desktop code refactoring

Signed-off-by: Peter Siegmund <developer@mars3142.org>

src/ui/UIWidget.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "model/AppContext.h"
+
+class UIWidget {
+public:
+    explicit UIWidget(void *appstate);
+
+    virtual ~UIWidget();
+
+    virtual void render() const = 0;
+
+    [[nodiscard]] AppContext *get_context() const;
+
+private:
+    AppContext *m_context{};
+};