Introduction to Qt

Qt is a cross-platform application framework that is widely used for developing application software with a graphical user interface (GUI) (in which cases Qt is classified as a widget toolkit), and also used for developing non-GUI programs such as command-line tools and consoles for servers. One of the major users of Qt is KDE.

This package is known to build and work properly using an LFS-7.6 platform.

Package Information

Qt Dependencies


Xorg Libraries



Cups-1.7.5, GTK+-2.24.24 (GTK+ 2 theme support), gst-plugins-base-0.10.36 (For QtWebKit HTML5 Video), MariaDB-10.0.13 or MySQL, PostgreSQL-9.3.5, PulseAudio-5.0, and unixODBC-2.3.2

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/qt4

Qt Installation Alternatives

The installation of Qt presents several challenges and choices. Complicating the Qt installation is the fact that there are two versions, Qt4 and Qt5, that have executable programs with identical names. If both packages are installed on one system, the only methods to manage which set of programs is used is to either control the users' PATH or to rename files either directly or via symbolic links. Both packages cannot be installed in the same directory.

If you are only going to install one of the Qt versions, the choice of installation methods is easier. You can either install the components in the several directories of the /usr hierarchy or install the entire package in a separate directory of your choice. We refer to these options below as "Method 1: Installing in /usr" and "Method 2: Installing in /opt".

If both versions of Qt are to be installed, one or both versions need to be installed in a separate directory. For the purposes here we use the /opt directory. The selection of which version is being used by individual users on a system is controlled by the PATH variable. Other systems can be designed, but the BLFS editors find the PATH method easiest.

The advantage of installing in /usr is that no updates to the /etc/ld.so.conf or /etc/man_db.conf files are required. The package files are distributed within several subdirectories of the /usr hierarchy. This is the method that most commercial distributions use. The disadvantage for BLFS users is that this Qt instance cannot be upgraded while it is in use. For instance, it cannot be upgraded from a running KDE environment. It also precludes having multiple versions of Qt on your system and does not allow reverting to an existing, known working instance of Qt.

The advantage of installing Qt in a custom directory such as /opt/qt-4.8.6 or /opt/qt-5.3.1 or is that it keeps all the package files consolidated in a dedicated directory hierarchy. By using this method, an update can be made without overwriting a previous installation and users can easily revert to a previous version by changing one symbolic link or merely changing the PATH variable. It also allows a developer to maintain multiple versions of Qt4 or Qt5 for testing.

Installation of Qt



If you did not install some of the recommended dependencies, examine ./configure --help output to check how to disable them or use internal versions bundled in the source tarball.



If Qt4 is being reinstalled into the same directory as an existing instance, run the commands done by root, such as make install, from a console or non-Qt4 based window manager. It overwrites Qt4 libraries that should not be in use during the install process.



The build time and space required for the full Qt is quite long. The instructions below do not build the tutorials and examples. Removing the -nomake lines will create a complete build.

Fix DoS vulnerability in the GIF image handler:

sed -i -e '631a if (image->isNull()) { state = Error; return -1; }' \

Method 1: Installing in /usr

Install Qt4 into the /usr hierarchy by running the following commands:

export QT4LINK=/usr

sed -i -e "/#if/d" -e "/#error/d" -e "/#endif/d" \
     config.tests/unix/libmng/libmng.cpp &&

sed -i '/CONFIG -/ a\isEmpty(OUTPUT_DIR): OUTPUT_DIR = ../..' \
     src/3rdparty/webkit/Source/WebKit2/DerivedSources.pro &&

./configure -prefix         /usr                 \
            -bindir         /usr/bin             \
            -plugindir      /usr/lib/qt4/plugins \
            -importdir      /usr/lib/qt4/imports \
            -headerdir      /usr/include/qt4     \
            -datadir        /usr/share/qt4       \
            -sysconfdir     /etc/xdg             \
            -docdir         /usr/share/doc/qt4   \
            -demosdir       /usr/share/doc/qt4/demos    \
            -examplesdir    /usr/share/doc/qt4/examples \
            -translationdir /usr/share/qt4/translations \
            -confirm-license   \
            -opensource        \
            -release           \
            -dbus-linked       \
            -openssl-linked    \
            -system-sqlite     \
            -no-phonon         \
            -no-phonon-backend \
            -no-nis            \
            -no-openvg         \
            -nomake demos      \
            -nomake examples   \
            -optimized-qmake   &&


This package does not come with a test suite.

