feat: implement soft reloading

src/cpp/scavenge.hpp

@@ -0,0 +1,49 @@
+#pragma once
+
+#include <qobject.h>
+#include <qqmlcomponent.h>
+#include <qqmlparserstatus.h>
+#include <qtmetamacros.h>
+
+extern QObject* SCAVENGE_PARENT; // NOLINT
+
+class Scavenger: public QObject, public QQmlParserStatus {
+	Q_OBJECT;
+	Q_INTERFACES(QQmlParserStatus);
+
+public:
+	explicit Scavenger(QObject* parent = nullptr): QObject(parent) {}
+	~Scavenger() override = default;
+
+	Scavenger(Scavenger&) = delete;
+	Scavenger(Scavenger&&) = delete;
+	void operator=(Scavenger&) = delete;
+	void operator=(Scavenger&&) = delete;
+
+	void classBegin() override;
+	void componentComplete() override {}
+
+protected:
+	// do early init, sometimes with a scavengeable target
+	virtual void earlyInit(QObject* old) = 0;
+};
+
+class Scavengeable {
+public:
+	Scavengeable() = default;
+	virtual ~Scavengeable() = default;
+
+	Scavengeable(Scavengeable&) = delete;
+	Scavengeable(Scavengeable&&) = delete;
+	void operator=(Scavengeable&) = delete;
+	void operator=(Scavengeable&&) = delete;
+
+	// return an old object that might have salvageable resources
+	virtual QObject* scavengeTargetFor(QObject* child) = 0;
+};
+
+QObject* createComponentScavengeable(
+    QObject& parent,
+    QQmlComponent& component,
+    QVariantMap& initialProperties
+);