feat: basic plugin system

The wayland plugin now uses it.

src/core/CMakeLists.txt

@@ -1,5 +1,6 @@
 qt_add_executable(quickshell
 	main.cpp
+	plugin.cpp
 	shell.cpp
 	variants.cpp
 	rootwrapper.cpp
@@ -17,5 +18,3 @@ qt_add_executable(quickshell
 )
 
 qt_add_qml_module(quickshell URI QuickShell)
-
-target_link_libraries(quickshell PRIVATE ${QT_DEPS} quickshell-waylandplugin)

src/core/main.cpp

@@ -8,6 +8,7 @@
 #include <qstandardpaths.h>
 #include <qstring.h>
 
+#include "plugin.hpp"
 #include "rootwrapper.hpp"
 
 int main(int argc, char** argv) {
@@ -38,6 +39,8 @@ int main(int argc, char** argv) {
 		return -1;
 	}
 
+	QuickshellPlugin::initPlugins();
+
 	// Base window transparency appears to be additive.
 	// Use a fully transparent window with a colored rect.
 	QQuickWindow::setDefaultAlphaBuffer(true);

src/core/plugin.cpp

@@ -0,0 +1,35 @@
+#include "plugin.hpp"
+#include <algorithm>
+
+#include <qvector.h> // NOLINT (what??)
+
+// defined by moc. see below comment.
+void qml_register_types_QuickShell(); // NOLINT
+
+static QVector<QuickshellPlugin*> plugins; // NOLINT
+
+void QuickshellPlugin::registerPlugin(QuickshellPlugin& plugin) { plugins.push_back(&plugin); }
+
+void QuickshellPlugin::initPlugins() {
+	plugins.erase(
+	    std::remove_if(
+	        plugins.begin(),
+	        plugins.end(),
+	        [](QuickshellPlugin* plugin) { return !plugin->applies(); }
+	    ),
+	    plugins.end()
+	);
+
+	for (QuickshellPlugin* plugin: plugins) {
+		plugin->init();
+	}
+
+	// This seems incredibly stupid but it appears qt will not register the module types
+	// if types are already defined for the module, meaning qmlRegisterType does not work
+	// unless the module types are already registered.
+	qml_register_types_QuickShell();
+
+	for (QuickshellPlugin* plugin: plugins) {
+		plugin->registerTypes();
+	}
+}

src/core/plugin.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <qcontainerfwd.h>
+#include <qfunctionpointer.h>
+
+class QuickshellPlugin {
+public:
+	QuickshellPlugin() = default;
+	virtual ~QuickshellPlugin() = default;
+	QuickshellPlugin(QuickshellPlugin&&) = delete;
+	QuickshellPlugin(const QuickshellPlugin&) = delete;
+	void operator=(QuickshellPlugin&&) = delete;
+	void operator=(const QuickshellPlugin&) = delete;
+
+	virtual bool applies() { return true; }
+	virtual void init() {}
+	virtual void registerTypes() {}
+
+	static void registerPlugin(QuickshellPlugin& plugin);
+	static void initPlugins();
+};
+
+// NOLINTBEGIN
+#define QS_REGISTER_PLUGIN(clazz)                                                                  \
+	[[gnu::constructor]] void qsInitPlugin() {                                                       \
+		static clazz plugin;                                                                           \
+		QuickshellPlugin::registerPlugin(plugin);                                                      \
+	}
+// NOLINTEND