Qt Quick development process

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Revision as of 16:03, 30 January 2022 by Petitlapin (talk | contribs) (Creating an aab and testing it)
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Learning Qt Quick

Some pointers to discover Qt Quick:

A step by step exercise to dig into Qt Quick with the QtCreator development environment:

The following list provided by Jerome from QtMob forum is a gold mine:

In order to debug QML you can use GammaRay from KDAB:


Here are some videos links to learn how to use it:

Coding Style

We follow this coding style.

Source code

Here is the official repository for the source code. Alternatively you can also get the code on GitHub.

Compilation prerequisites

For Debian based systems, in order to compile GCompris you need to install the following packages:

Compilation chain

sudo apt-get install cmake
sudo apt-get install cmake-curses-gui # Optional
sudo apt-get install g++
sudo apt-get install libgl1-mesa-dev
sudo apt-get install libssl-dev

Note that openssl is needed since GCompris 0.96 to be able to download the resource files in https.


sudo apt-get install qt5-default qtdeclarative5-dev qtmultimedia5-dev qml-module-qtquick-controls libqt5svg5-dev libqt5sensors5-dev qml-module-qtquick-particles2 qttools5-dev-tools qml-module-qtmultimedia libqt5multimedia5-plugins

In Ubuntu 18.04+ you need to install also qttools5-dev in order to get /usr/lib/x86_64-linux-gnu/cmake/Qt5LinguistTools/Qt5LinguistToolsConfig.cmake.


CMake is a cross-platform free software program for managing the build process of software using a compiler-independent method. The minimum version to compile GCompris is 3.5 (3.21 is required on Windows to build packages).

git clone https://invent.kde.org/education/gcompris.git
  • Initialize the git submodule(s)
cd gcompris
git submodule init && git submodule update
  • Download and Install the latest stable version of Qt (This includes QtCreator in the Tools/QtCreator directory. Minimum required version is 5.9. For running on Android, download the Android version (for now, to compile for Android, use either 5.9 or 5.12, build toolchain hasn't been updated for Qt 5.14 and above).
  • Start QtCreator and open the project file CMakeLists.txt at the root of the source code
  • Create a build directory and set it in Qt Creator
  • Compile and run it. (No need of giving any arguments to CMake, if QtCreator asks for it)

To compile from the command line you need:

  • mkdir build
  • cd build
  • cmake ..
  • make

To make it run on Android you need first to follow these instructions. If some errors occur, follow this cmake compilation trouble link.

Generate core API documentation

KDE uses kapidox, a wrapper around doxygen to generate API documentation. Kapidox uses doxyqml for generating documentation for QML code.

In GCompris we document all classes in the src/core/ directory.

To build this API documentation you need:

Then do

kgenapidox ./path/to/gcompris-checkout/

and find your documentation under apidocs/.

Adding a new activity


Let's say you want to create the algebra_by activity.

cd src/activities
./createit.sh algebra_by "Your Name" xx@yy.org

And you're done, you can run CMake again in QtCreator and your activity should appear on the list.


You must create a directory for your activity in src/activities. In it, create an ActivityInfo.qml, CMakeLists.txt and your qml entry point AlgebraBy.qml.

  • in src/activities/activities.txt add the directory name of your activity (keep the file sorted).
  • check algebra_by/ActivityInfo.qml that the name references you Qml activity entry point and that the icon point to your icon name (preferred format is svg).

Getting old menus

If your activity is an existing one, you can move its ported ActivityInfo and icon:

git mv tools/menus/algebra_by.qml src/activities/algebra_by/AlgebraBy.qml
git mv tools/menus/resource/algebra_by.svg src/activities/algebra_by/algebra_by

Extending another activity

If the activity is just an extension of an existing one you have to create it either manually or automatically and then change you .qml file to extend another one. The 'erase_clic' activity is a good example.

In your .qml file:

  • just import the activity you want to extend with for example: import "qrc:/gcompris/src/activities/erase"
  • instead of have your root item being an 'ActivityBase' you just create an object of the base type you want to extend like Erase.
  • Use a property to pass parameters to your base item and customize it

Coding guidelines

Take a look at this check list to have a high level check list before asking for a review.

Keep only small Javascript in the QML code, all the game logic must be in your Javascript file. This makes it easier to read the activity logic. It is possible to have several Javascript files if needed. The QML files must be seen as the graphical interface description and the Javascript the logic of the game.

Adding a configuration for a specific activity

Each activity can have a specific configuration (for example, changing the locale of the activity, having different modes...). A simple example can be found on Traffic activity where you can change between images and colors to display the cars.

