Qt4 Hildon Legacy



File:Intro.png Intro

Maemo Platform

The Maemo Platform is the software stack for Nokia Internet Tablets, which includes the Maemo operating system and the Maemo SDK. The Maemo Platform is mostly based on open source code, and has been developed by the Maemo Software department within Nokia in collaboration with many open source projects such as the Linux kernel, Debian, and GNOME.[1]


What is Hildon?

Hildon is an application framework for Linux operating system mobile devices (PDAs, mobile phones, etc), developed by Nokia for Maemo and now a part of GNOME, that focuses on providing a finger friendly interface.[2]


Developing on Maemo

Developing applications for Maemo is done with the Maemo SDK. The process from creating the first prototype of your application to distributing to a wide audience consists basically of three steps:

  • Share your application project in the Garage.
  • Make your application easy to install and put in the Extras.
  • Once your application has a high quality - be promoted to the Nokia user site.


Maemo SDK

The Maemo SDK is based around the Debian-oriented Scratchbox Cross Compilation Toolkit, which provides a sandbox environment in which development may take place. Scratchbox uses Qemu to emulate an ARMEL processor or sbrsh to remotely execute instructions. Scratchbox-compatible rootstraps are available for both x86 and ARMEL, so the majority of development and debugging takes place on x86, with final packaging being for ARMEL.[3]

Watch the Maemo SDK in action!

What is Scratchbox?

Scratchbox is a cross compilation toolkit designed to make embedded Linux application development easier. It also provides a full set of tools to integrate and cross compile an entire Linux distribution.[4]


File:Rocket.png Getting started

To start to develop with Maemo Qt, we need to install the Maemo SDK on a Linux machine.

Hey, I don't have a Linux machine!

That's not a big problem. You can run Maemo SDK in a virtual machine; You can download Maemo SDK virtual Image (Linux Ubuntu + Diablo and Fremantle SDK) from tablets-dev.nokia.com. You can get VMPlayer from here.

Installing the Maemo SDK

Maemo SDK can be installaed in any Linux environment. However Debian based distros (eg: Ubuntu) are recommended.

Documentation you need to install Maemo SDK is here.

Installing Qt packages in Scratchbox

Maemo Qt developers offers a set of Qt packages for Diablo (Maemo4.1 - OS2008) and Fremantle (Maemo5 - OS2009).


Diablo Qt packages are into the official Extras repository. In order to start to develop with those packages you need to add extras repository to your repository list.

1. Open /etc/apt/source.list with a text editor (eg: kate, gedit...)
2. Append the following line to that file: 
    deb http://repository.maemo.org/extras/ diablo free non-free
3. Then update your APT cache with
     apt-get update
4. Install Qt packages with
     apt-get install libqt4-dev


You don't need to add any extra repository for Fremantle since Qt packages are already available into the SDK.

Then you can install Qt with:

fakeroot apt-get install libqt4-gui libqt4-dev

How to compile a Qt application in scratchbox

Qt applications are usually built using QMake. Project like KDE instead replaced QMake with CMake for more flexibility.


QMake is a tool from Trolltech that helps simplify the build process for development project across different platforms

You can build your Maemo Qt application in 3 simple steps:

1. Generating project file [Required if there is not .pro file into the app source tree]
   qmake -project
2. Generating Makefile from the QMake project file:
   qmake file.pro
3. make


As told before it's not a standard tool but it's largely used from people and application coming from the KDE world. Because of some issue with CMake, Diablo CMake packages are currently useless since CMake segfaults. This issue has been solved in Fremantle and CMake packages that comes from Fremantle SDK work nicely.

- CMake projects has usually a CMakeLists.txt file instead of 
    - .pro file used by QMake projects
    - Makefile.am used by Autotools projects (standard in Unix/Linux)

Using CMake to build the project is extremely easy. In the directory containing CMakeLists.txt, supply the following two commands, where path is the path to the source code.

- cmake path
- make

Note: CMake is not installed by defualt in scratchbox. You can install it with

apt-get install cmake

Running a Qt application in:

A. Scratchbox

Diablo and Fremantle Qt applications can run into the device as into scratchbox.

