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README.Debian
Qt for Debian README
--------------------
1. Preface
This README is intended to give developers and users exact information
about how the qt-x11-free package provided by TrollTech AS has been packaged
for Debian in case you either want to faciliate it for development
of applications and libraries or plugins using the Qt class library. With
qt-x11-3.1.1, the Debian packages have been massively restructured to get
the most out of theoriginal Qt package and spit the contents up into
several packages so that they make the most sensefor several groups of
users; developers, application users, translators of Qt-based
applications and Debian packagers who are packaging applications developed
with Qt.2.
2. General Overview
As Qt is a huge package that contains a complete environment for
developers, it needs to be split up into several packages that make it
easier for everyone else to handle it and not to require
unnecessary disk space for end-users. Additionally, Qt can be configured
in several ways - and therefore also used in several ways. Qt development
usually requires the environment variable QTDIR. As Debian is placing
libraries and header files in a quite specific filesystem order, this
usually breaks setting a single environment variable to meet the
requirements of packages. Therefore, symlinks are used to set up the system
to meet both, the Debian filesystem standard and the QTDIR variable. All of
Qt (so the QTDIR path) is available in /usr/share/qt3. If you need to set
QTDIR, do export QTDIR=/usr/share/qt3
As far as the common build configuration goes, we note explicitely that the
Debian package of Qt will in very rare cases break the compilation (most
likely the linking) of applications on Debian which use Qt, in particular
utilizing styles in an incorrect way by deriving from one of the styles
that ship with Qt. In case you are a Debian packager and encounter
problems, contact Debian Qt/KDE Maintainers (debian-qt-kde@lists.debian.org).
We will tell you why things don't work and what you should communicate on
with the programmers of your application that you are packaging. The build
configuration generally is intended to provide a Qt version that is as
small as possible in terms of the memory size it requires. Therefore,
everything inside Qt that can be compiled as plugins has been compiled that
way. This includes:
- imageformats: jpeg and mng - codecs (for languages like arab, japanese
etc provided with Qt)
- sql drivers for databases (MySQL, ODBC and PostgreSQL)
The only exception is the imageformat png which has been compiled built-in
due to the fact that there is literally no program that uses no icons at
all and icons are to be used preferrably in png format. The plugins are all
located under /usr/lib/qt3/plugins. This is also the install location you
should choose as a package maintainer for
qt-plugins so the user doesn't have to customize his library path for
loading Qt plugins. The only exception is that KDE delivers a set of Qt
plugins as well (mainly styles and designer plugins); those are placed in
/usr/lib/trinity/plugins.
QMotif Extension: As this code is only available in commercial environments
(and produces a static library libqmotif.a anyway that those commercial
applications have to be linked against in addition to Qt), we left out all
header files of the libqt3-headers package that are belonging to this
QMotif extension.
Oracle Database driver, Sybase & Microsoft SQL Server driver: Those drivers
are only available in a commercial version of Qt due to license
incompatibilities with the GPL. If you need to faciliate those drivers,
please visit http://www.trolltech.com and have a read at
http://doc.trolltech.com/3.0/sql-driver.html.
3. Packages (End-User)
The Qt built has been split up into several packages that allow for easy
installation for all types of users. The End-user usually only requires to
have the following packages installed to run an application that links
against Qt:
Threaded version:libqt3-mt (the library libqt-mt.so.* and libqui.so.* for
loading designer-made user interfaces at runtime).
Optionally depending on the program's requirements:
libqt3-mt-odbc
libqt3-mt-mysql
libqt3-mt-psql
In addition to the libraries, it may make sense to install the program
qtconfig to customize the look and behaviorof Qt programs. If you have KDE
installed, the KDE control center will take this task automatically in most
cases. qtconfig is available in the package qt3-qtconfig.
Also, Qt programs can make use of the online-help tool that ships with Qt,
the Qt Assistant. The Assistant can be installed with the package
qt3-assistant.
Qt Configuration files
----------------------
Qt programs most often use QSettings to store their information in configuration
files. With Qt 3.2, the new option --sysconfdir has been introduced that allows
us to use /etc/qt3 as the system-wide location where qt-program specific global
configuration files can go. If you're a programmer that wants to get familiar with
that, please look at the examples, documentation and the code in designer or
assistant as well as qtconfig.
4. Packages (Package maintainers)
In addition to the library, a package maintainer will require an additional
set of packages to compile a package that requires Qt. Depending on the
version of the qt library, you will require a different set of packages;
the most common option should be to make your application link against the
multi-threaded version (-mt).Packages necessary for compiling Qt
applications from source:
libqt3-mt-dev (use libqt3-dev for linking against -lqt, this package only
contains the .so files and the header file for libqui.so)
libqt3-headers (header files for libqt and libqt-mt)
qt3-dev-tools (this package contains the tools uic and moc as well as
qmake, required for building Qt applications)
If, however, you encounter an older program not to compile with this set
read the FAQ at the end of this document.
5. Packages (Developers)
In addition to the packages that packagers require, a developer usually
will require the Qt API documentationas well as tools like the assistant,
linguist or designer. However, you should be fine with installing the API
documentation that you can browse with a webbrowser, optionally with the
assistant. They are available in /usr/share/doc/qt3-doc/html.
For a regular development environment, install qt3-designer and qt3-doc.
For faciliating Qt's extended environment to write plugins for the Qt
Designer or extend the Designer as well as utilizing the Qt Assistant by
calling it from within your program, install qt3-apps-dev, which contains
the static libraries and header files required for this functionality.
