Index: uspace/srv/hid/display/wmclient.c
===================================================================
--- uspace/srv/hid/display/wmclient.c	(revision 913add60dd2ff444e319a0f402067877d08cb574)
+++ uspace/srv/hid/display/wmclient.c	(revision 913add60dd2ff444e319a0f402067877d08cb574)
@@ -0,0 +1,187 @@
+/*
+ * Copyright (c) 2022 Jiri Svoboda
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/** @addtogroup display
+ * @{
+ */
+/**
+ * @file Display server WM client
+ */
+
+#include <adt/list.h>
+#include <errno.h>
+#include <stdlib.h>
+#include "display.h"
+#include "window.h"
+#include "wmclient.h"
+
+/** Create WM client.
+ *
+ * @param display Parent display
+ * @param cb WM client callbacks
+ * @param cb_arg Callback argument
+ * @param rwmclient Place to store pointer to new WM client.
+ * @return EOK on success, ENOMEM if out of memory
+ */
+errno_t ds_wmclient_create(ds_display_t *display, ds_wmclient_cb_t *cb,
+    void *cb_arg, ds_wmclient_t **rwmclient)
+{
+	ds_wmclient_t *wmclient;
+
+	wmclient = calloc(1, sizeof(ds_wmclient_t));
+	if (wmclient == NULL)
+		return ENOMEM;
+
+	list_initialize(&wmclient->events);
+	wmclient->cb = cb;
+	wmclient->cb_arg = cb_arg;
+
+	ds_display_add_wmclient(display, wmclient);
+
+	*rwmclient = wmclient;
+	return EOK;
+}
+
+/** Destroy WM client.
+ *
+ * @param wmclient WM client
+ */
+void ds_wmclient_destroy(ds_wmclient_t *wmclient)
+{
+	ds_wmclient_purge_events(wmclient);
+	ds_display_remove_wmclient(wmclient);
+	free(wmclient);
+}
+
+/** Get next event from WM client event queue.
+ *
+ * @param wmclient WM client
+ * @param event Place to store event
+ * @return EOK on success, ENOENT if event queue is empty
+ */
+errno_t ds_wmclient_get_event(ds_wmclient_t *wmclient, wndmgt_ev_t *event)
+{
+	link_t *link;
+	ds_wmclient_ev_t *wevent;
+
+	link = list_first(&wmclient->events);
+	if (link == NULL)
+		return ENOENT;
+
+	wevent = list_get_instance(link, ds_wmclient_ev_t, levents);
+	list_remove(link);
+
+	*event = wevent->event;
+	free(wevent);
+	return EOK;
+}
+
+/** Purge events from WM client event queue.
+ *
+ * @param client Client
+ */
+void ds_wmclient_purge_events(ds_wmclient_t *wmclient)
+{
+	link_t *cur;
+	link_t *next;
+	ds_wmclient_ev_t *wevent;
+
+	cur = list_first(&wmclient->events);
+	while (cur != NULL) {
+		next = list_next(cur, &wmclient->events);
+		wevent = list_get_instance(cur, ds_wmclient_ev_t, levents);
+
+		list_remove(cur);
+		free(wevent);
+		cur = next;
+	}
+}
+#include <io/log.h>
+/** Post window added event to the WM client's message queue.
+ *
+ * @param wmclient WM client
+ * @param wnd_id Window ID of the added window
+ *
+ * @return EOK on success or an error code
+ */
+errno_t ds_wmclient_post_wnd_added_event(ds_wmclient_t *wmclient,
+    sysarg_t wnd_id)
+{
+	ds_wmclient_ev_t *wevent;
+
+	log_msg(LOG_DEFAULT, LVL_NOTE, "post wnd added event wmclient=%p\n",
+	    (void *)wmclient);
+
+	wevent = calloc(1, sizeof(ds_wmclient_ev_t));
+	if (wevent == NULL)
+		return ENOMEM;
+
+	wevent->wmclient = wmclient;
+	wevent->event.etype = wmev_window_added;
+	wevent->event.wnd_id = wnd_id;
+	list_append(&wevent->levents, &wmclient->events);
+
+	/* Notify the client */
+	// TODO Do not send more than once until client drains the queue
+	if (wmclient->cb != NULL && wmclient->cb->ev_pending != NULL)
+		wmclient->cb->ev_pending(wmclient->cb_arg);
+
+	return EOK;
+}
+
+/** Post window removed event to the WM client's message queue.
+ *
+ * @param wmclient WM client
+ * @param wnd_id Window ID of the added window
+ *
+ * @return EOK on success or an error code
+ */
+errno_t ds_wmclient_post_wnd_removed_event(ds_wmclient_t *wmclient,
+    sysarg_t wnd_id)
+{
+	ds_wmclient_ev_t *wevent;
+
+	wevent = calloc(1, sizeof(ds_wmclient_ev_t));
+	if (wevent == NULL)
+		return ENOMEM;
+
+	wevent->wmclient = wmclient;
+	wevent->event.etype = wmev_window_removed;
+	wevent->event.wnd_id = wnd_id;
+	list_append(&wevent->levents, &wmclient->events);
+
+	/* Notify the client */
+	// TODO Do not send more than once until client drains the queue
+	if (wmclient->cb != NULL && wmclient->cb->ev_pending != NULL)
+		wmclient->cb->ev_pending(wmclient->cb_arg);
+
+	return EOK;
+}
+
+/** @}
+ */