To add configuration, you need to add the "config" value in the Bar. Then you have to add a DialogActivityConfig item where you will define the component item of the dialog. You need to define the following functions:

  • setDefaultValues to set the values when displaying the configuration.
  • onLoadData which is called to load the existing data from configuration.
  • onSaveData which is called to save the configuration in configuration file and where you can also send signals to dynamically change current activity settings.

The data should be set in "dataToSave" attribute which is a map (pairs of key, values) where the keys are strings and values are javascript var (can be strings, lists...).

Accessing the component items can be done using: dialogActivityConfig.configItem.

For the data to be loaded at start of activity, you also need to call "dialogActivityConfig.getInitialConfiguration()" on Component.onCompleted() of your pageComponent item.

Compilation on different platforms

Compiling GCompris for Desktop

You can still use QtCreator to develop. Within it, open the CMakeLists.txt on top-level of GCompris. Select a directory (create a folder at same level as the gcompris folder for example) and then click on "Run CMake" button then finish.

To compile GCompris on command line, you can create a directory GCompris-qt-build at same level as the gcompris folder, go into it and type "cmake ../gcompris && make". You have the possibility to check which activities you want to compile or not.

If you want to create an auto extractible package for linux platforms, you need to launch cmake using: "cmake -DBUILD_STANDALONE=ON ../gcompris && make".


  • If you get the error: "The imported target "Qt5::Gui" references the file "Qt5Gui_EGL_LIBRARY-NOTFOUND" but this file does not exist."
sudo apt-get install libgl1-mesa-glx

try again If this still shows the same error or tells you - /usr/bin/ld: cannot find -lGL - do :

on a 32 bits system
cd /usr/lib/i386-linux-gnu
sudo ln -s /usr/lib/i386-linux-gnu/mesa/libGL.so.1 libGL.so

on a 64 bits system
cd /usr/lib/x86_64-linux-gnu
sudo ln -s /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1 libGL.so
  • If you miss the GL/gl.h header, install it with sudo apt-get install mesa-common-dev

Compiling GCompris for Android

Install openjdk (for example it could be openjdk-8-jdk from your favorite package manager).

To build APK files for android, the minimum required version of Qt is now 5.12.6 (tested with 5.12.9, 5.13.0 and 5.13.1). It fails with 5.12.10 and 5.12.11.

It uses gradle, android ndk r21e and openssl 1.1.1m.

Clang is provided within the NDK android environment. You do not need to install ant anymore, and gradle will download itself automatically during the apk creation.

Step 1: Get ECM sources, build and install them.

ECM or Extra CMake Modules package reduces duplication in CMake scripts across KDE software. If the ECM version shipped with your distribution is not recent enough, try to get the most recent version from ECM git repository.

To get the sources (tested with 5.62 and 5.63), in your ~/home, type:

git clone https://anongit.kde.org/extra-cmake-modules.git
cd extra-cmake-modules
git fetch && git fetch --tags
git checkout v5.63.0

Build and install ECM:

cmake -DCMAKE_INSTALL_PREFIX=install . && make && make install

Step 2: Download and set PATH environment variable for android NDK.

Download Android NDK, Revision 21e (January 2021) Linux 64-bit (x86), from the following link:


Create an Android folder in your home:

mkdir ~/Android

Unzip android-ndk-r21e-linux-x86_64.zip in this directory.

Edit the file ~/.bashrc to add the following lines:

export ANDROID_NDK=~/Android/android-ndk-r21e

Then reload it:

source ~/.bashrc

Step 3: Download and install android sdk.

Create an android-sdk folder in ~/Android/ .

Download android sdk tools_r25.2.5-linux.zip using the following link: https://dl.google.com/android/repository/tools_r25.2.5-linux.zip .

Place it in the folder ~/Android/android-sdk .

Unzip it.

Execute the program android located in ~/Android/android-sdk/tools. It will open a gui application called Android SDK Manager.

Select the following tools:

- Android SDK Tools 25.2.5

- Android SDK Platform-tools 29.0.4

- Android SDK build-tools 28.0.3

Install them by clicking on the "Install packages" button.

Edit the file ~/.bashrc to add the following lines:

export ANDROID_SDK_ROOT=~/Android/android-sdk
export PATH=$PATH:~/Android/android-sdk/platform-tools:$ANDROID_SDK_ROOT/tools/bin

Then reload it

source ~/.bashrc

Step 4: Add Qt5_android environment variable.

