core/window: add QsWindow attached object to contained Items

src/core/proxywindow.cpp

@@ -11,6 +11,7 @@
 #include <qregion.h>
 #include <qtmetamacros.h>
 #include <qtypes.h>
+#include <qvariant.h>
 #include <qwindow.h>
 
 #include "generation.hpp"
@@ -123,6 +124,8 @@ void ProxyWindowBase::connectWindow() {
 		generation->registerIncubationController(this->window->incubationController());
 	}
 
+	this->window->setProperty("__qs_proxywindow", QVariant::fromValue(this));
+
 	// clang-format off
 	QObject::connect(this->window, &QWindow::visibilityChanged, this, &ProxyWindowBase::visibleChanged);
 	QObject::connect(this->window, &QWindow::xChanged, this, &ProxyWindowBase::xChanged);
@@ -344,3 +347,6 @@ QQmlListProperty<QObject> ProxyWindowBase::data() {
 
 void ProxyWindowBase::onWidthChanged() { this->mContentItem->setWidth(this->width()); }
 void ProxyWindowBase::onHeightChanged() { this->mContentItem->setHeight(this->height()); }
+
+QObject* ProxyWindowAttached::window() const { return this->mWindow; }
+QQuickItem* ProxyWindowAttached::contentItem() const { return this->mWindow->contentItem(); }

src/core/proxywindow.hpp

@@ -136,3 +136,18 @@ private:
 	void polishItems();
 	void updateMask();
 };
+
+class ProxyWindowAttached: public QsWindowAttached {
+	Q_OBJECT;
+
+public:
+	explicit ProxyWindowAttached(ProxyWindowBase* window)
+	    : QsWindowAttached(window)
+	    , mWindow(window) {}
+
+	[[nodiscard]] QObject* window() const override;
+	[[nodiscard]] QQuickItem* contentItem() const override;
+
+private:
+	ProxyWindowBase* mWindow;
+};

src/core/windowinterface.cpp

@@ -1 +1,29 @@
-#include "windowinterface.hpp" // NOLINT
+#include "windowinterface.hpp"
+
+#include <qobject.h>
+#include <qquickitem.h>
+#include <qvariant.h>
+
+#include "proxywindow.hpp"
+
+QsWindowAttached* WindowInterface::qmlAttachedProperties(QObject* object) {
+	auto* item = qobject_cast<QQuickItem*>(object);
+	if (!item) return nullptr;
+	auto* window = item->window();
+	if (!window) return nullptr;
+	auto* proxy = window->property("__qs_proxywindow").value<ProxyWindowBase*>();
+	if (!proxy) return nullptr;
+
+	auto v = proxy->property("__qs_window_attached");
+	if (auto* attached = v.value<QsWindowAttached*>()) {
+		return attached;
+	}
+
+	auto* attached = new ProxyWindowAttached(proxy);
+
+	if (attached) {
+		proxy->setProperty("__qs_window_attached", QVariant::fromValue(attached));
+	}
+
+	return attached;
+}

src/core/windowinterface.hpp

@@ -13,7 +13,15 @@
 #include "reload.hpp"
 
 class ProxyWindowBase;
+class QsWindowAttached;
 
+///! Base class of Quickshell windows
+/// Base class of Quickshell windows
+/// ### Attached properties
+/// `QSWindow` can be used as an attached object of anything that subclasses @@QtQuick.Item$.
+/// It provides the following properties
+/// - `window` - the `QSWindow` object.
+/// - `contentItem` - the `contentItem` property of the window.
 class WindowInterface: public Reloadable {
 	Q_OBJECT;
 	// clang-format off
@@ -101,6 +109,7 @@ class WindowInterface: public Reloadable {
 	Q_CLASSINFO("DefaultProperty", "data");
 	QML_NAMED_ELEMENT(QSWindow);
 	QML_UNCREATABLE("uncreatable base class");
+	QML_ATTACHED(QsWindowAttached);
 
 public:
 	explicit WindowInterface(QObject* parent = nullptr): Reloadable(parent) {}
@@ -131,6 +140,8 @@ public:
 
 	[[nodiscard]] virtual QQmlListProperty<QObject> data() = 0;
 
+	static QsWindowAttached* qmlAttachedProperties(QObject* object);
+
 signals:
 	void windowConnected();
 	void visibleChanged();
@@ -142,3 +153,17 @@ signals:
 	void colorChanged();
 	void maskChanged();
 };
+
+class QsWindowAttached: public QObject {
+	Q_OBJECT;
+	Q_PROPERTY(QObject* window READ window CONSTANT);
+	Q_PROPERTY(QQuickItem* contentItem READ contentItem CONSTANT);
+	QML_ANONYMOUS;
+
+public:
+	[[nodiscard]] virtual QObject* window() const = 0;
+	[[nodiscard]] virtual QQuickItem* contentItem() const = 0;
+
+protected:
+	explicit QsWindowAttached(QObject* parent): QObject(parent) {}
+};