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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Brief Technical FAQ</h1>
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| 33 |
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| 34 |
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| 35 | This document describes how to use more than one Qt version on one
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| 36 | machine and how to use Qt on X11 without a window manager. In addition
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| 37 | it explains the most common source of link errors with Qt.
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| 38 | <p> Other frequently asked questions can be found in the
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| 39 | <a href="http://www.trolltech.com/developer/faqs/">FAQ index</a> and
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| 40 | in the <a href="http://www.trolltech.com/developer/faqs/technical.html">Technical FAQ</a>.
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| 41 | <p> <ul>
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| 42 | <li> <a href="#linkerror">Link error, complaining about a lack of
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| 43 | <tt>vtbl</tt>, <tt>_vtbl</tt>, <tt>__vtbl</tt> or similar</a>
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| 44 | <li> <a href="#diffver">Using different versions of Qt on the same
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| 45 | machine</a>
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| 46 | <ul>
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| 47 | <li> <a href="#qtbin">Developers building for a single version of Qt on Unix - Qt binary packages</a>
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| 48 | <li> <a href="#qtsrc">Developers building for two versions of Qt on Unix - Qt sources</a>
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| 49 | </ul>
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| 50 | <li> <a href="#nowinman">Using Qt on X11 without a window manager</a>
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| 51 | <li> <a href="distributingqt.html">Distributing Qt Applications</a>
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| 52 | </ul>
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| 53 | <p> <a name="linkerror"></a>
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| 54 | <h2> Link error, complaining about a lack of <tt>vtbl</tt>, <tt>_vtbl</tt>, <tt>__vtbl</tt> or similar
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| 55 | </h2>
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| 56 | <a name="1"></a><p> This indicates that you've included the <a href="metaobjects.html#Q_OBJECT">Q_OBJECT</a> macro in a class
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| 57 | declaration and probably also run the <a href="moc.html#moc">moc</a>, but forgot to link the
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| 58 | moc-generated object code into your executable. See <a href="moc.html">Using the Meta Object Compiler</a> for details on how to use moc.
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| 59 | <p> <a name="diffver"></a>
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| 60 | <h2> Using different versions of Qt on the same machine
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| 61 | </h2>
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| 62 | <a name="2"></a><p> Qt programs need the following components of a Qt distribution:
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| 63 | <p> <dl>
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| 64 | <p> <dt>Header files - Compile time
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| 65 | <p> <dd>Programmers need to include the Qt header files. The Qt header files
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| 66 | are usually located in the <tt>include</tt> subdirectory of Qt distributions.
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| 67 | Care must be taken to include the header files of the relevant release of
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| 68 | Qt. Those with a command-line compiler will typically use options such as
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| 69 | <tt>/I%QTDIR%\include</tt>
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| 70 |
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| 71 | the relevant release of Qt.
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| 72 | <p> <dt>Meta Object Compiler and other tools - Compile time
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| 73 | <p> <dd>Programmers need to run <em>moc</em> and other tools such as <em>uic</em>. These
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| 74 | tools are usually located in the <tt>bin</tt> subdirectory of Qt distributions.
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| 75 | Either run <tt>"$QTDIR"/bin/moc</tt> and <tt>"$QTDIR"/bin/uic</tt> or add <tt>"$QTDIR"/bin</tt>
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| 76 | to your <tt>PATH</tt> and run <a href="moc.html#moc">moc</a> and <tt>uic</tt>. If you use <tt>qmake</tt> the
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| 77 | appropriate lines will be added to your Makefiles so that <em>uic</em> and
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| 78 | <em>moc</em> will be executed as required.
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| 79 | <p> <dt>Static or shared libraries - Link time
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| 80 | <p> <dd>Programmers need to link with the Qt static or shared libraries. The Qt
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| 81 | libraries are usually located in the <tt>lib</tt> subdirectory of Qt distributions.
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| 82 | Care must be taken to link with the libraries of the relevant release of
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| 83 | Qt. Those with a command-line compiler will typically use options such as
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| 84 | <tt>/L%QTDIR%\lib\qt.lib</tt> or <tt>-L"$QTDIR"/lib</tt> <tt>-lqt</tt> provided <tt>QTDIR</tt>
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| 85 | specifies the relevant release of Qt.