First step to run a Qt application is starting the SDK UI:

1. Run Xephyr. It's able to run a X Server inside another X Server.

Xephyr :2 -host-cursor -screen 800x480x16 -dpi 96 -ac -kb

2. Set display for application that runs inside scratchbox

[sbox-DIABLO_<target>:~] > export DISPLAY=:2

3. You can now run the SDK UI. Diablo or Fremantle desktop will appear into your Xephyr window:

[sbox-DIABLO_<target>:~] > af-sb-init.sh start

4. Now you are ready to run any Maemo or Maemo Qt application with

[sbox-DIABLO_<target>:~] > run-standalone.sh ./qtapps

Note: run-standalone.sh sets some variable needed by Qt to use the Hildon style.

B. device

Maemo Qt applications are linux binaries. They can run into the device without any problem if you copy it/them in "partitions" mounted with exec flag. (Eg: /home/user or /opt in Fremantle).

Eg: If we want to run quassel (Qt IRC Client) we have to launch it with:

Nokia-N900-44-1:/home/user# ./quassel

File:Hammer.png Porting Qt applications to Maemo


Porting a Qt desktop application to Maemo requires very little effort. This because the Maemo Qt libraries will take care of giving the Hildon look & Feel and enabling the virtual input methods for your application.

Overriding the Qt Maemo changes

Maemo Style

Hildon Style is the default Qt application style. Other style available are:

Qt application can use other Qt styles;

  • Running your application with the style flag:

./qt-test-application -style windows

Showing the status bar

Hildon applications don't have a status bar. Qt for Maemo hides the status bar by default. You can show it again by modifying your code.


Using the Kinetic Finger Scrolling (cf Gtk's PannableArea)

See Finger Scrolling

Adding Maemo changes to a Qt Application

Some methods of Qt for Maemo are not available in the "standard" Qt libs, so a Qt application with specific Maemo Qt code can't be built outside the Maemo SDK. To avoid this issue, the developer can use the preprocessor directives, for example:

#ifdef Q_WS_HILDON
   //Specific hildon code here 


Currently Qt Maemo lacks full support for Hildon widgets introduced in Maemo 5.

At the moment, creating a Qt application that follows Maemo 5 UI Style requires using custom Qt widgets, coded within the application itself.

There is work ongoing to provide Qt Hildon widgets for Maemo 5, see Qt Hildon Widgets

To get the benefits of the ongoing Maemo 5 hildon integration work in Qt, you must get the latest Qt source code and compile it yourself. See Building Qt from GIT repository.

File:Bug.png Debugging a Qt application



The GNU Project Debugger, or gdb for short, is a general purpose debugger that can be used for various debugging purposes.

Debugging a Qt application in Scratchbox


Debugging a Qt application on device

  1. Installing gdb on the device.
    1. Add the SDK tools repository to the catalogue list.
    2. install gdb by using apt-get (require around 6 MB of space)
  2. Install the debug symbols files in scratchbox (ARMEL target)
  3. apt-get install libqt4-dbg
  4. Run the application (device side)
  5. $gdbserver ./qtApplication
  6. Run the gdb client on your host PC (scratchbox side)
  7. [sbox-DIABLO_ARMEL: ~/TEST/svn/qt4-x11-4.4.0/examples/widgets/tablet] > gdb ./qtApplication
  8. Set the target of gdb
  9. (gdb) target remote
  10. Tell to gdb to continue to debug the application on the device
  11. (gdb) continue
  12. Wait some moments...
  13. If necessary you can put break points; eg: for void QWidget::setPalette ( const QPalette & )
  14. (gdb) break QWidget::setPalette(QPalette const&)
    Breakpoint 1 at 0x4026ae68
  15. Your application will appear on the device screen. Happy debugging!


File:Chart.png Profiling a Qt application


OProfile is a low overhead system-wide profiler for Linux. It can be used to find CPU usage bottlenecks in the whole system and within processes. It works fine in the device, but viewing the reports can take quite a long time (10 minutes) when fired up on N800/N810 devices. Therefore, it often makes sense to run opreport in scratchbox.

If you want to know more about OProfile in Maemo see the documentation.



