feat: add hard reload signal and wrap root object

CMakeLists.txt

@@ -26,6 +26,7 @@ qt_add_executable(qtshell
 	src/cpp/main.cpp
 	src/cpp/shell.cpp
 	src/cpp/variants.cpp
+	src/cpp/rootwrapper.cpp
 )
 
 qt_add_qml_module(qtshell URI QtShell)

src/cpp/main.cpp

@@ -5,10 +5,11 @@
 #include <qguiapplication.h>
 #include <qlogging.h>
 #include <qobject.h>
-#include <qqmlapplicationengine.h>
+#include <qquickwindow.h>
 #include <qstandardpaths.h>
 #include <qstring.h>
 
+#include "rootwrapper.hpp"
 #include "shell.hpp"
 
 int main(int argc, char** argv) {
@@ -43,21 +44,11 @@ int main(int argc, char** argv) {
 	CONFIG_PATH = configPath;
 
 	LayerShellQt::Shell::useLayerShell();
+	// Base window transparency appears to be additive.
+	// Use a fully transparent window with a colored rect.
+	QQuickWindow::setDefaultAlphaBuffer(true);
 
-	auto engine = QQmlApplicationEngine();
-	engine.load(configPath);
-
-	if (engine.rootObjects().isEmpty()) {
-		qCritical() << "failed to load config file";
-		return -1;
-	}
-
-	auto* shellobj = qobject_cast<QtShell*>(engine.rootObjects().first());
-
-	if (shellobj == nullptr) {
-		qCritical() << "root item was not a QtShell";
-		return -1;
-	}
+	auto root = RootWrapper(configPath);
 
 	return QGuiApplication::exec();
 }

src/cpp/rootwrapper.cpp

@@ -0,0 +1,64 @@
+#include "rootwrapper.hpp"
+#include <cstdlib>
+#include <utility>
+
+#include <qlogging.h>
+#include <qobject.h>
+#include <qqmlcomponent.h>
+#include <qqmlengine.h>
+#include <qurl.h>
+
+#include "shell.hpp"
+
+RootWrapper::RootWrapper(QUrl rootUrl):
+    QObject(nullptr), rootUrl(std::move(rootUrl)), engine(this) {
+	this->reloadGraph();
+
+	if (this->activeRoot == nullptr) {
+		qCritical() << "could not create scene graph, exiting";
+		exit(-1); // NOLINT
+	}
+}
+
+void RootWrapper::reloadGraph() {
+	if (this->activeRoot != nullptr) {
+		this->engine.clearComponentCache();
+	}
+
+	auto component = QQmlComponent(&this->engine, this->rootUrl);
+	auto* obj = component.beginCreate(this->engine.rootContext());
+	if (obj == nullptr) {
+		qWarning() << "failed to create root component";
+		return;
+	}
+
+	auto* qtsobj = qobject_cast<QtShell*>(obj);
+	if (qtsobj == nullptr) {
+		qWarning() << "root component was not a QtShell";
+		delete obj;
+		return;
+	}
+
+	component.completeCreate();
+
+	if (this->activeRoot != nullptr) {
+		this->activeRoot->deleteLater();
+		this->activeRoot = nullptr;
+	}
+
+	this->activeRoot = qtsobj;
+}
+
+void RootWrapper::changeRoot(QtShell* newRoot) {
+	if (this->activeRoot != nullptr) {
+		QObject::disconnect(this->destroyConnection);
+		this->activeRoot->deleteLater();
+	}
+
+	if (newRoot != nullptr) {
+		this->activeRoot = newRoot;
+		QObject::connect(this->activeRoot, &QtShell::destroyed, this, &RootWrapper::destroy);
+	}
+}
+
+void RootWrapper::destroy() { this->deleteLater(); }

src/cpp/rootwrapper.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <qobject.h>
+#include <qobjectdefs.h>
+#include <qqmlengine.h>
+#include <qtmetamacros.h>
+#include <qurl.h>
+
+#include "shell.hpp"
+
+class RootWrapper: public QObject {
+	Q_OBJECT;
+
+public:
+	explicit RootWrapper(QUrl rootUrl);
+
+	void reloadGraph();
+	void changeRoot(QtShell* newRoot);
+
+private slots:
+	void destroy();
+
+private:
+	QUrl rootUrl;
+	QQmlEngine engine;
+	QtShell* activeRoot = nullptr;
+	QMetaObject::Connection destroyConnection;
+};

src/cpp/shell.cpp

@@ -11,18 +11,25 @@
 #include <qqmllist.h>
 #include <qtmetamacros.h>
 
+#include "rootwrapper.hpp"
+
 QString CONFIG_PATH; // NOLINT
 
-QtShell::QtShell(): QObject(nullptr), path(CONFIG_PATH), dir(QFileInfo(this->path).dir()) {
-	CONFIG_PATH = "";
-}
+QtShell::QtShell(): QObject(nullptr), path(CONFIG_PATH), dir(QFileInfo(this->path).dir()) {}
 
-void QtShell::componentComplete() {
-	if (this->path.isEmpty()) {
-		qWarning() << "Multiple QtShell objects were created. You should not do this.";
+void QtShell::reload() {
+	auto* rootobj = QQmlEngine::contextForObject(this)->engine()->parent();
+	auto* root = qobject_cast<RootWrapper*>(rootobj);
+
+	if (root == nullptr) {
+		qWarning() << "cannot find RootWrapper for reload, ignoring request";
 		return;
 	}
 
+	root->reloadGraph();
+}
+
+void QtShell::componentComplete() {
 	for (auto* component: this->mComponents) {
 		component->prepare(this->dir);
 	}

src/cpp/shell.hpp

@@ -23,11 +23,14 @@ class QtShell: public QObject, public QQmlParserStatus {
 public:
 	explicit QtShell();
 
-	void classBegin() override {};
+	void classBegin() override {}
 	void componentComplete() override;
 
 	QQmlListProperty<ShellComponent> components();
 
+public slots:
+	void reload();
+
 private:
 	static void appendComponent(QQmlListProperty<ShellComponent>* list, ShellComponent* component);