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33
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 align="center" border="0" cellspacing="0" cellpadding="2"
61 summary="Standard AWT Desktop Properties">
62 <tr bgcolor="#ccccff">
63 <th valign="TOP" align="LEFT">Property Name</th>
64 <th valign="TOP" align="LEFT">Value Type</th>
65 <th valign="TOP" align="LEFT">Summary Description</th>
66 </tr>
67 <tr>
68 <td valign="TOP"><A href="#awt.font.desktophints">awt.font.desktophints</A></td>
69 <td valign="TOP"><a href="../../util/Map.html">java.util.Map</a></td>
70 <td valign="TOP">Font smoothing (text antialiasing) settings.</td>
71 </tr>
72 <tr>
73 <td valign="TOP"><A href="#sun.awt.enableExtraMouseButtons">sun.awt.enableExtraMouseButtons</A></td>
74 <td valign="TOP"><a href="../../lang/Boolean.html">java.lang.Boolean</a></td>
75 <td valign="TOP">Controls if mouse events from extra buttons are to be generated or not</td>
76 </tr>
77 </table>
78
79 <h2>Desktop Font Rendering Hints</h2>
80 <b>Desktop Property: <a id="awt.font.desktophints">"awt.font.desktophints"</A></b>
81 <p>
82 Modern desktops support various forms of text antialiasing (font smoothing).
83 <p>
84 These are applied by platform-specific heavyweight components.
85 However an application may want to render text using the same text
86 antialiasing on a drawing surface or lightweight (non-platform) component using
87 <a href="../Graphics2D.html"> <code>Graphics2D</code></a> methods.
88 This is particularly important when creating
89 <a href="../../../javax/swing/JComponent.html"> Swing components</a> which
90 are required to appear consistent with native desktop components or other
91 Swing components.
92
93 <h3>Basic Usage</h3>
94 The standard desktop property named
95 <b>"awt.font.desktophints"</b>
96 can be used to obtain the rendering hints that best match the desktop settings.
97
98 The return value is a
99 <a href="../../util/Map.html"> Map</a> of
100 <a href="../RenderingHints.html"> <code>RenderingHints</code></a> which
101 can be directly applied to a <code>Graphics2D</code>.
102 <p>
103 It is a <code>Map</code> as more than one hint may be needed.
104 If non-null this can be directly applied to the <code>Graphics2D</code>.
105 <pre><code>
106 Toolkit tk = Toolkit.getDefaultToolkit();
107 Map map = (Map)(tk.getDesktopProperty("awt.font.desktophints"));
108 if (map != null) {
109 graphics2D.addRenderingHints(map);
110 }
111 </code></pre>
112 <h3>Advanced Usage Tips</h3>
113
114 <h4>Listening for changes</h4>
115 <p>
116 An application can listen for changes in the property
117 using a <a href="../../beans/PropertyChangeListener.html">
118 <code>PropertyChangeListener</code></a> :
119 <pre><code>
120 tk.addPropertyChangeListener("awt.font.desktophints", pcl);
121 </code></pre>
122 Listening for changes is recommended as users can, on rare occasions,
123 reconfigure a desktop environment whilst applications are running
124 in a way that may affect the selection of these hints, and furthermore
125 many desktop environments support dynamic reconfiguration of these
126 running applications to conform to the new settings.
127 <p>
128 There is no direct way to discover if dynamic reconfiguration
129 is expected of running applications but the default assumption
130 should be that it is expected, since most modern desktop environments
131 do provide this capability.
132 <h4>Text Measurement</h4>
133 <p>
134 Text always needs to be measured using the same
135 <a href="../font/FontRenderContext.html"> <code>FontRenderContext</code></a>
136 as used for rendering. The text anti-aliasing hint is a component of
137 the <code>FontRenderContext</code>.
138 A <a href="../FontMetrics.html"> <code>FontMetrics</code></a>
139 obtained from the <code>Graphics</code> object on which the hint
140 has been set will measure text appropriately.
141 This is not a unique requirement for clients that specify this hint
142 directly, since the value of the <code>FontRenderContext</code> should
143 never be assumed, so is discussed here principally as a reminder.
144 <h4>Saving and restoring Graphics State</h4>
145 <p>
146 Sometimes an application may need to apply these hints on a shared
147 Graphics only temporarily, restoring the previous values after they
148 have been applied to text rendering operations.
149 The following sample code shows one way to do this.
150 <pre><code>
151 /**
152 * Get rendering hints from a Graphics instance.
153 * "hintsToSave" is a Map of RenderingHint key-values.
154 * For each hint key present in that map, the value of that
155 * hint is obtained from the Graphics and stored as the value
156 * for the key in savedHints.
