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<td valign="top" style="padding: 10px"><h1 style="padding: 0; margin: 0; border-bottom: 1px solid #000000;">The SWT FAQ</h1>
<p>If you have questions you believe should go in here, please let us know on
the <a href="http://dev.eclipse.org/mailman/listinfo/platform-swt-dev">SWT developer mailing list</a>.</p>
<ul>
<li><a href="#whatpackagesinSWT">What packages make up SWT?</a></li>
<li><a href="#supportJavaBeans">Does SWT support JavaBeans?</a></li>
<li><a href="#guibuilder">Is there a GUI Builder for SWT?</a></li>
<li><a href="#whatisasnippet">What is a snippet and why do I care?</a></li>
<p></p>
<li><a href="#howbuildjar">How do I build an SWT jar for my platform?</a></li>
<li><a href="#howbuilddll">How do I build the SWT JNI libraries for my platform?</a></li>
<li><a href="#buildeclipseexe">How do I build the Eclipse executable for my platform?</a></li>
<li><a href="#gtk64">How do I build the 64 bit version of SWT GTK?</a></li>
<p></p>
<li><a href="#gtkstartup">What do I need to run SWT on Linux/GTK?</a></li>
<li><a href="#carbonapp">On carbon, how do I run an SWT application from the command line?</a></li>
<li><a href="launcher.html">What are the arguments for the Eclipse Launcher?</a></li>
<li><a href="#javawebstart">How can I package my standalone SWT app for Java Web Start?</a></li>
<li><a href="#pocketpcstart">What do I need to do to run SWT on the PocketPC?</a></li>
<li><a href="#pocketpclibrary">Where is the SWT library for the PocketPC?</a></li>
<p></p>
<li><a href="#xpthemes">How do I make SWT use the Windows XP themes?</a></li>
<li><a href="#gtkfontsandcolors">On gtk, how do I change the default fonts and colors of widgets?</a></li>
<li><a href="#motiffontsandcolors">On motif, how do I change the default fonts and colors of widgets?</a></li>
<p></p>
<li><a href="#missingjar">Why do I get the error "java.lang.NoClassDefFoundError: org/eclipse/swt/internal/XXX/OS."?</a></li>
<li><a href="#missingdll">Why do I get the error "java.lang.UnsatisfiedLinkError: no swt-win32-3232 in java.library.path."?</a></li>
<li><a href="#konquerorUnzip">Why do I get an error beginning with "...SWTException: Unsupported or unrecognized format" on startup?</a></li>
<li><a href="#useUnzip">Why do I get the error "error while loading shared libraries: ./libXm.so.2: file too short" on startup?</a></li>
<li><a href="#missinglibXm">Why do I get the error "java.lang.UnsatisfiedLinkError: libXm.so.2: cannot open shared object file: No such file or directory."?</a></li>
<li><a href="#usingLesstif">Why do I get the warning "XmParseMappingCreate() is not implemented yet" on Linux/Motif?</a></li>
<p></p>
<li><a href="#swinginswt">Can I use Swing or AWT inside Eclipse?</a></li>
<li><a href="#subclassing">Why can't I subclass SWT widgets like Button and Table?</a></li>
<li><a href="#noeventfire">Why are some events like Selection not fired in response to programmatic widget changes?</a></li>
<li><a href="#printstacktrace">Why don't SWTError and SWTException override all printStackTrace methods?</a></li>
<li><a href="#whatisbrowser">What is the SWT Browser widget?</a></li>
<li><a href="#browserplatforms">Which platforms support the SWT Browser?</a></li>
<li><a href="#browserlinux">What do I need to run the SWT Browser inside Eclipse on Linux/GTK or Linux/Motif?</a></li>
<li><a href="#browserlinuxrcp">What do I need to run the SWT Browser in a standalone application on Linux/GTK or Linux/Motif?</a></li>
<li><a href="#browserlinuxibm">How can I get the SWT Browser to work with the IBM 1.4 VM?</a></li>
<li><a href="#browserplugins">Why can't I run Java applets in the SWT Browser?</a></li>
<li><a href="#printOnX">How do I print using my favorite Unix print program?</a></li>
<li><a href="#noprintimage">How do I print a snapshot of a widget?</a></li>
<li><a href="#smallprint">Why does everything I print seem so small?</a></li>
<li><a href="#printertrim">What does computeTrim mean for a Printer?</a></li>
<li><a href="#autotest">How can I implement user interaction test cases?</a></li>
<li><a href="#gtkselectiongone">On gtk, why does my widget's selection disappear when it loses focus?</a></li>
<p></p>
<li><a href="#swtawtosx">Why does the SWT_AWT bridge not work for me on OS X?</a></li>
<li><a href="#printOnGTK">Why is the Print menu item disabled in Eclipse on GTK (Linux, UNIX)?</a></li>
<li><a href="#printOnMotif">Why is the Print menu item disabled in Eclipse on Motif?</a></li>
<li><a href="#uithread">Why do I get the error "org.eclipse.swt.SWTException: Invalid thread access"?</a></li>
<li><a href="#noautolayout">Why do I have to resize my shell to get my changed widgets to lay out again?</a></li>
<li><a href="#nographicslibrary">Why do I get "SWTException: Unable to load graphics library" using GC?</a></li>
<li><a href="#scrollonlinux">Why doesn't mouse scrolling work on Linux/Motif?</a></li>
</ul>
<p></p>
<hr>
<p></p>
<dl>
<dt><strong><a name="whatpackagesinSWT"> Q: What packages make up SWT?</a></strong></dt>
<dd>A: Package names in SWT begin with the prefix <strong>org.eclipse.swt</strong>.<br>
<p>Here is the complete list:</p>
<ul>
<li>org.eclipse.swt
<li>org.eclipse.swt.accessibility
<li>org.eclipse.swt.awt
<li>org.eclipse.swt.browser
<li>org.eclipse.swt.custom
<li>org.eclipse.swt.dnd
<li>org.eclipse.swt.events
<li>org.eclipse.swt.graphics
<li>org.eclipse.swt.internal.* (Not API, do not reference classes in these packages)
<li>org.eclipse.swt.layout
<li>org.eclipse.swt.opengl
<li>org.eclipse.swt.ole.win32 (Windows only)
<li>org.eclipse.swt.printing
<li>org.eclipse.swt.program
<li>org.eclipse.swt.widgets
</ul>
<p>Classes that are not in these packages do not belong to SWT.</p>
</dd>
<dt><strong><a name="supportJavaBeans">Q: Does SWT support JavaBeans?</a></strong></dt>
<dd>A: To the extent that it makes sense, given the constraints of operating system
compatibility, SWT mirrors the beans behavior. An example of this is the use
of standard beans mechanisms for event dispatch (EventListener, EventObject and adapter
classes). Some aspects of the beans paradigm, such as the ability to create beans with
null constructors, run counter to the constraints of the underlying operating systems
that SWT runs on. For example, operating systems do not typically support creating a
widget without specifying its parent.
