Build prerequisites

Covers the platform-independent part of the build. For the rest, see Building on Windows, Building on Linux and Building on macOS.

Compiling/installing OpenSSL

If a precompiled binary distribution of OpenSSL is available for your platform, you can use it instead of building from source.

The steps for compiling OpenSSL vary depending on your platform. The package that you get from the OpenSSL website gives detailed instructions on how to compile on all supported platforms. OpenSSL itself may need additional software packages to compile depending on your system.

Make sure that OpenSSL is built as a shared library.

Windows

Get a prebuilt 64-bit OpenSSL 3.x distribution. The CI build installs it with vcpkg:

vcpkg install openssl:x64-windows

The Win64 OpenSSL 3.x package from http://www.slproweb.com/products/Win32OpenSSL.html works too. While installing it, make sure that the option to copy DLLs to the OpenSSL binaries directory is selected in the Additional Tasks page.

Whatever source you use, lay the files out in a folder called openssl which should be at the same level as the folder lmc:

openssl
 |-bin      (libcrypto-*.dll, libssl-*.dll)
 |-include  (openssl headers)
 |-lib      (libcrypto.lib, libssl.lib)

The build step copies the runtime DLLs from openssl\bin to the output folder.

Linux/X11

Many Linux distributions come with pre-compiled OpenSSL packages. If your system has one, you may be able to link the project to it. If your system lacks the package, or if you are unable to link with it, you need to build OpenSSL from source.

Specify the shared switch to ensure that OpenSSL is built as a shared library.

The CI build simply points the openssl folder at the system OpenSSL:

mkdir openssl
ln -sfn /usr/include openssl/include
ln -sfn /usr/lib/x86_64-linux-gnu openssl/lib

macOS

macOS does not ship a linkable OpenSSL. The CI build installs it with Homebrew:

brew install openssl@3

and points the openssl folder at the Homebrew prefix:

mkdir openssl
ln -sfn "$(brew --prefix openssl@3)/include" openssl/include
ln -sfn "$(brew --prefix openssl@3)/lib" openssl/lib

Configuring and building

Configure and build from the repository root:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release --target package-local --parallel

The package-local target stages the complete runtime bundle (the application binary, translations, the resource bundle, themes, sounds and the Qt image/platform/TLS plugins) into the LMC_RELEASE_DIR directory, which defaults to <build-dir>/release. The packaging scripts under lmc/setup expect the layout in lmc/release, so pass -DLMC_RELEASE_DIR="$PWD/lmc/release" when you plan to build the install packages (this is what the CI build does).

If OpenSSL is laid out in the openssl folder described above, pass -DOPENSSL_ROOT_DIR=$PWD/openssl to the configure command. Otherwise the system OpenSSL found by CMake is used.

Translations

The build also bundles Qt’s own translations (qtbase_*.qm: the strings of the standard dialogs) into lang/system next to the app’s translations. They are taken from the Qt used for the build, so the Qt translations must be present on the build machine: the qt6-translations-l10n package on Debian/Ubuntu, the translations component of the Qt installer on Windows/macOS. Configuration fails if none are found (override the lookup with -DLMC_QT_TRANSLATIONS_DIR=<abs path> if needed). With the reference Qt versions (6.4/6.8.3) there are no Qt translations for el_GR, ml_IN, ro_RO, sl_SI and sv_SE, so those locales keep English standard dialogs (for sl_SI this drops the previously vendored file - accepted).

The application’s own translation sources live in translations/ and are named lmc_<locale>.ts (Qt Linguist format); the build picks the directory up automatically (file(GLOB CONFIGURE_DEPENDS)), so adding a translation is just dropping a file there - the compiled .qm keeps the locale name (ru_RU.qm) in lang/ next to system/. With the Visual Studio generator, re-run configure after adding or removing a file.

Audio playback support

LAN Messenger can play sounds to accompany certain events. This behaviour is customizable in the Preferences dialog. Sounds are played through the Qt Multimedia module (QSoundEffect), so that module must be available at build and run time. On Linux install the Qt Multimedia development and runtime packages (qt6-multimedia-dev, libqt6multimedia6). If no audio output device is available, the sound options will be grayed out in the Preferences dialog.

System tray support

On desktops that do not have a system tray, the system tray options will be grayed out in the Preferences dialog.