xwayland-shell-v1: new protocol implementation

References: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/163

include/wlr/xwayland/shell.h

@@ -0,0 +1,57 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_XWAYLAND_SHELL_H
+#define WLR_XWAYLAND_SHELL_H
+
+#include <stdbool.h>
+#include <wayland-server-core.h>
+
+/**
+ * The Xwayland shell.
+ *
+ * This is a shell only exposed to Xwayland.
+ */
+struct wlr_xwayland_shell_v1 {
+	struct wl_global *global;
+
+	struct {
+		struct wl_signal new_surface; // struct wlr_xwayland_surface_v1
+	} events;
+
+	// private state
+
+	struct wl_listener display_destroy;
+};
+
+/**
+ * An Xwayland shell surface.
+ */
+struct wlr_xwayland_surface_v1 {
+	struct wlr_surface *surface;
+	uint64_t serial;
+
+	// private state
+
+	struct wl_resource *resource;
+	struct wlr_xwayland_shell_v1 *shell;
+	bool added;
+
+	struct wl_listener surface_destroy;
+};
+
+/**
+ * Create the xwayland_shell_v1 global.
+ *
+ * Compositors should add a global filter (see wl_display_set_global_filter())
+ * to only expose this global to Xwayland clients.
+ */
+struct wlr_xwayland_shell_v1 *wlr_xwayland_shell_v1_create(
+	struct wl_display *display, uint32_t version);
+
+#endif