From 211f454de98252e6ccb7b57ee2de34558df2aa56 Mon Sep 17 00:00:00 2001
From: outfoxxed <outfoxxed@outfoxxed.me>
Date: Wed, 13 Mar 2024 00:57:03 -0700
Subject: [PATCH] singleton: add reloadable Singleton type

---
 CMakeLists.txt           | 10 +++----
 src/core/CMakeLists.txt  |  1 +
 src/core/module.md       |  1 +
 src/core/rootwrapper.cpp |  2 ++
 src/core/singleton.cpp   | 64 ++++++++++++++++++++++++++++++++++++++++
 src/core/singleton.hpp   | 35 ++++++++++++++++++++++
 6 files changed, 108 insertions(+), 5 deletions(-)
 create mode 100644 src/core/singleton.cpp
 create mode 100644 src/core/singleton.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86b9fd38..ccdb5a81 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,13 +65,13 @@ find_package(Qt6 REQUIRED COMPONENTS ${QT_FPDEPS})
 qt_standard_project_setup(REQUIRES 6.6)
 set(QT_QML_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/qml_modules)
 
-file(GENERATE
-	OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/pchstub.cpp
-	CONTENT ""
-)
-
 # pch breaks clang-tidy..... somehow
 if (NOT NO_PCH)
+	file(GENERATE
+		OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/pchstub.cpp
+		CONTENT ""
+	)
+
 	add_library(qt-pch ${CMAKE_CURRENT_BINARY_DIR}/pchstub.cpp)
 	target_link_libraries(qt-pch PRIVATE ${QT_DEPS})
 	target_precompile_headers(qt-pch PUBLIC
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 0ddd7251..4ce42b92 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -16,6 +16,7 @@ qt_add_library(quickshell-core STATIC
 	floatingwindow.cpp
 	panelinterface.cpp
 	popupwindow.cpp
+	singleton.cpp
 )
 
 set_source_files_properties(main.cpp PROPERTIES COMPILE_DEFINITIONS GIT_REVISION="${GIT_REVISION}")
diff --git a/src/core/module.md b/src/core/module.md
index 73ecbb8b..a5aea16e 100644
--- a/src/core/module.md
+++ b/src/core/module.md
@@ -13,5 +13,6 @@ headers = [
 	"panelinterface.hpp",
 	"floatingwindow.hpp",
 	"popupwindow.hpp",
+	"singleton.hpp",
 ]
 -----
diff --git a/src/core/rootwrapper.cpp b/src/core/rootwrapper.cpp
index 68c11de9..382bf73a 100644
--- a/src/core/rootwrapper.cpp
+++ b/src/core/rootwrapper.cpp
@@ -16,6 +16,7 @@
 #include "qmlglobal.hpp"
 #include "reload.hpp"
 #include "shell.hpp"
+#include "singleton.hpp"
 #include "watcher.hpp"
 
 RootWrapper::RootWrapper(QString rootPath)
@@ -49,6 +50,7 @@ void RootWrapper::reloadGraph(bool hard) {
 
 	if (this->root != nullptr) {
 		QuickshellSettings::reset();
+		SingletonRegistry::instance()->flip();
 	}
 
 	QDir::setCurrent(this->originalWorkingDirectory);
diff --git a/src/core/singleton.cpp b/src/core/singleton.cpp
new file mode 100644
index 00000000..61d2e068
--- /dev/null
+++ b/src/core/singleton.cpp
@@ -0,0 +1,64 @@
+#include "singleton.hpp"
+
+#include <qlogging.h>
+#include <qmap.h>
+#include <qobject.h>
+#include <qqmlcontext.h>
+#include <qqmlengine.h>
+#include <qurl.h>
+
+#include "reload.hpp"
+
+void Singleton::componentComplete() {
+	auto* context = QQmlEngine::contextForObject(this);
+
+	if (context == nullptr) {
+		qWarning() << "not registering singleton not created in the qml context:" << this;
+		return;
+	}
+
+	auto url = context->baseUrl();
+
+	if (this->parent() != nullptr || context->contextObject() != this) {
+		qWarning() << "tried to register singleton" << this
+		           << "which is not the root component of its file" << url;
+		return;
+	}
+
+	SingletonRegistry::instance()->install(url, this);
+	this->ReloadPropagator::componentComplete();
+}
+
+SingletonRegistry::~SingletonRegistry() {
+	delete this->previousRegistry;
+	delete this->currentRegistry;
+}
+
+void SingletonRegistry::install(const QUrl& url, Singleton* singleton) {
+	QObject* old = nullptr;
+
+	if (this->previousRegistry != nullptr) {
+		old = this->previousRegistry->value(url);
+	}
+
+	if (this->currentRegistry == nullptr) {
+		this->currentRegistry = new QMap<QUrl, QObject*>();
+	}
+
+	this->currentRegistry->insert(url, singleton);
+	singleton->onReload(old);
+}
+
+void SingletonRegistry::flip() {
+	delete this->previousRegistry;
+	this->previousRegistry = this->currentRegistry;
+	this->currentRegistry = nullptr;
+}
+
+SingletonRegistry* SingletonRegistry::instance() {
+	static SingletonRegistry* instance = nullptr; // NOLINT
+	if (instance == nullptr) {
+		instance = new SingletonRegistry();
+	}
+	return instance;
+}
diff --git a/src/core/singleton.hpp b/src/core/singleton.hpp
new file mode 100644
index 00000000..2b9e8e75
--- /dev/null
+++ b/src/core/singleton.hpp
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <qobject.h>
+#include <qqmlintegration.h>
+#include <qtclasshelpermacros.h>
+#include <qtmetamacros.h>
+#include <qurl.h>
+
+#include "reload.hpp"
+
+///! The root component for reloadable singletons.
+/// All singletons should inherit from this type.
+class Singleton: public ReloadPropagator {
+	Q_OBJECT;
+	QML_ELEMENT;
+
+public:
+	void componentComplete() override;
+};
+
+class SingletonRegistry {
+public:
+	SingletonRegistry() = default;
+	~SingletonRegistry();
+	Q_DISABLE_COPY_MOVE(SingletonRegistry);
+
+	void install(const QUrl& url, Singleton* singleton);
+	void flip();
+
+	static SingletonRegistry* instance();
+
+private:
+	QMap<QUrl, QObject*>* previousRegistry = nullptr;
+	QMap<QUrl, QObject*>* currentRegistry = nullptr;
+};