Edit the file ~/.bashrc to add the following line:

export Qt5_android=~/Qt5.13.1/5.13.1/android_armv7/lib/cmake

Adapt the path (~/Qt5.13.1/5.13.1/) according to your Qt installation.

Reload it:

source ~/.bashrc

Step 5: Compile and build the apk.

Create the folder build_android at the same level as the GCompris-qt folder.

Go in this folder and run the command:

cmake -DCMAKE_TOOLCHAIN_FILE=~/extra-cmake-modules/install/share/ECM/toolchain/Android.cmake -DQt5_DIR=~/Qt5.13.1/5.13.1/android_armv7/lib/cmake/Qt5/ -DCMAKE_FIND_ROOT_PATH=~/Qt5.13.1/5.13.1/android_armv7/lib/ ../GCompris-qt

Here again you have to adapt the Qt path according to your installation (~/Qt5.13.1/5.13.1), and the path to Android.cmake from extra-cmake-modules as well (~/extra-cmake-modules/install/share/ECM/toolchain/Android.cmake).

After cmake has finished, execute the following commands:

make -j 4
make apk_debug

You should find the apk file created in build_android/android/ .

Deploying on android device

To deploy, plug you computer to your tablet. Go into you tablet preferences, switch on the developer mode.

Into the console, type the following command:

adb install -r GCompris-debug.apk

Creating an aab and testing it

Starting Qt5.14, you can know create aab directly. You need to specify in the cmake command which ABI you want to build using the variables: ANDROID_BUILD_ABI_abi=ON, where abi can be any of: armeabi-v7a, arm64-v8a, x86_64 or x86.

For example, to build an aab with all:

cmake -DCMAKE_TOOLCHAIN_FILE=/usr/share/ECM/toolchain/Android.cmake -DCMAKE_FIND_ROOT_PATH=~/Qt/5.15.2/android/lib/ -DQt5_DIR=~/Qt/5.15.2/android/lib/cmake/Qt5/ -DANDROID_BUILD_ABI_armeabi-v7a=ON -DANDROID_BUILD_ABI_arm64-v8a=ON -DANDROID_BUILD_ABI_x86_64=ON -DANDROID_BUILD_ABI_x86=ON ..
make -j 4
make aab_release

To test it, you need to download the bundletool tool and extract it somewhere. Then run:

java -jar <path/to/bundletool>/bundletool.jar build-apks --bundle=GCompris-Android-release-dl-2.1.aab --output=GCompris.apks

or to create release apks:

java -jar <path/to/bundletool>/bundletool.jar build-apks --bundle=GCompris-Android-release-dl-2.1.aab --output=GCompris.apks --ks=${PASS_FILE} --ks-pass=pass:${PASS_KEY} --ks-key-alias=gcompris --overwrite

To deploy it on your device, connect it (and make sure you have enabled the debug mode via USB using developer mode):

java -jar <path/to/bundletool>/bundletool.jar bundletool-all-1.8.2.jar install-apks --apks=GCompris.apks

Compiling GCompris for SailfishOS

You need to download and install the sailfishOS SDK (SDK). Once done, you need to start the mersdk virtual machine:

VBoxManage startvm MerSDK

And ssh into it:

ssh -p 2222 -i ~/SailfishOS/vmshare/ssh/private_keys/engine/mersdk mersdk@localhost

In order to build you need to install cmake and git:

sb2 -t SailfishOS-armv7hl -m sdk-install -R zypper install cmake git

Then, you need to log in armv7hl:

sb2 -t SailfishOS-armv7hl

Clone the source code and on a separate folder type:

cmake -DSAILFISHOS=1 -DBUILD_ARCH=armv7hl ../gcompris/ && make package

You will probably have the following error at the end: CPack Error: Problem copying the package: /home/mersdk/build_arm/_CPack_Packages/Linux/RPM/gcompris-0.34-Linux.rpm to /home/mersdk/build_arm/gcompris-0.34-Linux.rpm but it's ok. You can find the generated package at: /home/mersdk/build_ arm/_CPack_Packages/Linux/RPM/harbour-gcompris-qt-0.34-1.armv7hl.rpm.

If you want to build the translations, you need to install gettext (for msgattrib) and follow the chapter Qt_Quick_development_process#Getting_and_compiling_translations. /!\ Does a Subversion package exist? Maybe https://openrepos.net/content/nieldk/subversion-0?

