feat: add tutprial for c++ ui

logos-calc-cpp-ui/src/calc_ui_cpp_plugin.cpp

@@ -0,0 +1,42 @@
+#include "calc_ui_cpp_plugin.h"
+#include "calc_backend.h"
+#include "logos_api.h"
+#include <QDebug>
+#include <QQuickWidget>
+#include <QQmlContext>
+#include <QDir>
+#include <QUrl>
+
+CalcUiCppPlugin::CalcUiCppPlugin(QObject* parent) : QObject(parent) {}
+CalcUiCppPlugin::~CalcUiCppPlugin() {}
+
+QWidget* CalcUiCppPlugin::createWidget(LogosAPI* logosAPI)
+{
+    auto* backend = new CalcBackend(logosAPI);
+
+    auto* quickWidget = new QQuickWidget();
+    quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView);
+    quickWidget->rootContext()->setContextProperty("backend", backend);
+
+    // Dev mode: set QML_PATH to the directory containing Main.qml to load
+    // from the filesystem without rebuilding. Example: export QML_PATH=$PWD/src/qml
+    QString devSource = qgetenv("QML_PATH");
+    QUrl qmlUrl = devSource.isEmpty()
+        ? QUrl("qrc:/src/qml/Main.qml")
+        : QUrl::fromLocalFile(QDir(devSource).filePath("Main.qml"));
+
+    quickWidget->setSource(qmlUrl);
+
+    if (quickWidget->status() == QQuickWidget::Error) {
+        qWarning() << "CalcUiCppPlugin: failed to load QML";
+        for (const auto& e : quickWidget->errors())
+            qWarning() << e.toString();
+    }
+
+    return quickWidget;
+}
+
+void CalcUiCppPlugin::destroyWidget(QWidget* widget)
+{
+    delete widget;
+}