### Qt Standard Project Setup Handling

Source: https://github.com/oclero/qtappinstancemanager/blob/master/CMakeLists.txt

Conditional setup for qt_standard_project_setup() based on Qt version.

```cmake
# qt_standard_project_setup() is only available in Qt >= 6.3.
if(COMMAND qt_standard_project_setup)
  qt_standard_project_setup()
else()
  set(CMAKE_AUTOMOC ON)
  set(CMAKE_AUTOUIC ON)
  set(CMAKE_AUTORCC ON)
endif()
```

--------------------------------

### CMakeLists.txt for Multiple Instance Example

Source: https://github.com/oclero/qtappinstancemanager/blob/master/examples/multiple/CMakeLists.txt

This CMakeLists.txt file configures the build for the MultipleInstanceExample, setting up dependencies and target properties.

```cmake
find_package(Qt6 REQUIRED COMPONENTS Core)

add_executable(MultipleInstanceExample)
target_sources(MultipleInstanceExample
  PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp
)
target_link_libraries(MultipleInstanceExample
  PRIVATE
    ${PROJECT_NAMESPACE}::${PROJECT_NAME}
    Qt::Core
)

set_target_properties(MultipleInstanceExample PROPERTIES
  INTERNAL_CONSOLE ON
  EXCLUDE_FROM_ALL ON
  FOLDER examples
)
```

--------------------------------

### Target Installation

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Installs the QtAppInstanceManager target and its associated files.

```cmake
install(TARGETS ${PROJECT_NAME}
  EXPORT "${PROJECT_NAME}Targets"
  LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
  ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
  RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
  INCLUDES DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
)

install(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/include/"
  DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/"
)

install(EXPORT "${PROJECT_NAME}Targets"
  FILE "${PROJECT_NAME}Targets.cmake"
  NAMESPACE ${PROJECT_NAMESPACE}::
  DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
)

install(FILES
  "${CMAKE_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake"
  "${CMAKE_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake"
  DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
)
```

--------------------------------

### Single application example

Source: https://github.com/oclero/qtappinstancemanager/blob/master/README.md

Example of how to initialize QtAppInstanceManager to force only one instance running and handle messages from secondary instances.

```cpp
// Initialize instance manager to force only one instance running.
oclero::QtAppInstanceManager instanceManager;
instanceManager.setMode(QtAppInstanceManager::Mode::SingleInstance);

// When another instance will start, it will immediately quit the app and send its
// arguments to the primary instance.
QObject::connect(&instanceManager,
  &oclero::QtAppInstanceManager::secondaryInstanceMessageReceived,
  &instanceManager,
  [](const unsigned int id, QByteArray const& data) {
    // Do what you want:
    // - Raise the main window.
    // - Open a file in an another tab of your main window.
    // - ...
    qDebug() << "Secondary instance message received: " << data;
  });

// If you don't want for the app to quit, you can set the manual mode and handle this step by yourself.
instanceManager.setAppExitMode(QtAppInstanceManager::AppExitMode::Manual);
QObject::connect(&instanceManager,
  &QtAppInstanceManager::appExitRequested,
  &singleInstance,
  []() {
    // Do what you want.
    // Usually you should quit the app.
    qDebug() << "This app should exit";
    QCoreApplication::quit();
    std::exit(EXIT_SUCCESS);
  });
```

--------------------------------

### CMakeLists.txt for Single Instance Example

Source: https://github.com/oclero/qtappinstancemanager/blob/master/examples/single/CMakeLists.txt

This CMakeLists.txt file configures the build for a single instance Qt application, linking necessary libraries and setting target properties.

```cmake
find_package(Qt6 REQUIRED COMPONENTS Core)

add_executable(SingleInstanceExample)
target_sources(SingleInstanceExample
  PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp
)
target_link_libraries(SingleInstanceExample
  PRIVATE
    ${PROJECT_NAMESPACE}::${PROJECT_NAME}
    Qt::Core
)

set_target_properties(SingleInstanceExample PROPERTIES
  INTERNAL_CONSOLE ON
  EXCLUDE_FROM_ALL ON
  FOLDER examples
)
```

--------------------------------

### Project Setup

Source: https://github.com/oclero/qtappinstancemanager/blob/master/CMakeLists.txt

Basic CMake minimum version, parallel build setting, module path, and project definition.

```cmake
cmake_minimum_required(VERSION 3.21.0)

# Enable parallel build (not enabled by default on Windows).
set(CMAKE_BUILD_PARALLEL_LEVEL $ENV{NUMBER_OF_PROCESSORS})

enable_testing()

set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")

# Set project information.
project("QtAppInstanceManager"
  LANGUAGES CXX
  VERSION 1.3.2.0
  DESCRIPTION "A tool to communicate between the instances of your Qt application."
  HOMEPAGE_URL "https://github.com/oclero/QtAppInstanceManager"
)
set(PROJECT_NAMESPACE "oclero")

# Global flags.
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set_property(GLOBAL PROPERTY USE_FOLDERS ON)
if(NOT CMAKE_OSX_DEPLOYMENT_TARGET)
  set(CMAKE_OSX_DEPLOYMENT_TARGET "13.6")
endif()
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")
```