For Embedded Developers, the program qvfb (Qt Virtual Frambuffer) and
makeqpf (embedded fonts tool)have been packaged into
qt3-dev-tools-embedded. For developers that work on migrating their program
from any Qt version prior to Qt 3.x to the Qt 3.x platform you will find
additional tools in the qt3-dev-tools-compat.
For using the QTranslator class and where to find the qm-file for qt as
well as where to place your translations,see the next section.
If your program doesn't compile with those settings in case you have
started your project with Qt 1.x or 2.x, please read the FAQ section at the
end of this document.
5. Packages (Translators)
In order to translate a Qt program into any other language, the Qt 3 way to
do this is to let the developer create a ts-file containing the strings
that the program exposes on the user interface. The tools to create the
ts-file and to create the final qm (Q-message binary) file, lupdate and
lrelease, are included in qt3-dev-tools.The single translator that only
gets provided the ts file and has to return a translated ts file, it
is absolutely enough to install qt3-linguist; the package qt3-assistant can
be installed to access the online-help for the Qt Linguist itself.
In case you're converting an application using Qt prior to Qt 3, you may
want to uitilize the qt3-dev-tools-compat which include the necessary tools
to convert older qm files to the new ts file standard.
Locations of message translations:
Qt ships with a set of translations for the strings used inside Qt. Those
translations will be installed into /usr/share/qt3/translations (qm files
only), which equals $QTDIR/translations respectively
qInstallPath() + QString( "/translations" ).
The configure option --translationdir has been set to /usr/share/qt3/translations
accordingly since it was introduced in Qt 3.2.
To correctly enable your program to display the translations to the Qt
library and to load the translation of the program itself, we currently
suggest to either install your translations along with any other data files
into/usr/share/<appname>/, translation files into the subdirectory
translations (that is /usr/share/<appname>/translations) The code that your
application should use to load the Qt translation will have to look like
the following:
int main( int argc, char **argv )
{
QApplication app( argc, argv );
// translation file for Qt
QTranslator qt( 0 );
qt.load( QString( "qt_" ) + QTextCodec::locale(), qInstallPath() +
QString( "/translations" );
app.installTranslator( &qt );
// translation file for application strings
QTranslator myapp( 0 );
myapp.load( QString( "myapp_" ) + QTextCodec::locale(), "." );
// use a substitue for $prefix/share/appname/translations here
app.installTranslator( &myapp );
6. Frequently Asked Questions
Using Qt for Debian as a developer or packager
----------------------------------------------
Q: I want to compile a source package that utilizes qmake to build the
Makefiles. What do I need to do to makeit work ?
A: qmake requires two environment variables to be set, QTDIR and QMAKESPEC.
To make it work, do
export QTDIR=/usr/share/qt3
export QMAKESPEC=linux-g++
Then run qmake -o Makefile <projectfile>.pro
After that, the Makefile is correctly created to build your application on
Debian. As a packager, export thosetwo variables in the rules file before
calling qmake.
Q: I have an application that when linking gives me symbol referencing
errors to Q*Style. Why does my applicationnot link correctly ?
A: The author of the program is using the styles that ship with Qt directly
instead of using the QStylePlugin interface.If you are the author of the
program, change your program to use QStylePlugin. If you are a packager,
write to theauthor of the program that he is assuming that the styles
shipped with Qt are built-in to the library which is not the case on Debian
and that he please should fix this and use QStylePlugin.
Q: Where are all the examples and tutorials ? And how do I build them ?
A: Qt ships with examples and tutorials; so does the Linguist and Designer.
The tutorials and examples are compressed tarballs which you can unpack with
tar -zxvf into your home directory. Change into the qt3-examples directory
and run the provided ./build-examples script. All Qt examples and tutorials,
including those for designer and the linguist, will be compiled. You will
notice however, that those examples that inherit from style classes which
are not built-in into Qt but configured as a plugin will not compile due
to the fact that they can't link to the Qt library.
Q: I'm writing a pure Qt application and I want to ship it with a default
configuration file. Where does that global configuration file go if I make
use of the QSettings class ?
A: With qt-3.2.0, Trolltech has introduced a configure option to Qt called
--sysconfdir which we intentionally set to /etc/qt3 similar to /etc/trinity for
KDE programs. Install your application's system wide configuration file
to /etc/qt3.
Q: I'm compiling a program and I have a compile error due to a missing
include. Why isn't that include not present in the Debian packages anymore
? It compiled with older versions of Debian packages of Qt !
A: This may be due to two reasons: either the package still uses the old
includes from Qt 1.x or 2.x that got basically renamed by Trolltech due to
the naming convention. The filenames are now all following the scheme
ClassName -> classname.h.
Therefore, if you are the developer of the affected program, change your
sources according to this scheme. Qt ships with qtrename140, a tool
to help developers migrate their API to the Qt 3 version,
which can help you in the transition upgrade to Qt 3.
If you are affected by this as a packager, notify upstream to fix those
problems and in the meanwhile use libqt3-compat-headers as a build
dependency which includes the compatibility headers that just include the
right files from the new API again.
Q: I have a question not covered by this FAQ and README file. Who should I
turn to ?
A: Please turn to Debian Qt/KDE Maintainers (debian-qt-kde@lists.debian.org)
for any questions regarding Qt on Debian.
-- Ralf Nolden <nolden@kde.org> Sun, 26 Jan 2003 20:39:19 +0100
-- Ralf Nolden <nolden@kde.org> Mon, 1 Sep 2003 19:24:16 +0200
-- Modestas Vainius <modestas@vainius.eu> Fri, 22 Feb 2008 01:40:06 +0200