feat(wayland): custom layershell implementation

A fair amount of things are broken but not in the layershell interface
itself. The shell window platform extensions are next in line for
refactoring and relevent issues will be fixed then. Same for docs.

src/wayland/layershell.hpp

@@ -0,0 +1,122 @@
+#pragma once
+
+#include <qobject.h>
+#include <qscreen.h>
+#include <qtmetamacros.h>
+#include <qtypes.h>
+#include <qwindow.h>
+
+#include "../core/shellwindow.hpp"
+
+namespace Layer { // NOLINT
+Q_NAMESPACE;
+QML_ELEMENT;
+
+enum Enum {
+	Background = 0,
+	Bottom = 1,
+	Top = 2,
+	Overlay = 3,
+};
+Q_ENUM_NS(Enum);
+
+} // namespace Layer
+
+/// Type of keyboard focus that will be accepted by a [ShellWindow]
+///
+/// [ShellWindow]: ../shellwindow
+namespace KeyboardFocus { // NOLINT
+Q_NAMESPACE;
+QML_ELEMENT;
+
+enum Enum {
+	/// No keyboard input will be accepted.
+	None = 0,
+	/// Exclusive access to the keyboard, locking out all other windows.
+	Exclusive = 1,
+	/// Access to the keyboard as determined by the operating system.
+	///
+	/// > [!WARNING] On some systems, `OnDemand` may cause the shell window to
+	/// > retain focus over another window unexpectedly.
+	/// > You should try `None` if you experience issues.
+	OnDemand = 2,
+};
+Q_ENUM_NS(Enum);
+
+} // namespace KeyboardFocus
+
+namespace ScreenConfiguration { // NOLINT
+Q_NAMESPACE;
+QML_ELEMENT;
+
+enum Enum {
+	Window = 0,
+	Compositor = 1,
+};
+Q_ENUM_NS(Enum);
+
+} // namespace ScreenConfiguration
+
+class QSWaylandLayerSurface;
+
+class LayershellWindowExtension: public QObject {
+	Q_OBJECT;
+
+public:
+	LayershellWindowExtension(QObject* parent = nullptr): QObject(parent) {}
+	~LayershellWindowExtension() override = default;
+	LayershellWindowExtension(LayershellWindowExtension&&) = delete;
+	LayershellWindowExtension(const LayershellWindowExtension&) = delete;
+	void operator=(LayershellWindowExtension&&) = delete;
+	void operator=(const LayershellWindowExtension&) = delete;
+
+	// returns the layershell extension if attached, otherwise nullptr
+	static LayershellWindowExtension* get(QWindow* window);
+
+	// Attach this layershell extension to the given window.
+	// The extension is reparented to the window and replaces any existing extensions.
+	// Returns false if the window cannot be used.
+	bool attach(QWindow* window);
+
+	void setAnchors(Anchors anchors);
+	[[nodiscard]] Anchors anchors() const;
+
+	void setMargins(Margins margins);
+	[[nodiscard]] Margins margins() const;
+
+	void setExclusiveZone(qint32 exclusiveZone);
+	[[nodiscard]] qint32 exclusiveZone() const;
+
+	void setLayer(Layer::Enum layer);
+	[[nodiscard]] Layer::Enum layer() const;
+
+	void setKeyboardFocus(KeyboardFocus::Enum focus);
+	[[nodiscard]] KeyboardFocus::Enum keyboardFocus() const;
+
+	// no effect if configured
+	void setUseWindowScreen(bool value);
+	void setNamespace(QString ns);
+	[[nodiscard]] QString ns() const;
+	[[nodiscard]] bool isConfigured() const;
+
+signals:
+	void anchorsChanged();
+	void marginsChanged();
+	void exclusiveZoneChanged();
+	void layerChanged();
+	void keyboardFocusChanged();
+
+private:
+	// if configured the screen cannot be changed
+	QSWaylandLayerSurface* surface = nullptr;
+
+	bool useWindowScreen = false;
+	Anchors mAnchors;
+	Margins mMargins;
+	qint32 mExclusiveZone = 0;
+	Layer::Enum mLayer = Layer::Top;
+	QString mNamespace = "quickshell";
+	KeyboardFocus::Enum mKeyboardFocus = KeyboardFocus::None;
+
+	friend class QSWaylandLayerSurface;
+};