHints == null) {
165 savedHints = new RenderingHints(null);
166 } else {
167 savedHints.clear();
168 }
169 if (hintsToSave.size() == 0) {
170 return savedHints;
171 }
172 /* RenderingHints.keySet() returns Set<Object> */
173 for (Object o : hintsToSave.keySet()) {
174 RenderingHints.Key key = (RenderingHints.Key)o;
175 Object value = g2d.getRenderingHint(key);
176 savedHints.put(key, value);
177 }
178 return savedHints;
179 }
180
181
182 Toolkit tk = Toolkit.getDefaultToolkit();
183 Map map = (Map)(tk.getDesktopProperty("awt.font.desktophints"));
184 Map oldHints;
185 if (map != null) {
186 oldHints = getRenderingHints(graphic2D, map, null);
187 graphics2D.addRenderingHints(map);
188 ..
189 graphics2D.addRenderingHints(oldHints);
190 }
191 </code></pre>
192
193 <h3>Details</h3>
194 <ul>
195 <li>The return value will always be null or a <code>Map</code>
196 <br><br>
197 <li>If the return value is null, then no desktop properties are available,
198 and dynamic updates will not be available. This is a typical behaviour if
199 the JDK does not recognise the desktop environment, or it is one which
200 has no such settings. The <b>Headless</b> toolkit is one such example.
201 Therefore it is important to test against null before using the map.
202 <br><br>
203 <li>If non-null the value will be a <code>Map</code> of
204 <code>RenderingHints</code> such that every key is an instance of
205 <code>RenderingHints.Key</code> and the value is a legal value for that key.
206 <br><br>
207 <li>The map may contain the default value for a hint. This is
208 needed in the event there is a previously a non-default value for the hint
209 set on the <code>Graphics2D</code>. If the map did not contain
210 the default value, then <code>addRenderingHints(Map)</code> would leave
211 the previous hint which may not correspond to the desktop setting.
212 <p>
213 An application can use <code>setRenderingHints(Map)</code> to reinitialise
214 all hints, but this would affect unrelated hints too.
215 <br><br>
216 <li>A multi-screen desktop may support per-screen device settings in which
217 case the returned value is for the default screen of the desktop.
218 An application may want to use the settings for the screen on
219 which they will be applied.
220 The per-screen device hints may be obtained by per-device property names
221 which are constructed as the String concatenation
222 <pre><code>
223 "awt.font.desktophints" + "." + GraphicsDevice.getIDstring();
224 </code></pre>
225 <p>
226 An application can also listen for changes on these properties.
227 <p>
228 However this is an extremely unlikely configuration, so to help
229 ease of development, if only a single, desktop-wide setting is supported,
230 then querying each of these per-device settings will return null.
231 So to determine if there are per-device settings it is sufficient to
232 determine that there is a non-null return for any screen device using
233 the per-device property name.
234 </ul>
235 <h2>Mouse Functionality</h2>
236 <b>Desktop Property: <a id="sun.awt.enableExtraMouseButtons">"sun.awt.enableExtraMouseButtons"</A></b>
237 <p>
238 This property determines if events from extra mouse buttons (if they are exist and are
239 enabled by the underlying operating system) are allowed to be processed and posted into
240 {@code EventQueue}.
241 <br>
242 The value could be changed by passing "sun.awt.enableExtraMouseButtons"
243 property value into java before application starts. This could be done with the following command:
244 <pre>
245 java -Dsun.awt.enableExtraMouseButtons=false Application
246 </pre>
247 Once set on application startup, it is impossible to change this value after.
248 <br>
249 Current value could also be queried using getDesktopProperty("sun.awt.enableExtraMouseButtons")
250 method.
251 <br>
252 If the property is set to {@code true} then
253 <ul>
254 <li> it is still legal to create {@code MouseEvent} objects with
255 standard buttons and, if the mouse has more
256 then three buttons, it is also legal to use buttons from the range started
257 from 0 up to {@link java.awt.MouseInfo#getNumberOfButtons() getNumberOfButtons()}.
258
259 <li> it is legal to use standard button masks when using {@code Robot.mousePress()}
260 and {@code Robot.mouseRelease()} methods and, if the mouse has more then three buttons,
261 it is also legal to use masks for existing extended mouse buttons.
262 That way, if there are more then three buttons on the mouse then it is allowed to
263 use button masks corresponding to the buttons
264 in the range from 1 up to {@link java.awt.MouseInfo#getNumberOfButtons() getNumberOfButtons()}
265 </ul>
266 <br>
267 If the property is set to {@code false} then
268 <ul>
269 <li> it is legal to create {@code MouseEvent} objects with standard buttons
270 only: {@code NOBUTTON}, {@code BUTTON1}, {@code BUTTON2} and
271 {@code BUTTON3}
272 <li> it is legal to use standard button masks only:
273 {@code InputEvent.BUTTON1_DOWN_MASK}, {@code InputEvent.BUTTON2_DOWN_MASK},
274 {@code InputEvent.BUTTON3_DOWN_MASK}
275 </ul>
276
277 This property should be used when there is no need in listening mouse events fired as a result of
278 activity with extra mouse button.
279 By default this property is set to {@code true}.
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