QML live-reload

live_reload.hpp

#include <QFileSystemWatcher>
#include <QQmlApplicationEngine>
#include <QTimer>
#include <QUrl>
#include <QDirIterator>

void init_live_reload(QQmlApplicationEngine *engine, const QString &path) {
    auto *fs_watcher = new QFileSystemWatcher(engine);
    QDirIterator it(path, QDirIterator::Subdirectories);
    while (it.hasNext()) {
        it.next();
        auto i = it.fileInfo();
        if (i.isFile())
            fs_watcher->addPath(i.absoluteFilePath());
    }

    QObject::connect(fs_watcher, &QFileSystemWatcher::fileChanged, [=](const QString &file) {
        QTimer::singleShot(50, [=] {
            static QQuickItem *previousItem = nullptr;
            auto window = qobject_cast<QQuickWindow *>(engine->rootObjects().first());
            fs_watcher->addPath(file);

            auto loader = window->findChild<QObject*>("AppLoader");
            auto prev_source = loader->property("source");
            loader->setProperty("source", "");
            engine->clearComponentCache();
            loader->setProperty("source", prev_source);

        });
    });
}

main.cpp

#include <QtGui>
#include <QtQuick>
#include <filesystem>
#include <QQmlComponent>
#include "hotreload.hpp"


namespace fs = std::filesystem;

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

  init_live_reload(&engine, "path/to/root/qml");
  QUrl url((fs::path(__FILE__).parent_path() / "qml" / "mainwindow.qml").c_str());
  engine.load(url);
  return QGuiApplication::exec();
}

Main.qml

// every time this file is edited the loader will refresh it.
import QtQuick
import QtQuick.Controls
import QtQuick.Controls.Material
import DogModule

Pane {
    anchors.fill: parent;
    Rectangle{
        width:234;
        height: 234;
    }

}

mainwindow.qml

import QtQuick
import QtQuick.Controls
import QtQuick.Controls.Material

ApplicationWindow {
    id: root
    width: 500
    height: 400
    visible: true
    Material.theme: Material.Dark
    Material.accent: Material.Orange
    Loader{objectName: "AppLoader"
        source: "./Main.qml"
    }
}

Yeah QML tooling's are awful...