View source for Kdenlive/Development

Kdenlive is rather easy to build (at least on supported platforms), and this page should show you the simple steps to get there. If you encounter any problem during the process or spot any information that should be added/updated, please don't hesitate to reach out to the [[#Developer_Mailing_List| Developer's mailing list]] or on the [https://t.me/kdenlive_dev Telegram Kdenlive Developers' group] .

== Pre-requisites and Supported Platforms ==

Kdenlive is primarily developed on GNU/Linux. There is an effort to  [[Kdenlive/Development/WindowsBuild|build Kdenlive on Microsoft Windows]], but it's still a work in progress.

Currently supported distributions are:

* Ubuntu 20.04 LTS Focal Fossa and derivatives
* Arch Linux

You should be able to build it on any platform that provides up to date versions of the following dependencies  '''Qt >= 5.7''', '''KF5 >= 5.50''','''MLT >= 6.20.0'''.

To get a recent enough version fo MLT on Ubuntu, you have to add [https://launchpad.net/~kdenlive/+archive/ubuntu/kdenlive-master Kdenlive's ppa]

<pre>
sudo add-apt-repository ppa:kdenlive/kdenlive-master
sudo apt update
</pre>

It is recommended to uninstall the official kdenlive packages to avoid potential conflicts. 

<pre>
sudo apt remove kdenlive kdenlive-data
</pre>

== Installing dependencies ==


=== Development tooling ===

You will need classical development tools (like git, gcc ...) but also cmake :
<pre>
sudo apt install build-essential git cmake extra-cmake-modules libsm-dev
</pre>

=== KDE Frameworks 5, based on Qt5 ===

On Ubuntu the following packages will pull all the necessary dependencies:

<pre>
sudo apt install libkf5archive-dev libkf5bookmarks-dev libkf5coreaddons-dev libkf5config-dev \
libkf5configwidgets-dev libkf5dbusaddons-dev libkf5kio-dev libkf5widgetsaddons-dev \
libkf5notifyconfig-dev libkf5newstuff-dev libkf5xmlgui-dev libkf5declarative-dev \
libkf5notifications-dev libkf5guiaddons-dev libkf5textwidgets-dev libkf5purpose-dev \
libkf5iconthemes-dev kdoctools-dev libkf5crash-dev libkf5filemetadata-dev  kio \
kinit qtdeclarative5-dev libqt5svg5-dev qml-module-qtquick-controls \
qtmultimedia5-dev qtquickcontrols2-5-dev breeze-icon-theme
</pre>

=== Multimedia stack ===

If your distribution packages a recent enough version of  MLT (>= 6.20.0), you can install it directly along with ffmpeg and frei0r plug-ins. Otherwise, you'll have to add our ppa or compile it yourself (see above)

<pre>
sudo apt install libmlt++-dev libmlt-dev melt frei0r-plugins ffmpeg
</pre>

=== Dependencies for localization  ===

There are some additional dependencies required by the specific script to fetch the translations: 
<pre>
sudo apt install ruby subversion gnupg2 gettext
</pre>

== Getting the source code ==

=== Cloning the git  repo ===
The easiest  way to get Kdenlive source code is to clone the git repo:

<pre>
git clone https://invent.kde.org/multimedia/kdenlive.git
</pre>

=== Selecting the  branch ===

You should generally base your developments on the master branch

<pre>
cd kdenlive
git checkout master
</pre>

or if you want to get the code for a given release

<pre>
cd kdenlive
git checkout release/20.04
</pre>

==  Building Kdenlive ==
Create a directory for the build inside the kdenlive directory:

<pre>
mkdir build
cd build
</pre>

To avoid problems with plugins and libraries, it is easier to install Kdenlive in /usr:

<pre>
cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON -DCMAKE_INSTALL_PREFIX=/usr -DRELEASE_BUILD=OFF
</pre>

Alternately you can build it with debug flags (advanced users only ;-)  and you need to have clang installed ) :

<pre>
cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON \
-DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Debug \
-DCMAKE_CXX_COMPILER=/usr/bin/clang++ \
-DECM_ENABLE_SANITIZERS='address' \
-DBUILD_TESTING=ON -DBUILD_FUZZING=ON -DBUILD_COVERAGE=OFF \
-DRELEASE_BUILD=OFF
</pre>


You may get a warning "Qt5 WebEngineWidgets not found. You cannot use your Freesound.org credentials, only preview files can be downloaded from the Online Resources Widget": as this is a very specific feature requiring a rather large dependency, you can just ignore it. But if you want to use that feature, you must install qtwebengine5-dev.