File:Chart.png Qt benchmarks

2D graphic benchmark tools:

3D graphic benchmark tools:

  • TODO

File:Package.png Packaging a Qt application for Maemo

Main article: Packaging a Qt application

File:Helmet.png Maemo Qt API Reference

Maemo Qt is based on Qt for X11. It shares same APIs avoiding API breaks. In this way every Qt application that runs in other platforms (Windows, Mac OS X, Linux, S60, etc.) can run in Maemo devices as well. To Develop a Qt application you can use the Official Qt 4.5 API documentation and the list below to see what are the Maemo changes.


 QString QDesktopServices::storageLocation(StandardLocation type) returns specific Maemo locations for these types:
 - DesktopLocation:   QDir::homePath() + QLatin1String("/MyDocs"),            instead of QDir::homePath() + QLatin1String("/Desktop")
 - DocumentsLocation: QDir::homePath() + QLatin1String("/MyDocs/.documents"), instead of QDir::homePath() + QLatin1String("/MyDocs/.documents")
 - PicturesLocation:  QDir::homePath() + QLatin1String("/MyDocs/.images"),    instead of QDir::homePath() + QLatin1String("/Pictures")
 - MusicLocation:     QDir::homePath() + QLatin1String("/MyDocs/.sounds"),    instead of QDir::homePath() + QLatin1String("/Music")
 - MoviesLocation:    QDir::homePath() + QLatin1String("/MyDocs/.videos"),    instead of QDir::homePath() + QLatin1String("/MyDocs/.videos")
 QTabletEvents are able to get the pressure value from the touchscreen.
  - The eventdeviceType is for the touchscreen is set to QTabletEvent::Stylus.
  - QTabletEvents won't be used anymore in Fremantle
 Finger poke is emulated in scratchbox by the Middle Mouse button (NOTE: There is no Fullscreen VKB in scratchbox)

 QInputEvents don't move the cursor. 
 It's mandatory to get working the HIM moving the cursor via QInputMethodEvents.
 Why is it mandatory?  
 Because if the user select text with the finger from the right to the left, we are able to remove the highlighted text, but the
 cursor will be moved on the last char instead to stay on the first one.
 To do that some changes has been added to some widget function like: widget::inputMethodEvent(QInputMethodEvent *e).
 Modifing that function in some custom widgets may be necessary.
 Don't reimplementing that function will break some fullscreen virtual keyboard features.
 Hardcoded Keys:
 In the QMainWindow:
 - F6 - Toggle fullscreen the application
 - F4 - Shows/Hides the application context menu
 - Zoom in  - is a standard key sequence QKeySequence::ZoomIn
 - Zoom out - is a standard key sequence QKeySequence::ZoomOut
 Input Method:
 Maemo Qt uses the Hildon IM as default Input method.
 Each kind of widget can set the IM mode. This allows the input method to focus on the type of input that the application is expecting.
 Eg: spinboxes can receive only numeric characters (1-9).
 NOTE: Qt widgets like QTextEdit, QLineEdit... set the right input method mode automatically. 
 A developer can change it by using:
   void QInputContext::setInputMode(int mode);
 It will update immediately the Hildon Input method to use the selected IM mode.  
 HIC Modes:
   HILDON_GTK_INPUT_MODE_ALPHA 	alphabetical characters and whitespace
   HILDON_GTK_INPUT_MODE_NUMERIC 	numbers 0-9 and the '-' character
   HILDON_GTK_INPUT_MODE_SPECIAL 	special characters
   HILDON_GTK_INPUT_MODE_HEXA 	hexadecimal characters; numbers 0-9, characters a-f, and A-F
   HILDON_GTK_INPUT_MODE_TELE 	telephone numbers; numbers 0-9, whitespace, and the characters "pwPW/().-+*#?,"
   HILDON_GTK_INPUT_MODE_FULL 	unrestricted entry mode, combination of the alpha, numeric and special modes.
   HILDON_GTK_INPUT_MODE_MULTILINE 	the client contains multiple lines of text or accepts linebreaks in the input.
   HILDON_GTK_INPUT_MODE_INVISIBLE 	do not echo or save the input in the IM when entering sensitive information such as passwords.
   HILDON_GTK_INPUT_MODE_AUTOCAP 	automatically capitalize the first letter at the start of a sentence.
   HILDON_GTK_INPUT_MODE_DICTIONARY 	enable predictive dictionaries and learning based on the input.
   For a password field we need to set a specific IM mode:
   QInputContext qic = widget->inputContext();
 If you are developing a Custom widget able to receive input text, you can instruct your widget to use the right IM Mode just returning
 the mode.
 - How does it work?
 The Hildon IM sends a XMessage to pop up the "Virtual Keyboard" (or better the Main HIM UI) when an input widget receive the focus.
 The IM before to raise the VKB, makes an inputMethodQuery to the widget retrieving the IM mode.
 If the developer of the custom widget doesn't set the mode property, the IM will use HILDON_GTK_INPUT_MODE_FULL (the default mode) for that widget.
 Setting the ImMode is quite easy. Check the code below for more understanding.
 #ifdef Q_WS_HILDON
 #include <QInputContext>
 QVariant QAbstractSpinBox::inputMethodQuery(Qt::InputMethodQuery query) const
   Q_D(const QAbstractSpinBox);
   switch(query) {
       case Qt::ImMode:{
           int mode = HILDON_GTK_INPUT_MODE_NUMERIC;
           return QVariant(mode);
           return d->edit->inputMethodQuery(query);