--------------------------------

### Add the library as a dependency in your CMakeLists.txt

Source: https://github.com/oclero/qtappinstancemanager/blob/master/README.md

Example of how to add the library as a dependency using FetchContent in CMake.

```cmake
include(FetchContent)
FetchContent_Declare(QtAppInstanceManager
 G IT_REPOSITORY "https://github.com/oclero/qtappinstancemanager.git"
)
FetchContent_MakeAvailable(QtAppInstanceManager)
```

--------------------------------

### Subdirectories

Source: https://github.com/oclero/qtappinstancemanager/blob/master/CMakeLists.txt

Adds subdirectories for library, tests, and examples based on defined variables.

```cmake
# The library.
add_subdirectory(src)

# Tests.
if(QTAPPINSTANCEMANAGER_TESTS)
  add_subdirectory(tests)
endif()

# Examples.
if(QTAPPINSTANCEMANAGER_EXAMPLES)
  add_subdirectory(examples/single)
  add_subdirectory(examples/multiple)
endif()
```

--------------------------------

### Visual Studio Startup Project

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Sets the startup project for Visual Studio when targeting Windows.

```cmake
# Select correct startup project in Visual Studio.
if(WIN32)
  set_property(DIRECTORY PROPERTY VS_STARTUP_PROJECT ${PROJECT_NAME})
endif()
```

--------------------------------

### Package Configuration File Generation

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Generates the package configuration file and version file for CMake.

```cmake
# Install target
configure_package_config_file(
  "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/config.cmake.in"
  "${CMAKE_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake"
  INSTALL_DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
)

write_basic_package_version_file(
  "${CMAKE_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake"
  VERSION "${PROJECT_VERSION}"
  COMPATIBILITY AnyNewerVersion
)
```

--------------------------------

### Include the necessary header

Source: https://github.com/oclero/qtappinstancemanager/blob/master/README.md

Include the main header file for QtAppInstanceManager in your C++ code.

```cpp
#include <oclero/QtAppInstanceManager.hpp>
```

--------------------------------

### CMakeLists.txt Configuration

Source: https://github.com/oclero/qtappinstancemanager/blob/master/tests/CMakeLists.txt

This snippet shows the CMake configuration for setting up the test executable, including finding Qt packages, defining sources, include directories, and linking libraries.

```cmake
set(TESTS_TARGET_NAME ${PROJECT_NAME}Tests)

find_package(Qt6 REQUIRED COMPONENTS Core Test)

add_executable(${TESTS_TARGET_NAME})
set_target_properties(${TESTS_TARGET_NAME}
  PROPERTIES
    CMAKE_AUTOMOC ON
    CMAKE_AUTORCC ON
    INTERNAL_CONSOLE ON
    EXCLUDE_FROM_ALL ON
    FOLDER tests
)
set(TESTS_SOURCES
  ${CMAKE_CURRENT_SOURCE_DIR}/src/main.cpp
  ${CMAKE_CURRENT_SOURCE_DIR}/src/QtAppInstanceManagerTests.hpp
  ${CMAKE_CURRENT_SOURCE_DIR}/src/QtAppInstanceManagerTests.cpp
)
target_sources(${TESTS_TARGET_NAME}
  PRIVATE
    ${TESTS_SOURCES}
)
target_include_directories(${TESTS_TARGET_NAME}
    PRIVATE
      ${CMAKE_CURRENT_SOURCE_DIR}
)
target_link_libraries(${TESTS_TARGET_NAME}
  PRIVATE
    ${PROJECT_NAMESPACE}::${PROJECT_NAME}
    Qt::Core
    Qt::Test
)
add_test(NAME ${TESTS_TARGET_NAME}
  COMMAND $<TARGET_FILE:${TESTS_TARGET_NAME}>
  WORKING_DIRECTORY $<TARGET_FILE_DIR:${TESTS_TARGET_NAME}>)

source_group(TREE ${CMAKE_CURRENT_SOURCE_DIR} FILES ${TESTS_SOURCES})
```

--------------------------------

### Qt Integration

Source: https://github.com/oclero/qtappinstancemanager/blob/master/CMakeLists.txt

Includes GNUInstallDirs and finds the Qt6 package with required components.

```cmake
# Include GNUInstallDirs for standard installation paths.
include(GNUInstallDirs)

# Find Qt.
find_package(Qt6 REQUIRED COMPONENTS Core Network)
```

