Retrieve wl_seat instance from compositor

It turns out that activating a toplevel with a NULL wl_seat parameter
causes a protocol error, which crashes the calling app.  So make sure
we've fetched a wl_seat from the server before trying to activate a
window.

libxfce4windowing/xfw-screen-wayland.c

@@ -21,7 +21,7 @@
 
 #include <gdk/gdkwayland.h>
 #include <string.h>
-#include <wayland-client-protocol.h>
+#include <wayland-client.h>
 
 #include "protocols/wlr-foreign-toplevel-management-unstable-v1-client.h"
 
@@ -37,6 +37,7 @@ struct _XfwScreenWaylandPrivate {
     GdkScreen *gdk_screen;
     struct wl_registry *wl_registry;
     struct zwlr_foreign_toplevel_manager_v1 *toplevel_manager;
+    struct wl_seat *wl_seat;
     XfwWorkspaceManager *workspace_manager;
     GList *windows;
     GList *windows_stacked;
@@ -92,7 +93,8 @@ xfw_screen_wayland_init(XfwScreenWayland *screen) {
     screen->priv = xfw_screen_wayland_get_instance_private(screen);
 }
 
-static void xfw_screen_wayland_constructed(GObject *obj) {
+static void
+xfw_screen_wayland_constructed(GObject *obj) {
     XfwScreenWayland *screen = XFW_SCREEN_WAYLAND(obj);
     GdkDisplay *gdk_display;
     struct wl_display *wl_display;
@@ -165,6 +167,9 @@ xfw_screen_wayland_finalize(GObject *obj) {
     if (screen->priv->toplevel_manager != NULL) {
         zwlr_foreign_toplevel_manager_v1_destroy(screen->priv->toplevel_manager);
     }
+    if (screen->priv->wl_seat != NULL) {
+        wl_seat_release(screen->priv->wl_seat);
+    }
     if (screen->priv->wl_registry != NULL) {
         wl_registry_destroy(screen->priv->wl_registry);
     }
@@ -216,6 +221,15 @@ registry_global(void *data, struct wl_registry *registry, uint32_t id, const cha
                                                           id,
                                                           &zwlr_foreign_toplevel_manager_v1_interface,
                                                           MIN((uint32_t)zwlr_foreign_toplevel_manager_v1_interface.version, version));
+    } else if (strcmp(wl_seat_interface.name, interface) == 0) {
+        if (screen->priv->wl_seat != NULL) {
+            g_debug("We already had a wl_seat, but now we're getting a new one");
+            wl_seat_release(screen->priv->wl_seat);
+        }
+        screen->priv->wl_seat = wl_registry_bind(screen->priv->wl_registry,
+                                                 id,
+                                                 &wl_seat_interface,
+                                                 MIN((uint32_t)wl_seat_interface.version, version));
     }
 }
 
@@ -260,6 +274,11 @@ _xfw_screen_wayland_get_gdk_screen(XfwScreenWayland *screen) {
     return screen->priv->gdk_screen;
 }
 
+struct wl_seat *
+_xfw_screen_wayland_get_wl_seat(XfwScreenWayland *screen) {
+    return screen->priv->wl_seat;
+}
+
 void
 _xfw_screen_wayland_set_active_window(XfwScreenWayland *screen, XfwWindow *window) {
     if (screen->priv->active_window != window) {

libxfce4windowing/xfw-screen-wayland.h

@@ -25,6 +25,7 @@
 #endif
 
 #include <glib-object.h>
+#include <wayland-client.h>
 
 #include "xfw-window.h"
 #include "xfw-workspace.h"
@@ -51,7 +52,8 @@ struct _XfwScreenWaylandClass {
 
 GType xfw_screen_wayland_get_type(void) G_GNUC_CONST;
 
-GdkScreen * _xfw_screen_wayland_get_gdk_screen(XfwScreenWayland *screen);
+GdkScreen *_xfw_screen_wayland_get_gdk_screen(XfwScreenWayland *screen);
+struct wl_seat *_xfw_screen_wayland_get_wl_seat(XfwScreenWayland *screen);
 void _xfw_screen_wayland_set_active_window(XfwScreenWayland *screen, XfwWindow *window);
 XfwWorkspace *_xfw_screen_wayland_get_window_workspace(XfwScreenWayland *screen, XfwWindow *window);
 

libxfce4windowing/xfw-util.h

@@ -41,11 +41,13 @@ G_BEGIN_DECLS
 /**
  * XfwErrorCode:
  * @XFW_ERROR_UNSUPPORTED: the operation attempted is not supported.
+ * @XFW_ERROR_INTERNAL: an internal error has occurred.
  *
  * An error code enum describing possible errors returned by this library.
  **/
 typedef enum _XfwErrorCode {
     XFW_ERROR_UNSUPPORTED = 0,
+    XFW_ERROR_INTERNAL,
 } XfwErrorCode;
 
 /**

libxfce4windowing/xfw-window-wayland.c

@@ -313,9 +313,18 @@ xfw_window_wayland_get_workspace(XfwWindow *window) {
 
 static gboolean
 xfw_window_wayland_activate(XfwWindow *window, guint64 event_timestamp, GError **error) {
-    // FIXME: make sure NULL for seat means "compositor picks what seat", and doesn't crash or fail
-    zwlr_foreign_toplevel_handle_v1_activate(XFW_WINDOW_WAYLAND(window)->priv->handle, NULL);
-    return TRUE;
+    XfwWindowWayland *wwindow = XFW_WINDOW_WAYLAND(window);
+    struct wl_seat *wl_seat = _xfw_screen_wayland_get_wl_seat(XFW_SCREEN_WAYLAND(wwindow->priv->screen));
+
+    if (wl_seat != NULL) {
+        zwlr_foreign_toplevel_handle_v1_activate(wwindow->priv->handle, wl_seat);
+        return TRUE;
+    } else {
+        if (error != NULL) {
+            *error = g_error_new(XFW_ERROR, XFW_ERROR_INTERNAL, "Cannot activate window as we do not have a wl_seat");
+        }
+        return FALSE;
+    }
 }
 
 static gboolean