To compile the translations of the application, you need KDE Frameworks >= 5.76, make sure to delete the "po" subdirectory from your build folder if it exists, and use this cmake command to configure the project :
<pre>
cmake .. -DKDE_INSTALL_USE_QT_SYS_PATHS=ON -DCMAKE_INSTALL_PREFIX=/usr -DKDE_L10N_SYNC_TRANSLATIONS=ON -DRELEASE_BUILD=OFF
</pre>

Then build and install:
<pre>
make -j5
sudo make install
</pre>

You can then start your compiled version by simply entering:
<pre>
kdenlive
</pre>

If you have compiled it in debug mode, you may encounter errors like
<pre>
SUMMARY: AddressSanitizer: new-delete-type-mismatch (/usr/bin/kdenlive+0x643020) 
==6982==HINT: if you don't care about these errors you may set ASAN_OPTIONS=new_delete_type_mismatch=0
==6982==ABORTING
</pre>

As the hint says, the you can solve this with 
<pre>
export ASAN_OPTIONS=new_delete_type_mismatch=0
</pre>

== Next Steps ==

Now that you've got a working dev environment, you can [https://invent.kde.org/multimedia/kdenlive/-/issues?label_name%5B%5D=Junior+Job find some nice first issues to solve].

You can also gain more general knowledge by [https://techbase.kde.org/Development/Tutorials exploring the tutorials on TechBase].

== IDE Setup ==
Pick your favourite!

=== Setting up KDevelop ===
Open KDevelop and go to Project > Open/Import project
Then select the CMakeLists.txt file in the kdenlive source folder. 
You can now start hacking on Kdenlive!

=== Setting up QtCreator ===
After checking out Kdenlive from git—when working on refactoring, you may want to clone two copies, one with the next branch and another one on the refactoring branch—, you can open the CMakeLists.txt in QtCreator, which will load the project if cmake succeeds. If you run/debug Kdenlive, make sure that kdenlive and not kdenlive_render is selected as an active project.

If you let QtCreator restore the previous session (File > Session manager), it will remember the open documents. Environment variables (see below) can be set in Projects > Build Environment.

== MLT documentation ==
Kdenlive uses MLT’s C++ API called mlt++. This API is not documented as it is simply a wrapper to C functions. For example, the documentation of <code>Mlt::Consumer::position()</code> can be found in <code>framework/mlt_consumer.c:mlt_consumer_position()</code>. The actual C function name is usually a combination of the class name and the function name, but can also be found by consulting <code>mlt++/MltConsumer.cpp:position()</code>.

== Environment variables ==
If kdenlive crashes on startup (e.g. in QtCreator) and shows a message like:
    kdenlive(24309) KXMLGUIClient::setXMLFile: cannot find .rc file "kdenliveui.rc" for component "kdenlive"
then you have to ensure the .rc file is found. If CMake is configured to install Kdenlive to /usr/local, the .rc file is put there, but when kdenlive is then run from the build directory, the KXMLGUIClient will not search there. Solution: Set the environment variable KDEDIRS to <code>$KDEDIRS:/usr/local</code>.

You can get more information about the paths that are checked by running kdenlive like this:
    strace build/src/kdenlive 2>&1 | grep kdenliveui.rc

== Wayland ==
To avoid flickering here are some Kdenlive envvars that work with Sway?
<pre>
QT_QPA_PLATFORM=wayland-egl
SDL_VIDEODRIVER=wayland
XDG_SESSION_TYPE=wayland
</pre>

== Contact ==

=== Chat ===

There are several chat groups on Telegram and [[Matrix]]. The groups existing on both services are bridged via a bot so you can choose your preferred one. Not all groups exist an all services.

==== Telegram ====

* [https://t.me/kdenlive Main group]
* [https://t.me/kdenlive_dev Developer group]
* [https://t.me/kdenlivemanual Manual Contributors group] 

==== Matrix ====

* [https://webchat.kde.org/#/room/#kdenlive:kde.org Main group]
* [https://webchat.kde.org/#/room/#kdenlive-dev:kde.org Developer group] 

=== Mailing List ===
The kdenlive developer mailing list archives can be found [http://mail.kde.org/pipermail/kdenlive/ here]

A searchable archive of the kdenlive developer mailing list can be found [http://www.mail-archive.com/kdenlive@kde.org/ here]

Information on how to subscribe can be found [https://mail.kde.org/mailman/listinfo/kdenlive here]