You can also build for emulator (replace all armv7hl above with i486). To install on emulator, run the SailfishOS emulator and copy the rpm into it. You can copy it from the mersdk vm using the shared folders to get it from the mersdk and on your host:

scp -P 2223 -i ~/SailfishOS/vmshare/ssh/private_keys/SailfishOS_Emulator/nemo harbour-gcompris-qt-0.34_1-1.i486.rpm nemo@localhost:RPMS
ssh -p 2223 -i ~/SailfishOS/vmshare/ssh/private_keys/SailfishOS_Emulator/nemo nemo@localhost
pkcon install-local harbour-gcompris-qt-0.34-1_1.i486.rpm

It should now appear on the emulator.

Compiling GCompris for Ubuntu click

You need to have a ubuntu OS installed and the ubuntu sdk (sudo apt-get install ubuntu-sdk).

Clone the source code in a GCompris-qt folder.

Then, you need to create the chroot environment (it can take some time) and log into it:

sudo click chroot -a armhf -f ubuntu-sdk-14.10 create
sudo click chroot -a armhf -f ubuntu-sdk-14.10 run

You can use a newer one instead of 14.10.

Inside the chroot, you need to manually install the QtQuickControls module and run the compilation command:

apt-get install qml-module-qtquick-controls:armhf
cmake -DWITH_UBUNTU=on -DUBUNTU_CLICK=1 -DQt5_DIR=/usr/lib/arm-linux-gnueabihf/cmake/Qt5/ ../GCompris-qt/ && export QT_SELECT=qt5-arm-linux-gnueabihf && make && make DESTDIR=/tmp/click/ install

To compile and embed translations, you need to follow the chapter Qt_Quick_development_process#Getting_and_compiling_translations.

Then outside the chroot, you need to run the click command to create the package:

click build /tmp/click/

This will create the click package.

Compiling GCompris for Windows

Compilation on Windows has been tested with mingw only. Download and install Qt for Windows with mingw (http://www.qt.io/). You also need to install NSIS (NSIS homepage).

Then, in a in Qt/mingw console:

cmake -G"MinGW Makefiles" ..\gcompris && mingw32-make && mingw32-make package.

The package creation can take some time because of the dependencies retrieval.

Compiling GCompris for Mac OS X

Compilation on OSX is quite similar to Linux.
Install CMake. The minimum version to compile GCompris is 2.8. Download and install Qt for OSX. Box2D compilation is not yet supported in macOSX, you have to disable it during compilation. Then in console:

$ git clone https://github.com/gcompris/GCompris-qt.git 
$ cd GCompris-qt
$ git submodule init && git submodule update
$ export Qt5_DIR=$HOME/Qt5.7.0/5.7/clang_64/lib/cmake/Qt5/
(This path would vary with your Qt5 folder location)
$ mkdir build
$ cd build
$ cmake -DQML_BOX2D_MODULE=disabled  ..
$ make

This should successfully build GCompris on your Mac. To run, start the GCompris-qt.app file in build/bin/ folder.

Issues: If you face issues regarding no 'svg/image load'.

-Copy the plugins from




Getting and compiling translations

By default, no translation are present in the git repository. We need to get them from the KDE svn KDE i10n svn. You can see the translation status at GCompris translation status.

You need to have subversion and msgattrib installed.

To get all the translation files, you need to create the Makefile using cmake (see above) and type:

make getSvnTranslations

This will copy all the po files to a po/ folder in the source directory.

Once you have done this, you need to run again cmake in order to have all the translations handled. Then, to build the translations used by GCompris, type:

make BuildTranslations

Then go into the bin directory and type ./gcompris-qt to launch the software (or running from QtCreator). In the configuration dialog box, you can choose your language. Restart the application to see the language change.

If you're compiling using Qt Creator, you can go to the Projects tab and in Build Steps, add a build step and check BuildTranslations.

Getting translations from the Gtk version

When adding a Gtk ported activity in the QtQuick version, if you used the strings for texts of the Gtk version, you can update all existing translation files. For this, first you need to update existing translation files using (this will add the new strings which will be untranslated for now):

make UpdateTranslations

Then, using the convertPo.py tool (and the updateAll.sh which applies it to all translations), you can update the files to get the translations from the Gtk version (if they existed).

Adding resources

  • For resources, you have to put them in the resource directory of your activity
  • A compiled qrc file named youractivity.rcc is auto generated by the compilation chain
  • You must run cmake again to have new resources included in the qrc
  • If you change a resource, a simple make will update the rcc file
  • To reference your resource, use a qrc:/ url in the source. The path is:

Reviewing an activity

The Reviewing an activity page contains info to help reviewing an activity.