always set the same monitor and tags for child clients of a client

fixes #272

client.h

@@ -26,6 +26,25 @@ client_surface(Client *c)
 	return c->surface.xdg->surface;
 }
 
+static inline Client *
+client_from_wlr_surface(struct wlr_surface *s)
+{
+	struct wlr_xdg_surface *surface;
+
+#ifdef XWAYLAND
+	struct wlr_xwayland_surface *xsurface;
+	if (s && wlr_surface_is_xwayland_surface(s)
+			&& (xsurface = wlr_xwayland_surface_from_wlr_surface(s)))
+		return xsurface->data;
+#endif
+	if (s && wlr_surface_is_xdg_surface(s)
+			&& (surface = wlr_xdg_surface_from_wlr_surface(s))
+			&& surface->role == WLR_XDG_SURFACE_ROLE_TOPLEVEL)
+		return surface->data;
+
+	return NULL;
+}
+
 /* The others */
 static inline void
 client_activate_surface(struct wlr_surface *s, int activated)
@@ -117,6 +136,20 @@ client_get_title(Client *c)
 	return c->surface.xdg->toplevel->title;
 }
 
+static inline Client *
+client_get_parent(Client *c)
+{
+	Client *p;
+#ifdef XWAYLAND
+	if (client_is_x11(c) && c->surface.xwayland->parent)
+		return client_from_wlr_surface(c->surface.xwayland->parent->surface);
+#endif
+	if (c->surface.xdg->toplevel->parent)
+		return client_from_wlr_surface(c->surface.xdg->toplevel->parent->surface);
+
+	return NULL;
+}
+
 static inline int
 client_is_float_type(Client *c)
 {
@@ -235,25 +268,6 @@ client_restack_surface(Client *c)
 	return;
 }
 
-static inline Client *
-client_from_wlr_surface(struct wlr_surface *s)
-{
-	struct wlr_xdg_surface *surface;
-
-#ifdef XWAYLAND
-	struct wlr_xwayland_surface *xsurface;
-	if (wlr_surface_is_xwayland_surface(s)
-			&& (xsurface = wlr_xwayland_surface_from_wlr_surface(s)))
-		return xsurface->data;
-#endif
-	if (wlr_surface_is_xdg_surface(s)
-			&& (surface = wlr_xdg_surface_from_wlr_surface(s))
-			&& surface->role == WLR_XDG_SURFACE_ROLE_TOPLEVEL)
-		return surface->data;
-
-	return NULL;
-}
-
 static inline void *
 toplevel_from_popup(struct wlr_xdg_popup *popup)
 {

dwl.c

@@ -1388,7 +1388,7 @@ void
 mapnotify(struct wl_listener *listener, void *data)
 {
 	/* Called when the surface is mapped, or ready to display on-screen. */
-	Client *c = wl_container_of(listener, c, map);
+	Client *p, *c = wl_container_of(listener, c, map);
 	int i;
 
 	/* Create scene tree for this client and its border */
@@ -1432,7 +1432,14 @@ mapnotify(struct wl_listener *listener, void *data)
 	wl_list_insert(&fstack, &c->flink);
 
 	/* Set initial monitor, tags, floating status, and focus */
+	if ((p = client_get_parent(c))) {
+		/* Set the same monitor and tags than its parent */
+		c->isfloating = 1;
+		wlr_scene_node_reparent(c->scene, layers[LyrFloat]);
+		setmon(c, p->mon, p->tags);
+	} else {
 		applyrules(c);
+	}
 	printstatus();
 
 	if (c->isfullscreen)