<p></p>
The essence of the problem is that if you allow a widget to be created with a null
constructor, then you can't actually create the o/s resources at the time the constructor
runs (you would have to wait until later, after the parent has been set). We can not
do this, since we <em>always</em> create the o/s resources in the constructor, and for
performance/efficiency/consistency reasons do not keep slots in the object to hold
whatever state would be required if the object were to be created later.
</dd>
<dt><strong><a name="guibuilder">Q: Is there a GUI Builder for SWT?</a></strong></dt>
<dd>A: SWT itself does not provide a GUI Builder (also known as "GUI Designer", "GUI Editor",
"Visual Builder", "Visual Designer", "Visual Editor", or "Visual Composition Editor").
There are, however, several mature 'third-party' products listed at
<a href="http://www.eclipseplugincentral.com/">http://www.eclipseplugincentral.com/</a>.
Or you can follow the progress on the <a href="http://www.eclipse.org/vep/">Eclipse Visual Editor Project</a>.
</dd>
<dt><strong><a name="whatisasnippet">Q: What is a snippet and why do I care?</a></strong>
</dt>
<dd>A: A snippet is a <em>minimal stand alone</em> program that demonstrates functionality or
lack of functionality.
<p>Why is this important? Posting a snippet to the news group is the
quickest way to get help. Including a snippet in a bug report is the fastest
way to get a bug fixed. Taking the time to construct a snippet helps you understand
the API of the library you are calling and focuses your thinking. For example, the
SWT team uses C and Java snippets internally to prove or disprove problems in the operating system.
Often, something you think is a bug is actually caused by something elsewhere
in your program.
<p>Snippets isolate problems. Code speaks louder than words.
<p>Here is a minimal stand alone SWT program to help you get started:
<pre>public static void main (String [] args) {
Display display = new Display ();
Shell shell = new Shell (display);
shell.open ();
while (!shell.isDisposed ()) {
if (!display.readAndDispatch ()) display.sleep ();
}
display.dispose ();
}</pre>
For a list of sample snippets, see the <a href="snippets">SWT snippets page</a>.
</dd>
<dt><strong><a name="howbuildjar">Q: How do I build an SWT jar for my platform?</a></strong>
</dt>
<dd>A: The SWT jar can be built from the eclipse CVS repository using an Ant task:
<ol>
<li>Connect a CVS client (such as eclipse) to <strong>:pserver:anonymous@dev.eclipse.org:/home/eclipse</strong>.
<li>Check out the projects <strong>org.eclipse.swt</strong> and <strong>org.eclipse.swt.</strong><em>WS.OS.ARCH</em> where <em>WS.OS.ARCH</em> are the names of the
windowing system, operating system and architecture of interest, respectively. For example, <strong>org.eclipse.swt.gtk.linux.x86</strong>.
<li>In the project <strong>org.eclipse.swt.</strong><em>WS.OS.ARCH</em>, locate the file <strong>build.xml</strong>. This is an Ant script.
<li>Run Ant on the target <strong>build.jars</strong>. If you are using eclipse as your development environment, you can run
Ant by selecting the file in the <strong>Navigator</strong> or <strong>Packages</strong> view, then selecting <strong>Run Ant...</strong> from the context
menu.
<li>This will create a file called <strong>swt.jar</strong> in the root of the
<strong>org.eclipse.swt.</strong><em>WS.OS.ARCH</em> project.
</ol>
</dd>
<dt><strong><a name="howbuilddll">Q: How do I build the SWT JNI libraries for my platform?</a></strong>
</dt>
<dd>A: SWT uses JNI to interact with the native widgets in the
operating system. The SWT JNI libraries must be compiled for the
windowing system, operating system and hardware architecture of
interest. The libraries can be built either from the code in the CVS
repository or from an eclipse SDK download.
<p>In order to build the required libraries and run Eclipse, you
will require a JDK (Java Development Kit) version that is supported
by Eclipse. Check eclipse.org for details.</p>
<p><strong>Building the SWT JNI libraries from the eclipse SDK download:</strong>
<ol>
<li>Download an Eclipse distribution from
<a href="http://www.eclipse.org/downloads/index.php">http://www.eclipse.org/downloads/index.php</a>.</li>
<li>Unzip the distribution. This will create a directory called <tt>eclipse</tt>.
This directory is subsequently referred to as <em>&lt;eclipseRoot&gt;</em>.
<li>In the directory <tt><em>&lt;eclipseRoot&gt;</em>/plugins/org.eclipse.rcp.source.platform_X.X.X</tt>,
find the source zip in the SWT subdirectory.
<li>Unzip contained file <tt>src.zip</tt>.
<li>Edit the file <strong>build.sh</strong> (or <strong>build.bat</strong> on Windows)
in the current directory. Set the environment variables defined in that file to
match the location of your JRE, etc. Save the file and close it.
<li>Run the <tt>build</tt> command (<strong>sh build.sh</strong> for UNIX and Linux
platforms, <strong>build.bat</strong> for Windows). This will create the appropriate
library file(s) in the current directory. For example, this will create
<tt>swt-XXXX.dll</tt> files on windows, or <tt>libswt-XXXX.so</tt> files on Linux
and Solaris.
</ol>
<p>This description was originally contributed by Colin R Devilbiss.</p>
<p><strong>Building the SWT JNI libraries from the eclipse CVS repository:</strong><br>
<strong>NOTE</strong>: These instructions require you to use Eclipse
<ol>
<li>Follow <a href="cvs.php">these instructions</a> to checkout SWT from CVS.
<li>Compile the project. This will create a folder called bin under the org.eclipse.swt project.
<li>Change directory into <tt>org.eclipse.swt/bin/library</tt>
<li>Edit the file <strong>build.sh</strong> (or <strong>build.bat</strong> on Windows)
in the current directory. Set the environment variables defined in that file to
match the location of your JRE, etc. Save the file and close it.
<li>Run the <tt>build</tt> command (<strong>sh build.sh</strong> for UNIX and Linux
platforms, <strong>build.bat</strong> for Windows). This will create the appropriate
library file(s) in the current directory. For example, this will create
<tt>swt-XXXX.dll</tt> files on windows, or <tt>libswt-XXXX.so</tt> files on Linux
and Solaris.
</ol>
</dd>
<dt><strong><a name="buildeclipseexe">Q: How do I build the Eclipse executable for my platform?</a></strong>
</dt>
<dd>A: Eclipse is launched by a binary executable which puts up a splash screen and launches a Java VM.
The executable must be compiled for the windowing system, operating system and hardware architecture of interest.
The libraries can be built either from the code in the CVS repository or from an eclipse SDK download.
<p><strong>Building the Eclipse executable from the eclipse SDK download:</strong>
<ol>
<li>In order to build the required libraries and run Eclipse,
you will require a JDK (Java Development Kit) of version 1.4.2 or later.
Download an Eclipse distribution from
<a href="http://www.eclipse.org/downloads/index.php">http://www.eclipse.org/downloads/index.php</a>.</li>
<li>Unzip the distribution. This will create a directory called <tt>eclipse</tt>.
This directory is subsequently referred to as <em>&lt;eclipseRoot&gt;</em>.
<li>In the directory <tt><em>&lt;eclipseRoot&gt;</em>/plugins/org.eclipse.platform.source_X.X.X</tt>,
find the <tt>launchersrc.zip</tt> file under <tt>org.eclipse.platform_X.X.X</tt>.