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| 86 | <p> <dt>Shared libraries - Run time
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| 87 | <p> <dd>Users of programs linked with shared Qt libraries need these same
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| 88 | shared libraries to run these programs. The Qt libraries are usually
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| 89 | located in the <tt>lib</tt> subdirectory of Qt distributions. Shared libraries
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| 90 | are made available to programs in places such as <tt>C:\windows\system</tt> on
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| 91 | Windows platforms, directories listed in file <tt>/etc/ld.so.conf</tt> on Linux,
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| 92 | standard <tt>lib</tt> directories on Unix, or directories listed in environment
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| 93 | variables <tt>LD_LIBRARY_PATH</tt>, <tt>SHLIB_PATH</tt>, or <tt>LIBPATH</tt> on various Unix
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| 94 | flavours. Make the relevant Qt libraries available using one of these
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| 95 | mechanisms.
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| 96 | <p> </dl>
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| 97 | <p> Qt distributions consist of different files needed at compile time,
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| 98 | link time, or run time. Trolltech distributes Qt in the form of a
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| 99 | source package that contain all these files once they have been built.
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| 100 | <p> Other vendors distribute Qt in the form of binary packages. Binary packages
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| 101 | usually consist of two parts:
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| 102 | <p> <ul>
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| 103 | <li> shared libraries in the run time package, usually called <tt>qt3</tt>.
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| 104 | <p> <li> header files, static libraries, the moc and other tools in the developers'
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| 105 | kit, usually called <tt>qt3-dev</tt>.
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| 106 | <p> </ul>
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| 107 | <p> Depending on how you are using Qt, you need to make specific parts of
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| 108 | the Qt distribution available to your programs. Typical situations are
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| 109 | described below.
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| 110 | <p> <a name="qtbin"></a>
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| 111 | <h3> Developers building for a single version of Qt on Unix - Qt binary packages
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| 112 | </h3>
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| 113 | <a name="2-1"></a><p> You build programs with a single version of Qt, but you still need
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| 114 | to run programs linked with another version of Qt. You are typically
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| 115 | a Linux developer who builds programs for Qt 3.x on a KDE desktop based
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| 116 | on Qt 2.x. Qt packages are usually split into a shared library
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| 117 | package with a name like <tt>qt</tt> and a developer package with a name
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| 118 | like <tt>qt-dev</tt>. You will need the appropriate packages:
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| 119 | <p> <ul>
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| 120 | <p> <li> To build programs you will need the header files, the libraries,
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| 121 | the moc and other tools from Qt 3.x. They are included in the developer
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| 122 | package of Qt 3.x (<tt>qt3-dev</tt> or similar).
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| 123 | <p> <li> To run programs you will need the shared libraries of Qt 3.x and
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| 124 | Qt 2.x. They are included in the regular packages of Qt 3.x (<tt>qt3</tt>
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| 125 | or similar) and Qt 2.x (<tt>qt2</tt> or similar).
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| 126 | <p> </ul>
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| 127 | <p> Just install the packages, <tt>qt2</tt>, <tt>qt3</tt>, and <tt>qt3-dev</tt>. You may
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| 128 | need to set the environment variable <tt>QTDIR</tt> to point to Qt 3.x.
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| 129 | <p> <a name="qtsrc"></a>
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| 130 | <h3> Developers building for two versions of Qt on Unix - Qt sources
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| 131 | </h3>
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| 132 | <a name="2-2"></a><p> You build and run programs for Qt 2.x and Qt 3.x. You will need:
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| 133 | <p> <ul>
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| 134 | <p> <li> the header files, the libraries, the moc and other tools from Qt 3.x
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| 135 | and Qt 2.x to build programs,
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| 136 | <p> <li> the shared libraries of Qt 3.x and Qt 2.x to run programs.
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| 137 | <p> </ul>
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| 138 | <p> Get the source distributions of both Qt 2.x and Qt 3.x.
