Förstå CMakeLists

Att begripa hur CMakeLists.txt-filer fungerar

CMake

In our introductory tutorial, we used CMake as the build system for our application, but we only really paid close attention to one of our CMakeLists.txt files. Here, we're going to go over how it works in a bit more detail.

CMake är användbart eftersom det låter oss automatisera mycket av grejorna som måste göras innan kompilering.

CMakeLists.txt

You might remember this CMakeLists.txt file from the first tutorial:

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cmake_minimum_required(VERSION 3.16)
project(helloworld)

set(KF_MIN_VERSION "5.68.0")
set(QT_MIN_VERSION "5.12.0")

find_package(ECM ${KF_MIN_VERSION} REQUIRED NO_MODULE)

set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH})

include(KDEInstallDirs)
include(KDECMakeSettings)
include(KDECompilerSettings NO_POLICY_SCOPE)

find_package(Qt5 ${QT_MIN_VERSION} REQUIRED NO_MODULE COMPONENTS Core Quick Test Gui QuickControls2 Widgets)
find_package(KF5 ${KF_MIN_VERSION} REQUIRED COMPONENTS Kirigami2 I18n CoreAddons)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_subdirectory(src)

feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES)

Den första raden, project(helloworld) definierar projektets namn.

After that, we set the versions of our needed tools. cmake_minimum_required(VERSION 3.16) sets the version of CMake we will be calling. We then use set() to define variables (KF5_MIN_VERSION and QT_MIN_VERSION) containing the versions of KDE Frameworks and Qt.

Then we get to a section where we include a number of necessary CMake and KDE settings by using extra-cmake-modules. You shouldn't worry too much about these lines for now and we won't need to change them in this tutorial.

Den följande sektionen är viktig, eftersom den anger vilka beroenden vi tar med vid kompileringstid. Låt oss titta på den första raden:

find_package(KF5 ${KF5_MIN_VERSION} COMPONENTS Kirigami2 I18n CoreAddons WidgetsAddons)

find_package() finds and loads the external component.
Det första ordet är ramverket (KF5).
Därefter anropar vi variabeln med versionerna vi angav på den andra raden.
COMPONENTS är en parameter som föregår de specifika komponenterna för ramverket vi inkluderar.
Varje ord efter COMPONENTS refererar till en specifik komponent.

Anmärkning

If you are looking to add any components listed in the KDE API documentation to your application, you may check the right sidebar for how to add the component with CMake. For instance, for Kirigami2 , you will find something like find_package(KF5Kirigami2), which with the addition of extra-cmake-modules becomes something like find_package(KF5 COMPONENTS Kirigami2).

Pay close attention to your included components, as omitting ones used in our code will stop our application from compiling.

The final line, add_subdirectory(src), points CMake into the src/ directory.

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add_executable(helloworld main.cpp resources.qrc)
target_link_libraries(helloworld Qt5::Quick Qt5::Qml Qt5::Gui Qt5::QuickControls2 Qt5::Widgets KF5::Kirigami2 KF5::I18n)

Eftersom mycket av själva arbetet görs av den första filen, är den här mycket kortare.

set() is used to set helloworld_SRCS to main.cpp and resources.qrc (if we decide to create additional C++ files we'll need to add them here too)
add_executable() takes care of naming our executable and grabbing the files needed to create it
target_link_libraries dynamically links the libraries used in our code to our executable.

Anmärkning

Note that these libraries should match the components that we included in our previous CMakeLists.txt file - otherwise these components will not be included and our application won't compile.

Inställningen är användbar när vi utvecklar de flesta program i Kirigami.

Listvyer

Förstå sig på main.cpp