<li>Unzip the file <tt>launchersrc.zip</tt>. This will create a directory called <tt>library</tt>.
<li>Change directory into <tt>library/<em>WS</em></tt>, where <em>WS</em> is the name of the windowing system
e.g. win32, motif, gtk, photon, or carbon.
Modify any incorrect <tt>_HOME</tt> variables defined at the top of the appropriate <tt>.mak</tt> file.
<li>Run the <tt>build</tt> command (<strong>sh build.sh</strong> for UNIX and Linux, <strong>build.bat</strong> for Windows).
This will create an executable launcher called <tt>eclipse</tt>.
Move this <tt>eclipse</tt> executable to <em>&lt;eclipseRoot&gt;</em>.
</ol>
<p>This description was originally contributed by Colin R Devilbiss.</p>
</dd>
<dt><strong><a name="gtk64">Q: How do I build the 64 bit version of SWT GTK?</a></strong></dt>
<dd>Follow these steps to extract the 64 bit SWT GTK source code and produce your own build.
<ol>
<li>Start Eclipse and download the following projects from dev.eclipse.org: org.eclipse.swt, org.eclipse.swt.gtk.linux.x86_64, org.eclipse.swt.tools</li>
<li>Open the file build.xml located into the org.eclipse.swt.gtk.linux.x86_64 fragment. Run Ant to execute the ant task build.nativeLibraries defined in build.xml.</li>
<li>Refresh the project org.eclipse.swt.gtk.linux.x86_64</li>
</ol>
The project org.eclipse.swt.gtk.linux.x86_64 now contains the 64 bit native libraries. The 64 bit java and C source code
has been copied under the org.eclipse.swt.gtk.linux.x86_64/src folder.
</dd>
<dt><strong><a name="gtkstartup">Q: What do I need to run SWT on Linux/GTK?</a></strong></dt>
<dd>A: SWT requires the following libraries with the specified versions or later:
<p>For Eclipse 3.0:</p>
<ul>
<li>GTK 2.2.1</li>
<li>ATK 1.2.0</li>
<li>glib 2.2.1</li>
<li>Pango 1.2.1</li>
<li>Freetype 2.1.3</li>
</ul>
<p>For Eclipse 2.1:</p>
<ul>
<li>GTK 2.0.6</li>
<li>ATK 1.0.1</li>
<li>glib 2.0.4</li>
<li>Pango 1.0.3</li>
<li>Freetype 2.1.2</li>
</ul>
</dd>
<dt><strong><a name="carbonapp">Q: On carbon, how do I run an SWT application from the command line?</a></strong></dt>
<dd>A: If you run a Java application that uses Carbon via JNI, the application is not registered with the OS as
a 'normal' UI application. As a consequence, it has no entry in the dock and it cannot be activated. AWT
(or Swing) based applications don't have this problem because they seem to use undocumented SPI to register
themselves.
<p>To work around this problem you'll have to pass the -XstartOnFirstThread option to the
java executable as follow:</p>
<pre>
java -XstartOnFirstThread -cp swt.jar:. ControlExample
</pre>
<p>If you want to run a bundled application, take a look at this
<a href="http://www.eclipse.org/swt/macosx/">article</a>.</p>
</dd>
<dt><strong><a name="javawebstart">Q: How can I package my standalone SWT app for Java Web Start?</a></strong></dt>
<dd>A: Follow the steps below to deploy your SWT app with Java Web
Start. You can also follow the article from Jeff Gunther on how to
<a href="http://www-106.ibm.com/developerworks/opensource/library/os-jws/">Deploy
an SWT application using Java Web Start</a>.
<p>NOTE: As of 2.1, SWT Java Web Start apps can only be deployed
on Windows and GTK. <p>Example: Package the SWT ControlExample
application.</p>
<ol>
<li>Create the file "<a href="swtexamples.jnlp.txt">swtexamples.jnlp</a>".
In the file, replace the value of the codebase attribute with your own URI.
<li>Create the file "<a href="swt.jnlp.txt">swt.jnlp</a>"
In the file, replace the value of the codebase attribute with your own URI.
<li>Create the following folders and files:
<ul>
<li>root (e.g. d:/jws or the URL of your website)
<ul>
<li>apps/swtexamples/swtexamples.jar contains the SWT ControlExample
<li>apps/swtexamples/swtexamples.jnlp (Java Web Start extension file)
<li>swt/swt.jnlp (Java Web Start extension file)
<li>swt/os/linux/x86/swtNativeLib.jar contains the GTK linux native libraries: libswt-gtk-xxxx.so, libswt-pi-gtk-xxxx.so, libswt-gnome-gtk-xxxx.so
<li>swt/os/win32/x86/swtNativeLib.jar contains the Win32 native library: swt-win32-xxxx.dll
<li>swt/ws/linux/swt.jar contains the SWT Linux GTK jar library
<li>swt/ws/linux/swt-pi.jar contains the SWT Linux GTK jar library
<li>swt/ws/win32/swt.jar contains the SWT Win32 jar library
</ul>
</ul>
<br>- The swtexamples.jar can be found in the Example Plug-ins section of the Eclipse download page.
<br>- The SWT jars and native libraries can also be downloaded from the Eclipse download page.
<br>- You need to create the swtNativeLib.jar files described previously. Create empty jars with the name 'swtNativeLib.jar'. Add the native SWT library into the swtNativeLib.jar file you just created. As indicated previously, insert the SWT Win32 native library (swt-win32-xxxx.dll) into the swt/os/win32/x86/swtNativeLib.jar file. Insert the SWT GTK linux native libraries in the swt/os/linux/x86/swtNativeLib.jar.
<li>Sign the jar files
<br>Each jar file must be signed with your own key certificate.
<li>Create a web page linking to the extension file root/apps/swtexamples/swtexamples.jnlp
</ol>
<p>This description was originally contributed by &Oslash;yvind Harboe.</p>
</dd>
<dt><strong><a name="pocketpcstart">Q: What do I need to do to run SWT on the PocketPC?</a></strong>
</dt>
<dd>A: There is an experimental version of SWT for WinCE devices. If you wish to
give it a try, the following steps may help you with getting started.
<ol>
<li>Install a VM on your PocketPC.
<br>The port is tested using the J9 VM for ARM WinCE PocketPC.
<ul>
<li>For information on how to get the J9 VM, see at the WebSphere Studio Device Developer website (which ships J9):
<br><a href="http://www.embedded.oti.com/wdd">http://www.embedded.oti.com/wdd</a>
<li>For questions on how to use the J9 VM, see the WebSphere newsgroup:
<br><a href="news://news.software.ibm.com/ibm.software.websphere.studio.device-developer">ibm.software.websphere.studio.device-developer</a>
</ul>
<li>Get the swt.jar and SWT dll for PocketPC. See <a href="#pocketpclibrary">Where is the SWT library for the PocketPC?</a>
<li>Copy the swt.jar and SWT dll to your device.
<li>Copy your SWT app to your device.
<br>For example, compile the following class inside Eclipse and copy the resulting
class file to your device.
