Track X11 enter / leave events - c

Question

I need to be notified when mouse enters or leaves a window (any window, that's why I'm grabbing on the root window). I have a solution using xcb_input_xi_grab_device() but it works only half way. When I run the app, I do get enter/leave events but the mouse pointer disappears and it consumes all mouse events and other windows stop (children of the root window) reacting to clicks.
Using XCB_INPUT_GRAB_OWNER_OWNER should allow passing-through the events but it doesn't work.
app.c:
#include <stdio.h>
#include <xcb/xcb.h>
#include <xcb/xinput.h>
xcb_input_device_id_t find_device(xcb_connection_t *conn)
{
xcb_input_xi_query_device_reply_t *reply = xcb_input_xi_query_device_reply(
conn, xcb_input_xi_query_device(conn, XCB_INPUT_DEVICE_ALL), NULL);
xcb_input_xi_device_info_iterator_t iter =
xcb_input_xi_query_device_infos_iterator(reply);
xcb_input_device_id_t device_id;
int found = 0;
while (iter.rem) {
xcb_input_xi_device_info_t *device = iter.data;
switch (device->type) {
case XCB_INPUT_DEVICE_TYPE_MASTER_POINTER:
case XCB_INPUT_DEVICE_TYPE_SLAVE_POINTER:
case XCB_INPUT_DEVICE_TYPE_FLOATING_SLAVE:
device_id = device->deviceid;
found = 1;
break;
}
if (found) {
break;
}
xcb_input_xi_device_info_next(&iter);
}
free(reply);
return device_id;
}
int main()
{
xcb_connection_t *conn = xcb_connect(NULL, NULL);
xcb_screen_t *screen = xcb_setup_roots_iterator(xcb_get_setup(conn)).data;
uint32_t mask =
XCB_INPUT_XI_EVENT_MASK_ENTER | XCB_INPUT_XI_EVENT_MASK_LEAVE;
xcb_generic_error_t *error;
xcb_input_xi_grab_device_reply_t *reply = xcb_input_xi_grab_device_reply(
conn,
xcb_input_xi_grab_device(conn, screen->root, XCB_CURRENT_TIME,
XCB_CURSOR_NONE, find_device(conn),
XCB_INPUT_GRAB_MODE_22_ASYNC,
XCB_INPUT_GRAB_MODE_22_ASYNC,
XCB_INPUT_GRAB_OWNER_OWNER, 1, &mask),
&error);
free(reply);
if (error) {
printf("failed to grab device\n");
free(error);
return -1;
}
xcb_flush(conn);
xcb_generic_event_t *event;
while ((event = xcb_wait_for_event(conn))) {
xcb_ge_event_t *generic_event = event;
switch (generic_event->event_type) {
case XCB_INPUT_ENTER:
printf("enter\n");
break;
case XCB_INPUT_LEAVE:
printf("leave\n");
break;
}
free(event);
}
return -1; // never reached
}
cc -O2 app.c -o app `pkg-config --cflags --libs xcb xcb-xinput`
I also tried to achieve it with xcb_grab_button(), xcb_input_xi_select_events(), xcb_input_xi_passive_grab_device() or xcb_grab_pointer() but then the problem is the same. Either the mouse events are not passed-through or I don't receive enter/leave events at all.