[This section is just a draft]

Portrait mode and listening for orietnation changes

If you want to run your application in portrait mode then you can add these lines to your application. The code goes in your main widget construtor.

#ifdef Q_WS_HILDON
//Includes for portrait mode support
# include <X11/Xlib.h>
# include <X11/Xatom.h>
# include <QtGui/QX11Info>

#ifndef Q_WS_HILDON
int value = 1;
Atom portraitSupport = XInternAtom(QX11Info::display(), "_HILDON_PORTRAIT_MODE_SUPPORT", false);
Atom portraitRequest = XInternAtom(QX11Info::display(), "_HILDON_PORTRAIT_MODE_REQUEST", false);
XChangeProperty(QX11Info::display(), winId(), portraitSupport, XA_CARDINAL, 32, PropModeReplace, (uchar *)&value, 1);
XChangeProperty(QX11Info::display(), winId(), portraitRequest, XA_CARDINAL, 32, PropModeReplace, (uchar *)&value, 1);

If you want to listen for orientation changes and then switching the view to landscape or potrait mode automatically than take a look at[ http://wiki.maemo.org/Maemo_Qt_Extra_Lib... for more info

QPrint* and QSystemTray support missing

Printing (QPrint*) and System tray support is missing in current
Qt 4.5.3-xxxx-maemo4 packages.
Since incompatibility with KDE and other Qt application, they will be enabled again in next Qt 4.5.3 packages.

File:Helmet.png Contributing to the Maemo Qt Project

Maemo Qt is a community project. Contributing to the forum, sending us patches, give us feedbacks, tracking bugs are all activities that help us to improve the quality of our work.

Here there is a list of things that every person interested in helping us should read.

Be updated

Any Maemo Qt developer should be updated and should participate to the discussions, for that he must join the Mailing list. BTW the mailing list is not for Maemo Qt Developers but it's open to Maemo Qt application developers too.

Introduction to Git

If you are a git newbie you maybe find interesting these links:

Understanding the structure of our Git repository

These info are here:Qt Maemo Git Process.


Make sure each scratchbox target has

 fakeroot apt-get build-dep libqt4-gui

(you may need to apt-get install libgl-dev too as it's not in the Build-Depends: yet)

Building Qt from GIT rep

  • Clone the repository:
git clone git://gitorious.org/+qt-maemo-developers/qt/qt-maemo.git 

or if you are a member of our team:

git clone git@gitorious.org:+qt-maemo-developers/qt/qt-maemo.git
  • Change dir
cd qt-maemo
  • Copy the remote 4.5 branch in your workingcopy
git checkout -b 4.5 origin/4.5
  • Checkout ONE of these branches:
git checkout -b qt-diablo    origin/qt-diablo
git checkout -b qt-n900 origin/qt-n900
git checkout -b qt-mer       origin/qt-mer
  • Build the packages:
dpkg-buildpackage -rfakeroot -b