<pre>
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
public class HelloWorld {
public static void main(String[] args) {
Display display = new Display();
/*
* Create a Shell with the default style
* i.e. full screen, no decoration on PocketPC.
* Alternative: 'new Shell(display, SWT.CLOSE)'
* to get the Pocket PC 'Ok' button.
*/
Shell shell = new Shell(display);
/*
* Set a text so that the top level Shell
* also appears in the Pocket PC task list
*/
shell.setText("HelloWorld");
/*
* Set a menubar to follow UI guidelines
* on Pocket PC
*/
Menu mb = new Menu(shell, SWT.BAR);
shell.setMenuBar(mb);
/*
* Add widgets
*/
FillLayout layout = new FillLayout();
layout.type = SWT.VERTICAL;
shell.setLayout(layout);
Label label = new Label(shell, SWT.CENTER);
label.setText("Hello World");
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch())
display.sleep();
}
}
}
</pre>
<li>Run your SWT application.
<br>One way to start your application is to create a shortcut file.
<ol>
<li>On your desktop, create a file 'HelloWorld.lnk'. Insert the following line.
<pre>68#\j9\bin\j9.exe -Djava.home=\j9
-cp:\java\swt.jar;\java HelloWorld</pre>
This is assuming that you have installed the J9 VM in the folder \j9, and that
you have copied the swt.jar and your application HelloWorld.class into the folder \java.
It also assumes that the SWT dll was copied into the folder \j9\bin where it will be
found by the VM.
<li>Save the shortcut file. Copy the file to your device.
<li>Using the file explorer on your device, click on the shortcut file.
<br>If everything is correctly setup, the SWT app should come up.
</ol>
</ol>
</dd>
<dt><strong><a name="pocketpclibrary">Q: Where is the SWT library for the PocketPC?</a></strong></dt>
<dd>A: There is an experimental version of SWT for WinCE devices. The swt.jar and ARM Pocket PC
dll are available from the Eclipse download page.
<p>Choose which swt.jar fits your project requirements. You can also build a custom
version. A custom version allows you, for example, to exclude image decoders or layouts, to
further reduce the size.</p>
<ol>
<li>win32-ce-arm-ppc.zip
<ul>
<li>J2SE profile</li>
<li>Emulated Drag and Drop (no OLE support)</li>
<li>Native widgets only (no custom widgets)</li>
<li>No class file debug information (for reduced size)</li>
</ul>
<br>
<li>win32-ce-arm-ppc-j2me.zip
<ul>
<li>J2ME profile (CLDC)</li>
<li>Emulated Drag and Drop (no OLE support)</li>
<li>Native widgets only (no custom widgets)</li>
<li>No class file debug information (for reduced size)</li>
</ul>
<br>
<li>Custom SWT library
<ol>
<li>From Eclipse, check out the projects org.eclipse.swt and org.eclipse.swt.win32.wce_ppc.arm
from the head stream. These projects reside in the Eclipse repository
<li>Build the swt.jar
<br>Open the file org.eclipse.swt.win32.wce_ppc.arm/build_custom.xml
<br>The file contains indications on how to build the swt.jar as recommended for WinCE PocketPC.
<li>Get the corresponding dll
<br>The latest dll is available under org.eclipse.swt.win32.wce_ppc.arm
</ol>
</ol>
</dd>
<dt><strong><a name="xpthemes">Q: How do I make SWT use the Windows XP themes?</a></strong></dt>
<dd> A: In order for an application to use Windows XP themes, there must be a manifest file
located in the same place as the executable that launches the application.
Here is a <a href="javaw.exe.manifest">sample manifest file</a> to download.
<p>The name of the manifest file must match the name of the executable.
In the case of eclipse, the executable is <tt>javaw.exe</tt> and the manifest file
must have the name <tt>javaw.exe.manifest</tt>. The manifest file must be in the
<tt>jre\bin</tt> folder for the VM you use to launch Eclipse. Note: the
<tt>eclipse.exe</tt> executable does not launch Eclipse; <tt>eclipse.exe</tt>
displays a splash screen and then invokes the Java VM.</p>
<p>Note: As of SWT 3.2, the manifest file is no longer needed.</p>
</dd>
<dt><strong><a name="gtkfontsandcolors">Q: On GTK, how do I change the default fonts and colors of widgets?</a></strong></dt>
<dd>A: GTK uses a file called <tt>.gtkrc</tt> which is located in your home directory.
On some versions of Linux, this file is called <tt>.gtkrc-2.0</tt>.
Here is an example of the content of that file which sets the font and colors for Eclipse:
<pre>
style "eclipse" {
font_name = "Sans 12"
bg[NORMAL] = "#d6d3ce"
bg[ACTIVE] = "#c7c2bc"
bg[INSENSITIVE] = "#828282"
bg[PRELIGHT] = "#3a6ea5"
fg[NORMAL] = "#000000"
fg[ACTIVE] = "#000000"
fg[INSENSITIVE] = "#d4d0c8"
fg[PRELIGHT] = "#ffffff"
}
class "GtkWidget" style "eclipse"
</pre>
<p>To turn off anti-aliasing of fonts you should use the facilities
available in your desktop if possible, such as the Gnome Font
Properties dialog. An alternate approach is to ensure that your
~/fonts.conf or system-wide fonts.conf file contains the following:</p>
<pre>
&lt;match target="font"&gt;
&lt;edit name="antialias" mode="assign"&gt;&lt;bool&gt;false&lt;/bool&gt;&lt;/edit&gt;
&lt;edit name="hinting" mode="assign"&gt;&lt;bool&gt;true&lt;/bool&gt;&lt;/edit&gt;
&lt;edit name="autohint" mode="assign"&gt;&lt;bool&gt;false&lt;/bool&gt;&lt;/edit&gt;
&lt;/match&gt;
</pre>
</dd>
<dt><strong><a name="motiffontsandcolors">Q: On motif, how do I change the default fonts and colors of widgets?</a></strong></dt>
<dd>A: Motif uses a file called <tt>.Xdefaults</tt> which is located in your home directory.
Here is an example of the content of that file which sets the font and colors for Eclipse:
<pre>Eclipse*spacing:0
Eclipse*XmForm.background:#e8e7e3
Eclipse*XmList.background:#e8e7e3
Eclipse*XmTextField.background:#e8e7e3
Eclipse*background:#d6d3ce
Eclipse*fontList:-misc-fixed-medium-r-normal-*-10-100-75-75-c-60-iso8859-1
</pre>
After creating/modifying this file, you must run "xrdb ~/.Xdefaults" or restart X to make the changes take effect.
</dd>
<dt><strong><a name="missingjar">Q: Why do I get the error "java.lang.NoClassDefFoundError: org/eclipse/swt/internal/XXX/OS."?</a></strong></dt>
<dd>A: On some platforms such as GTK, SWT is broken into multiple jars. Therefore,
you must ensure that all required jars are on the classpath. The required jars are:
<ul>
<li>swt.jar (all platforms)</li>
<li>swt-pi.jar (some platforms like GTK and Carbon)</li>
<li>swt-mozilla.jar (for Browser widget on GTK and Motif)</li>
<li>swt-gtk.jar (on Linux Motif)</li>
</ul>
</dd>
<dt><strong><a name="missingdll">Q: Why do I get the error "java.lang.UnsatisfiedLinkError: no swt-win32-3232 in java.library.path."?</a></strong></dt>
<dd>A: You need to place the SWT JNI libraries that allow Java to use
the native widgets in a place where the Java Virtual Machine
will find them.