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| 139 | <p> <ol type=1>
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| 140 | <p> <li> Install and build Qt 2.x and Qt 3.x, usually in <tt>/opt</tt> or
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| 141 | <tt>/usr/local</tt>. In the case of <tt>/opt</tt>:
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| 142 | <p> <pre>
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| 143 | $ cd /opt
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| 144 | $ gunzip -c \c qt-x11-2.3.1.tar.gz | tar xf -
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| 145 | $ cd qt-2.3.1
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| 146 | $ setenv QTDIR /opt/qt-2.3.1
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| 147 | $ configure [options]
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| 148 | $ make
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| 149 |
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| 150 | $ cd /opt
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| 151 | $ gunzip -c qt-x11-free-3.0.0.tar.gz | tar xf -
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| 152 | $ cd qt-3.0.0
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| 153 | $ setenv QTDIR /opt/qt-3.0.0
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| 154 | $ configure [options]
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| 155 | $ make
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| 156 | </pre>
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| 157 |
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| 158 | <p> <li> Make shared libraries available to programs at run time. Either
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| 159 | add both <tt>/opt/qt-2.3.1/lib</tt> and <tt>/opt/qt-3.0.0/lib</tt> to your environment
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| 160 | variable <tt>LD_LIBRARY_PATH</tt> or file <tt>/etc/ld.so.conf</tt> or whataver mechanism
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| 161 | you're using, or make links to the libraries in a standard directory like
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| 162 | <tt>/usr/local/lib</tt>:
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| 163 | <p> <pre>
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| 164 | cd /usr/local/lib
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| 165 | ln -s /opt/qt-2.3.1/lib/libqt.so.2 .
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| 166 | ln -s /opt/qt-2.3.1/lib/libqt-mt.so.2 .
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| 167 | ln -s /opt/qt-2.3.1/lib/libqutil.so.1 .
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| 168 | ln -s /opt/qt-3.0.0/lib/libqt.so.3 .
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| 169 | ln -s /opt/qt-3.0.0/lib/libqui.so.1 .
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| 170 | </pre>
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| 171 |
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| 172 | <p> </ol>
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| 173 | <p> To develop with Qt 2.x use:
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| 174 | <p> <pre>
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| 175 | setenv QTDIR /opt/qt-2.3.1
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| 176 | setenv PATH ${QTDIR}/bin:${PATH}
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| 177 | </pre>
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| 178 |
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| 179 | <p> To develop with Qt 3.x use:
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| 180 | <p> <pre>
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| 181 | setenv QTDIR /opt/qt-3.0.0
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| 182 | setenv PATH ${QTDIR}/bin:${PATH}
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| 183 | </pre>
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| 184 |
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| 185 | <p> Setting <tt>QTDIR</tt> ensures that the proper resources are used, such as the
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| 186 | documentation appropriate to the version of Qt you're using. Also
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| 187 | your Makfiles may refer to <tt>"$QTDIR"/include</tt> and <tt>"$QTDIR"/lib</tt> to
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| 188 | include the proper header files and link with the proper libraries.
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| 189 | Setting the <tt>PATH</tt> ensures that the proper version of moc and other
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| 190 | tools is being used.
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| 191 | <p> <a name="nowinman"></a>
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| 192 | <h2> Using Qt on X11 without a window manager
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| 193 | </h2>
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| 194 | <a name="3"></a><p> When using Qt without a window manager on Unix/X11, you will most
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| 195 | likely experience focus problems. Without a window manager, there is
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| 196 | no focus handling on X11, and no concept of an active window
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| 197 | either. If you want your application to work in such an environment,
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| 198 | you have to explicitly mark a window as active <em>after</em> showing it:
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| 199 | <p> <pre>
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| 200 | yourWindow->show();
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| 201 | yourWindow->setActiveWindow();
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| 202 | </pre>
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| 203 |
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| 204 | <p> Note that setActiveWindow() won't work if the widget does not become
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| 205 | physically visible during this event cycle. However, without a window
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| 206 | manager running, this is guaranteed to happen. For the curious reader:
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| 207 | setActiveWindow() emulates a window manager by explicitly setting the
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| 208 | X Input Focus to a widget's top level window.
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| 209 | <p>
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| 210 | <!-- eof -->
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| 211 | <p><address><hr><div align=center>
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| 212 | <table width=100% cellspacing=0 border=0><tr>
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| 213 | <td>Copyright © 2007
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| 214 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 215 | <td align=right><div align=right>Qt 3.3.8</div>
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| 216 | </table></div></address></body>
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| 217 | </html>
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