3 files changed, 117 insertions, 0 deletions
diff --git a/mobile-widgets/CMakeLists.txt b/mobile-widgets/CMakeLists.txt
index 1eecb7d3b..6c1747dbc 100644
--- a/mobile-widgets/CMakeLists.txt
+++ b/mobile-widgets/CMakeLists.txt
@@ -1,6 +1,7 @@
 # mobile backend functions
 
 set(SUBSURFACE_MOBILE_SRCS
+	qmlinterface.cpp
 	qmlmanager.cpp
 	qml/kirigami/src/columnview.cpp
 	qml/kirigami/src/delegaterecycler.cpp
diff --git a/mobile-widgets/qmlinterface.cpp b/mobile-widgets/qmlinterface.cpp
new file mode 100644
index 000000000..78aba6a5c
--- /dev/null
+++ b/mobile-widgets/qmlinterface.cpp
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "qmlinterface.h"
+
+#include <QQmlEngine>
+
+QMLInterface *QMLInterface::instance()
+{
+	static QMLInterface *self = new QMLInterface;
+	return self;
+}
+
+void QMLInterface::setup(QQmlContext *ct)
+{
+	// Register interface class
+	ct->setContextProperty("Backend", QMLInterface::instance());
+
+	// Make enums available as types
+	qmlRegisterUncreatableType<QMLInterface>("org.subsurfacedivelog.mobile",1,0,"Enums","Enum is not a type");
+
+	// relink signals to QML
+}
diff --git a/mobile-widgets/qmlinterface.h b/mobile-widgets/qmlinterface.h
new file mode 100644
index 000000000..59981e0d1
--- /dev/null
+++ b/mobile-widgets/qmlinterface.h
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef QMLINTERFACE_H
+#define QMLINTERFACE_H
+#include <QObject>
+#include <QQmlContext>
+// This class is a pure interface class and may not contain any implementation code
+// Allowed are:
+//     header
+//        Q_PROPERTY
+//        signal/slot for Q_PROPERTY functions
+//        the functions may contain either
+//             a) a function call to the implementation
+//             b) a reference to a global variable like e.g. prefs.
+//        Q_INVOCABLE functions
+//        the functions may contain
+//             a) a function call to the implementation
+//    source
+//        connect signal/signal to pass signals from implementation
+
+
+class QMLInterface : public QObject {
+	Q_OBJECT
+
+	// Q_PROPERTY used in QML
+
+public:
+	static QMLInterface *instance();
+
+	// function to do the needed setup and do connect of signal/signal
+	static void setup(QQmlContext *ct);
+
+	// Duplicated enums, these enums are properly defined in the C/C++ structure
+	// but duplicated here to make them available to QML.
+
+	// Duplicating the enums poses a slight risk for forgetting to update
+	// them if the proper enum is changed (e.g. assigning a new start value).
+
+	// remark please do not use these enums outside the C++/QML interface.
+	enum UNIT_SYSTEM {
+		METRIC,
+		IMPERIAL,
+		PERSONALIZE
+	};
+	Q_ENUM(UNIT_SYSTEM);
+
+	enum LENGTH {
+		METERS,
+		FEET
+	};
+	Q_ENUM(LENGTH);
+
+	enum VOLUME {
+		LITER,
+		CUFT
+	};
+	Q_ENUM(VOLUME);
+
+	enum PRESSURE {
+		BAR,
+		PSI,
+		PASCALS
+	};
+	Q_ENUM(PRESSURE);
+
+	enum TEMPERATURE {
+		CELSIUS,
+		FAHRENHEIT,
+		KELVIN
+	};
+	Q_ENUM(TEMPERATURE);
+
+	enum WEIGHT {
+		KG,
+		LBS
+	};
+	Q_ENUM(WEIGHT);
+
+	enum TIME {
+		SECONDS,
+		MINUTES
+	};
+	Q_ENUM(TIME);
+
+	enum DURATION {
+		MIXED,
+		MINUTES_ONLY,
+		ALWAYS_HOURS
+	};
+	Q_ENUM(DURATION);
+
+private:
+	QMLInterface() {}
+};
+#endif // QMLINTERFACE_H
+