<p>The SWT JNI libraries are included in the SWT download.
<p>A Java application can be informed of the location of the libraries in several ways:
<p></p>
<ol>
<li>Set the library path in the VM launch arguments.
<p>In the Launch Configuration Dialog of eclipse select the Arguments
page, and in the VM arguments field enter:
<tt>-Djava.library.path={runtime-library-path}</tt>
Where the runtime-library-path is the absolute path to the directory containing
the native code library (see above).
<p>This solution means that the SWT libraries have to be manually
added to every project that uses SWT.</p><p></p>
<li>Set the library location in an environment variable.
<p>For Windows this is done by editing the PATH environment variable to
include the above mentioned runtime-library-path.
<br>in Win 9X this is done by editing the Autoexec.bat file,
<br>on NT or 2K the variable is edited through <strong>My Computer</strong> &gt; <strong>Properties</strong> &gt; <strong>Advanced</strong> &gt; <strong>Environment Variables</strong>.
<p>On linux/unix, modify the LD_LIBRARY_PATH environment variable to include the runtime-library-path.
<p></p>
<li>Copy the SWT library to a directory that is already on the Java library path. For example, the jre/bin directory.
<p>The disadvantage of this solution is that every time you upgrade eclipse you have to remember to copy the native code library.</p>
</ol>
<p>Starting with Eclipse 3.1, the SWT plugin that comes with Eclipse, includes the JNI libraries in the SWT jar.
This was done to support OSGi and Eclipse RCP. If you are using the plugin you must extract the libraries
to include them in the path.</p>
</dd>
<dt><strong><a name="konquerorUnzip">Q: Why do I get an error beginning with "...SWTException: Unsupported or unrecognized format" on startup?</a></strong></dt>
<dd>A: There is a bug in the Konqueror decompressor which causes Eclipse to be improperly extracted
if used. To avoid this the Eclipse archive should first be downloaded to your machine and
then extracted using unzip at the command line.
</dd>
<dt><strong><a name="useUnzip">Q: Why do I get the error "error while loading shared libraries: ./libXm.so.2: file too short" on startup?</a></strong>
</dt>
<dd>A: You must use unzip, not jar, to extract your eclipse download. Jar does not extract the libXm.so.2 link file properly.
</dd>
<dt><strong><a name="missinglibXm">Q: Why do I get the error "java.lang.UnsatisfiedLinkError: libXm.so.2: cannot open shared object file: No such file or directory."?</a></strong></dt>
<dd>A: On motif, the SWT library links against the open motif library libXm.so.2. On most platforms, the open motif library is installed
and added to the library path by default. However, on some Linux platforms, either open motif is not installed or is not on the default library
path, or lesstif is installed. Eclipse (and the standalone version of SWT) includes the libXm.so.2 library in the root of the Eclipse install.
<p>You need to either launch Eclipse from the installed directory or modify the LD_LIBRARY_PATH environment variable to
include the location of libXm.so.2. </p>
<p>Note <code>-Djava.library.path</code> is used by the VM to locate libraries for System.loadLibrary calls. However, it does
not update the LD_LIBRARY_PATH and therefore does not help libraries locate other libraries.</p>
</dd>
<dt><strong><a name="usingLesstif">Q: Why do I get the warning "XmParseMappingCreate() is not implemented yet" on Linux/Motif?</a></strong></dt>
<dd>A: This warning is shown if you're accessing installed LessTif libraries instead of the
shipped OpenMotif libraries. If you see this warning, add the eclipse install directory
to your LD_LIBRARY_PATH before launching eclipse. For example, if you are using csh: <br>
<pre>setenv LD_LIBRARY_PATH /opt/eclipse:${LD_LIBRARY_PATH}</pre>
</dd>
<dt><strong><a name="swinginswt">Q: Can I use Swing or AWT inside Eclipse?</a></strong></dt>
<dd>A: Yes. As of Eclipse 3.2, Swing and AWT can be embedded in SWT on Windows, Motif, GTK and OS X.
However it is important to note that a supporting JDK is required on some platforms in order for this
to work. Specifically, Motif and GTK require that JDK 1.5 or newer be used, and OS X requires that
the JDK specified in <a href="#swtawtosx">Why does the SWT_AWT bridge not work for me on OS X?</a> be used.
<p>See this <a href="http://dev.eclipse.org/viewcvs/index.cgi/%7Echeckout%7E/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet135.java">snippet</a> for an example of how to use the API.
</dd>
<dt><strong><a name="subclassing">Q: Why can't I subclass SWT widgets like Button and Table?</a></strong></dt>
<dd>A: You can but it is not recommended. The article <a href="http://eclipse.org/articles/Article-Writing%20Your%20Own%20Widget/Writing%20Your%20Own%20Widget.htm">Creating Your Own Widget using SWT</a> describes the reasons in detail:
<h3>Subclassing Widgets Directly</h3>
<p>In extreme circumstances, you may need to subclass a widget other than
<i>Canvas</i> or <i>Composite</i>. We recommend against doing this unless all
other avenues have been explored and exhausted. Try to wrap the widget first,
before subclassing it. Here is why:</p>
<ul>
<li>Subclasses may inherit a lot of API that makes no sense, and must be
overridden. In Java, you cannot override a method and change the return
type; therefore you cannot reimplement some methods.</li>
<li>Subclassing is typically not the safest way to extend a class that
you do not own. For a simplified list of the common arguments, see the
article by <strong>Bill Venners</strong> in the Nov '98 issue of <i>Java
World</i> called <i>"Inheritance versus composition: Which one should
you choose?"</i> at: <a href="http://www.javaworld.com/javaworld/jw-11-1998/jw-11-techniques.html">
http://www.javaworld.com/javaworld/jw-11-1998/jw-11-techniques.html</a></li>
<li>Widget subclasses are almost certainly guaranteed to be
platform-specific unless great care is taken to ensure that they work on
all platforms.</li>
<li>Subclassed widgets can be affected by changes in the non-API
implementation of the superclass.</li>
<li>Subclassing may cause bad system-level bugs, and runs the risk of
leaking resources. For example, if a subclass reimplements a method
without making certain that dispose code from the superclass method is
still called, then the new method will leak system resources.</li>
<li>Binary incompatibility across releases becomes possible. If a method
signature or field name changes, or new methods or fields are added,
there may be a name conflict in the widget subclass. Only <i>Canvas</i>
and <i>Composite</i> are guaranteed not to have name conflicts in future
releases.</li>
<li>See any paper by Leonid Mikhajlov on the <i>"Fragile Base Class
Problem"</i>. You can find his paper "A Study of The Fragile Base Class
Problem" at: <a href="http://www.cas.mcmaster.ca/~emil/publications/fragile/">http://www.cas.mcmaster.ca/~emil/publications/fragile/</a></li>
</ul>
<p>Subclassing <i>Canvas</i> or <i>Composite</i> is the best way to
ensure that your widget works on all SWT platforms. The 'is-a' test in
this case tests whether your widget is-a basic or compound widget.
