Qt5: QML hello world with Cmake (+nix package manager)

README.md

Demonstration of QML with Qt5 + Cmake + nix

If you have nix installed compile and run with:

$ nix build
$ ./result/bin/demo 

Explaination: we load the .qml file with qrc:///main.qml: it uses for that the file qml.qrc (the name is not important) that lists the resource files. This 'qml.qrc file is then given to qt5_add_resources(…) in CMakeLists.txt in order to compile the resources and include them in the final binary. Note that resources must be compiled: other methods involve qmake or a manual compilation.

CMakeLists.txt

cmake_minimum_required(VERSION 3.1.0)

project(demo VERSION 1.0.0 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)

if(CMAKE_VERSION VERSION_LESS "3.7.0")
    set(CMAKE_INCLUDE_CURRENT_DIR ON)
endif()

# Add here any library you need
find_package(Qt5 COMPONENTS Widgets Qml Quick REQUIRED)

# Add the resource file as it *must* be compiled (also possible with
# qmake or manually with rcc)
# https://doc.qt.io/qt-5/resources.html
# https://doc.qt.io/qt-5/qtcore-cmake-qt5-add-resources.html
set(SOURCES main.cpp) # A variable is needed as I guess it will add more sources inside
qt5_add_resources(SOURCES qml.qrc)

add_executable(demo
    ${SOURCES}
)

# Add here any library you need
target_link_libraries(demo Qt5::Widgets Qt5::Qml Qt5::Quick)

# Install the binary
install(TARGETS demo DESTINATION bin)

derivation_demo.nix

{ lib
, stdenv
, cmake
, qt5
, wrapQtAppsHook
}:
stdenv.mkDerivation rec {
  pname = "";
  version = "";

  src = ./.;
  nativeBuildInputs = [ cmake wrapQtAppsHook ];
  buildInputs = [
    qt5.qtbase
  ];
}

flake.lock

{
  "nodes": {
    "nixpkgs": {
      "locked": {
        "lastModified": 1668650906,
        "narHash": "sha256-JuiYfDO23O8oxUUOmhQflmOoJovyC5G4RjcYQMQjrRE=",
        "owner": "NixOS",
        "repo": "nixpkgs",
        "rev": "3a86856a13c88c8c64ea32082a851fefc79aa700",
        "type": "github"
      },
      "original": {
        "id": "nixpkgs",
        "type": "indirect"
      }
    },
    "root": {
      "inputs": {
        "nixpkgs": "nixpkgs"
      }
    }
  },
  "root": "root",
  "version": 7
}

flake.nix

{
  description = "A very basic flake";

  outputs = { self, nixpkgs }: let
    pkgs = nixpkgs.legacyPackages.x86_64-linux;
  in {

    packages.x86_64-linux.default = pkgs.libsForQt5.callPackage ./derivation_demo.nix {};

  };
}

main.cpp

//https://riptutorial.com/qml/example/14475/creating-a-qtquick-window-from-cplusplus
#include <QGuiApplication>
#include <QQmlApplicationEngine>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
	    
    return app.exec();
}

main.qml

import QtQuick 2.5
import QtQuick.Window 2.2

Window { // Must be this type to be loaded by QQmlApplicationEngine.
    visible: true
    title: qsTr("Hello World")
    Text {
        text: qsTr("Hello World")
        anchors.centerIn: parent
    }
}

qml.qrc

<RCC>
    <qresource prefix="/">
        <file>main.qml</file>
    </qresource>
</RCC>