Remove references to the build directory from the .pc files by running the following command:

find . -name "*.pc" -exec perl -pi -e "s, -L$PWD/?\S+,,g" {} \;

Now as the root user:

make install &&
rm -rf /usr/tests

Remove references to the build directory from installed files by running the following command as the root user:

for file in 3Support CLucene Core DBus Declarative DesignerComponents \
            Designer Gui Help Multimedia Network OpenGL Script \
            ScriptTools Sql Svg Test UiTools WebKit XmlPatterns Xml phonon; do

     [ -e /usr/lib/libQt${file}.prl ] &&
     sed -r '/^QMAKE_PRL_BUILD_DIR/d;s/(QMAKE_PRL_LIBS =).*/\1/' \
         -i /usr/lib/libQt${file}.prl
unset file

Method 2: Installing in /opt/qt-4.8.6

This section provides for installing Qt4 almost all of the files in the /opt directory.

export QT4DIR=/opt/qt-4.8.6 &&
export QT4LINK=/opt/qt4 &&

sed -i -e "/#if/d" -e "/#error/d" -e "/#endif/d" \
     config.tests/unix/libmng/libmng.cpp &&

sed -i '/CONFIG -/ a\isEmpty(OUTPUT_DIR): OUTPUT_DIR = ../..' \
     src/3rdparty/webkit/Source/WebKit2/DerivedSources.pro &&

./configure -prefix     $QT4DIR  \
            -sysconfdir /etc/xdg \
            -confirm-license     \
            -opensource          \
            -release             \
            -dbus-linked         \
            -openssl-linked      \
            -system-sqlite       \
            -plugin-sql-sqlite   \
            -no-phonon           \
            -no-phonon-backend   \
            -no-nis              \
            -no-openvg           \
            -nomake demos        \
            -nomake examples     \
            -optimized-qmake     &&


Now, as the root user:

make install
ln -svfn $QT4DIR /opt/qt4

Remove references to the build directory from installed files by running the following command as the root user:

for file in `basename -a -s .prl $QT4DIR/lib/lib*.prl`; do
       sed -r -e '/^QMAKE_PRL_BUILD_DIR/d'    \
              -e 's/(QMAKE_PRL_LIBS =).*/\1/' \
              -i $QT4DIR/lib/${file}.prl

   perl -pi -e "s, -L$PWD/?\S+,,g" $QT4DIR/lib/pkgconfig/${file##lib}.pc

unset file

Continuing for Both Methods

For all methods, install images and create the menu entries for installed applications. Be sure that the QT4LINK variable is defined in root's environment and as the root user:

install -v -Dm644 src/gui/dialogs/images/qtlogo-64.png \
                  /usr/share/pixmaps/qt4logo.png       &&

install -v -Dm644 tools/assistant/tools/assistant/images/assistant-128.png \
                  /usr/share/pixmaps/assistant-qt4.png &&

install -v -Dm644 tools/designer/src/designer/images/designer.png \
                  /usr/share/pixmaps/designer-qt4.png  &&

install -v -Dm644 tools/linguist/linguist/images/icons/linguist-128-32.png \
                  /usr/share/pixmaps/linguist-qt4.png  &&

install -v -Dm644 tools/qdbus/qdbusviewer/images/qdbusviewer-128.png \
                  /usr/share/pixmaps/qdbusviewer-qt4.png &&

install -dm755 /usr/share/applications &&

cat > /usr/share/applications/assistant-qt4.desktop << EOF
[Desktop Entry]
Name=Qt4 Assistant 
Comment=Shows Qt4 documentation and examples

cat > /usr/share/applications/designer-qt4.desktop << EOF
[Desktop Entry]
Name=Qt4 Designer
Comment=Design GUIs for Qt4 applications

cat > /usr/share/applications/linguist-qt4.desktop << EOF
[Desktop Entry]
Name=Qt4 Linguist 
Comment=Add translations to Qt4 applications

cat > /usr/share/applications/qdbusviewer-qt4.desktop << EOF
[Desktop Entry]
Name=Qt4 QDbusViewer 
GenericName=D-Bus Debugger
Comment=Debug D-Bus applications

cat > /usr/share/applications/qtconfig-qt4.desktop << EOF
[Desktop Entry]
Name=Qt4 Config 
Comment=Configure Qt4 behavior, styles, fonts

Command Explanations

sed -i ...: First command fixes detection of libmng 2.0 and second one prevents configure script from writing to the root directory if building as privileged user.

-confirm-license: Accept license without prompting user during configuration.

-opensource: Install the opensource version of Qt.

-release: This switch disables building with debugging symbols.

-nomake examples -nomake demos: These switches disable building programs that are only of interest to a developer using Qt.

-system-sqlite: This switch enables use the system version of SQLite.

-no-nis: This switch disables support for Network Information Service (NIS) which has been deprecated in recent versions of Glibc.