Subclassing anything else requires asking if the new widget <b>is an SWT
native widget of the type being subclassed</b>. For example, a 100% Java
portable <i>PictureLabel</i> is not an SWT native <i>Label</i>.</p>
<p>When subclassing anything other than <i>Composite</i> or
<i>Canvas</i> you must override the method <b>protected void
checkSubclass()</b> to do nothing. Make sure you read the method comment
before overriding it.</p>
</dd>
<dt><strong><a name="noeventfire">Q: Why are some events like Selection not fired in response to programmatic widget changes?</a></strong></dt>
<dd>A: This is a design decision that was made in order to minimize
notification of potentially unwanted events. For example, when the
selection of a control is changed programmatically, SWT does not issue a
selection event. If this were not the case then changing the selection
multiple times would send multiple notifications and run application
listener code multiple times, thereby leading to a potential performance
problem. Clients that wish to notify widget listeners of changes made
programatically can do so by creating an <code>Event</code> object and
invoking <code>Widget.notifyListeners(int, Event)</code> on the widget.
Note that some programmatically-triggered events are sent, typically in
response to low-level widget operations such as focus, move and resize
changes.
</dd>
<dt><strong><a name="printstacktrace">Q: Why don't SWTError and SWTException override all printStackTrace methods?</a></strong></dt>
<dd>A: SWTError and SWTException each contain a slot which records the original
exception (if it is known) that caused the SWTError or SWTException to be thrown.
The printStackTrace() method in these classes has been overridden to print the
stacktrace of the original exception as well.
<p>The problem with the other two API methods (i.e. printStackTrace(PrintStream) and
printStackTrace(PrintWriter)) is that the classes mentioned in their arguments
(PrintStream and PrintWriter) are not available in the CLDC class library.
Because we need to maintain compatability with CLDC, we can not override them.
</dd>
<dt><strong><a name="whatisbrowser">Q: What is the SWT Browser widget?</a></strong></dt>
<dd>A: The SWT Browser widget is used to display HTML documents. It is
designed to provide a basic and portable API sufficient for essential
HTML browsing and rendering on the platforms on which it is implemented.
</dd>
<dt><strong><a name="browserplatforms">Q: Which platforms support the SWT Browser?</a></strong></dt>
<dd>A: The SWT Browser is currently available on the following platforms:
<br>
<ol>
<li>Windows (Internet Explorer 5 and above)</li>
<li>Mac (Panther OS X 10.3 and above. Safari based)</li>
<li>Linux GTK and Linux Motif (Mozilla 1.4 GTK2 and above, or Firefox 1.0 and above)
<br>The following Linux distributions meet the Mozilla/Firefox requirements for using the Browser widget:
<ul>
<li>RedHat Enterprise Linux 3 (Mozilla)</li>
<li>RedHat Enterprise Linux 4 (Firefox)</li>
<li>Suse 9 (Mozilla)</li>
</ul>
Other Linux distributions require a supported version of Mozilla to be installed. <a href="#browserlinux">See instructions</a>
<li>Photon</li>
</ol>
</dd>
<dt><strong><a name="browserlinux">Q: What do I need to run the SWT Browser inside Eclipse on Linux/GTK or Linux/Motif?</a></strong></dt>
<dd>A: You need one of the following:
<ul>
<li>Mozilla version 1.4 GTK2 - Mozilla 1.6 GTK2 can be used with SWT 3.0.</li>
<li>Mozilla version 1.4 GTK2 - Mozilla 1.7.8 GTK2 can be used with SWT 3.1.</li>
<li>Firefox can be used with SWT 3.1 (Linux only), provided that it has been compiled with linkable Gecko libraries. It is
important to note that Firefox downloads from mozilla.org currently do <em>not</em> satisfy this criteria, but Firefox installations
that are included in major Linux distributions <em>typically</em> do. Attempting to use a statically-linked Firefox install will
display the error message "No more handles [NS_InitEmbedding...error -2147221164]".</li>
</ul>
<br>The version of Mozilla or Firefox installed on your system varies with your Linux distribution.
<br>The following Linux distributions meet the Mozilla requirements for using the Browser widget.
<ul>
<li>RedHat Enterprise Linux 3</li>
<li>Suse 9</li>
</ul>
<br>The following Linux distributions meet the Firefox requirements for using the Browser widget.
<ul>
<li>RedHat Enterprise Linux 4
<br>Note that you may need to set the environment variable MOZILLA_FIVE_HOME to the folder containing your Firefox install. e.g. <code>setenv MOZILLA_FIVE_HOME /usr/lib/firefox-1.0.4</code></li>
</ul>
<br>If you use the IBM 1.4 VM <a href="#browserlinuxibm">check this.</a>
<br>
<br>Instructions for RedHat 9 users:
<br>You need the Mozilla version 1.4 GTK2 RPMs for RedHat 9. Mozilla 1.5 GTK2 or Mozilla 1.6 GTK2 can also be used. These can be downloaded from
<a href="http://www.mozilla.org/releases/">Mozilla.org</a>.
<br>
<ol>
<li>Uninstall any prior Mozilla version</li>
<li>Install the Mozilla RPMs</li>
<li>Run Mozilla once. Verify the application opens HTML documents correctly. Check the version number in the Mozilla About dialog.. Verify you now have the Mozilla configuration file /etc/gre.conf.</li>
<li>Start Eclipse. Eclipse is now ready to use the Browser widget.</li>
</ol>
<br>Instructions for other Linux distributions:
<br>You need the Mozilla version 1.4 GTK2 for your distribution. Mozilla 1.5 GTK2 or Mozilla 1.6 GTK2 can also be used.
<ol>
<li>If you are using SWT 3.0, download the Mozilla 1.6 Xft and GTK2 build from <a href="http://www.mozilla.org/releases/#1.6">Mozilla.org</a>. If you are using SWT 3.1, you can choose to use a more recent Mozilla 1.7.x GTK2 from <a href="http://www.mozilla.org/releases/">Mozilla.org</a>.</li>
<li>Uninstall any prior Mozilla version.</li>
<li>Extract and install the Mozilla build.</li>
<li>Run Mozilla once. Verify the application run correctly and check the version number in the Mozilla About dialog.</li>
<li>Set the environment variable MOZILLA_FIVE_HOME to the folder containing your Mozilla install. e.g. <code>setenv MOZILLA_FIVE_HOME /usr/lib/mozilla</code></li>
<li>Start Eclipse. Eclipse is now ready to use the Browser widget.</li>
</ol>
</dd>
<dt><strong><a name="browserlinuxrcp">Q: What do I need to run the SWT Browser in a standalone application on Linux GTK or Linux Motif?</a></strong></dt>
<dd>A: Follow the steps below to use the SWT Browser widget in your standalone SWT application.