Checking out all the remote branches

  • Clone the repository:
git clone git://gitorious.org/+qt-maemo-developers/qt/qt-maemo.git 

or if you are a member of our team:

git clone git@gitorious.org:+qt-maemo-developers/qt/qt-maemo.git
  • Change dir
cd qt-maemo
  • Check out our script branch
git checkout -b maemo-qt-scripts origin/maemo-qt-scripts
  • Save a copy of the script outside the working directories
cp maemo-qt-scripts/copy-all-remote-branches-locally/copy.sh ../
  • Launch the copy.sh script

Commit changes in SVN [OLD]

If you are a Maemo Qt developer and you want to save your changes in the Garage SVN but your project is not ready to go to the main line (trunk/qt-x11), you should create a private branch and then work there until the merging with the mainline.

For that you have to create a your directory in branches/ named developer_name-qt. After that you can copy trunk/qt-x11 in your directory.

svn copy --username developer_name https://garage.maemo.org/svn/qt4/trunk/qt-x11 https://garage.maemo.org/svn/qt4/branches/developer_name-qt -m "Creating private branch of trunk/qt-x11"

NOTE: Subversion uses cheap copy, so them don't increase the size of the repository. Then feel free to create your own branch.

Merging branches changes in the mainline [OLD]

Before to merge your changes in the mainline, the code must be full working, cleaned and tested. A review from another developer is also needed in order to reduce the possibility to add errors.

File:Help-contents.png F.A.Q.

I'm trying to compile a Qt application for ARMEL, but I got the error below. What's wrong?

/targets/FREMANTLE_X86/usr/include/qt4/QtCore/qatomic_i386.h:127: error: impossible constraint in 'asm'

You are using x86 include files, then you have to update your Makefile. Running qmake before make will be solve this issue.

I'm trying to compile a Qt packcage for x86, but I got the error below. What's wrong?

In file included from maemo/gconfsymbols.cpp:41:
maemo/gconfsymbols_p.h:49:25: gconf/gconf.h: No such file or directory

Your scratchbox does not have /bin/sh, so when calling pkg-config from qmake, CFLAGS and LIBS are not set correctly. Running ln -s /scratchbox/tools/bin/sh /bin/sh will be solve this issue.

I'm trying to compile a diablo Qt package, so I just created a symbolic link, debian, for debian.diablo, and then run dpkg-buildpackage command, but I got a build error because the symbolic link was deleted.

When running dpkg-buildpackage, all symbolic links will be deleted, so need to rename the folder from debian.diablo to debian to make a build of diablo Qt package.

I installed Qt (libqt4-dev) to scratchbox and tried to build a sample application, but I got the error because some header files such as qhildonstyle.h, and qvfbhdr.h etc. were missing.

libqt4-dev should copy all header files, but now, at least in 4.5.2-1maemo1, some files are missing. Please download file below and extract to your scratchbox system.


Installing Qt on N900

If you have already a fremantle device then you can install new Qt packages from extras-devel. The step to follow are:

" >> /etc/apt/sources.list.d/hildon-application-manager.list

  • apt-get install libqt4-gui

The basic packages will be so installed.

Current known issues:

  • libqt4-opengl depends by libgles2, but it is not installable anymore.Has it been replaced with libgles2-sgx-img?

Where are the Hildon Widgets for Qt

Short answer : they've not been written.... yet.

Qt allows you to create your own widgets very easily. However, in order to provide as consistent an appearance as possible for the Maemo platform the community will be creating a set of Qt Hildon Widgets

Is it possible to create fremantle desktop widgets with Qt?

Yes, but unfortunately you can't load them with the widget manager since hildon widgets are GTK shared object file.

A simple Qt hildon-desktop widget is in Extras-devel; Browse your application manager and look for qt-example-hildondesktopwidget.

How to minimize a Qt application?

QDBusConnection c = QDBusConnection::sessionBus();
QDBusMessage m = QDBusMessage::createSignal("/","com.nokia.hildon_desktop","exit_app_view");


  1. Maemo Platform on Wikipedia
  2. Hildon on Wikipedia
  3. Maemo SDK on Wikipedia
  4. Scratchbox on Wikipedia