157 */
158 RenderingHints getRenderingHints(Graphics2D g2d,
159 RenderingHints hintsToSave,
160 RenderingHints savedHints) {
161 if (savedHints == null) {
162 savedHints = new RenderingHints(null);
163 } else {
164 savedHints.clear();
165 }
166 if (hintsToSave.size() == 0) {
167 return savedHints;
168 }
169 /* RenderingHints.keySet() returns Set<Object> */
170 for (Object o : hintsToSave.keySet()) {
171 RenderingHints.Key key = (RenderingHints.Key)o;
172 Object value = g2d.getRenderingHint(key);
173 savedHints.put(key, value);
174 }
175 return savedHints;
176 }
177
178
179 Toolkit tk = Toolkit.getDefaultToolkit();
180 Map map = (Map)(tk.getDesktopProperty("awt.font.desktophints"));
181 Map oldHints;
182 if (map != null) {
183 oldHints = getRenderingHints(graphic2D, map, null);
184 graphics2D.addRenderingHints(map);
185 ..
186 graphics2D.addRenderingHints(oldHints);
187 }
188 </code></pre>
189
190 <h3>Details</h3>
191 <ul>
192 <li>The return value will always be null or a <code>Map</code>
193 <br><br>
194 <li>If the return value is null, then no desktop properties are available,
195 and dynamic updates will not be available. This is a typical behaviour if
196 the JDK does not recognise the desktop environment, or it is one which
197 has no such settings. The <b>Headless</b> toolkit is one such example.
198 Therefore it is important to test against null before using the map.
199 <br><br>
200 <li>If non-null the value will be a <code>Map</code> of
201 <code>RenderingHints</code> such that every key is an instance of
202 <code>RenderingHints.Key</code> and the value is a legal value for that key.
203 <br><br>
204 <li>The map may contain the default value for a hint. This is
205 needed in the event there is a previously a non-default value for the hint
206 set on the <code>Graphics2D</code>. If the map did not contain
207 the default value, then <code>addRenderingHints(Map)</code> would leave
208 the previous hint which may not correspond to the desktop setting.
209 <p>
210 An application can use <code>setRenderingHints(Map)</code> to reinitialise
211 all hints, but this would affect unrelated hints too.
212 <br><br>
213 <li>A multi-screen desktop may support per-screen device settings in which
214 case the returned value is for the default screen of the desktop.
215 An application may want to use the settings for the screen on
216 which they will be applied.
217 The per-screen device hints may be obtained by per-device property names
218 which are constructed as the String concatenation
219 <pre><code>
220 "awt.font.desktophints" + "." + GraphicsDevice.getIDstring();
221 </code></pre>
222 <p>
223 An application can also listen for changes on these properties.
224 <p>
225 However this is an extremely unlikely configuration, so to help
226 ease of development, if only a single, desktop-wide setting is supported,
227 then querying each of these per-device settings will return null.
228 So to determine if there are per-device settings it is sufficient to
229 determine that there is a non-null return for any screen device using
230 the per-device property name.
231 </ul>
232 <h2>Mouse Functionality</h2>
233 <b>Desktop Property: <a id="sun.awt.enableExtraMouseButtons">"sun.awt.enableExtraMouseButtons"</A></b>
234 <p>
235 This property determines if events from extra mouse buttons (if they are exist and are
236 enabled by the underlying operating system) are allowed to be processed and posted into
237 {@code EventQueue}.
238 <br>
239 The value could be changed by passing "sun.awt.enableExtraMouseButtons"
240 property value into java before application starts. This could be done with the following command:
241 <pre>
242 java -Dsun.awt.enableExtraMouseButtons=false Application
243 </pre>
244 Once set on application startup, it is impossible to change this value after.
245 <br>
246 Current value could also be queried using getDesktopProperty("sun.awt.enableExtraMouseButtons")
247 method.
248 <br>
249 If the property is set to {@code true} then
250 <ul>
251 <li> it is still legal to create {@code MouseEvent} objects with
252 standard buttons and, if the mouse has more
253 then three buttons, it is also legal to use buttons from the range started
254 from 0 up to {@link java.awt.MouseInfo#getNumberOfButtons() getNumberOfButtons()}.
255
256 <li> it is legal to use standard button masks when using {@code Robot.mousePress()}
257 and {@code Robot.mouseRelease()} methods and, if the mouse has more then three buttons,
258 it is also legal to use masks for existing extended mouse buttons.
259 That way, if there are more then three buttons on the mouse then it is allowed to
260 use button masks corresponding to the buttons
261 in the range from 1 up to {@link java.awt.MouseInfo#getNumberOfButtons() getNumberOfButtons()}
262 </ul>
263 <br>
264 If the property is set to {@code false} then
265 <ul>
266 <li> it is legal to create {@code MouseEvent} objects with standard buttons
267 only: {@code NOBUTTON}, {@code BUTTON1}, {@code BUTTON2} and
268 {@code BUTTON3}
269 <li> it is legal to use standard button masks only:
270 {@code InputEvent.BUTTON1_DOWN_MASK}, {@code InputEvent.BUTTON2_DOWN_MASK},
271 {@code InputEvent.BUTTON3_DOWN_MASK}
272 </ul>
273
274 This property should be used when there is no need in listening mouse events fired as a result of
275 activity with extra mouse button.
276 By default this property is set to {@code true}.
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