<ol>
<li>A supported version of Mozilla or Firefox must be installed (<a href="#browserlinux">instructions here</a>).</li>
<li>Set the environment variable MOZILLA_FIVE_HOME to your Mozilla/Firefox installation folder. e.g. <code>setenv MOZILLA_FIVE_HOME /usr/lib/mozilla</code></li>
<li>Set the environmnent variable LD_LIBRARY_PATH to include MOZILLA_FIVE_HOME. e.g. <code>setenv LD_LIBRARY_PATH ${MOZILLA_FIVE_HOME}:${LD_LIBRARY_PATH}</code></li>
<li>Your standalone SWT application can now use the Browser widget.
</ol>
<br>If you use the IBM 1.4 VM <a href="#browserlinuxibm">check this.</a>
<br>
</dd>
<dt><strong><a name="browserlinuxibm">Q: How can I get the SWT Browser to work with the IBM 1.4 VM?</a></strong></dt>
<dd>A: The IBM 1.4 VM accidentally removes certain entries of the environment variable LD_LIBRARY_PATH. This occurs in particular
for entries starting with /usr/lib. It will leave untouched entries such as /usr/../usr/lib.
<br>Instructions for Red Hat Enterprise Linux 3 users:
<ol>
<li>Mozilla is installed in <code>/usr/lib/mozilla-1.x</code> on this platform. Set the environment variable MOZILLA_FIVE_HOME to <code>/usr/../usr/lib/mozilla-1.x</code></li>
<li>Start Eclipse. If you are not using Eclipse, add MOZILLA_FIVE_HOME to LD_LIBRARY_PATH before starting your standalone SWT application.</li>
<li>The Browser widget should now work with the IBM VM.</li>
</ol>
</dd>
<dt><strong><a name="browserplugins">Q: Why can't I run Java applets in the SWT Browser?</a></strong></dt>
<dd>A: Applets usually don't show up in the SWT Browser. On Windows (Internet Explorer), the Java
plugin fails to run a second Java virtual machine to execute the applet because two Java virtual machines cannot run
in the same process. On Linux (Mozilla), the Java plug-in has been reported to work because it executes in its own process.
<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=59506">See bug 59506</a> .
</dd>
<dt><strong><a name="printOnX">Q: How do I print using my favorite Unix print program?</a></strong></dt>
<dd>A: You can use the External Tools support in Eclipse to print files using external programs.
Just create a new Program launch config from the External Tools dialog that launches your
favorite printing utility and you can pass the selected resource as a parameter.
<ol>
<li>Select the file you want to print.</li>
<li><i>Run &gt; External Tools &gt; External Tools...</i></li>
<li>Select "Program" in the Configurations: list.</li>
<li>Click New</li>
<li>Type: Print Selected File<br>
in the Name: field.</li>
<li>Type the full path name of your favorite printing program in the Location: field.
For example: /usr/bin/lpr</li>
<li>Type: ${container_loc}/${resource_name}<br>
in the Arguments: field.</li>
<li>Click Apply</li>
<li>Click Run</li>
</ol>
</dd>
<dt><strong><a name="noprintimage">Q: How do I print a snapshot of a widget?</a></strong></dt>
<dd>A: To print an image, the image needs to be created on the <em>printer</em>.
A common mistake is to try to print an image that was created on a <em>display</em>.
<p>First take the snapshot into an image that was created on the display,
and then get the imageData and create a new Image just for printing.
Something like this:
<pre> // Take the snapshot into a display Image
Point size = myWidget.getSize();
Image image = new Image(display, size.x, size.y);
GC gc = new GC(myWidget);
gc.copyArea(image, 0, 0);
gc.dispose();
// Get the ImageData and create a new printer Image from it
ImageData imageData = image.getImageData();
Image printImage = new Image(printer, imageData);</pre>
<p>Then print using <em>printImage</em>.
(Remember to dispose both images when you are done with them).
<p>This is true for all graphic objects that you want to use for printing:
Fonts, Colors, and Images. You need to recreate them on the printer before
you can use them for drawing on the printer GC. You might get lucky sometimes,
if the printer happens to have this font or that color, but you won't get lucky
on all platforms and for all printers, and you won't get lucky for images.
So get into the habit of thinking "Did I create this graphics resource
on the same device that I am now trying to draw to?"
</dd>
<dt><strong><a name="smallprint">Q: Why does everything I print seem so small?</a></strong></dt>
<dd>A: When you are printing something from the screen to a printer device, you
need to think about scaling. What is happening is that your figure is being drawn
in something like 72 x 72 dots per inch on the screen, but then you are printing
it to something like a 300 x 300 or 600 x 600 DPI printer. What you have to do is
ask both the screen and the printer what their DPI is, and then figure out what
scale factor you need to use when you draw to the printer GC. The code might look
like this:
<pre>
Point screenDPI = display.getDPI();
Point printerDPI = printer.getDPI();
int scaleFactor = printerDPI.x / screenDPI.x;
</pre>
Please see the ImageAnalyzer example in the org.eclipse.swt.examples project
for an example of printing an image to a printer. Look at method
menuPrint(). Note however that this is a pretty rough example, and it does
not take into account what happens if the image is larger than the page - it
just clips.
<p>Text printing takes some thought also. You need to wrap words, put your page
breaks in the right place, know where your margins are, etc. The SWT
StyledText widget does its own text printing. If you need to see a more
complicated example of printing a document, wrapping, margins, multi-page,
etc., then please look at the inner class Printing in StyledText in
org.eclipse.swt.custom. An instance of this class is created by the
StyledText.print(Printer) API method.
<p>Note also that when printing, any graphics objects that you use to draw,
such as fonts, colors, and images, need to be re-created on the printer
device before you can draw them to the printer GC.
<p>We also recommend that you run your print job in a separate thread and not in
the UI thread, because printing a long document to a slow printer can hang
your entire UI while the printer spools.
<p>Unfortunately, printing is not simply a matter of just passing in the
printer GC instead of the screen GC. Printing has to be designed into your
drawing classes. You don't have scrollbars anymore, so you have to either
cut stuff off and print it on another page, or reorganize it, or scale it
down, or wrap it somehow. Maybe you want to give some control to your users,
and let them specify how many inches something should be, or whatever -
maybe give them a ruler. There is no magic bullet - you
will definitely have to give it some thought.
</dd>
<dt><strong><a name="printertrim">Q: What does computeTrim mean for a Printer?</a></strong></dt>
<dd>A: The "trim" is the area of the page that the printer cannot print on.
Usually, computeTrim is used as follows: <br><code>Rectangle trim = printer.computeTrim(0, 0, 0, 0);</code>
<p>A printer that can print edge-to-edge would have a trim.x and trim.y of 0,0.
The trim.width and trim.height would be the same as the width and height of the physical paper.
</p>
<p>A 600 dot per inch printer that cannot print on the leftmost 0.18 inch of the paper would have a trim.x of -108.
So to print starting at precisely 1" from the left edge, take 600 (i.e. 1") and "add" -108 (i.e. subtract 0.18") to get the starting x position.
Trim positions are negative because they are relative to the 0,0 position of the client area (or 'printable area') of the paper.