-no-phonon -no-phonon-backend: These switches disable building of the bundled Phonon library. Better version is provided by phonon-4.8.0 package.

-dbus-linked -openssl-linked: These switches enable explicit linking of the D-Bus and OpenSSL libraries into Qt libraries instead of dlopen()-ing them.

-no-openvg: This switch disables OpenVG support in Qt.

-optimized-qmake: This switch enables building of the optimized qmake program.

-no-dbus: Use this switch if you don't have D-Bus installed.

Configuring Qt

Configuration Information

If you installed Qt in /usr, create an environment variable needed by certain packages. As the root user:

cat > /etc/profile.d/qt4.sh << EOF
# Begin /etc/profile.d/qt4.sh

export QT4DIR

# End /etc/profile.d/qt4.sh

If you installed Qt in a location other than /usr, you need to update the following configuration files so that Qt is correctly found by other packages and system processes.

As the root user, update the /etc/ld.so.conf file and the dynamic linker's run-time cache file:

cat >> /etc/ld.so.conf << EOF
# Begin Qt addition
# End Qt addition


As the root user, create the /etc/profile.d/qt4.sh file:

cat > /etc/profile.d/qt4.sh << EOF
# Begin /etc/profile.d/qt4.sh
pathappend /opt/qt4/bin           PATH
pathappend /opt/qt4/lib/pkgconfig PKG_CONFIG_PATH
export QT4DIR
# End /etc/profile.d/qt4.sh

Choosing Qt Program Versions

If you install both Qt4 and Qt5, you can use some simple scripts to select the currently active set of Qt programs. As the root user, create the following scripts:

cat > /usr/bin/setqt4 << 'EOF'
if [ "x$QT5DIR" != "x/usr" ]; then pathremove  $QT5DIR/bin; fi
if [ "x$QT4DIR" != "x/usr" ]; then pathprepend $QT4DIR/bin; fi
echo $PATH
cat > /usr/bin/setqt5 << 'EOF'
if [ "x$QT4DIR" != "x/usr" ]; then pathremove  $QT4DIR/bin; fi
if [ "x$QT5DIR" != "x/usr" ]; then pathprepend $QT5DIR/bin; fi
echo $PATH

You should now be able to use the appropriate Qt version by running source setqt4 or source setqt5 as desired. (Setting the PATH wont work in a subshell.) Another technique that can be used is to create appropriate alias additions to your ~/.bashrc like alias setqt4='source setqt4'.


Installed Programs: assistant, designer, lconvert, linguist, lrelease, lupdate, moc, pixeltool, qcollectiongenerator, qdbuscpp2xml, qdbus, qdbusviewer, qdbusxml2cpp, qdoc3, qhelpconverter, qhelpgenerator, qmake, qmlplugindump, qmlviewer, qt3to4, qtconfig, qttracereplay, rcc, uic3, uic, xmlpatterns, and xmlpatternsvalidator
Installed Libraries: libQtUiTools.a, libQt3Support.so, libQtCLucene.so, libQtCore.so, libQtDBus.so, libQtDeclarative.so, libQtDesignerComponents.so, libQtDesigner.so, libQtGui.so, libQtHelp.so, libQtMultimedia.so, libQtNetwork.so, libQtOpenGL.so, libQtScript.so, libQtScriptTools.so, libQtSql.so, libQtSvg.so, libQtTest.so, libQtWebKit.so, libQtXmlPatterns.so, and libQtXml.so, and several plugins under /opt/qt4/imports and /opt/qt4/plugins
Installed Directories: /usr/include/qt4, /usr/lib/qt4, /usr/share/doc/qt4, and /usr/share/qt4 OR /opt/qt4 and /opt/qt-4.8.6

Short Descriptions


is a tool for presenting on-line documentation.


is a full-fledged GUI builder. It includes powerful features such as preview mode, automatic widget layout, support for custom widgets, and an advanced property editor.


provides support for translating applications into local languages.


is a simple command line tool. It reads a Qt project file and produces message files used by the application.


reads a Qt project file, finds the translatable strings in the specified source, header and Qt Designer interface files, and produces or updates the translation files listed in the project file.


generates Qt meta object support code.


is a desktop magnifier and as you move your mouse around the screen it will show the magnified contents in its window.


uses information stored in project files to determine what should go in the makefiles it generates.


qt3to4 is a tool to help update Qt3 code to Qt4.


is used to customize the appearance of Qt applications.


is a resource compiler used in conjunction with designer.


is a Qt user interface compiler.


is a tool to generate Qt4 code out of user interface files generated by the Qt3 version of designer.

Last updated on 2014-09-15 22:13:43 -0700