--------------------------------

### Include Directories Configuration

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Configures public and private include directories for the QtAppInstanceManager library.

```cmake
target_include_directories(${PROJECT_NAME}
  PUBLIC
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
  PRIVATE
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/source>
)
```

--------------------------------

### Multiple application instances

Source: https://github.com/oclero/qtappinstancemanager/blob/master/README.md

This C++ code demonstrates how to use the QtAppInstanceManager to handle multiple application instances, including receiving messages from other instances and reacting to role changes.

```c++
oclero::QtAppInstanceManager instanceManager;

// If we are the FIRST instance to launch,
// we'll receive messages from other instances that will launch after us.
QObject::connect(&instanceManager,
                 &oclero::QtAppInstanceManager::secondaryInstanceMessageReceived,
                 &instanceManager,
  [](const unsigned int id, QByteArray const& data) {
    qDebug() << "Message received from secondary instance: " << data;
  });

// If we are another instance, we are able to receive messages from the primary one.
QObject::connect(&instanceManager,
                 &oclero::QtAppInstanceManager::primaryInstanceMessageReceived,
                 &instanceManager,
  [](QByteArray const& data) {
    qDebug() << "Message received from primary instance: " << data;
  });

// If ever the first instance to launch unexpectly shuts down,
// one of the secondary instances will immediately take of the role of the primary one.
QObject::connect(&instanceManager,
                 &oclero::QtAppInstanceManager::instanceRoleChanged,
                 &instanceManager,
  [&instanceManager]() {
    // There is a short period of time before roles are assigned again.
    if (!instanceManager.isPrimaryInstance() && !instanceManager.isSecondaryInstance()) {
      qDebug() << "Waiting for new role...";
    } else {
      qDebug() << "New role: " << (instanceManager.isPrimaryInstance() ? "Primary" : "Secondary");
    }
  });
```

--------------------------------

### Source Grouping

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Organizes source files into groups based on their directory structure.

```cmake
# Create source groups.
source_group(TREE ${CMAKE_CURRENT_SOURCE_DIR}
  FILES
    ${HEADERS}
    ${SOURCES}
)
```

--------------------------------

### Target Properties

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Sets various properties for the QtAppInstanceManager target, including output name, versioning, and build-related flags.

```cmake
set_target_properties(${PROJECT_NAME}
  PROPERTIES
    OUTPUT_NAME ${PROJECT_NAME}
    PROJECT_LABEL ${PROJECT_NAME}
    FOLDER src
    SOVERSION ${PROJECT_VERSION_MAJOR}
    VERSION ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    DEBUG_POSTFIX _debug
    CMAKE_AUTORCC ON
    CMAKE_AUTOMOC ON
    CMAKE_AUTOUIC ON
)
```

--------------------------------

### QtAppInstanceManager Library Creation

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Defines the library target for QtAppInstanceManager, including source and header files, and sets up alias for external use.

```cmake
set(HEADERS
  ${CMAKE_CURRENT_SOURCE_DIR}/include/oclero/QtAppInstanceManager.hpp
)

set(SOURCES
  ${CMAKE_CURRENT_SOURCE_DIR}/source/oclero/QtAppInstanceManager.cpp
  ${CMAKE_CURRENT_SOURCE_DIR}/source/oclero/LocalEndpoint.cpp
  ${CMAKE_CURRENT_SOURCE_DIR}/source/oclero/LocalEndpoint.hpp
)

# Create target.
qt_add_library(${PROJECT_NAME} STATIC
  ${HEADERS}
  ${SOURCES}
)
add_library(${PROJECT_NAMESPACE}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
```

--------------------------------

### Export Targets

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Exports the targets for use by other CMake projects.

```cmake
export(EXPORT "${PROJECT_NAME}Targets"
  FILE "${CMAKE_BINARY_DIR}/cmake/${PROJECT_NAME}Targets.cmake"
  NAMESPACE ${PROJECT_NAMESPACE}::
)
```

--------------------------------

### Compile Options

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Sets compile options for the QtAppInstanceManager library, with specific options for MSVC and other compilers.

```cmake
target_compile_options(${PROJECT_NAME}
  PRIVATE
    $<$<CXX_COMPILER_ID:MSVC>:/MP /WX /W4>
    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wall -Wextra -Werror>
)
```

--------------------------------

### Link Libraries

Source: https://github.com/oclero/qtappinstancemanager/blob/master/src/CMakeLists.txt

Links the QtAppInstanceManager library with Qt Core and Qt Network modules.

```cmake
target_link_libraries(${PROJECT_NAME}
  PRIVATE
    Qt::Core
    Qt::Network
)
```

--------------------------------

### Link with the library in CMake

Source: https://github.com/oclero/qtappinstancemanager/blob/master/README.md

How to link the QtAppInstanceManager library to your project in CMake.

```cmake
target_link_libraries(your_project oclero::QtAppInstanceManager)
```

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