</p>
</dd>
<dt><strong><a name="autotest">Q: How can I implement user interaction test cases?</a></strong></dt>
<dd>A: The method <code>org.eclipse.swt.widgets.Display.post(Event)</code> can be used to
post mouse and keyboard events into the OS, which emulates a user
performing the specified action. Also, open source application
<a href="http://sourceforge.net/projects/abbot/">"Abbot for SWT"</a> assists
in the writing of automated test suites.
</dd>
<dt><strong><a name="gtkselectiongone">Q: On GTK, why does my widget's selection disappear when it loses focus?</a></strong></dt>
<dd>A: This effect may be seen if KDE color settings are being
utilized. This can be fixed by unchecking the "Apply KDE colors to
non-KDE apps" option in the KDE colors control panel.
</dd>
<dt><strong><a name="swtawtosx">Q: Why does the SWT_AWT bridge not work for me on OS X?</a></strong></dt>
<dd>A: This was an SWT-AWT incompatibility that existed prior to eclipse 3.2.
This problem has since been fixed in SWT, but requires that an OS X jre that has
support for this fix be used as well. Specifically, the jre must be version 1.5.0
Release 4 (or greater), and the additional "SWT Compatibility Libraries" must
be installed. These libraries can be downloaded from the Downloads section
of <a href="http://connect.apple.com">Apple Developer Connection</a>. It's
free to create an account at Apple Developer Connection to access the download,
which is approximately 180K. For more information about this issue see
<a href="https://bugs.eclipse.org/bugs/show_bug.cgi?id=67384">bug 67384</a>.
</dd>
<dt><strong><a name="printOnGTK">Q: Why is the Print menu item disabled in Eclipse on GTK (Linux, UNIX)?</a></strong></dt>
<dd>A: Printing on GTK has not been implemented yet. You can use the
External Tools support in Eclipse to print files using lpr or some other
printing utility. See <a href="#printOnX">here</a> for the steps to set this up.
<p>20060719 Update: Printing on GTK has now been implemented. To use it, get the latest eclipse and run at least GTK+ 2.10.</p>
</dd>
<dt><strong><a name="printOnMotif">Q: Why is the Print menu item disabled in Eclipse on Motif?</a></strong></dt>
<dd>A: Printing on Motif requires that Xprint be installed on your machine.
<p>A good FAQ regarding Xprint can be found at
<a href="http://xprint.mozdev.org/docs/Xprint_FAQ.html">http://xprint.mozdev.org/docs/Xprint_FAQ.html</a>.</p>
</dd>
<dt><strong><a name="uithread">Q: Why do I get the error "org.eclipse.swt.SWTException: Invalid thread access"?</a></strong></dt>
<dd>A: In SWT, by definition the thread that creates the Display is a UI-thread. This thread is responsible for
reading and dispatching events from the operating system event queue, and invoking listeners in response to these events.
Listener code is executed in the UI-thread. This makes an SWT application generally quite responsive, behaving like most
other operating system programs. However, any long operation, when executed by a listener, will run in the UI-thread
and prevent it from reading and dispatching events, thus hanging the application.
<p>If a listener has a large amount of work to perform, instead of performing that work in the UI-thread, it can
fork a separate thread so the UI-thread can continue dispatching events. If the other thread needs to execute code
that accesses an SWT object, such as changing the string in a label, there is a concurrency issue. At the very
least, some kind of synchronization is necessary to prevent the operating system or SWT from crashing, hanging or
behaving unpredictably.</p>
<p>SWT implements a single-threaded UI model often called apartment threading. In this model, only the UI-thread
can invoke UI operations. SWT strictly enforces this rule. If you try and access an SWT object from outside the
UI-thread, you get the exception "org.eclipse.swt.SWTException: Invalid thread access". Different operating systems
have different rules governing threads, UI components and synchronization. Some use a single-threaded UI model
like SWT. Others allow only one thread at a time in the window system library, controlling access through a
global lock. This type of multi-threaded UI model is often called free threading. Currently, in order to be
simple, efficient and portable, SWT is apartment threaded.</p>
<p>To allow background threads to perform operations on objects belonging to the UI-thread, the methods
syncExec(Runnable runnable) and asyncExec(Runnable runnable) of Display are used. These are the only
methods in SWT that can be called from any thread. They allow a runnable to be executed by the UI-thread,
either synchronously, causing the background thread to wait for the runnable to finish, or asynchronously
allowing the background thread to continue execution without waiting for the result. A runnable that is
executed using syncExec() most closely matches the equivalent direct call to the UI operation because a
Java method call always waits for the result before proceeding, just like syncExec().</p>
<p>The following code sets the text of a label from a background thread and waits for the operation to complete:
<pre>display.syncExec(
new Runnable() {
public void run(){
label.setText(text);
}
});
</pre>
</dd>
<dt><strong><a name="noautolayout">Q: Why do I have to resize my shell to get my changed widgets to lay out again?</a></strong></dt>
<dd>A: A layout is only performed automatically on a Composite's children when the Composite
is resized, including when it is initially shown. To make a Composite lay out its
children under any other circumstances, such as when children are created or disposed,
its <em>layout()</em> method must be called. For an example of this see SWT snippet
<a href="http://dev.eclipse.org/viewcvs/index.cgi/%7Echeckout%7E/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet98.java">create and dispose children of a composite</a>.
</dd>
<dt><strong><a name="nographicslibrary">Q: Why do I get "SWTException: Unable to load graphics library" using GC?</a></strong></dt>
<dd>A: Support for advanced graphics operations such as path for curvers and
lines, alpha blending, antialiasing, patterns and transformations was
added to SWT 3.1. On Windows, <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdicpp/gdiplus/gdiplus.asp">GDI+</a>
is required. On X Windows platforms (i.e. GTK and Motif),
<a href="http://cairographics.org/introduction">Cairo 0.4.0</a> is
required. If your Windows platform does not have GDI+ by default, you can
<a href="http://www.microsoft.com/downloads/details.aspx?FamilyID=6a63ab9c-df12-4d41-933c-be590feaa05a&amp;DisplayLang=en">download</a>
a redistributable package from Microsoft.
</dd>
<dt><strong><a name="scrollonlinux"> Q: Why doesn't mouse scrolling work on Linux/Motif?</a></strong></dt>
<dd>A: Mouse scrolling on Linux/Motif relies on the IMWheel driver. Here is how it works:
<ol>
<li>The X Server gets the wheel event.</li>
<li>Your /etc/X11/XF86Config must contain "ZAxisMap 4 5" (or the equivalent "Option"
line if you use XFree86 4.x) in the Mouse section. This maps the wheel to emulated
mouse buttons "4" and "5".</li>
<li>IMWheel has a global hook on the mouse, only looking for button4/5 events.
When it sees one, it looks in /etc/X11/imwheel which is a table of what to do for
which application. E.g., GTK-based applications support the idea of 5-button mice
natively, so the imwheel file says "do nothing (pass through) for gtk".
On the other hand, no known Motif-based app seems to know about these, so imwheel
eats the mouse event and emits an accelerator event for "PgUp" or whatever your
preference is. It has some clever pre-sets for xterm, netscape, and so on.</li>
</ol>
</dd>
</dl>
</table>
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