About

Single application library for Qt without network dependency. Based on Dmitry Sazonov's code.

Dependencies

• Qt >= 5.9.2
• Compiler with standard >= C++17
• CMake >= 3.18.0
• Ninja >= 1.12.1 (Optional)

Build

CMake flags

A list of additional CMake flags are listed below:

Flag	Default value	Description
USE_QT5	OFF	Use Qt 5 instead of the higher major version available.
GENERATE_PKG_CONFIG	OFF	Generate pkg-config file.
STATIC_LIB	OFF	Build as a static library.

---

Subproject

If you want to use the library directly inside your application source code, include the singleapplication directory and add the library on your CMakeLists.txt file:

add_subdirectory(singleapplication)
target_link_libraries(YOUR_TARGET singleapplication)

---

System library

First you will need to get the sources and create a build directory. In-source builds are not allowed.

git clone https://github.com/AlfredoRamos/singleapplication.git
cd singleapplication

After that, build and install the library on your system.

Note: If you don't want to use the Ninja build system and use Make instead, simply remove the -G Ninja flag.

cmake -S . -B build -G Ninja -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release
cmake --build build --clean-first
cmake --install build --prefix build/pkg/usr/ --strip

Once the files are installed on your system, add the library in your CMakeLists.txt file:

find_package(singleapplication REQUIRED)
target_link_libraries(YOUR_TARGET singleapplication)

Alternatively, if you built the library with the -DGENERATE_PKG_CONFIG=ON flag, you can use the library with pkg-config:

find_package(PkgConfig REQUIRED)
pkg_check_modules(singleapplication REQUIRED IMPORTED_TARGET singleapplication)
target_link_libraries(YOUR_TARGET PkgConfig::singleapplication)

---

Usage

In the main.cpp file of your Qt/C++ application include the library, create a new instance of SingleApplication, and add a check if another instance is already running using SingleApplication::createInstance():

// Subproject
//#include "singleapplication.hpp"

// System library
//#include <singleapplication.hpp>

int main(int argc, char *argv[])
{
	SingleApplication *guard = new SingleApplication("key_string");

	if (!guard->createInstance()) {
		// Another instance of this application is already running
		return 0;
	}

	QApplication a(argc, argv);
	//...
}

The constructor of the SingleApplication class only accepts one parameter and must be a QString.

You can specify random generated QString or using information from the application, like QCoreApplication::applicationName().